Enzymatic degradation of cellulose in soil: A review

Promoting LDPE microplastic biodegradability: The combined effects of solar and gamma irradiation on photodegradation

Low-Density Polyethylene (LDPE) is non-biodegradable and breaks down into microplastics (MP) when exposed to sunlight and weathering. This poses a threat to ecosystems, contributing to the micropollutants found in urban treated wastewater. Our study aimed to investigate the effects of solar and gamma irradiation on the biodegradability of LDPE MP. We pretreated them with simulated solar irradiation without (photolysis) and with (photocatalysis) TiO2 nanoparticles followed by gamma irradiation, leading to the appearance of cracks and roughness on the surface. Simultaneously, thermal stability decreased, and the carbonyl index and crystallinity increased, indicating oxidation and chain scission. Aerobic biodegradability was measured in a static respirometer at 58ºC, using green compost as inoculum, and proved to be effective for screening biodegradability of the pretreated LDPE. The combination of photocatalysis and gamma irradiation produced a synergistic effect on photodegradation, making it the most effective method for promoting biodegradation, revealed by the increased specific oxygen uptake rate (SOUR), which is expressed as millimoles O2 per mol of carbon per hour, and the greatest biodegradation kinetics constant (kO2=0.0178 h-1). The primary mechanism driving biodegradation involved the formation of carbonyl groups, which initiated biological activity.

From winery by-product to soil improver? - A comprehensive review of grape pomace in agriculture and its effects on soil properties and functions

Grape pomace (GP), a by-product of winemaking, is rich in organic carbon and nutrients, offering potential as an alternative to synthetic soil amendments. However, its broader use in agriculture remains limited due to uncertainties about long-term environmental and agronomic impacts. This review assesses the potential of GP as a soil amendment, highlighting its ability to enhance soil organic matter, nutrient availability, and soil physicochemical properties. At the same time, concerns remain regarding its acidic nature, wide carbon-to‑nitrogen (C/N) ratio, and bioactive compounds, such as mycotoxins and (poly)phenols, which could negatively impact soil microbial communities and nutrient cycling. Furthermore, residual contaminants such as pesticides and heavy metals in GP may pose ecotoxicological risks, potentially disrupting soil ecosystem functions and contaminating surrounding environments. Besides these challenges, research on the efficiency, fate and mobility of GP in soil, particularly in relation to soil type, climate, and agricultural practices, is limited. Furthermore, the effects of various (pre)treatments (e.g., composting, fermentation) on GP properties and soil interactions require more systematic investigation. Future research should focus on long-term field trials, advanced analytical methods, and effective monitoring frameworks. It is essential to refine regulatory guidance based on comprehensive risk assessments to ensure safe application and maximize GP's agronomic and environmental benefits. Overcoming these challenges could transform GP into a valuable resource for sustainable agriculture, contributing to soil health, climate resilience, and a circular economy.

Biodegradation pathways in compost-enriched soil of cotton fabrics treated with chitosan and a natural dye: Chemical and biological evaluation

This study investigated the biodegradation of cotton fabrics finished with chitosan, a natural antimicrobial biomacromolecule. Chitosan also possesses crosslinking properties that favor the attachment of anionic natural dyes, such as Carmine Red, onto cellulosic textile fibers. Herein, dyed and undyed chitosan-finished cotton samples were buried in compost-added soil (in its original form, rich in microorganisms, or after sterilization at 105 °C) for 10, 30, and 90 days. The comparison between dyed and undyed fabric behavior suggested that the dyed samples were more degradable in terms of fabric disruption and weight loss (e.g., +83 %), probably due to the availability of Carmine Red to microorganisms' attack. Nevertheless, the soil medium (sterilized/non-sterilized) and burial time emerged as the most impactful parameters in the biodegradation process. Indeed, fabrics buried 90 days in non-sterilized soil showed the strongest modifications related to chemical functional groups, morphology (fiber rupture) and thermal features (loss in crystallinity). In a multifaceted and novel approach, high-throughput sequencing combined with bioinformatics analysis was used to qualitatively analyze soil in contact with the various treated cotton specimens. The outcomes showed different biota communities in correspondence with the diverse burying conditions and fabric finishing, thus evidencing the non-negligible effect of bio-based textiles in soil.

