Lignolytic mushroom Lenzites elegans WDP2: Laccase production, characterization, and bioremediation of synthetic dyes

Biodegradation and detoxification study of triphenylmethane dye (Brilliant green) in a recirculating packed-bed bioreactor by bacterial consortium

In the last few decades, Brilliant green (BG) dye is widely employed to colour the fabric materials in various industries (e.g. textile, pulp and paper, etc.). The wastewater containing BG dye emerges as a major challenge among the researchers due to its toxic, mutagenic, and carcinogenic effects on human beings and marine life. In this context, the present study is mainly focused on the biodegradation of BG dye present in wastewater. The biodegradation of BG dye was performed in an indigenously designed recirculating packed bed bioreactor (RPBBR). Modified Polypropylene-Polyurethane foam (PP-PUF), a support packing material, was immobilised with a newly isolated bacterial consortium of Enterobacter asburiae strain SG43 (BGT1) and Alcaligenes sp. SY1 (BGT2). The bioreactor was operated under various organic loading rates (OLRs) of 2.7, 1.27, 0.93, 0.71, and 0.53 kg COD/m3.d-1 with a hydraulic retention time (HRT) of 4 days. The bioreactor exhibited the maximum BG dye removal efficiency of 91%. Proton Nuclear Magnetic Resonance (1H NMR), UV-Vis spectroscopy, Gas chromatography-mass spectrometry (GC-MS), and Fourier Transform Infrared Spectroscopy (FTIR) depicted the biodegradation of BG dye. Phaseolus mungo seeds germinated in BG dye biodegraded wastewater was significantly high (83.56%) than the untreated wastewater (32.4%), which was reasonably subjected to the detoxification of treated wastewater.

Removal of organic and inorganic contaminants from the air, soil, and water by algae

Rapid increases in human populations and development has led to a significant exploitation of natural resources around the world. On the other hand, humans have come to terms with the consequences of their past mistakes and started to address current and future resource utilization challenges. Today's primary challenge is figuring out and implementing eco-friendly, inexpensive, and innovative solutions for conservation issues such as environmental pollution, carbon neutrality, and manufacturing effluent/wastewater treatment, along with xenobiotic contamination of the natural ecosystem. One of the most promising approaches to reduce the environmental contamination load is the utilization of algae for bioremediation. Owing to their significant biosorption capacity to deactivate hazardous chemicals, macro-/microalgae are among the primary microorganisms that can be utilized for phytoremediation as a safe method for curtailing environmental pollution. In recent years, the use of algae to overcome environmental problems has advanced technologically, such as through synthetic biology and high-throughput phenomics, which is increasing the likelihood of attaining sustainability. As the research progresses, there is a promise for a greener future and the preservation of healthy ecosystems by using algae. They might act as a valuable tool in creating new products.

Structural insights, biocatalytic characteristics, and application prospects of lignin-modifying enzymes for sustainable biotechnology-A review

Lignin modifying enzymes (LMEs) have gained widespread recognition in depolymerization of lignin polymers by oxidative cleavage. LMEs are a robust class of biocatalysts that include lignin peroxidase (LiP), manganese peroxidase (MnP), versatile peroxidase (VP), laccase (LAC), and dye-decolorizing peroxidase (DyP). Members of the LMEs family act on phenolic, non-phenolic substrates and have been widely researched for valorization of lignin, oxidative cleavage of xenobiotics and phenolics. LMEs implementation in the biotechnological and industrial sectors has sparked significant attention, although its potential future applications remain underexploited. To understand the mechanism of LMEs in sustainable pollution mitigation, several studies have been undertaken to assess the feasibility of LMEs in correlating to diverse pollutants for binding and intermolecular interactions at the molecular level. However, further investigation is required to fully comprehend the underlying mechanism. In this review we presented the key structural and functional features of LMEs, including the computational aspects, as well as the advanced applications in biotechnology and industrial research. Furthermore, concluding remarks and a look ahead, the use of LMEs coupled with computational frameworks, built upon artificial intelligence (AI) and machine learning (ML), has been emphasized as a recent milestone in environmental research.

