Enzymatic hydrolysis of corn stover lignin by laccase, lignin peroxidase, and manganese peroxidase

Molecular characterization and environmental response of dissolved organic matter in reserve quiescent groundwater wells of the North China plain: Insights from spectroscopy and mass spectrometry

Dissolved organic matter (DOM) plays a critical role in aquatic ecosystems. However, the characteristics of DOM in groundwater source wells and interactions with environmental factors remain poorly understood. This study investigated the spectral properties, molecular composition, and environmental drivers across vertical groundwater gradients in Shijiazhuang using spectroscopy, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICRMS), multivariate statistics and molecular network analysis. Three components were identified: two humic-like substances (C1, C3) and one protein-like component (C2) Humic-like substances exhibited significant vertical stratification, with bottom groundwater DOM showing higher humification and autochthonous characteristics. Multivariate statistical analysis indicated that NO3--N and dissolved oxygen (DO) were keystone factors influencing the vertical differences of DOM. Surface-layer DOM was driven by dissolved total phosphorus (DTP), pH, DO and NO3--N, while the bottom layer was jointly regulated by pH, total phosphorus (TP), total nitrogen (TN) and NO3--N. DOM components correlated significantly with fluorescence index (FI), humification index (HIX), chemical oxygen demand (CODMn) and dissolved total nitrogen (DTN). FT-ICRMS analysis revealed that DOM molecular composition was dominated by CHO (38.71 %-52.07 %) and CHON (22.30 %-34.44 %) compounds, with lignin-like (LIG) (60.91 %-80.56 %) serving as the core molecular formulae. Redundancy analysis (RDA) identified that TN, DO, and NH4+-N were key drivers regulating the DOM molecules distribution. Furthermore, molecular network analysis demonstrated that LIG molecular formulae played a crucial role in the network, significantly enhancing the chemical stability of the DOM molecular network. These findings elucidate DOM dynamics in groundwater systems at a molecular scale, providing critical insights for resource protection and risk management.

Engineering Bacterial Laccase with Improved Catalytic Activity and Thermostability by Rational Design

Laccases (benzenediol:oxygen oxidoreductases) are important multi-copper oxidases with widespread applications in industry. Here, Bacillus subtilis laccase CotA that has been widely studied was engineered to improve catalytic activity and thermostability via rational design. After iterative mutation of beneficial mutation sites, a triple mutant of CotA laccase (DTA) was obtained, whose catalytic activity and thermostability were improved by 2.7-fold and 1.4-fold compared with the wild-type (WT) CotA, respectively. The enhanced activity of DTA is primarily due to strengthened intermolecular forces in the active site, while its improved thermostability is attributed to increased hydrophobic residues, augmented protein surface flexibility, collectively rendering DTA a more active and stable enzyme with potential industrial applications. Compared to WT, DTA can degrade mycotoxins aflatoxin B1 (55.09% vs 44.51%) and ZEN (zearalenone) (71.59% vs 41.09%) more efficiently, and DTA can also better pretreat lignocellulose, promoting the hydrolysis of cellulose by cellulase. All these indicate that DTA has the potential to be used in industry.

Enhancing aerobic composting of cow dung and wheat straw with nanobubble water: Improved lignocellulose degradation and nutrient enrichment for increased crop biomass

Cow dung and wheat straw are rich in lignocellulose, which has a complex structure, making it difficult to biodegrade. This study investigated the promotion of composting effectiveness and product fertility by adding nanobubble water (Air, CO2, He, and N2) during aerobic composting of cow dung and wheat straw. Nanobubble water prolonged the high-temperature period by 1-2 days, increased the activity of soil urease and soil ligninase, reduced the lignocellulose content by 1.4 %-6.1 %, and increased the total potassium/total phosphorus ratio of the final compost products by 1.8 %-3.5 %/31.6 %-43.0 %. Nanobubble water of N2 significantly increased the total nitrogen of final compost products by 8.3 %. The lignocellulose content was significantly positively correlated with the moisture content, but significantly negatively correlated with the relative abundances of Georgenia and Marinimicrobium. The final compost products of the nanobubble water groups significantly increased the total biomass of cabbage by 37.1 %-195.3 %. The results showed that adding nanobubble water to aerobic compost of cow dung and wheat straw improved the biodegradation of lignocellulose and enriched the nutrient elements (total nitrogen, total phosphorus, and total potassium) of the final compost products. Among the four types of nanobubble water, N2-containing nanobubble water is the most promising.

The potential of Trichoderma asperellum for degrading wheat straw and its key genes in lignocellulose degradation

This study explored Trichoderma asperellum's lignocellulose degradation potential in wheat straw (WS) and NaOH-treated WS via solid-state fermentation (SSF) over 30 days. Compared to the control, WS treated with T. asperellum (TW) and NaOH-treated WS with T. asperellum (TN) showed increased dry matter loss rates of 15.67 and 15.76%, respectively. Cellulose degradation reached 33.51 and 28.00%, while hemicellulose degradation increased to 31.56 and 63.86%. Crude protein (CP) content rose to 10.96 and 7.44%, and reducing sugar content to 10.86 and 12.41 mg/g, respectively. T. asperellum effectively reduced lignocellulose content and enhanced substrate nutrition, supporting subsequent uses of WS as fertilizer, feed, or for bioethanol production. Enzymatic activity and structural analyses were performed to further confirm the lignocellulose-degrading ability of T. asperellum and to analyze the degradation mechanisms. Transcriptomic analysis revealed that, compared with the control group, the TN group had 4,548, 4,399, and 6,051 differentially expressed genes (DEGs) at 5, 10, and 30 days, respectively, mainly involved in cellulose and hemicellulose degradation, carbohydrate metabolism, carbohydrate transport, glycoside hydrolases, and polysaccharide binding. T. asperellum can modify lignin by expressing dye-decolorizing peroxidase genes, and multiple key genes were identified for further research into its genetic regulation in lignocellulose degradation.

Unlocking lignin valorization and harnessing lignin-based raw materials for bio-manufacturing

Lignin, an energy-rich and adaptable polymer comprising phenylpropanoid monomers utilized by plants for structural reinforcement, water conveyance, and defense mechanisms, ranks as the planet's second most prevalent biopolymer, after cellulose. Despite its prevalence, lignin is frequently underused in the process of converting biomass into fuels and chemicals. Instead, it is commonly incinerated for industrial heat due to its intricate composition and resistance to decomposition, presenting obstacles for targeted valorization. In contrast to chemical catalysts, biological enzymes show promise not only in selectively converting lignin components but also in seamlessly integrating into cellular structures, offering biocatalysis as a potentially efficient pathway for lignin enhancement. This review comprehensively summarizes cutting-edge biostrategies, ligninolytic enzymes, metabolic pathways, and lignin-degrading strains or consortia involved in lignin degradation, while critically evaluating the underlying mechanisms. Metabolic and genetic engineering play crucial roles in redirecting lignin and its derivatives towards metabolic pathways like the tricarboxylic acid cycle, opening up novel avenues for its valorization. Recent advancements in lignin valorization are scrutinized, highlighting key challenges and promising solutions. Furthermore, the review underscores the importance of innovative approaches, such as leveraging digital systems and synthetic biology, to unlock the commercial potential of lignin-derived raw materials as sustainable feedstocks. Artificial intelligence-driven technologies offer promise in overcoming current challenges and driving widespread adoption of lignin valorization, presenting an alternative to sugar-based feedstocks for bio-based manufacturing in the future. The utilization of available lignin residue for synthesis of high-value chemicals or energy, even alternative food, addresses various crises looming in the food-energy-water nexus.