Lignocellulose degradation in bacteria and fungi: cellulosomes and industrial relevance

Lignocellulose biomass is one of the most abundant resources for sustainable biofuels. However, scaling up the biomass-to-biofuels conversion process for widespread usage is still pending. One of the main bottlenecks is the high cost of enzymes used in key process of biomass degradation. Current research efforts are therefore targeted at creative solutions to improve the feasibility of lignocellulosic-degrading enzymes. One way is to engineer multi-enzyme complexes that mimic the bacterial cellulosomal system, known to increase degradation efficiency up to 50-fold when compared to freely-secreted enzymes. However, these designer cellulosomes are instable and less efficient than wild type cellulosomes. In this review, we aim to extensively analyze the current knowledge on the lignocellulosic-degrading enzymes through three aspects. We start by reviewing and comparing sets of enzymes in bacterial and fungal lignocellulose degradation. Next, we focus on the characteristics of cellulosomes in both systems and their feasibility to be engineered. Finally, we highlight three key strategies to enhance enzymatic lignocellulose degradation efficiency: discovering novel lignocellulolytic species and enzymes, bioengineering enzymes for improved thermostability, and structurally optimizing designer cellulosomes. We anticipate these insights to act as resources for the biomass community looking to elevate the usage of lignocellulose as biofuel.

Effects of field conditions on the degradation of cellulose-based and PLA nonwoven mulches

The impact of the field conditions on needle-punched mulches made of cellulose fibres and PLA biopolymer during the 300 days of exposure was investigated. The study observed the degradation of nonwoven mulches during specific exposure periods (30, 90, 180 and 300 days), evaluating their mechanical, morphological and chemical properties. The impact of nonwoven mulches on soil temperature and moisture, consequently on the number of microorganisms developed beneath mulches after 300 days of exposure, were analysed and associated with obtained results complementing comprehension of nonwoven mulch degradation. The findings show that nonwoven mulches made from jute, hemp, viscose and PLA fibres change when exposed to environmental conditions (soil, sunlight, rainfall, snow, ice accumulation, air and soil temperatures, wind). The changes include alterations in colour, structure shifts and modifications in properties. The results highlight the degradation pathways of cellulose and PLA mulches, revealing that cellulose-based fibres degrade through the removal of amorphous components, leading to increased crystallinity and eventual structural breakdown. WAXD findings demonstrated that microbial and environmental factors initially enhance crystalline regions in cellulose fibres but ultimately reduce tensile strength and flexibility due to amorphous phase loss. FTIR analysis confirmed the molecular changes in cellulose chains, particularly in pectin and lignin, while SEM provided direct evidence of surface damage and fibre disintegration. Furthermore, it was found that fibre types of nonwoven mulch influence soil moisture retention and soil microbial activity due to a complex interplay of fibre composition, environmental conditions and nonwoven fabric characteristics. Comprehensive mechanical, morphological and chemical results of different types of nonwoven mulch during the 300 days of exposure to the field conditions provide valuable insights into sustainable practices for using nonwoven mulches for growing crops.

Tunable Mechanical Properties in Biodegradable Cellulosic Bioplastics Achieved via Ring-Opening Polymerization

The development of bioplastics is advancing globally to promote a sustainable society. In this study, we designed cellulosic dual-network bioplastics to address the need for sustainable materials with balanced mechanical properties and biodegradability. Cellulose was used as the first network, and the second network was functionalized to enhance mechanical strength while preserving biodegradability. The dynamic covalent moieties within the second network were generated through dithiolane ring-opening polymerization. The ultimate tensile strength and flexural elongation were controlled within 8.8-193 MPa and 3.3-32.5%, respectively, depending on the degree of dynamic bonds. Moreover, the bioplastics exhibited gradual biodegradability, achieving approximately 30% degradation within 2 weeks. Interestingly, our bioplastics demonstrated the ability to coexist with plants, as their degradation did not negatively affect cell viability or plant growth. This study provides a promising approach to developing advanced bioplastics that reach sustainability goals while offering tunable mechanical properties.