Eco-friendly detoxification of hazardous Congo red dye using novel fungal strain Trametes flavida WTFP2: Deduced enzymatic biomineralization process through combinatorial in-silico and in-vitro studies

Growing textile industry is a major global concern, owing to the presence of recalcitrant hazardous pollutants, like synthetic dyes in discharged effluents. To explore new bioresources for mycoremediation, a high laccase-producing novel white-rot fungus (WRF), Trametes flavida WTFP2, was employed. T. flavida is an underexplored member of Polyporales. Using bioinformatic tools, 8 different cis-acting RNA elements were identified in the 5.8 S ITS gene sequence, where CRISPR (CRISPR-DR15), sRNA (RUF1), and snoRNA (ceN111) are uniquely present. Molecular docking was adopted to predict the catalytic interaction of chosen toxic diazo colorant, Congo red (CR), with four dye-degrading enzymes (laccase, lignin peroxidase, azoreductase, and aryl alcohol oxidase). With 376.41 × 10³ U/L laccase production, novel WRF exhibited dye-decolorization potential. WTFP2 effectively removed 99.48 ± 0.04% CR (100 mg/L) and demonstrated remarkable recyclability and persistence in consecutive remediation trials. Mycelial dye adsorption was not only substantial driver of colorant elimination; decolorization using active T. flavida was regulated by enzymatic catalysis, as outlined by in-vitro growth, induction of extracellular enzymes, and FESEM. Fifteen metabolites were identified using HRLCMS-QTOF, and novel CR degradation pathway was proposed. Furthermore, microbial and phyto-toxicity tests of metabolites suggested complete detoxification of toxic dye, making the process clean, green, and economically sustainable.

Enhancing the Nutritional and Functional Properties of Auricularia auricula through the Exploitation of Walnut Branch Waste

As the third most edible fungus in the world, Auricularia auricular needs a lot of sawdust for cultivation; thus, it is a win–win method to develop waste wood sawdust suitable for black agaric cultivation. This study evaluated the growth, agronomic characters and nutritional quality of A. auricula cultured on different ratios of miscellaneous sawdust and walnut waste wood sawdust, and comprehensively analyzed the feasibility of cultivating black agaric with walnut sawdust using principal component method (PCA). The results showed that the macro mineral elements and phenolic substances in walnut sawdust were significantly higher than those of miscellaneous sawdust by 18.32–89.00%. The overall activity of extracellular enzymes reached the highest when the ratio of the substrate was 0:4 (miscellaneous sawdust: walnut sawdust). The mycelia of 1:3 substrates grew well and fast. In addition, the growth cycle for A. auricula was significantly lower for 0:4 (116 d) than for 4:0 (126 d). Then, the single bag yield and biological efficiency (BE) were highest at 1:3. Moreover, the nutrients and mineral elements of A. auricula cultivated in walnut sawdust were significantly higher than that of miscellaneous sawdust, expect for total sugar and protein, and the highest overall value was found at 1:3. Finally, the results of comprehensive evaluation by PCA showed that the D value was the highest when the substrate was 1:3 and the lowest when the substrate was 4:0. Therefore, the substrate ratio of 1:3 was the most suitable for the growth of A. auricula. In this study, the high yield and quality of A. auricula were cultivated by waste walnut sawdust, which provided a new way to utilize walnut sawdust.

Degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) by fungi originating from Vietnam

Three different fungi were tested for their ability to degrade 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid and for the role of laccases and cytochromes P450-type in this process. We studied a white-rot fungus Rigidoporus sp. FMD21, which has a high laccase activity, for its efficiency to degrade these herbicides. A positive correlation was found between its laccase activity and the corresponding herbicide degradation rate. Even more, the doubling of the enzyme activity in this phase corresponded with a doubling of the herbicide degradation rate. It is, therefore, tempting to speculate that laccase is the most dominant enzyme in the degradation of 2,4-D and 2,4,5-T under these conditions. In addition, it was shown that Rigidoporus sp. FMD21 partly relies on cytochromes P450-type for the breakdown of the herbicides as well. Two filamentous fungi were isolated from soil contaminated with herbicides and dioxins located at Bien Hoa airbase. They belong to genera Fusarium and Verticillium of the phylum Ascomycota as judged by their 18S rRNA gene sequences. Both isolated fungi were able to degrade the herbicides but with different rates. Their laccase activity, however, was very low and did not correlate with the rate of breakdown of the herbicides. These data indicate that the white-rot fungus most likely synthesizes laccase and cytochromes P450-type for the breakdown of the herbicides, while the types of enzyme used for the breakdown of the herbicides by the two Ascomycota remain unclear.