Manganese Peroxidase Participates in the Liquid-Solid-Gas Triphase Regulation on Microbial Degradation of Lignocellulose in Solid-State Fermentation

The three-phase structure of solid-state fermentation (SSF) directly affects substrate degradation and fermentation efficiency. However, the mechanism of three-phase regulation on lignocellulose utilization and microbial metabolism is still unclear. Based on comparative transcriptome analysis, a lignocellulose degrading enzyme, manganese peroxidase (GlMnP), which was significantly affected by water stress meanwhile related to triphase utilization, was screened to reveal the mechanism using Ganoderma lucidum as the reference strain. The results showed that GlMnP directly participates in lignocellulose degradation by positively regulating the activity of carboxymethylcellulase (CMCase), filter paper (FPAse), and laccase (LACase) enzymes, and indirectly participates in lignocellulose degradation by negatively regulating the redox levels in microorganisms. In addition, GlMnP can also control microbial glycolysis rate to enhance lignocellulose utilization. The results indicated that GlMnP participates in the liquid-solid-gas triphase regulation on lignocellulose degradation by G. lucidum in SSF.

Laccase Functional Analysis: Substrates, Activity Assays, Challenges, and Prospects

Enzyme functional analysis is a multifaceted process that can be used for various purposes, such as screening for specific activities, as well as developing, optimising, and validating processes or final products. Functional analysis methods are crucial for assessing enzyme performance and catalytic properties. Laccase, a well-known blue multi-copper oxidase, holds immense potential in diverse industries such as pharmaceuticals, paper and pulp, food and beverages, textiles, and biorefineries due to its clean oxidation process and versatility in handling a wide range of substrates. Despite its prominence, the use of laccase encounters challenges in selecting appropriate functional analysis substrates and methods. This review delves into the substrates utilised in qualitative and quantitative techniques for laccase activity analysis. Although laccase catalyses mono-electron oxidation of aromatic hydroxyl, amine, and thiol compounds efficiently, using molecular oxygen as an electron acceptor, the review identifies limitations in the specificity of the commonly employed substrates, concerns regarding the stability of certain compounds and highlights potential strategies.

Efficient degradation of corn straw at low temperature using a novel co-cultured consortium LHWA

Straw degradation was slow under low temperature environments. A cold-tolerant consortium LHWA was constructed by Bacillus cereus, Acinetobacter lwoffii, Penicillium griseofulvum, and Talaromyces funiculosus. The consortium and culture conditions were optimized. Under 4 °C cultivation, liquid fermentation showed a 55.52 % straw weight loss rate after 30 days with inoculum (8.4 %, w/v), peptone (0.4 %, w/v) and Fe2+ concentration (0.06 %, w/v); solid fermentation showed 58.36 % straw weight loss rate after 60 days. According to transcriptomic analysis, the mechanism of cold resistance in B. cereus is to improve the fluidity of the cell membrane, including changing the composition of fatty acids, increasing the expression of cold stress response proteins and cold shock proteins. The constructed consortium LHWA significantly improved the straw degradation efficiency under cold environments.

Extraction of high-purity lignin from the kraft pulping black liquor by enzyme purification process with alkaline-resistant xylanase and cellulase

In this study, the response surface methodology was first utilized to optimize the enzyme treatment conditions as reaction pH, temperature, time and enzyme dosage of 9.5, 45 °C, 94.5 min and 100 U/L. Under these parameters, the kraft pulping black liquor was treated with alkaline-resistant xylanase and cellulase, followed by acid precipitation to obtain enzyme-purified lignin (EPL). The yield, purity and physicochemical characteristics of EPL were contrasted with acid-purified lignin (APL) prepared at the same pH values. Results showed that the enzyme purification method generated lignin with lower molecular weight of 3532 g/mol, greater purity of 96.79 % and higher yield of 2.89 %. Compared with APL, EPL exhibited stronger UV absorption capacity. SEM images revealed that EPL had a rough and porous surface, whereas the surface of APL was relatively smooth. TGA analysis indicated the thermal stability of EPL (Tmax = 333.5 °C) was superior to APL (Tmax = 309.2 °C). Moreover, no significant differences were observed in the chemical functional groups and molecular structures of APL and EPL, suggesting that the addition of alkaline-resistant xylanase and cellulase didn't change the chemical structure of lignin. The favorable properties of EPL make it a promising application in the development of high-value composite materials and biodegradable plastics.

Kraft lignin biobleaching by a dye-decolorizing peroxidase from the Antarctic Pseudomonas sp. AU10 strain

Pseudomonas sp. AU10 is an Antarctic psychrotolerant bacterium that produces a dye-decolorizing peroxidase (DyP-AU10). The recombinant enzyme (rDyP-AU10) is a heme-peroxidase that decolors dyes and modifies kraft lignin. In this work, we report the best activity parameters for lignin modification (at 45 °C and pH 4) and show that the enzyme increases the number of aldehydes, ketones, and phenolic compounds. The analyses of the HPLC profile of samples also support that rDyP-AU10 induces the chemical change of kraft lignin. The enzyme also acts as a biobleaching agent on cellulose pulps, as shown by the reduction in kappa number. We also included experiments with a commercial laccase from Trametes versicolor and performed experiments using single enzymes and, in combination. The results show that rDyP-AU10 and the commercial laccase do not have a synergic activity as a modifying system, on cellulose pulp as substrates. However, results suggest that rDyP-AU10 holds potential as a member of the portfolio of lignin-modifying enzymes.

Lignocellulolytic Bacterial Engineering for Tailoring the Microstructure of Hard Carbon as a Sodium-Ion Battery Anode with Fast Plateau Kinetics

Lignocellulosic biomass-derived pyrolysis hard carbon (LCB-HC) shows promising commercial potential as an anode material for sodium-ion batteries (SIBs). LCB compromises multiple biopolymer carbon sources, including cellulose, hemicellulose, and lignin, which influence the formation and microstructure of pyrolysis HC. However, the poor plateau kinetics of LCB-HC is one of the main obstacles that severely limits its energy density with high power density, which could be attributed to the narrow interlayer distance and the lack of abundant closed pores for the intercalation/filling of Na+. Herein, we proposed a bottom-up approach to tailoring the microstructure of LCB-HC by regulating the components of the LCB precursor at the molecular level using bioenzymes secreted by lignocellulolytic bacteria. This mild and efficient enzymatic hydrolysis pathway partially depolymerized the biopolymers of basswood specifically, thereby enabling the construction of a small curved-graphite domain architecture with increased closed pores and an enlarged interlayer distance of LCB-HC, benefiting the low-voltage plateau Na+ storage with accelerated kinetics. As a result, the basswood-derived HC delivers a reversible capacity of 366.4 mAh g-1 and performed remarkable plateau capacity retainability with a high proportion of 74.3% even with increased current density to 1000 mA g-1. Such a microbial-chemistry-assisted approach provided insights into tailoring the microstructure of LCB-HC to construct high-performance SIB anode materials.

Construction of a laccase/CeO2/attapulgite nanocomposite for photoenzymatic catalytic CO2 reduction coupled with biomass oxidation

Herein, a photoenzymatic synergistic catalytic material, i.e. laccase/CeO2/attapulgite, was prepared for simultaneous CO2 conversion and biomass conversion. Based on the synergistic effect of the photoenzyme in the prepared composites, a remarkable CO (27.15 μmol gcat-1 h-1) and CH4 (64.88 μmol gcat-1 h-1) production rate and a benzaldehyde yield of 84.1% were gained.