Heterogeneous biocatalysis by magnetic nanoparticle immobilized biomass-degrading enzymes derived from microbial cultures

Recombinant enzymes have become increasingly popular and are frequently used as environmentally safe biocatalysts due to their wide range of applications and high specificity. Purifying these enzymes from the host cells, media, and other contaminants is essential for their characterization and applications. The widely utilized method for protein purification by nickel-nitrilotriacetic acid (Ni-NTA) resin-based affinity chromatography is a time-consuming, labor-intensive, and resource-demanding technique. In this study, we synthesized NTA-Ni@Fe3O4 nanoparticles (NPs) to capture enzymes from cell lysates and microbial culture media and developed a model system to show the efficacy of immobilizing and recycling biomass-degrading enzymes known as cellulases. Cellulases, which play an important role in biomass degradation and biofuel production, were baited with NTA-Ni@Fe3O4 NPs and purified in a single step. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis indicates efficient purification of the immobilized enzymes on the NPs from the cell lysate and extracellular media. Additionally, we successfully showed that cellulase-immobilized NTA-Ni@Fe3O4NPs can serve as a heterogeneous catalyst for the hydrolysis of p-nitrophenyl-β-D-glucopyranoside (pNPGlc) and carboxymethylcellulose (CMC). The NTA-Ni@Fe3O4 NPs immobilized with enzymes showed recyclability for up to five cycles. The applications of this methodology may be extended to various industries requiring efficient enzyme purification and recycling for promising advancements in biotechnology and sustainable biomanufacturing processes.

A novel bacterial approach to cassava waste fermentation: Reducing cyanide toxicity and improving quality to ensure livestock feed safety

Background

Indonesia has a high production of cassava, and cassava waste has significant potential as an alternative feed. However, the high levels of hydrogen cyanide (HCN) and crude fiber in cassava waste pose safety risks for its use as animal feed.

Aim

This study aimed to identify the morphology and molecular characteristics of cyanolytic and cellulolytic bacteria from cassava waste and evaluate their potential in reducing cyanide levels and improving its nutritional value to ensure feed safety.

Methods

The first step of this research involved the isolation and screening of cyanolytic and cellulolytic bacteria from cassava waste using DNA sequence homology analysis and constructing a phylogenetic tree. The second step evaluated the potential of the identified bacteria to improve cassava waste as a safe feed. The bacteria were used as inoculants in cassava waste fermentation, employing a factorial, completely randomized design with two factors: types of inoculants and fermentation duration. Data were analyzed using analysis of variance followed by Duncan's Multiple Range Test.

Results

This study identified two novel bacterial strains, namely Proteus vulgaris HT3, and Citrobacter freundii HT1. The application of these bacteria as inoculants in cassava waste fermentation at different durations significantly reduced cyanide content, crude fiber, and pH, while significantly increasing protein content. This improved the quality of cassava feed as a safe feed.

Conclusion

Cassava waste fermented for 15 days with C. freundii HT1 produced the best feed quality and safety, with the lowest HCN and crude fiber and high crude protein content.

Sequestration of Cr(VI) onto polyethyleneimine-derivatized cellulose and its effect on the enzymatic degradation and microbiome viability

The extremely hazardous nature of Cr(VI) necessitates its sequestration in a sustainable and effective manner. Cellulose-derived materials, known for their eco-friendly properties, are widely employed in environmental remediation. To improve its adsorption capabilities for heavy metals, cellulose is often derivatized with moieties like amine, thiol, carboxylic acid, etc. The current work compares the efficacy of cellulose derivatized with polyethyleneimine-a nitrogen-rich biocompatible polymer-obtained via two synthetic approaches, resulting in adsorbents termed PEI-MAAC and PEI-DAC. PEI-MAAC represents cellulose grafted with methacrylic acid followed by PEI immobilization, while PEI-DAC involves PEI immobilization on dialdehyde cellulose. The adsorption of Cr(VI) over the two categories of adsorbents is initially optimized for key parameters, including pH, adsorbent dosage and metal concentration. Further analysis of adsorption isotherms and kinetics revealed the superior efficacy of PEI-DAC. To evaluate the environmental impact of these Cr(VI)-adsorbed cellulose-derived materials, their enzymatic degradation behavior and effects on the soil microbiome have been explored. It has been found that the Cr(VI) adsorption retards the enzymatic degradation rate of these materials, while no significant adverse effects on the soil microbiome have been observed. The study highlights the potential of cellulose-derived materials as sustainable candidates for heavy metal sequestration and environmental remediation.