Research on the treatment mechanism of anthraquinone dye wastewater by algal-bacterial symbiotic system

This study analyzed the role of algae and bacteria in algal-bacterial symbiotic systems for the treatment of dyeing wastewater. The mechanism was investigated by constructing an algae-bacteria tandem system (A system) and a bacteria-algae tandem system (B system). The results showed that the chemical oxygen demand (COD) removal and decolorization rates of A system reached 91% and 90%, respectively, under optimal conditions, which were higher than that of B system. The degradation pathways of A and B systems differed according the degradation product analysis. High-throughput sequencing analysis revealed that Proteobacteria were the dominant bacteria in A and B systems. Armatimonadetes increased considerably in A system. These results show that algae mainly contributed to the preliminary degradation of anthraquinone dye, and resulting products were easily degraded by bacteria. This study provides guidance on the optimization of the system. It can be better adapted to the actual needs of wastewater treatment plants.

Production, partial purification and characterization of ligninolytic enzymes from selected basidiomycetes mushroom fungi

In recent years, many research on the quantity of lignocellulosic waste have been developed. The production, partial purification, and characterisation of ligninolytic enzymes from various fungi are described in this work. On the 21st day of incubation in Potato Dextrose (PD) broth, Hypsizygus ulmarius developed the most laccase (14.83 × 10⁻⁶ IU/ml) and manganese peroxidase (24.11 × 10⁻⁶ IU/ml), while Pleurotus florida produced the most lignin peroxidase (19.56 × ⁻⁶ IU/ml). Laccase (Lac), lignin peroxidase (LiP), and manganese peroxidase (MnP), all generated by selected basidiomycetes mushroom fungi, were largely isolated using ammonium sulphate precipitation followed by dialysis. Laccase, lignin peroxidase, and manganese peroxidase purification findings indicated 1.83, 2.13, and 1.77 fold purity enhancements, respectively. Specific activity of purified laccase enzyme preparations ranged from 305.80 to 376.85 IU/mg, purified lignin peroxidase from 258.51 to 336.95 IU/mg, and purified manganese peroxidase from 253.45 to 529.34 IU/mg. H. ulmarius laccase (376.85 IU/mg) with 1.83 fold purification had the highest specific activity of all the ligninolytic enzymes studied, followed by 2.13 fold purification in lignin peroxidase (350.57 IU/mg) and manganese peroxidase (529.34 IU/mg) with 1.77-fold purification. Three notable bands with molecular weights ranging from 43 to 68 kDa and a single prominent band with a molecular weight of 97.4 kDa were identified on a Native PAGE gel from mycelial proteins of selected mushroom fungus. The SDS PAGE profiles of the mycelial proteins from the selected mushroom fungus were similar to the native PAGE. All three partially purified ligninolytic isozymes display three bands in native gel electrophoresis, with only one prominent band in enzyme activity staining. The 43 kDa, 55 kDa, and 68 kDa protein bands correspond to laccase, lignin peroxidase, and manganese peroxidase, respectively.