Efficient Expression and Activity Optimization of Manganese Peroxidase for the Simultaneous Degradation of Aflatoxins AFB1, AFB2, AFG1, and AFG2

Aflatoxins (AFs), notorious mycotoxins that pose significant risks to human and animal health, make biodegradation extremely crucial as they offer a promising approach to managing and reducing their harmful impacts. In this study, we identified a manganese peroxidase from Punctularia strigosozonata (PsMnp) through protein similarity analysis, which has the capability to degrade four AFs (AFB1, AFB2, AFG1, and AFG2) simultaneously. The gene encoding this enzyme was subject to codon optimization, followed by cold shock induction expression using the pColdII vector, leading to the soluble expression of manganese peroxidase (Mnp) in Escherichia coli. This study tackled the problem of inclusion body formation that often occurs during Mnp expression in E. coli. After optimizing the degradation conditions, the degradation rates for AFB1, AFB2, AFG1, and AFG2 were 87.9, 72.8, 77.3, and 85.6%, respectively. Molecular docking and molecular dynamics simulations indicated that PsMnp facilitated the degradation of AFs through hydrophobic and polar interactions among various amino acid residues. This research offers novel insights into the rapid discovery of enzymes capable of degrading AFs and establishes a theoretical foundation for the efficient expression of mycotoxin detoxification enzymes.

Influences of superfine-grinding and mix enzymolysis alone or combined with hydroxypropylation or acetylation on the hypolipidemic and hypoglycemic properties of coconut endosperm residue fiber

Coconut endosperm residue is an abundant and low-cost resource of dietary fiber, but the low soluble fiber content limits its functional properties and applications in the food industry. To improve the hypolipidemic and hypoglycemic properties, coconut endosperm residue fiber (CERF) was modified by superfine-grinding and mix enzymatic hydrolysis alone, or combined with acetylation or hydroxypropylation. The effects of these modifications on the structure and functional properties were studied using scanning electron microscopy, Fourier-transformed infrared spectroscopy, and in vitro tests. After these modifications, the microstructure of CERF became more porous, and its soluble fiber content, surface area, water adsorption, and expansion capacities were all improved (p < 0.05). Moreover, superfine-grinding and mix enzymolysis combined with acetylation treated CERF showed the highest surface hydrophobicity (48.96) and cholesterol and cholate adsorption abilities (33.72 and 42.04 mg∙g‒1). Superfine-grinding-, mix enzymolysis-, and hydroxypropylation-treated CERF exhibited the highest viscosity (17.84 cP), glucose adsorption capacity (29.61 µmol∙g‒1), and glucose diffusion inhibition activity (73.96%), and water-expansion ability (8.60 mL∙g‒1). Additionally, superfine-grinding and mix enzymatic hydrolyzed CERF had the highest α-amylase inhibiting activity (42.76%). Therefore, superfine-grinding and mix enzymolysis alone or combined with hydroxypropylation were better choices to improve hypoglycemic properties of CERF; meanwhile, superfine-grinding and mix enzymolysis combined with acetylation can effectively improve its hypolipidemic properties. PRACTICAL APPLICATION: This study offered three composite modification methods to improve the soluble fiber content and in vitro hypolipidemic and hypoglycemic properties of coconut endosperm residue fiber. These modification methods were practicable and low-cost. Moreover, it provides good choices to improve the functional properties and applications of other dietary fibers in the food industry.

Enhancing Manganese Peroxidase: Innovations in Genetic Modification, Screening Processes, and Sustainable Agricultural Applications

Manganese peroxidase (MnP), a vital extracellular enzyme for the degradation of lignin and other organic pollutants, has demonstrated immense potential for agricultural and environmental applications, including straw pretreatment, feed fermentation, mycotoxin degradation, and water treatment. However, current research remains in its exploratory phase, with naturally sourced MnP unable to meet industrial-scale demands and no mature commercial enzyme preparations available on the market. This comprehensive review innovatively constructs a framework for MnP research, probing into its molecular conformation and catalytic principles, while providing an overview of the advancements in high-throughput screening and In silco designing strategies. Specifically, this review focuses on the practical applications of MnP in sustainable agriculture, elaborating on its potential and challenges in straw resource utilization, efficient feed fermentation, mycotoxin control, and water quality improvement. Furthermore, this review summarizes the recent achievements in optimizing MnP activity through enzyme engineering techniques and discuss customized mutation strategies tailored to specific agricultural and environmental requirements, thereby laying a solid theoretical foundation and scientific basis for the industrial production and commercialization of MnP.

Increased Antioxidant Performance of Lignin by Biodegradation Obtained from an Extract of the Mushroom Pleurotus eryngii

The aim of this study was to evaluate the antioxidant properties of the products derived from the biodegradation of lignin by the ligninolytic enzymes present in an aqueous extract of the mushroom P. eryngii. A mixture obtained after the incubation of lignin for 18 h with P. eryngii extract was tested in vitro for its total polyphenol content, reducing power, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl (OH) radical-scavenging activities. The results showed that the enzymatic treatment of lignin enhanced its antioxidant performance. The biocompatibility of the products of lignin biodegradation and their ability to scavenge reactive oxygen species (ROS) were also tested on the astrocytic cell line DI-TNC1. The results obtained indicated that a lignin mixture incubated for 18 h does not affect cell viability or inhibit the H2O2-induced ROS production. These results suggest that the enzymatic degradation of lignin represents an efficient and ecofriendly approach to obtain lignin derivatives potentially useful for antioxidant applications.

Sequential pretreatment with hydroxyl radical and manganese peroxidase for the efficient enzymatic saccharification of corn stover

BACKGROUND

White rot fungi produce various reactive oxygen species and ligninolytic enzymes for lignocellulose deconstruction. However, their interactions during the deconstruction of lignocellulosic structural barriers for efficient enzymatic saccharification remain unclear.

RESULTS

Herein, the extracellular enzyme activities and secretomic analysis revealed the sequential expression of hydroxyl radical (⋅OH) and manganese peroxidases (MnPs) for lignocellulose deconstruction by the white rot fungus Irpex lacteus. Subsequently, in vitro functional studies found that ⋅OH possessed the ability to disrupt the smooth surface structure of corn stover, resulting in increased enzymatic saccharification and cellulose accessibility. Purified recombinant MnPs from I. lacteus were able to cleave the β-O-4 bond in phenolic and non-phenolic lignin model dimers without the help of any mediators. Furthermore, the sequential pretreatment of corn stover with ⋅OH and MnP exhibited significant synergistic effects, increasing enzymatic saccharification and cellulose accessibility by 2.9-fold and 1.8-fold, respectively.

CONCLUSIONS

These results proved for the first time the synergistic effects of ⋅OH and MnP pretreatment in improving the enzymatic saccharification and cellulose accessibility of corn stover. These findings also demonstrated the potential application of ⋅OH and MnP pretreatment for the efficient enzymatic saccharification of corn stover.

Rational Design for Enhancing Cellobiose Dehydrogenase Activity and Its Synergistic Role in Straw Degradation

Addressing the demand for efficient biological degradation of straw, this study employed rational design coupled with structural biology and enzyme engineering techniques to enhance the catalytic activity of cellobiose dehydrogenase (PsCDH, CDH form Pycnoporus sanguineus). By predicting and modifying the active site and key amino acids of PsCDH, several CDH immobilized enzyme preparations with higher catalytic activities were successfully obtained. The excellent mutant T1 (C286Y/A461H/F464R) exhibited a 2.7-fold increase in enzyme activity compared to the wild type. Simulated calculations indicated that the enhancement of catalytic activity was primarily due to the formation of additional intermolecular interactions between CDH and the substrate, as well as the enlargement of the substrate pocket to reduce steric hindrance effects. Additionally, molecular dynamics simulation analysis revealed a potential correlation between structural stability and enzyme activity. When PsCDH was added to a multienzyme synergistic straw degradation system, the cellulose degradation rate increased by 1.84-fold. Moreover, mutant T1 further increased the degradation of lignocellulose in the mixed system. This study provides efficient enzyme sources and modification strategies for the high-efficiency biological conversion of straw and unconventional feedstock degradation, thereby possessing significant academic value and application prospects.

