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Abstract:The utilization of lignocellulosic materials can significantly increase the reserves of renewable resources on the planet. Termites are widely distributed in tropical and subtropical regions. Mainly, they can rely on intestinal microbes such as bacteria, archaea and fungi as well as the protozoa to degrade lignocellulose in food and play an important role in the cycle of carbon and nitrogen. This paper summarizes the studies on the termite gut microbes that have been proven to degrade lignocellulose in recent years. We hope to provide basic information for the subsequent study of lignocellulose degradation.

Abstract:Lignocellulose is the most abundant organic polymer on earth. Termites are one of the oldest but most successful and efficient lignocellulose degraders. Understanding the mechanism of effective degradation of highly resistant plant polymers by termites has important guidance for industrial biomass energy conversion and biomimetic design. The lignocellulases produced by termites and their symbiotic microorganisms play an important role in the conversion and utilization of lignocellulose. This article summarizes the research progress in producing cellulase, xylanase and laccase by termites themselves and their intestinal protozoa, bacteria and fungi, and suggests future problems and prospects. This review is helpful for a comprehensive understanding of the lignocellulytic gene type, source, distribution, expression, and enzyme activity and function of lignocellulases in termite digestive system.

Abstract:The resource utilization and harmless disposal of tobacco waste require efficient microbial degradation of refractory substances such as lignin and nicotine. This paper reviews the progress in biodegradation of refractory substances in tobacco waste. Up to now, an increasing number of strains capable of degrading lignin and nicotine have been isolated, and there are many publications on the mechanism and application of lignin and nicotine microbial degradation. However, there are few publications about their application in tobacco waste treatment. Lignin and nicotine-degrading bacteria also exhibit potential for lignin abatement and nicotine removal of waste tobacco leaves (tobacco stems). However, it is necessary to evaluate both the degradation ability and the adaptability to the real environment. Strains capable of degrading both lignin and nicotine are preferable for application, but few such strains have been isolated. The research of complex microflora based on complete genome analysis and microbiome technology, is obligated and will promote the development and application of microbial disposal technology for waste tobacco leaves containing lignin, nicotine and other refractory substances.

Abstract:[Objective] The dynamic trends of biochemical property of black soldier fly (Hermetia illucens L., BSF) larvae vermicompost during the subsequent secondary composting was observed through the culture experiment, and the associated succession of microbial ecology of the BSF vermicompost and the stabilization mechanisms were also discussed. [Methods] Dynamic incubation experiment was conducted in which drums containing BSF vermicompost were buried into a full-scale biomass composting heap, and periodic sampling was conducted at intervals of 7 days during the 49-day testing period. 16S rRNA high-throughput sequencing was used to analyze the bacterial diversity, community structure and metabolic function of BSF vermicompost. [Results] After two weeks of rapid rising to 68.7℃, the temperature of BSF vermicompost gradually decreased to 37.7℃ on the 49th day. When the experiment ended, the total organic carbon, dissolved organic matter (DOM) and pH value reached 67.3%, 18.4 g/kg and 8.0, respectively. The bacterial diversity of Shannon index, Simpson index and Chao1 index increased rapidly with the process of composting, and then decreased slowly to 7.45, 0.98 and 985 at the end. 16S rRNA sequencing shows that dominant phyla included Bacteroidetes, Firmicutes, Proteobacteria and Actinobacteria among the microbial communities. Meanwhile, Corynebacteriaceae decreased from 35.7% at the beginning to 6.5% at the end, Flavobacteriaceae gradually increased from 3.22% to 12.6%, and Porphyromonadaceae increased rapidly to 11.5% and then slowly decreased to 5.1% at the same level as the initial level. PICRUSt predicted that the average relative abundances of amino acid sugar and nucleotide sugar metabolism, carbon fixation pathway, and methane metabolism remained strong throughout the whole secondary composting process of BSF vermicompost, and all of them peaked at the middle stage of composting (day 15-35) then declined. The average relative abundances of fatty acid metabolism, unsaturated fatty acid biosynthesis metabolism, polycyclic aromatic hydrocarbon degradation and sulfur metabolism were shown as decreasing first with following of rising again. [Conclusion] During the secondary composting of BSF vermicompost, the biochemical features of materials and their microbial ecology have significantly changed along with apparent reductions of moisture, DOM, and total organic matters, thus promoting the rapid maturation and stabilization of BSF vermicompost, which is conducive to the farmland reuse of BSF vermicompost as a novel organic fertilizer.