Advances in understanding dietary fiber: Classification, structural characterization, modification, and gut microbiome interactions

Gut microbiota and their metabolites profoundly impact host physiology. Targeted modulation of gut microbiota has been a long-term interest in the scientific community. Numerous studies have investigated the feasibility of utilizing dietary fibers (DFs) to modulate gut microbiota and promote the production of health-beneficial bacterial metabolites. However, the complexity of fiber structures, microbiota composition, and their dynamic interactions have hindered the precise prediction of the impact of DF on the gut microbiome. We address this issue with a new perspective, focusing on the inherent chemical and structural complexity of DFs and their interaction with gut microbiota. The chemical and structural complexity of fibers was thoroughly elaborated, encompassing the fibers' molecular composition, polymorphism, mesoscopic structures, porosity, and particle size. Advanced characterization techniques to investigate fiber structural properties were discussed. Additionally, we examined the interactions between DFs and gut microbiota. Finally, we summarized processing techniques to modify fiber structures for improving the fermentability of DF by gut microbiota. The structure of fibers, such as their crystallinity, porosity, degree of branching, and pore wettability, significantly impacts their interactions with gut microbiota. These structural differences also substantially affect fiber's fermentability and capability to modulate the composition of gut microbiota. Conventional approaches are not capable of investigating complex fiber properties and their influences on the gut microbiome; therefore, it is of the essence to involve advanced material characterization techniques and artificial intelligence to unveil more comprehensive information on this topic.

Geographic Distribution Pattern Determines Soil Microbial Community Assembly Process in Acanthopanax senticosus Rhizosphere Soil

The geographic distribution patterns of soil microbial communities associated with cultivated Acanthopanax senticosus plants in Northeast China were investigated. High-throughput sequencing revealed that the diversity and community assembly of bacterial and fungal communities in the inter-root soil varied significantly with geographic location. The study found that bacterial communities were predominantly assembled through stochastic processes at most sites, while fungal communities showed greater variation, with both stochastic and deterministic processes involved. The complexity of bacterial-fungal co-occurrence networks also varied with longitude and latitude, demonstrating both positive and negative interactions. PICRUSt 2.0 and FUNGuild were used to predict the potential functions of soil bacterial and fungal microbiota, respectively, during different land use patterns. The average taxonomic distinctness (AVD) index indicated varying degrees of community stability across sites. Key microbial taxa contributing to community variability were identified through Random Forest modeling, with Bacteriap25 and Sutterellaceae standing out among bacteria, and Archaeorhizomyces and Clavaria among fungi. Soil chemical properties, including pH, TN, TP, EC, and SOC, significantly correlated with microbial diversity, composition, and co-occurrence networks. Structural equation modeling revealed that geographic distribution patterns directly and indirectly influenced soil chemical properties and microbial communities. Overall, the study provides insights into the geographic distribution patterns of soil microbial communities associated with A. senticosus and highlights the need for further research into the underlying mechanisms shaping these patterns.

Exploring the Rhizospheric Microbial Communities under Long-Term Precipitation Regime in Norway Spruce Seed Orchard

The rhizosphere is the hotspot for microbial enzyme activities and contributes to carbon cycling. Precipitation is an important component of global climate change that can profoundly alter belowground microbial communities. However, the impact of precipitation on conifer rhizospheric microbial populations has not been investigated in detail. In the present study, using high-throughput amplicon sequencing, we investigated the impact of precipitation on the rhizospheric soil microbial communities in two Norway Spruce clonal seed orchards, Lipová Lhota (L-site) and Prenet (P-site). P-site has received nearly double the precipitation than L-site for the last three decades. P-site documented higher soil water content with a significantly higher abundance of Aluminium (Al), Iron (Fe), Phosphorous (P), and Sulphur (S) than L-site. Rhizospheric soil metabolite profiling revealed an increased abundance of acids, carbohydrates, fatty acids, and alcohols in P-site. There was variance in the relative abundance of distinct microbiomes between the sites. A higher abundance of Proteobacteria, Acidobacteriota, Ascomycota, and Mortiellomycota was observed in P-site receiving high precipitation, while Bacteroidota, Actinobacteria, Chloroflexi, Firmicutes, Gemmatimonadota, and Basidiomycota were prevalent in L-site. The higher clustering coefficient of the microbial network in P-site suggested that the microbial community structure is highly interconnected and tends to cluster closely. The current study unveils the impact of precipitation variations on the spruce rhizospheric microbial association and opens new avenues for understanding the impact of global change on conifer rizospheric microbial associations.