Bacterial valorization of lignin for the sustainable production of value-added bioproducts

As the most abundant aromatic biopolymer in the biosphere, lignin represents a promising alternative feedstock for the industrial production of various value-added bioproducts with enhanced economical value. However, the large-scale implementation of lignin valorization remains challenging because of the heterogeneity and irregular structure of lignin. General fragmentation and depolymerization processes often yield various products, but these approaches necessitate tedious purification steps to isolate target products. Moreover, microbial biocatalytic processes, especially bacterial-based systems with high metabolic activity, can depolymerize and further utilize lignin in an eco-friendly way. Considering that wild bacterial strains have evolved several metabolic pathways and enzymatic systems for lignin degradation, substantial efforts have been made to exploit their potential for lignin valorization. This review summarizes recent advances in lignin valorization for the production of value-added bioproducts based on bacterial systems. Additionally, the remaining challenges and available strategies for lignin biodegradation processes and future trends of bacterial lignin valorization are discussed.

Construction of lignocellulose-degrading compound microbial inoculum and its effects on green waste composting

The high content of recalcitrant lignocellulose in green waste (GW) makes composting and degradation challenging. Conventional GW composting typically employs single-strain microbial inoculants (MIs) with limited enzyme production capabilities, resulting in low composting efficiency and suboptimal compost product quality. In this study, Bacillus amyloliquefaciens (J1), Clonostachys rogersoniana (B2), and Streptomyces thermoviolaceus (J3) was utilized to optimize cultivation conditions and strain ratios based on enzyme activity indicators. The aim was to develop a potent three-strain lignocellulose-degrading MIs and test the hypothesis that its performance is superior to that of single-strain and two-strain MIs in terms of lignocellulose degradation and compost maturation. The results indicated that, the optimal treatment was T7, which was inoculated with a three-strain MIs composed of the spore suspensions of J1, B2, and J3 with a volume ratio of 3:3:2. Specifically, compared to the control (without MI), T7 increased the content of particle size between 0.25 and 2.00 mm and humic acid by 17% and 291%, respectively. Furthermore, T7 enhanced the degradation rates of cellulose, hemicellulose, and lignin by 197%, 145%, and 113%, respectively, and increased the activities of laccase, manganese peroxidase, lignin peroxidase, and carboxymethyl cellulase by 605%, 269%, 180%, and 228%, respectively. Additionally, T7 increased the relative abundance of bacteria (e.g. Pseudomonas) and fungi (e.g. Parascedosporium) that facilitated lignocellulose degradation, enhanced the alpha diversity index and promoted the formation of a microbial community structure characterized by prominent dominant species and greater diversity. Remarkably, the inoculation with the three-strain MI yielded high-quality compost within 32 days.

Effect of time series on the degradation of lignin by Trametes gibbosa: Products and pathways

Lignin is the third most abundant organic resource in nature. The utilization of white-rot fungi for wood degradation effectively circumvents environmental pollution associated with chemical treatments, facilitating the benign decomposition of lignin. Trametes gibbosa is a typical white-rot fungus with rapid growth and strong wood decomposition ability. The lignin content decreased from 23.62 mg/mL to 17.05 mg/mL, which decreased by 27 % in 30 days. The activity of manganese peroxidase increased steadily by 9.44 times. The activities of laccase and lignin peroxidase had the same trend of change and reached peaks of 49.88 U/L and 10.43 U/L on the 25th day, respectively. The change in H2O2 content in vivo was opposite to its trend. For FTIR and GC-MS analysis, the fungi attacked the side chain structure of lignin phenyl propane polymer and benzene ring to crack into low molecular weight aromatic compounds. The side chains of low molecular weight aromatic compounds are oxidized, and long-chain carboxylic acids are formed. Additionally, the absorption peak in the vibration region of the benzene ring skeleton became complex, and the structure of the benzene rings changed. In the beginning, fungal growth was inhibited. Fungal autophagy was aggravated. The metal cation binding proteins of fungi were active, and the genes related to detoxification metabolism were upregulated. The newly produced compounds are related to xenobiotic metabolism. The degradation peak focused on the redox process, and the biological function was enriched in the regulation of macromolecular metabolism, lignin metabolism, and oxidoreductase activity acting on diphenols and related substances as donors. Notably, genes encoding key degradation enzymes, including lcc3, lcc4, phenol-2-monooxygenase, 3-hydroxybenzoate-6-hydroxylase, oxalate decarboxylase, and acetyl-CoA oxidase were significantly upregulated. On the 30th day, the N-glycan biosynthesis pathway was significantly enriched in glycan biosynthesis and metabolism. Weighted correlation network analysis was performed. A total of 1452 genes were clustered in the coral1 module, which were most related to lignin degradation. The genes were significantly enriched in oxidoreductase activity, peptidase activity, cell response to stimulation, signal transduction, lignin metabolism, and phenylpropane metabolism, while the rest were concentrated in glucose metabolism. In this study, the lignin degradation process and products were revealed by T. gibbosa. The molecular mechanism of lignin degradation in different stages was explored. The selection of an efficient utilization time of lignin will help to increase the degradation rate of lignin. This study provides a theoretical basis for the biofuel and biochemical production of lignin. SYNOPSIS: Trametes gibbosa degrades lignin in a pollution-free way, improving the utilization of carbon resources in an environmentally friendly spontaneous cycle. The products are the new way towards sustainable development and low-carbon technology.

Analysis of Straw Degradation and Whole Genome of Acrophialophora multiforma

Lignin is one of the main components in plants, which can transform value-added bioenergy and chemicals. At the same time, due to the close combination of lignin and hemicellulose in the structure, it becomes a barrier for cellulose utilization. Therefore, the effective degradation of lignin is of great significance for the utilization of these resources. In this study, the lignin degrading ability of Acrophialophora multiforma strain GZUIFR 22.397 was preliminarily investigated through straw degradation experiments and enzyme activity determination. Then, the whole genome of strain A. multiforma GZUIFR 22.397 was sequentially analyzed and annotated through multiple gene function annotation databases to comprehensively evaluate its lignin degrading potential. The results showed that the weight loss of straw reached 5.98 ± 3.95%. Laccase activity was 77.49 ± 2.65 U/L, lignin peroxidase activity was 160.57 ± 29.07 U/L, and manganese peroxidase activity was 294.83 ± 3.77 U/L. The genome of A. multiforma strain GZUIFR 22.397 spans 33.81 megabases and encompasses 9,370 genes. Among these, 6,122 genes have been annotated in the Gene Ontology (GO), 2,286 in the Cluster of Orthologous Groups of proteins (KOG), 2,283 in the Kyoto Encyclopedia of Genes and Genomes (KEGG), and 603 in the Carbohydrate Active enZYmes Database (CAZy). Concurrently, the genome analysis predicted the presence of 9 genes for laccase, 2 genes for lignin peroxidase, and 2 genes for manganese peroxidase. In summary, these results indicated that A. multiforma GZUIFR 22.397 has lignin degrading ability, and laid the foundation for deciphering the molecular mechanism of A. multiforma GZUIFR 22.397 to degrade lignin.