Response of Trametes hirsuta to hexavalent chromium promotes laccase-mediated decolorization of reactive black 5

The recalcitrant azo dyes combined with heavy metals constitute a major challenge for the bioremediation of industrial effluents. This study aimed to investigate the effect and mechanism of action of a white-rot fungus Trametes hirsuta TH315 on the simultaneous removal of hexavalent chromium [Cr(VI)] and azo dye (Reactive Black 5, RB5). Here, this study discovered that toxic Cr(VI) (1 mM) greatly promoted RB5 decolorization (from 57.15% to 83.65%) by white-rot fungus Trametes hirsuta with high Cr(VI)-reducing ability (>96%), resulting in the simultaneous removal of co-contaminants. On the basis of transcriptomic and biochemical analysis, our study revealed that the oxidative stress in co-contaminants mainly caused by Cr(VI), and a number of dehydrogenases and oxidases showed up-regulation in response to Cr(VI) stress. It was noteworthy that the oxidative stress caused by Cr(VI) in co-contaminants can both significantly induce glutathione S-transferase and laccase expression. Glutathione S-transferase potentially involved in antioxidation against Cr(VI) stress. Laccase was found to play a key role in RB5 decolorization by T. hirsuta. These results suggested that the simultaneous removal of co-contaminants by T. hirsuta could be achieved with Cr(VI) exposure. Overall, the elucidation of the molecular basis in details will help to advance the general knowledge about the fungus by facing harsh environments, and put forward a further possible application of fungi on environmental remediation.

Ligninolytic Enzyme Production and Decolorization Capacity of Synthetic Dyes by Saprotrophic White Rot, Brown Rot, and Litter Decomposing Basidiomycetes

An extensive screening of saprotrophic Basidiomycetes causing white rot (WR), brown rot (BR), or litter decomposition (LD) for the production of laccase and Mn-peroxidase (MnP) and decolorization of the synthetic dyes Orange G and Remazol Brilliant Blue R (RBBR) was performed. The study considered in total 150 strains belonging to 77 species. The aim of this work was to compare the decolorization and ligninolytic capacity among different ecophysiological and taxonomic groups of Basidiomycetes. WR strains decolorized both dyes most efficiently; high decolorization capacity was also found in some LD fungi. The enzyme production was recorded in all three ecophysiology groups, but to a different extent. All WR and LD fungi produced laccase, and the majority of them also produced MnP. The strains belonging to BR lacked decolorization capabilities. None of them produced MnP and the production of laccase was either very low or absent. The most efficient decolorization of both dyes and the highest laccase production was found among the members of the orders Polyporales and Agaricales. The strains with high MnP activity occurred across almost all fungal orders (Polyporales, Agaricales, Hymenochaetales, and Russulales). Synthetic dye decolorization by fungal strains was clearly related to their production of ligninolytic enzymes and both properties were determined by the interaction of their ecophysiology and taxonomy, with a more relevant role of ecophysiology. Our screening revealed 12 strains with high decolorization capacity (9 WR and 3 LD), which could be promising for further biotechnological utilization.

Effluents detoxification from pulp and paper industry using microbial engineering and advanced oxidation techniques

Due to the high demand of paper and related items, pulp and paper industry is flourishing day by day. With increased production, come the hazards associated with the toxic elements present in the effluents. Various microorganisms are currently employed in the remediation of these toxic effluents. In addition, various techniques like ozonation, electrocoagulation, UV treatment, Fenton's reagent, and photo-Fenton based techniques are used in advanced oxidation processes to reduce these toxins from effluents. This review highlights various above mentioned advanced techniques and innovative processes along with the biological remediation of these toxic effluents with the help of some potential microbial consortia or their combinatory effects. Moreover, the present review will also disclose the ideas on utilizing the tools of metabolic engineering, systems biology, and artificial intelligence towards microbial engineering for relatively better bioremediation processes. In the future, these techniques might be helpful in increasing the capability of microbial consortia towards detoxification of effluents to make them environmentally safe. Finally, this review gives well-synchronized approaches to get more insights into these innovative methodologies and techniques and their use for various industrial applications.