Abstract:[Objective] The aim was to attain the optimal conditions for the degradation of corn straw by microbial lignin-degradation consortium and define the functional microbes that are important for the degradation of corn straw. [Methods] Based on the results of single factor experiments, such as culture temperature, pH, media loading quantity and inoculation concentration, the response surface method was adopted to optimize the culture conditions for the degradation of corn straw by the consortium. The changes of community structure in different stages of degradation were analyzed by high-throughput sequencing of bacterial 16S rRNA amplicons. [Results] The optimum degradation conditions were as follows:fermentation temperature 32℃, pH 8.2, loading volume 40%, inocula concentration 10%, under which the degradation rate of lignin was up to 44.5%. Compared with the non-optimized treatment, the increased rate of lignin degradation was 13.3%. At the phylum level, Proteobacteria, Bacteroidetes and Firmicutes were dominant. The dominant genera included Proteiniphilum (11.9%), Sphaerochaeta (8.4%), Ruminofilibacter (8.4%), Pannonibacter (6.7%), Pseudomonas (6.1%) and Rhizobium (5.7%) in initial stage. In the peak stage of lignin degradation, the abundance of Anaerocolumna (24.0%), Caenispirillum (9.2%) and Thauera (7.0%) increased significantly, it was 16.5, 3.0 and 5.9 times higher than that at the initial stage of degradation. Meanwhile, the abundance of Ruminofilibacter (10.9%) was still very high and ranks second. The mainly dominant genera at the end of degradation were Ruminofilibacter (25.4%), Pseudomonas (9.7%), Sphaerochaeta (8.8%), Caenispirillum (8.4%), Pannonibacte (4.3%), Thauera (4.0%) and Desulfomicrobium (3.4%). [Conclusion] The optimal conditions of corn straw degradation and the dynamic changes of bacterial consortium structure were clarified. Pseudomonas, Pannonibacter, Thauera, Ruminofilibacter and Anaerocolumna were main bacteria that have played an important role in the process of corn straw degradation.

Abstract:[Objective] A novel bifunctional mannanase-acetyl esterase 44884 from lignocellulose-degraded consortium EMSD5 was investigated, including its interdomain synergism. The effect of carbohydrate-binding module (CBM) on the properties of catalytic domain was also studied, to provide references for improving and applying bifunctional enzymes. [Methods] Mannanase-acetyl esterase 44884 and its truncated mutants, as well as site-directed mutant were expressed in E. coli. The differences in the enzymatic properties of the wild type strain and mutants were evaluated by thin-layer chromatography (TLC) and dinitrosalicylic acid (DNS) assay. [Results] Mannanase-acetyl esterase 44884 and its mutants were successfully overexpressed in E. coli. The mannanase domain and acetyl esterase domain showed synergistic effect, and mannanase-acetyl esterase 44884 showed higher production of reducing sugars and acetic acid than the combination of mannanase domain and acetyl esterase domain. Two CBM65 from mannanase-acetyl esterase 44884 could bind mannan and Avicel, and not change the optimal conditions of catalytic domains. Although two CBM65 significantly decreased the thermostability of catalytic domain, they specifically improved the natural substrate hydrolysis of their adjacent catalytic domains.[Conclusion] The synergistic action between different domain of mannanase-acetyl esterase 44884 was illustrated, in which two CBM65 could improve the mannan hydrolysis of mannanase-acetyl esterase 44884 by binding to substrate.

Abstract:[Objective] In order to utilize all sugars in the raw materials and produce high value-added products, this research aims to construct a recombinant Saccharomyces cerevisiae strain that could assimilate L-arabinose and reduce xylose to xylitol. [Methods] Firstly, we used CRISPR/Cas9 gene editing technique to sequentially introduce genes in L-arabinose metabolism pathway and gene of xylose reductase into the Saccharomyces cerevisiae host strain to endow it the ability to metabolize L-arabinose and convert xylose into xylitol. Secondly, we used adaptive evolutionary engineering method to improve L-arabinose utilization efficiency of the recombinant strain. Finally, we verified the ability of the recombinant strain to metabolize L-arabinose and transfer xylose to xylitol by mixed sugar fermentation. [Results] By introducing the L-arabinose metabolic pathway of Lactobacillus plantarum, the engineered S. cerevisiae strain obtained good ability to grow on L-arabinose. After introducing the xylose reductase gene of Candida tropicalis, the strains were able to efficiently reduce xylose to xylitol using glucose as auxiliary carbon source, yet the utilization of L-arabinose decreased. After repeated batch acclimation with L-arabinose as the sole carbon source, the L-arabinose utilization ability of strains restored and improved. We isolated evolved strain KAX3-2 with good phenotype and evaluated its fermentation capacity using medium containing xylose (50 g/L) and L-arabinose (20 g/L). After 72 h fermentation, the utilization ratio of L-arabinose and xylose reached 42.1% and 65.9%, respectively, and the yield of xylitol was 64%. [Conclusion] This study successfully constructed a S. cerevisiae strain KAX3-2 which could utilize L-arabinose and convert xylose to xylitol efficiently as well as provided the base for the construction of strains with higher L-arabinose utilization efficiency and xylitol yield.