Sustainable approach for the treatment of dye-containing wastewater – a critical review

In the world’s rapidly expanding economy, textile industries are recognized as a substantial contributor to economic growth, but they are one of the most significant polluting industrial sectors. Dye-contaminated water sources can pose serious public health concerns, including toxicity, mutagenicity, and carcinogenicity among other adverse health effects. Despite a limited understanding of efficacious decolorization methodologies, the pursuit of a sustainable strategy for the treatment of a wide spectrum of dyes remains a formidable challenge. This article conducted an exhaustive review of extant literature pertaining to diverse physical, chemical, biological, and hybrid processes with the aim of ascertaining their efficacy. It also elucidates the advantages and disadvantages, cost considerations, as well as scalability impediments of the treatment methodologies, thereby facilitating the identification of optimal strategies for establishing techno-economically efficient processes in the sustainable handling of these effluents. The hybrid configuration exhibited superior efficiency and was documented to surmount the limitations and constraints inherent to individual techniques. The study also revealed that most of the proven and established dye removal techniques share a common limitation viz., the generation of secondary pollution (i.e., sludge generation, toxic intermediates, etc.) to the ecosystem.

Building microbial consortia to enhance straw degradation, phosphorus solubilization, and soil fertility for rice growth

Straw pollution and the increasing scarcity of phosphorus resources in many regions of China have had severe impacts on the growing conditions for crop plants. Using microbial methods to enhance straw decomposition rate and phosphorus utilization offers effective solutions to address these problems. In this study, a microbial consortium 6 + 1 (consisting of a straw-degrading bacterium and a phosphate-solubilizing bacterium) was formulated based on their performance in straw degradation and phosphorus solubilization. The degradation rate of straw by 6 + 1 microbial consortium reached 48.3% within 7 days (The degradation ability was 7% higher than that of single bacteria), and the phosphorus dissolution rate of insoluble phosphorus reached 117.54 mg·L- 1 (The phosphorus solubilization ability was 29.81% higher than that of single bacteria). In addition, the activity of lignocellulosic degrading enzyme system was significantly increased, the activities of endoglucanase, β-glucosidase and xylanase in the microbial consortium were significantly higher than those in the single strain (23.16%, 28.02% and 28.86%, respectively). Then the microbial consortium was processed into microbial agents and tested in rice pots. The results showed that the microbial agent significantly increased the content of organic matter, available phosphorus and available nitrogen in the soil. Ongoing research focuses on the determination of the effects and mechanisms of a functional hybrid system of straw degradation and phosphorus removal. The characteristics of the two strains are as follows: Straw-degrading bacteria can efficiently degrade straw to produce glucose-based carbon sources when only straw is used as a carbon source. Phosphate-solubilizing bacteria can efficiently use glucose as a carbon source, produce organic acids to dissolve insoluble phosphorus and consume glucose at an extremely fast rate. The analysis suggests that the microbial consortium 6 + 1 outperformed individual strains in terms of both performance and application effects. The two strains within the microbial consortium promote each other during their growth processes, resulting in a significantly higher rate of carbon source consumption compared to the individual strains in isolation. This increased demand for carbon sources within the growth system facilitates the degradation of straw by the strains. At the same time, the substantial carbon consumption during the metabolic process generated a large number of organic acids, leading to the solubilization of insoluble phosphorus. It also provides a basis for the construction of this type of microbial consortium.

Effects of mixed enzymolysis alone or combined with acetylation or carboxymethylation on the role of jujube kernel fibre as a biosorbent for wastewater treatment

Jujube kernel fibre (JKF) could serve as a renewable, abundant, low-cost, and environmentally friendly adsorbent for wastewater if its adsorption capacities are improved. However, data on the modification of JKF, especially on the combination of biological and chemical modifications, are scarce. Therefore, for the first time, we studied the effect of mixed enzymolysis alone or combined with acetylation or carboxymethylation on the structure and adsorption capacities of JKF. After these modifications, the microstructure of JKF became more porous, and its soluble fibre and extractable polyphenol contents, surface area and adsorption capacities for nitrite, copper, and lead ions were all significantly improved (P < 0.05). Meanwhile, mixed enzymatic hydrolysis and acetylation treated JKF showed the highest surface hydrophobicity (43.57) and oil-adsorption ability (4.47 g g-1), while mixed enzymatic hydrolysis and carboxymethylation treated JKF exhibited the highest water adsorption ability (10.66 g g-1), water expansion ability (8.50 mL g-1), and lead and copper ion chelating abilities. Additionally, mixed enzymatic hydrolyzed JKF had the highest nitrite-ion-adsorption ability (10.57 μmol g-1). It can be concluded that mixed enzymolysis combined with carboxymethylation is an optimal way to increase the hydration properties and heavy-metal-adsorption capacity of JKF, while mixed enzymolysis combined with acetylation is an effective approach to enhance the oil-adsorption capacity of JKF.

Effect of combined bacteria on the flax dew degumming process: Substance degradation sequence and changes in functional bacteria taxa

In this study, 16S rDNA high-throughput sequencing, Fourier transform infrared spectroscopy, and two-dimensional correlation spectroscopy techniques were used to analyze the mechanisms driving the sequence of degradation of gummy substances by the microbial community and hydrolytic enzymes during the flax dew degumming process. The results revealed that the inoculation of combined bacteria induced quorum sensing, modulated hydrolytic enzyme production, and reshaped the community structure. Lignin-degraded genera (Pseudomonas and Sphingobacterium) were enriched, and the relative abundances of pectin- and cellulose-degraded genera (Chryseobacterium) decreased in the early degumming stages. Hemicellulose-degraded genera (Brevundimonas) increased over the degumming time. Moreover, the abundance of lignin hydrolytic enzymes improved in the early stages, while the abundance of pectin hydrolytic enzymes increased at the end of degumming. Various types of functional bacteria taxa changed the sequence of substance degradation. Electron scanning microscopy and differential scanning calorimetry results indicated that the degumming, facilitated by the inoculation of combined bacteria, was nearly completed by 21 d. The fibers exhibited smoother and more intact properties, along with higher thermal stability, as indicated by a melting temperature of 71.54 °C. This study provides a reference for selecting precise degumming bacterial agents to enhance degumming efficiency.

Recent Progress on Conversion of Lignocellulosic Biomass by MOF-Immobilized Enzyme

The enzyme catalysis conversion of lignocellulosic biomass into valuable chemicals and fuels showed a bright outlook for replacing fossil resources. However, the high cost and easy deactivation of free enzymes restrict the conversion process. Immobilization of enzymes in metal-organic frameworks (MOFs) is one of the most promising strategies due to MOF materials' tunable building units, multiple pore structures, and excellent biocompatibility. Also, MOFs are ideal support materials and could enhance the stability and reusability of enzymes. In this paper, recent progress on the conversion of cellulose, hemicellulose, and lignin by MOF-immobilized enzymes is extensively reviewed. This paper focuses on the immobilized enzyme performances and enzymatic mechanism. Finally, the challenges of the conversion of lignocellulosic biomass by MOF-immobilized enzyme are discussed.

Class III plant peroxidases: From classification to physiological functions

Peroxidases (EC 1.11.1.7) are involved in a wide range of physiological processes, hence their broad distribution across biological systems. These proteins can be classified as haem or non-haem enzymes. According to the RedOxiBase database, haem peroxidases are approximately 84 % of all known peroxidase enzymes. Class III plant peroxidases are haem-enzymes that share similar three-dimensional structures and a common catalytic mechanism for hydrogen peroxide degradation. They exist as large multigene families and are involved in metabolizing Reactive Oxygen Species (ROS), hormone synthesis and decomposition, fruit growth, defense, and cell wall synthesis and maintenance. As a result, plant peroxidases gained attention in research and became one of the most extensively studied groups of enzymes. This review provides an update on the database, classification, phylogeny, mechanism of action, structure, and physiological functions of class III plant peroxidases.