Transcriptomic Analysis of Two Lentinula edodes Genotypes With Different Cadmium Accumulation Ability

Lentinula edodes, also known as Xiang'gu, is commonly eaten in cultures around the world. However, L. edodes is particularly susceptible to enrichment with heavy metals, particularly cadmium (Cd), which is toxic to human health. Understanding the molecular mechanism and mining key genes involved in Cd enrichment will facilitate genetic modification of L. edodes strains. Two L. edodes genotypes, Le4625 (with higher Cd enrichment capability) and Le4606 (with lower Cd enrichment capability) were used in this study. The Cd concentrations in the mycelia of the tested genotypes differed significantly after Cd (0.1 mg/L) exposure; and the Cd content in Le4625 (1.390 ± 0.098 mg/kg) was approximately three-fold that in Le4606 (0.440 ± 0.038 mg/kg) after 7 h of Cd exposure. A total of 24,592 transcripts were assessed by RNA-Seq to explore variance in Cd accumulation. Firstly, differentially expressed genes (DEGs) were analyzed separately following Cd exposure. In comparison with Ld4625, Ld4606 showed a greater number of Cd-induced changes in transcription. In Ld4606, DEGs following Cd exposure were associated with transmembrane transport, glutathione transfer and cytochrome P450, indicating that these genes could be involved in Cd resistance in L. edodes. Next, Le4606 and Le4625 were exposed to Cd, after which DEGs were identified to explore genetic factors affecting Cd accumulation. After Cd exposure, DEGs between Le4606 and Le4625 encoded proteins involved in multiple biological pathways, including transporters on the membrane, cell wall modification, oxidative stress response, translation, degradation, and signaling pathways. Cadmium enrichment in cells may activate MAPK signaling and the anti-oxidative stress response, which can subsequently alter signal transduction and the intracellular oxidation/reduction balance. Furthermore, several possible candidate genes involved in the Cd accumulation were identified, including the major facilitator superfamily genes, heat shock proteins, and laccase 11, a multicopper oxidase. This comparison of the transcriptomes of two L. edodes strains with different capacities for Cd accumulation provides valuable insight into the cultivation of mushrooms with less Cd enrichment and also serves as a reference for the construction of engineered strains for environmental pollution control.

An effective in-situ method for laccase immobilization: Excellent activity, effective antibiotic removal rate and low potential ecological risk for degradation products

In this study, we used a simple in-situ biomineralization method to immobilize Bacillus subtilis (B. subtilis)-derived laccase into the copper-Trimesic acid framework (Cu-BTC), and the synthesized Laccase@Cu-BTC particles were used to degrade tetracycline and ampicillin. Compared with free laccase, the Laccase@Cu-BTC showed 16.5-fold of activity recovery, higher thermo-tolerant performance, more excellent acid-proof ability and reusability. Without any mediators, Laccase@Cu-BTC displayed high degradation efficiency (nearly 100%) for tetracycline and ampicillin in some actual water. The degradation mechanism and proposed degradation pathways of tetracycline and ampicillin were discussed technically. Besides, bacteriostatic assay and survival test of Escherichia coli (E. coli) and B. subtilis confirmed the loss of antibiotic activity for tetracycline and ampicillin, as well as the low ecotoxicity of the degradation products. Our research demonstrates that Laccase@Cu-BTC has excellent performance in the effective removal of antibiotics and the detoxification of degradation products, which make it a promising candidate for environmental recovery.

M. B. Morais A, Freitas AC, C. F. R. Ferreira I, Pintado M. Valorization of Mushroom By-Products as a Source of Value-Added Compounds and Potential Applications

Nowadays, the food sector is highly concerned with environmental issues and foreseen to develop strategies to reduce waste and losses resulting from activities developed in the food system. An approach is to increment added value to the agro-industrial wastes, which might provide economic growth and environmental protection, contributing to a circular economy. Mushroom by-products represent a disposal problem, but they are also promising sources of important compounds, which may be used due to their functional and nutritional properties. Research has been developed in different fields to obtain value added solutions for the by-products generated during mushroom production and processing. Bioactive compounds have been obtained and applied in the development of nutraceutical and pharmaceutical formulations. Additionally, other applications have been explored and include animal feed, fertilizer, bioremediation, energy production, bio-based materials, cosmetics and cosmeceuticals. The main purpose of this review is to highlight the relevant composition of mushroom by-products and discuss their potential as a source of functional compounds and other applications. Future research needs to explore pilot and industrial scale extraction methods to understand the technological feasibility and the economic sustainability of the bioactive compounds extraction and valorization towards different applications.