Omics approaches in understanding the benefits of plant-microbe interactions

Plant-microbe interactions are pivotal for ecosystem dynamics and sustainable agriculture, and are influenced by various factors, such as host characteristics, environmental conditions, and human activities. Omics technologies, including genomics, transcriptomics, proteomics, and metabolomics, have revolutionized our understanding of these interactions. Genomics elucidates key genes, transcriptomics reveals gene expression dynamics, proteomics identifies essential proteins, and metabolomics profiles small molecules, thereby offering a holistic perspective. This review synthesizes diverse microbial-plant interactions, showcasing the application of omics in understanding mechanisms, such as nitrogen fixation, systemic resistance induction, mycorrhizal association, and pathogen-host interactions. Despite the challenges of data integration and ethical considerations, omics approaches promise advancements in precision intervention and resilient agricultural practices. Future research should address data integration challenges, enhance omics technology resolution, explore epigenomics, and understand plant-microbe dynamics under diverse conditions. In conclusion, omics technologies hold immense promise for optimizing agricultural strategies and fortifying resilient plant-microbe alliances, paving the way for sustainable agriculture and environmental stewardship.

Agriculture 4.0: Polymer Hydrogels as Delivery Agents of Active Ingredients

The evolution from conventional to modern agricultural practices, characterized by Agriculture 4.0 principles such as the application of innovative materials, smart water, and nutrition management, addresses the present-day challenges of food supply. In this context, polymer hydrogels have become a promising material for enhancing agricultural productivity due to their ability to retain and then release water, which can help alleviate the need for frequent irrigation in dryland environments. Furthermore, the controlled release of fertilizers by the hydrogels decreases chemical overdosing risks and the environmental impact associated with the use of agrochemicals. The potential of polymer hydrogels in sustainable agriculture and farming and their impact on soil quality is revealed by their ability to deliver nutritional and protective active ingredients. Thus, the impact of hydrogels on plant growth, development, and yield was discussed. The question of which hydrogels are more suitable for agriculture-natural or synthetic-is debatable, as both have their merits and drawbacks. An analysis of polymer hydrogel life cycles in terms of their initial material has shown the advantage of bio-based hydrogels, such as cellulose, lignin, starch, alginate, chitosan, and their derivatives and hybrids, aligning with sustainable practices and reducing dependence on non-renewable resources.

Isolation, screening and characterization of efficient cellulose-degrading fungal and bacterial strains and preparation of their consortium under in vitro studies

In this investigation, cellulose-degrading fungi and bacteria were isolated from different partially decomposed cellulose-rich substrates, such as groundnut residues, rice straw, and rotten wood, following dilution plating techniques on carboxymethyl cellulose agar media and screening for potential cellulose degradation ability. The development of a clear halo zone surrounding the microbial colonies during the initial screening process using the Congo red test (20 isolates) suggested cellulose hydrolysis, and the highest cellulase production activity was implied by the isolates with the largest clear zone ratio (9 isolates). Using both macroscopic and microscopic examinations, as well as standard biochemical tests outlined in Bergey's Manual of Determinative Bacteriology, the genus-level identification of fungi and bacteria was accomplished. In order to molecularly identify the 4 isolated fungal and bacterial strains at the species level after being ultimately selected for cellulase production potential under in vitro studies, fungal and bacterial DNA was extracted and amplified by PCR using the universal primers ITS1 and ITS4 for fungi (ITS rRNA, 5.8S rRNA) and 8F and 1492R for bacterial isolates (16S rRNA). After sequencing, the PCR results were compared to other comparable sequences in GenBank (NCBI). Based on the available NCBI data, phylogenetic analysis of their ribosomal gene partial sequences revealed that DAJ2 (PP086700) shares 100% homology with Aspergillus foetidus, DTJ4 (PP086699) shares 99.74% similarity with Trichoderma atrobrunnium, DBJ6 (PP082584) shares 100% identity with Priestia megaterium, and DMB9 (PP082585) shares 99.88% homology with Micrococcus yunnanensis. The cellulolytic potential of Phanerochaete chrysosporium is well established. Therefore, it was considered a standard culture for comparison and was collected from the MTCC, Chandigarh, India. Overall, all 4 selected isolates and the check organism were mutually compatible or synergistic with each other, and their consortium is useful for the accelerated decomposition of organic constituents during rapid composting.