Label-free comparative proteomic analysis of Pleurotus eryngii grown on sawdust, bagasse, and peanut shell substrates

The white rot fungi Pleurotus eryngii are environmental microorganisms that can effectively break down lignocellulosic biomass. However, understanding of the mechanisms by which P. eryngii is effective in degrading lignocellulose is still limited. This work aimed to examine the extracellular secretory proteins implicated in the breakdown of lignocellulose in P. eryngii and identify degradation tactics across various cultivation substrates. Thus, a comparative analysis of the secretory proteins based on Nanoliquid chromatography combined with tandem mass spectrometry was conducted among P. eryngii cultivated on sawdusts, bagasse, peanut shells, and glucose. In total, 647, 616, 604, and 511 proteins were identified from the four samples, respectively. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis of protein expression differences identified pathways (hydrolytic enzymes, catalytic activity, metabolic processes, cellular processes, and response to stimuli) significantly enriched in proteins associated with lignocellulose degradation in P. eryngii. An integrated analysis of proteome data revealed specifically or differentially expressed genes secreted by P. eryngii in different cultivation substrates. The most prevalent carbohydrate-active enzymes involved in lignocellulose degradation in the secretome of the four samples were laccase (Lac), manganese peroxidase (MnP), aryl alcohol oxidase (AaO), and copper radical oxidase (CRO). Among them, Lac 2 mainly involved in the lignin degradation of sawdust peanut shells, and bagasse by P. eryngii, and Mnp 3 was mainly involved in the degradation of peanut shells. AaO and Lac 4 were mainly involved in glucose substrate defense and oxidative stress. It was found that exogenous addition of sawdust and peanut shells significantly increased lignolytic enzyme abundance. These findings provide insight and guidance for improving agricultural waste resource recovery. In this study, the secretomes of P. eryngii grown on four different carbon sources were compared. The findings revealed the extracellular enzymes implicated in the degradation of lignocellulose, offering avenues for further investigation into the biotransformation mechanisms of P. eryngii biomass and the potential utilization of agricultural wastes. SIGNIFICANCE: The cost of the substrate for mushroom cultivation has increased as the production of edible fungus has risen year after year. Therefore, the use of these locally available lignocellulosic wastes as substrates offers a cost-cutting option. Further, the overuse of wood for the cultivation of edible mushrooms is also detrimental to the conservation of forest resources or the ecological environment. Consequently, the use of other agricultural wastes as an alternative to sawdust or other woody substrates is a viable approach for cultivating P. eryngii. The distribution of extracellular lignocellulosic degrading enzymes, inferred in the present study could help improve the cultivation efficiency of P. eryngii vis-à-vis managing agricultural waste.

Crop residue heterogeneity: Decomposition by potential indigenous ligno-cellulolytic microbes and enzymatic profiling

The continuous depletion of fossil resources, energy-crisis and environmental pollution has gained popularity for careful selection of suitable microbial consortium to efficiently decompose crop residue and facilitate nutrient cycling. While crop residue is commonly incorporated into soil, the impact of the heterogeneity of residue on decomposition and biological mechanisms involved in extracellular carbon (C) cycle related enzyme activities remain not fully understood. To address this problem, an incubation study was conducted on chemical heterogeneity of straw and root residue with indigenous ligno-cellulolytic microbial consortium on extracellular enzymes as their activity is crucial for making in-situ residue management decisions under field condition. The activity of extracellular enzymes in different substrates showed differential variation with the type of enzyme and ranged from 16.9 to 77.6 µg mL-1, 135.7 to 410.8 µg mL-1, 66.9 to 177.1 µg mL-1 and 42.1 to 160.9 µg mL-1 for cellulase, xylanase, laccase and lignin peroxidase, respectively. Extracellular enzyme activities were sensitive to heterogeneity of biochemical constituent's present in straw and root residues and enhanced the decomposition processes with indigenous ligno-cellulolytic microbial consortium (Bacillus altitudinis, Streptomyces flavomacrosporus and Aspergillus terreus). Correlation matrix elucidated A. terreus and B. altitudinis as potential indigenous ligno-cellulolytic microbial inoculant influencing soil enzymatic activity (p < 0.001). This research work demonstrates a substantial impact of chemically diverse crop residues on the decomposition of both straw and root. It also highlights the pivotal role played by key indigenous decomposers and interactions between different microorganisms in governing the decomposition of straw and root primarily through release of extracellular enzyme. Consequently, it is novel bio-emerging strategy suggested that incorporation of the crop residues under field conditions should be carried out in conjunction with the potential indigenous ligno-cellulolytic microbial consortium for efficient decomposition in the short period of time under sustainable agriculture system.

Efficient crop straws biotreatment using the fungus Cerrena Unicolor GC.u01

Lignin is main composition of agricultural biomass which can be decomposed through enzymatic hydrolysis by fungi. However, there are still needs to identify more efficient and effective fungal stain for biomass valorization. In this study, lignin degrading fungi from birch forest were screened for sustainable degradation of waste agricultural straws. The most effective strain was identified as Cerrena unicolor GC.u01 using 18 S rDNA gene-sequencing technology. Three different crop straws (corn stalk, rice and wheat straws) were used for the biotreatment studies. The activities of lignin degrading enzymes, laccase (Lac), cellulase and xylanase, secreted by C. unicolor were also determined. Scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analyzer (TGA) were further used to monitor the effects of the biotreatment process. The results showed that C. unicolor degraded 34.3% rice straw lignin, a percentage which was higher than other isolated strains after 15 d straw liquid fermentation. The highest Lac activity (8.396 U•mL- 1) was observed with corn stalk on the 7 d. Cellulase and xylanase activities, in the same biomass, were higher than those of wheat and rice straws after 15 d. Furthermore, SEM, FTIR and TGA analyses showed that C. unicolor pretreatment process had significant effects on corn stalk, rice and wheat straws' structures. The newly isolated stain of C. unicolor demonstrated high lignin degradation potential that can provide effective, ecofriendly means of valorizing biomass to industrial useable raw-material.

Lignin bioconversion based on genome mining for ligninolytic genes in Erwinia billingiae QL-Z3

BACKGROUND

Bioconversion of plant biomass into biofuels and bio-products produces large amounts of lignin. The aromatic biopolymers need to be degraded before being converted into value-added bio-products. Microbes can be environment-friendly and efficiently degrade lignin. Compared to fungi, bacteria have some advantages in lignin degradation, including broad tolerance to pH, temperature, and oxygen and the toolkit for genetic manipulation.

RESULTS

Our previous study isolated a novel ligninolytic bacterial strain Erwinia billingiae QL-Z3. Under optimized conditions, its rate of lignin degradation was 25.24% at 1.5 g/L lignin as the sole carbon source. Whole genome sequencing revealed 4556 genes in the genome of QL-Z3. Among 4428 protein-coding genes are 139 CAZyme genes, including 54 glycoside hydrolase (GH) and 16 auxiliary activity (AA) genes. In addition, 74 genes encoding extracellular enzymes are potentially involved in lignin degradation. Real-time PCR quantification demonstrated that the expression of potential ligninolytic genes were significantly induced by lignin. 8 knock-out mutants and complementary strains were constructed. Disruption of the gene for ELAC_205 (laccase) as well as EDYP_48 (Dyp-type peroxidase), ESOD_1236 (superoxide dismutase), EDIO_858 (dioxygenase), EMON_3330 (monooxygenase), or EMCAT_3587 (manganese catalase) significantly reduced the lignin-degrading activity of QL-Z3 by 47-69%. Heterologously expressed and purified enzymes further confirmed their role in lignin degradation. Fourier transform infrared spectroscopy (FTIR) results indicated that the lignin structure was damaged, the benzene ring structure and groups of macromolecules were opened, and the chemical bond was broken under the action of six enzymes encoded by genes. The abundant enzymatic metabolic products by EDYP_48, ELAC_205 and ESOD_1236 were systematically analyzed via liquid chromatography-mass spectrometry (LC-MS) analysis, and then provide a speculative pathway for lignin biodegradation. Finally, The activities of ligninolytic enzymes from fermentation supernatant, namely, LiP, MnP and Lac were 367.50 U/L, 839.50 U/L, and 219.00 U/L by orthogonal optimization.