Microbial degradation, spectral analysis and toxicological assessment of malachite green by Streptomyces chrestomyceticus S20

Malachite green (MG), a triphenylmethane dye is extensively used for coloring silk, aquaculture and textile industries, it has also has been reported toxic to life forms. This study aimed to investigate the biodegradation potential of MG by actinobacteria. The potent actinobacterial strain S20 used in this study was isolated from forest soil (Sabarimala, Kerala, India) and identified as Streptomyces chrestomyceticus based on phenotype and molecular features. Strain S20 degraded MG up to 59.65 ± 0.68% was studied in MSM medium and MG (300 mg l^-1) and degradation was increased (90-99%) by additions of 1% glucose and yeast extract into the medium at pH 7. The treated metabolites from MG by S20 characterized by FT-IR and GC-MS. The results showed MG has been degraded into nontoxic compounds evaluated by (1) phytotoxic assay on Vigna radiata, (2) microbial toxicity on Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus, Streptococcus sp. and Escherichia coli, (3) cytotoxicity assay in a human cell line (MCF 7). The toxicity studies demonstrated that the byproducts from MG degradation by S. chrestomyceticus S20 were no toxic to plants and microbes and less toxic to human cells as compared to the parent MG. Perhaps this is the first work reported on biodegradation of MG by S. chrestomyceticus which could be a potential candidate for the removal of MG from various environments.

Sequential electrochemical oxidation and bio-treatment of the azo dye congo red and textile effluent

Textile effluent is often difficult to manage as it contains a high concentration of toxic and recalcitrant synthetic dyes. In this study, congo Red and textile effluent were treated by electrochemical oxidation using RuO₂-IrO₂ coated titanium electrode as an anode followed by biodecolorization using Pseudomonas stutzeri MN1 and Acinetobacter baumannii MN3. Effluent pre-treatment is often necessary to minimize the inhibitory effects of textile dyes on dye degrading bacterial during bio-treatment. The pre-treatment of Congo Red by electrochemical oxidation for 10 min resulted in a decolorization rate of 98% at a pH, NaCl concentration, and current density of 7, 2 g L^-1, and 20 mA cm^-2. Subsequent bio-treatment of the pretreated Congo Red enhanced the biodegradation to 93%. The COD removal efficiency in real textile effluent following electrochemical pretreatment and biological treatment using bacterial consortium were 3.8% and 93%, respectively. Therefore, integrating electrochemical oxidation and microbial consortia offers an effective and environmentally friendly approach for treating complex industrial effluents.

Bioprocess optimization of laccase production through solid substrate fermentation using Perenniporia tephropora-L168 and its application in bioremediation of triaryl-methane dye

Laccases are multi copper oxidases that can oxidize both phenolic and nonphenolic lignin related compounds. Consequently, there has been continuous demand for laccases for the oxidative degradation of phenolic dyes in effluents. In view of this, the present work was focused on laccase production by solid substrate fermentation using a newly isolated fungus Perenniporia tephropora-L168. To intensify the laccase production, the process parameters pH, nitrogen, inducer, and substrate: water ratio were optimized by using statistical model. A set of optimal conditions noted were pH 3, nitrogen 0.001 g/L; inducer 0.5% and substrate: water ratio (1:10), which yielded laccase 1,160 U/g. The crude laccase exhibited noteworthy potential to degrade a triaryl-methane dye especially Malachite green. Also, during bioremediation studies, the statistical process optimization could achieve 81% decolourization within 180 min. The laccase treatment brought chemical transformation in malachite green as evident from UV-Visible spectra, FTIR, HPLC while toxicity against bacteria and fungi was also reduced. During phytotoxicity study, effect of treated and untreated dye on germination of seed was analyzed. Interestingly, the germination index for Vigna aconitifolia and Vigna radiata was increased by two and fourfold, respectively. Overall, this work demonstrates optimized production of laccase using Perenniporia tephropora-L168 and its efficient bioremediation potential for triaryl-methane dye.

