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The study was designed to explore the efficiency of magnetite nanoparticles (Fe3O4 NPs)/bacterial cell assembly to biodegrade lignin and lignocellulose, decontaminate pulp and paper-contaminated wastewater and optimize lignin adsorption by Fe3O4 NPs. Water samples were collected from three paper and carton manufacturing companies, Alexandria Governorate, Egypt. Pseudomonas otitidis MCC10330, the most active and promising strain among 10 previously screened indigenous and exogenous isolates, was selected and decorated with magnetic Fe3O4 Nanoparticles, that were prepared by the co-precipitation method, characterized and used to decontaminate paper and pulp effluent in a batch mode bioassay for 4 h. Fe3O4 NPs/bacterial cell assembly achieved the highest removals (64.1, 52.0, 54.3 and 66.6%) of TSS, COD, BOD, and Total Tannin and Lignin after 1, 4 and 4 h, reaching residual concentrations (RCs) of 322, 216, 112 and 7 mg/L, which are still slightly higher (5.35, 2.7 and 1.86-fold) than their maximum permissible limits (MPLs), respectively. RCs of pH, DO and TDS in the treated effluent are accepted for safe discharging. Maximum lignin adsorption and removal (82.14%) using Fe3O4 NPs was achieved at the optimized conditions (pH 6, Fe3O4 NPs dosage of 100 mg and 10 min contact time). Results confirmed that the proposed magnetite-coated Pseudomonas otitidis treatment system is highly efficient and recommended to treat the highly contaminated pulp and paper wastewater. Also, as far as we know, this integrated assemblage is the first time to be used as a novel, very promising, eco-friendly, renewable and economical biotechnological approach to minimize/eliminate the involved pollutants with the least running time. [ABSTRACT FROM AUTHOR]

The ability of some white rot basidiomycetes to remove lignin selectively from wood indicates that low molecular weight oxidants have a role in ligninolysis. These oxidants are likely free radicals generated by fungal peroxidases from compounds in the biodegrading wood. Past work supports a role for manganese peroxidases (MnPs) in the production of ligninolytic oxidants from fungal membrane lipids. However, the fatty acid alkylperoxyl radicals initially formed during this process are not reactive enough to attack the major structures in lignin. Here, we evaluate the hypothesis that the peroxidation of fatty aldehydes might provide a source of more reactive acylperoxyl radicals. We found that Gelatoporia subvermispora produced trans-2-nonenal, trans-2-octenal, and n-hexanal (a likely metabolite of trans-2,4-decadienal) during the incipient decay of aspen wood. Fungal fatty aldehydes supported the in vitro oxidation by MnPs of a nonphenolic lignin model dimer, and also of the monomeric model veratryl alcohol. Experiments with the latter compound showed that the reactions were partially inhibited by oxalate, the chelator that white rot fungi employ to detach Mn3+ from the MnP active site, but nevertheless proceeded at its physiological concentration of 1 mM. The addition of catalase was inhibitory, which suggests that the standard MnP catalytic cycle is involved in the oxidation of aldehydes. MnP oxidized trans-2-nonenal quantitatively to trans-2-nonenoic acid with the consumption of one O2 equivalent. The data suggest that when Mn3+ remains associated with MnP, it can oxidize aldehydes to their acyl radicals, and the latter subsequently add O2 to become ligninolytic acylperoxyl radicals. IMPORTANCE The biodegradation of lignin by white rot fungi is essential for the natural recycling of plant biomass and has useful applications in lignocellulose bioprocessing. Although fungal peroxidases have a key role in ligninolysis, past work indicates that biodegradation is initiated by smaller, as yet unidentified oxidants that can infiltrate the substrate. Here, we present evidence that the peroxidase-catalyzed oxidation of naturally occurring fungal aldehydes may provide a source of ligninolytic free radical oxidants. [ABSTRACT FROM AUTHOR]