CONCLUSIONS

Our findings provide that QL-Z3 and its enzymes have the potential for industrial application and hold great promise for the bioconversion of lignin into bioproducts in lignin valorization.

Characterization and mechanism of simultaneous degradation of aflatoxin B1 and zearalenone by an edible fungus of Agrocybe cylindracea GC-Ac2

Contamination with multiple mycotoxins is a major issue for global food safety and trade. This study focused on the degradation of aflatoxin B1 (AFB1) and zearalenone (ZEN) by 8 types of edible fungi belonging to 6 species, inclulding Agaricus bisporus, Agrocybe cylindracea, Cyclocybe cylindracea, Cyclocybe aegerita, Hypsizygus marmoreus and Lentinula edodes. Among these fungi, Agrocybe cylindracea strain GC-Ac2 was shown to be the most efficient in the degradation of AFB1 and ZEN. Under optimal degradation conditions (pH 6.0 and 37.4°C for 37.9 h), the degradation rate of both AFB1 and ZEN reached over 96%. Through the analysis of functional detoxification components, it was found that the removal of AFB1 and ZEN was primarily degraded by the culture supernatant of the fungus. The culture supernatant exhibited a maximum manganese peroxidase (MnP) activity of 2.37 U/mL. Interestingly, Agrocybe cylindracea strain GC-Ac2 also showed the capability to degrade other mycotoxins in laboratory-scale mushroom substrates, including 15A-deoxynivalenol, fumonisin B1, B2, B3, T-2 toxin, ochratoxin A, and sterigmatocystin. The mechanism of degradation of these mycotoxins was speculated to be catalyzed by a complex enzyme system, which include MnP and other ligninolytic enzymes. It is worth noting that Agrocybe cylindracea can degrade multiple mycotoxins and produce MnP, which is a novel and significant discovery. These results suggest that this candidate strain and its enzyme system are expected to become valuable biomaterials for the simultaneous degradation of multiple mycotoxins.

Dual Enzymolysis Assisted by Acrylate or Phosphate Grafting: Influences on the Structural and Functional Properties of Jujube Residue Dietary Fiber

Jujube residue is an abundant and low-cost dietary fiber resource, but its relatively lower hydration and functional properties limit its utilization as an ingredient of functional food. Thus, cellulase and hemicellulase hydrolysis, enzymatic hydrolysis assisted by phosphate grafting (EPG), and enzymatic hydrolysis assisted by acrylate grafting (EAG) were used to improve the functional properties of jujube residue dietary fiber (JRDF) in this study. The results evidenced that these modifications all increased the porosity of the microstructure of JRDF and increased the soluble fiber content, surface area, and hydration properties, but reduced its brightness (p < 0.05). Moreover, JRDF modified by enzymolysis combined with acrylate grafting offered the highest extractable polyphenol content, oil, sodium cholate, and nitrite ion sorption abilities. Meanwhile, JRDF modified via enzymolysis assisted by phosphate grafting showed the highest soluble fiber content (23.53 g∙100 g-1), water-retention ability (12.84 g∙g-1), viscosity (9.37 cP), water-swelling volume (10.80 mL∙g-1), and sorption ability of copper (II) and lead (II) ions. Alternatively, JRDF modified with cellulase hydrolysis alone exhibited the highest glucose adsorption capacity (21.9 g∙100 g-1) at pH 7.0. These results indicate that EPG is an effective way to improve the hypolipidemic effects of JRDF, while EAG is a good choice to enhance its hydration and hypoglycemic properties.

Bacterial transformation of lignin: key enzymes and high-value products

Lignin, a natural organic polymer that is recyclable and inexpensive, serves as one of the most abundant green resources in nature. With the increasing consumption of fossil fuels and the deterioration of the environment, the development and utilization of renewable resources have attracted considerable attention. Therefore, the effective and comprehensive utilization of lignin has become an important global research topic, with the goal of environmental protection and economic development. This review focused on the bacteria and enzymes that can bio-transform lignin, focusing on the main ways that lignin can be utilized to produce high-value chemical products. Bacillus has demonstrated the most prominent effect on lignin degradation, with 89% lignin degradation by Bacillus cereus. Furthermore, several bacterial enzymes were discussed that can act on lignin, with the main enzymes consisting of dye-decolorizing peroxidases and laccase. Finally, low-molecular-weight lignin compounds were converted into value-added products through specific reaction pathways. These bacteria and enzymes may become potential candidates for efficient lignin degradation in the future, providing a method for lignin high-value conversion. In addition, the bacterial metabolic pathways convert lignin-derived aromatics into intermediates through the "biological funnel", achieving the biosynthesis of value-added products. The utilization of this "biological funnel" of aromatic compounds may address the heterogeneous issue of the aromatic products obtained via lignin depolymerization. This may also simplify the separation of downstream target products and provide avenues for the commercial application of lignin conversion into high-value products.

Sustainability analysis of orange peel biorefineries

Biorefineries are constantly evolving since new technological advances in enzyme and microbial processes are boosting research for producing new bio-based products. Nevertheless, the step towards real process implementation must overcome a series of stages based on process sustainability in the early design stages. Orange peel (OP) has been profiled as a potential raw material for producing different products. Few studies have estimated the sustainability of OP-based biorefineries considering the upstream influence on the final process performance. This research aims to perform the sustainability assessment of several OP valorization pathways based on experimental data applying the biorefinery concept. Steam distillation and polyphenolic compound extraction prior to saccharification and anaerobic digestion increase the process performance. A glucose concentration and biogas yield of 21.43 g/L (0.44 g/g OP, db) and 415 mL/g SV were obtained, respectively. An essential oil extraction yield of 1.17 g/100 g OP (db) with a d-limonene content of 91.62% was produced. Moreover, hesperidin, apigenin, and naringenin yields of 7.88 mg/g, 0.475 mg/g, and 0.675 mg/g were obtained. An OP-based biorefinery addressed to produce essential oil, polyphenolic compounds, and biogas with a processing 25 tons/day (wb) has a sustainability index of 66.88%, higher than the values obtained with lesser upstream stages. In conclusion, an integral OP upgrading leads to better enzymatic and anaerobic digestion performances, as well as, a high process sustainability.

Hydrated lime promoted the polysaccharide content and affected the transcriptomes of Lentinula edodes during brown film formation

Brown film formation, a unique developmental stage in the life cycle of Lentinula edodes, is essential for the subsequent development of fruiting bodies in L. edodes cultivation. The pH of mushroom growth substrates are usually adjusted with hydrated lime, yet the effects of hydrated lime on cultivating L. edodes and the molecular mechanisms associated with the effects have not been studied systemically. We cultivated L. edodes on substrates supplemented with 0% (CK), 1% (T1), 3% (T2), and 5% (T3) hydrated lime (Ca (OH)2), and applied transcriptomics and qRT-PCR to study gene expression on the brown film formation stage. Hydrated lime increased polysaccharide contents in L. edodes, especially in T2, where the 5.3% polysaccharide content was approximately 1.5 times higher than in the CK. The addition of hydrated lime in the substrate promoted laccase, lignin peroxidase and manganese peroxidase activities, implying that hydrated lime improved the ability of L. edodes to decompose lignin and provide nutrition for its growth and development. Among the annotated 9,913 genes, compared to the control, 47 genes were up-regulated and 52 genes down-regulated in T1; 73 genes were up-regulated and 44 were down-regulated in T2; and 125 genes were up-regulated and 65 genes were down-regulated in T3. Differentially expressed genes (DEGs) were enriched in the amino acid metabolism, lipid metabolism and carbohydrate metabolism related pathways. The carbohydrate-active enzyme genes up-regulated in the hydrated lime treatments were mostly glycosyl hydrolase genes. The results will facilitate future optimization of L. edodes cultivation techniques and possibly shortening the production cycle.