Enzymatic degradation and detoxification of azo dye Congo red by a new laccase from Oudemansiella canarii

A single laccase with molecular weight of 41 kDa was produced by the white-rot fungus Oudemansiella canarii cultured on solid state fermentation using a mixture of sugarcane bagasse-wheat bran as substrate. The enzyme (5 U) was able to decolourize 80% of 50 mg/L Congo red within 24 h at 30 °C and pH 5.5. The relationship between the decolorization rate and dye concentration obeyed Michaelis-Menten kinetics, with K_M and V_max values of 46.180 ± 6.245 µM and 1.840 ± 0.101 µmol/min, respectively. Fourier transform infrared spectroscopy (FTIR) and mass spectrometry allowed to conclude that the laccase acts not only on the dye chromophore group, but also that it cleaves different covalent bonds, causing an effective fragmentation of the molecule. The action of the laccase caused a significant reduction in toxicity, as indicated by the Microtox test. In conclusion, O. canarii laccase could be useful in future biological strategies aiming at degrading azo dyes.

Laser Mutagenesis of Phellinus igniarius Protoplasts for the Selective Breeding of Strains with High Laccase Activity

Phellinus igniarius is a medicinal fungus that utilizes lignin as a nutrient substrate. This fungus has a weak lignin degradation ability and, as a result, a slow growth rate. Laccases are crucial enzymes for lignin degradation in P. igniarius, and thus, the cultivation of strains with high laccase activity is expected to increase the growth rate of P. igniarius. To generate P. igniarius strains with high laccase activity, we performed laser mutagenesis of P. igniarius protoplasts and screened for mutants with high laccase activity. Our results showed that the laser power density and P. igniarius protoplast survival rate exhibited a power-function relationship. The power density threshold value between lethality and growth promotion was 0.24 mW/mm². Mutagenesis was carried out using a laser beam diameter of 3 mm and an irradiation period of 40 min. After five generations of selection, we identified a high laccase activity strain, termed SJZ2. The laccase activity in SJZ2 during 4 h of fermentation was increased by 36.84% in comparison with the control and ranged from 0.20216 to 0.27664 U. The Km and Vmax of the laccase produced by SJZ2 were 0.21 mmol/mL and 0.53 mmol/L/min, respectively. This study demonstrated the feasibility of laser mutagenesis of P. igniarius protoplasts for the selection of high laccase activity. This study characterized the key factors in the laser mutagenesis process of P. igniarius protoplasts and provided a reference for the application of lasers in biological mutagenesis. Future studies should evaluate the bioactive functionality and stability of this novel strain of P. igniarius, particularly the organoleptic and medical characteristics of the fruiting bodies.

Perspectives of Microbial Inoculation for Sustainable Development and Environmental Management

How to sustainably feed a growing global population is a question still without an answer. Particularly farmers, to increase production, tend to apply more fertilizers and pesticides, a trend especially predominant in developing countries. Another challenge is that industrialization and other human activities produce pollutants, which accumulate in soils or aquatic environments, contaminating them. Not only is human well-being at risk, but also environmental health. Currently, recycling, land-filling, incineration and pyrolysis are being used to reduce the concentration of toxic pollutants from contaminated sites, but too have adverse effects on the environment, producing even more resistant and highly toxic intermediate compounds. Moreover, these methods are expensive, and are difficult to execute for soil, water, and air decontamination. Alternatively, green technologies are currently being developed to degrade toxic pollutants. This review provides an overview of current research on microbial inoculation as a way to either replace or reduce the use of agrochemicals and clean environments heavily affected by pollution. Microorganism-based inoculants that enhance nutrient uptake, promote crop growth, or protect plants from pests and diseases can replace agrochemicals in food production. Several examples of how biofertilizers and biopesticides enhance crop production are discussed. Plant roots can be colonized by a variety of favorable species and genera that promote plant growth. Microbial interventions can also be used to clean contaminated sites from accumulated pesticides, heavy metals, polyaromatic hydrocarbons, and other industrial effluents. The potential of and key processes used by microorganisms for sustainable development and environmental management are discussed in this review, followed by their future prospects.