Abstract:Lignocellulose is the most abundant renewable resource on the earth. There are about 900 million tons of agricultural straw produced annually in China. Most of them cannot be effectively used, and thus not only causes a waste of resources, but also causes many serious environmental problems. The recalcitrance of lignin is one of the main challenges restricting the industrialization of lignocellulose. Although the degradation and transformation of lignin have been studied for many years, it is still challenged to commercially valorize the lignin because of its inherent heterogeneity. In recent years, the "biological funneling" transformation characteristics of microorganisms have been widely studied and will potentially provide a new direction for the valorization of lignin. This review mainly summarizes the research processes of microbial lignin depolymerization and transformation, and discusses the current opportunities and challenges of lignin biological valorization.

Abstract:[Objective] Here we studied the biodegradation characteristics of single and mixed polycyclic aromatic hydrocarbons (PAHs) pollutants by Irpex lacteus F17 using phenanthrene, anthracene, and fluoranthene. [Methods] We determined the concentration of PAHs during biodegradation using gas chromatography-mass spectrometer (GC-MS). We used pseudo first order reaction kinetics model to fit the biodegradation results of PAHs. [Results] After 15 days of degradation, the biodegradation rate was phenanthrene (97.8%) > anthracene(89.3%) > fluoranthene (81.5%). The degradation process of phenanthrene, anthracene and fluoranthene had the characteristics of pseudo first order reaction kinetics. The biodegradation rate of phenanthrene was the fastest, followed by anthracene, and fluoranthene was the slowest. Compared with the degradation of single PAHs, mixed PAHs showed different characteristics on the growth and manganese peroxidase synthesis of Irpex lacteus F17. In addition, water solubility was likely to be an important control factor for the biodegradation of mixed pollutants. The water solubility was in the following order:phenanthrene > fluoranthene > anthracene. Therefore, when we added phenanthrene or fluoranthene into anthracene degradation system, microorganisms may preferentially degrade these pollutants and inhibit the degradation of anthracene. The addition of anthracene or phenanthrene could also inhibit the biodegradation of fluoranthene. However, the addition of anthracene or fluoranthene with poor water solubility had no significant effect on the biodegradation of phenanthrene. [Conclusion] The competition role was the main characteristic for the biodegradation of mixed PAHs.

Abstract:Antibiotics are regarded as a new group of environmental pollutants in recent years because of they are difficult to degrade and highly ecotoxic even in low concentrations. More and more attentions have been paid to their residues and removals in environmental. With the wide use, sulfamethoxazole residual and the detection frequency in wastewater is increasing. As one of the few microbial degradable antibiotics, sulfamethoxazole degraded by microbes is one of the most promising methods. This article summarizes the degradation efficiency and degradation conditions of sulfamethoxazole by different soil, sediment, activated sludge, mixed flora, enzymes and isolated strains. Meanwhile, degradation pathways reported in the literature are summarized. Two specific factors affecting the degradation of sulfamethoxazole are also discussed. Finally, we look forward to the perspective of molecular biology and bioinformatics in new researches, as well as the construction of degrading bacterial consortium from different pollutants in future applications.

Abstract:Persistent Organic Pollutants (POPs) are a class of synthetic pollutants that are continuously produced along with the development of human agrochemicals and industrial technology. They are characterized by high toxicity, long-lasting, long migration and high bioaccumulation. The remediation of POPs has always been a research hotspot in the field of environmental science and technology. Among them, microbial degradation is considered to have broad application prospects because of no secondary pollution, low-cost, fast and simple. This review presents an overview of the recent advances in the microbial catabolism of various POPs, including microbial resources that are capable of catabolizing these POPs and the mechanisms involved in the catabolism. Furthermore, the potential and application of the computational metabolic modeling, synthetic biology, and genomics in the biodegradation of POPs have also been discussed. Taken together, these results will provide valuable theoretical basis for the bioremediation of POPs contaminated sites using highly efficient degrading microorganisms.

Abstract:Oxygen heterocycles are a kind of refractory organic pollutants commonly found in polluted environments. These compounds are of immense concern from point view of the environment because they are known for their toxic and carcinogenic properties. Here, we review the research progress in the biodegradation of typical oxygen-containing monoheterocyclic compounds tetrahydrofuran, 1,4-dioxane and oxygen-containing fused heterocyclic compounds dibenzofuran and dibenzo-p-dioxin. We address the degradation performance of bacteria, the degradation pathways and degradation-related genes. In addition, we discuss the research status of dioxins, and propose further research directions of biodegradation of oxygen heterocycles and their dioxin derivatives.