Lignin-Degrading Bacteria in Paper Mill Sludge

The effluents generated in the paper industry, such as black liquor, have a high content of lignin and other toxic components; however, they represent a source of lignin-degrading bacteria with biotechnological potential. Therefore, the present study aimed to isolate and identify lignin-degrading bacteria species in paper mill sludge. A primary isolation was carried out from samples of sludge present in environments around a paper company located in the province of Ascope (Peru). Bacteria selection was made by the degradation of Lignin Kraft as the only carbon source in a solid medium. Finally, the laccase activity (Um-L^-1) of each selected bacteria was determined by oxidation of 2,2'-azinobis-(3-etilbencenotiazolina-6-sulfonate) (ABTS). Bacterial species with laccase activity were identified by molecular biology techniques. Seven species of bacteria with laccase activity and the ability to degrade lignin were identified. The bacteria Agrobacterium tumefasciens (2), Klebsiella grimontii (1), and Beijeinckia fluminensis (1) were reported for first time. K. grimowntii and B. fluminensis presented the highest laccase activity, with values of 0.319 ± 0.005 UmL^-1 and 0.329 ± 0.004 UmL^-1, respectively. In conclusion, paper mill sludge may represent a source of lignin-degrading bacteria with laccase activity, and they could have potential biotechnological applications.

Strengthening Fenton-like reactions to improve lignocellulosic degradation performance by increasing lignocellulolytic enzyme core microbes during rice straw composting

This study aimed to explore the effect of Fenton-like reactions on lignocellulosic degradation performance and identify their driving factors during composting. Rice straw was pretreated by inoculating Aspergillus fumigatus Z1 and then adding Fe (II), which resulted in Fenton-like reactions. The treatment groups included CK (control), Fe (addition of Fe (II)), Z1 (inoculation of A. fumigatus Z1), and Fe + Z1 (inoculation of A. fumigatus Z1 and addition of Fe (II)). The results suggested that Fenton-like reactions can produce lignocellulolytic enzymes and degrade lignocellulose, due to the variation in microbial community composition and diversity. In addition, functional modular microbes were identified by network analysis, which can produce endoglucanase and xylanase. Regarding ligninase, bacteria were more favorable for producing manganese peroxidase, and fungi were more favorable for producing laccase. Additionally, reducing sugars, organic matter, total nitrogen and amino acids were key microhabitat factors of functional modular bacteria, while organic matter, reducing sugars, amino acids and C/N were key microhabitat factors of functional modular fungi, thereby promoting the degradation of lignocellulose. This study provides technical support for lignocellulosic degradation based on Fenton-like reactions.

Efficient preparation of nitrogen-doped lignin-based carbon nanotubes and the selectivity of nitrogen speciation for photothermal therapy

In this study, the lignin was pre-modified using small-molecule nitrogen-containing compounds, and then the nitrogen-doped lignin-based carbon nanotubes (L-NCNTs) were fabricated by pyrolysis using the modified lignin as raw materials. The obtained L-NCNTs were multi-walled carbon nanotubes with diameters between 10 and 80 nm. The modification of lignin had an important effect on the nitrogen morphology of L-NCNTs, and promoted the high selectivity of pyridine-N in the L-NCNTs. Defects and pyridinic-N structure were conducive to boosting photothermal properties of the L-NCNTs. The photothermal conversion efficiency of the L-NCNTs after 808 nm laser irradiation for 5 min reached 58.8 %. The L-NCNTs can be used as photothermal agents in drug delivery system to achieve mild photothermal therapy, and it is basically non-toxic to normal cells, indicating good biocompatibility. This work provides new ideas for development of lignin-based high value-added products from biomass.

Customized valorization of waste streams by Pseudomonas putida: State-of-the-art, challenges, and future trends

Preventing catastrophic climate events warrants prompt action to delay global warming, which threatens health and food security. In this context, waste management using engineered microbes has emerged as a long-term eco-friendly solution for addressing the global climate crisis and transitioning to clean energy. Notably, Pseudomonas putida can valorize industry-derived synthetic wastes including plastics, oils, food, and agricultural waste into products of interest, and it has been extensively explored for establishing a fully circular bioeconomy through the conversion of waste into bio-based products, including platform chemicals (e.g., cis,cis-muconic and adipic acid) and biopolymers (e.g., medium-chain length polyhydroxyalkanoate). However, the efficiency of waste pretreatment technologies, capability of microbial cell factories, and practicability of synthetic biology tools remain low, posing a challenge to the industrial application of P. putida. The present review discusses the state-of-the-art, challenges, and future prospects for divergent biosynthesis of versatile products from waste-derived feedstocks using P. putida.

Nature-inspired pretreatment of lignocellulose - Perspective and development

As sustainability gains increasing importance in addition to cost-effectiveness as a criterion for evaluating engineering systems and practices, biological processes for lignocellulose pretreatment have attracted growing attention. Biological systems such as white and brown rot fungi and wood-consuming insects offer fascinating examples of processes and systems built by nature to effectively deconstruct plant cell walls under environmentally benign and energy-conservative environments. Research in the last decade has resulted in new knowledge that advanced the understanding of these systems, provided additional insights into these systems' functional mechanisms, and demonstrated various applications of these processes. The new knowledge and insights enable the adoption of a nature-inspired strategy aiming at developing technologies that are informed by the biological systems but superior to them by overcoming the inherent weakness of the natural systems. This review discusses the nature-inspired perspective and summarizes related advancements, including the evolution from biological systems to nature-inspired processes, the features of biological pretreatment mechanisms, the development of nature-inspired pretreatment processes, and future perspective. This work aims to highlight a different strategy in the research and development of novel lignocellulose pretreatment processes and offer some food for thought.

Highly catalytic supramolecular host-guest complex for high value directional conversion of lignin to syringyl monomer

In order to meet the challenge of enzyme catalysis of waste lignin, laccase (LAC)- guaiacyl(G)-type monomers noncovalent supramolecular system (LGS) were constructed for conversion of lignin. In this contribution, the catalytic effect of LGS formed by LAC and G-type monomers was studied. LAC changes the secondary structure conformation of its binding site to accommodate the G-type monomer, which is bound by hydrogen bonding and hydrophobic interactions. A mechanistic study highlights that the non-covalent complexation accelerates the internal electron transfer rate of LGS and syringol substrate for subsequent coupling reactions. In the presence of guaiacol/4-ethylguaiacol/vanillin-LAC, the conversion of dealkali lignin were 16.44, 29.12 and 22.72, respectively, higher than that in the presence of LAC alone. And the product of syringyl monomer was significantly increased in the actual lignin catalysis. Our work explains the mechanisms underlying existing enzyme-substrate interactions and enhanced catalytic system can be used for efficient utilization of waste.

Recent Advancements and Challenges in Lignin Valorization: Green Routes towards Sustainable Bioproducts

The aromatic hetero-polymer lignin is industrially processed in the paper/pulp and lignocellulose biorefinery, acting as a major energy source. It has been proven to be a natural resource for useful bioproducts; however, its depolymerization and conversion into high-value-added chemicals is the major challenge due to the complicated structure and heterogeneity. Conversely, the various pre-treatments techniques and valorization strategies offers a potential solution for developing a biomass-based biorefinery. Thus, the current review focus on the new isolation techniques for lignin, various pre-treatment approaches and biocatalytic methods for the synthesis of sustainable value-added products. Meanwhile, the challenges and prospective for the green synthesis of various biomolecules via utilizing the complicated hetero-polymer lignin are also discussed.