Abstract:Polycyclic aromatic hydrocarbons are a group of persistent organic pollutants that require strict control according to the national standard for soil environmental quality of China. Remediation using microbial process is recognized as economical and eco-friendly technology with great potential. Recent advances in microbial remediation with regards to biotransformation mechanisms and microbial response to soil pollution open up new perspectives on the field-scale bioremediation and management for polycyclic aromatic hydrocarbon-contaminated soil. The review provides an overview of microbial remediation of soil polluted by polycyclic aromatic hydrocarbons, surveying comprehensively from remediation technology, biodegradation characteristics, to microbial response to soil pollution. At last, some theoretical bottlenecks in development of microbial remediation techniques are discussed.

Abstract:Nitroaromatic compounds are important chemical materials and wildly used in the chemical syntheses of pharmaceuticals, dyes and pesticides. Inevitably, as hazardous pollutants, nitroaromatic compounds have been extensively introduced into our surrounding environments because of anthropogenic activities. Microorganisms play an important role in degrading these recalcitrant contaminants. In the past decades, microbial degradation of nitroaromatics has been investigated extensively, leading to dramatic progress in understanding the microbial strategies and associated mechanisms for the degradation of these pollutants. Here we present an integrated review of the bacterial degradation of nitroaromatic compounds and their halogenated derivatives in the catabolic pathway and mechanism, microbial chemotaxis, together with bioremediation of nitroaromatics-contaminated environment. In addition, we propose future research. This review will increase our current understanding of the microbial degradation process of these toxic and recalcitrant pollutants.

Abstract:[Objective] The main component of agricultural mulch film is polyethylene. Because it is difficult to be degraded, its waste often causes "white pollution". In this study, polyethylene degrading bacteria were screened from the soil covered with agricultural mulch all the year round, and the degradation efficiency of polyethylene products was also explored. [Methods] Polyethylene-degrading bacteria were enriched, screened and purified using the inorganic salt medium with polyethylene as the sole carbon source. The isolated bacteria were identified by colony, morphological staining, physiological and biochemical characteristics and 16S rRNA gene phylogenetic analysis. The growth curves of isolated strain were detected under different concentrations (0, 0.05%, 0.10% 0.25%, 0.50%, 1%, 2% and 3%) of polyethylene. Finally, the biodegradation of the agricultural mulch film was detected using scanning electron microscopy and light microscopy. [Results] A strain (named as SW1) which could degrade polyethylene was isolated from soil and identified as of Nocardia sp. The growth of SW1 was dependent on the concentration of polyethylene. It grew fastest in the inorganic salt medium containing 2% polyethylene. At 48 h, the concentration of the bacterial solution began to increase; at 60 h, it reached the maximum. Meanwhile, no growth was found in the inorganic salt medium without polyethylene. In the inorganic salt medium containing agricultural mulch film, after culture at 35℃ for 15 d, a large number of bacteria were observed to be embedded in the film or attached to the surface of the film by scanning electron microscopy, the surface of the film was rough, and began to be damaged. After culture for 60 d, the membrane of the inoculated group was damaged in a large area and cavity appeared. [Conclusion] Nocardia sp. SW1 isolated from farm soil can degrade polyethylene products effectively. This study enriches the degradation microbial resources of polyethylene products, and provides scientific data and reference for the biodegradation of polyethylene plastic waste.

Abstract:Polycyclic aromatic hydrocarbons (PAHs) are harmful persistent organic pollutants and extremely detrimental to the ecological environment and human health. Biodegradation represents the major route to remove PAHs and other organic chemicals from contaminated environments. Many aerobic bacteria capable of PAHs degradation have been isolated and characterized. However, little is known about their fate in the absence of oxygen. There is an increasing number of investigations of anaerobic degradation of PAHs under various reducing conditions. This paper reviews recent studies of the anaerobic PAHs-biodegradation and identifies limitations that block our understanding of this process. Strategies that can be used to promote the biodegradation efficiency are also discussed.

Abstract:The National Natural Science Foundation of China (NSFC) supports basic research on RNA virus. The projects include virus tracing, structure and function, genetics and evolution, as well as, interaction with the host. The research reveals the material basis and mechanism of virus production, transmission and pathogenicity. It provides a theoretical basis for disease diagnosis, prevention and treatment. This article mainly counts the status of projects funded by NSFC in terms of project types, talent training and funding achievements, etc. It analyzes the problems of project funding in the field and attempts to provide suggestions for future development.