Pure cellulose nanofibers (CNFs) rapidly degrade in soil, limiting their prospective applications in agriculture. We incorporated lignin into CNFs as an antimicrobial and crosslinking agent to control the biodegradation rate. CNFs with different lignin concentrations were prepared by mechanochemical treatment in the presence of choline chloride-urea deep eutectic solvent. These were characterized using conductometric titration, scanning electron microscopy, and FT-IR. The fibers were applied to soil to determine the effect of lignin on soil respiration and nanocellulose degradation, and were used as a substrate for radish and cress seed germination. Modifying the lignin content of the fibers successfully modulated the biodegradation rate in soil. Fibers containing 35% lignin degraded 5.7% in 14 days, while fibers with 20% lignin degraded 20.8% in 14 days. Nanofiber suspensions showed low chemical inhibition for the germination of radish and cress seeds but higher lignin contents reduced the imbibition rate as a seed coating. This study presents the first use of lignin to control the biodegradation rate of cellulose nanofibers in a one-pot, scalable and sustainable system, allowing the advancement of lignocellulose nanofibers for applications such as seed coatings, mulches, and controlled release fertilizers. [ABSTRACT FROM AUTHOR]

Laccase is a copper-containing oxidase enzyme that is present in many microorganisms, plants, and fungi. It plays an important role in the biodegradation of lignin and is known as a lignin-modifying enzyme. Due to the irregular structure of lignin molecules, laccase can utilize a wide range of substrates, such as toxic substances and antibiotics. In this study, laccase from Streptomyces sp. CS29 was studied for properties including optimal pH and temperature, as well as its stability. The effects of some chemicals, metal ions, and organic solvents on laccase activity were also examined. We found that the tested metal ions had different effects on laccase activity. It was observed that 10 and 20 mM Ca2+, 20 mM Zn2+, and 10 mM K+ increased laccase activity, while 10 and 20 mM Fe2+ inhibited it. Laccase activity was also inhibited by 100 mM EDTA and urea but was activated by 50 and 100 mM SDS. Finally, 20% of organic solvents, including ethanol, ethyl acetate, DMSO, acetone, and methanol, decreased laccase activity. Additionally, the crude laccase was tested for sulfamethoxazole degradation. The optimal pH for sulfamethoxazole degradation was pH 3.0 with a 97.90% degradation rate. Furthermore, we used the three-dimensional structure of laccase, obtained from whole genome sequencing data, to investigate the molecular interactions between laccase and sulfamethoxazole. The results of the computational study supported the wet lab experiments in which sulfamethoxazole was degraded by laccase sufficiently. Overall, the results suggest that laccase from Streptomyces sp. CS29 has potential for utilization in bioremediation or environmental biotechnology applications. [ABSTRACT FROM AUTHOR]

Low lignin solubility in aqueous solution is one of the major bottlenecks for lignin biodegradation and bioconversion. Alkaline solution contributes to improving lignin solubility, whereas most microbes can not survive in alkaline conditions. Herein, lignin dissolution behaviors in different pH solutions were systematically investigated, which indicated that solution pH above 10.5 contributed to high solubility of alkali lignin. To match with alkaline lignin aqueous system, several alkali-tolerant ligninolytic bacteria were isolated, most of which are distinct to previously reported ones. Then, the ligninolytic capabilities of these isolates were assessed in different pH conditions by determining their assimilation on alkali lignin, lignin-derived monomers and dimers, their decolorization capabilities, and their lignin peroxidase activities. Thereafter, the underlying ligninolytic and alkali-tolerant mechanisms of Sutcliffiella sp. NC1, an alkalophilic bacterium, was analyzed on the basis of its genome information. The results not only provide valuable information for lignin biodegradation and lignin valorization, but also expand knowledge on alkali-tolerant bacteria.

Lignin recalcitrance is a key issue in producing value-added products from lignocellulose biomass. In situ biodegradable lignin-modifying enzymes-producing bacteria are considered a suitable solution to lignin biodegradation problems, but exploitation of ligninolytic bacteria is still limited to date. Hence, this study aimed to isolate and characterize potential lignin peroxidase ligninolytic bacteria from decomposing soil, sawdust, and cow dung at Richard Bay, South Africa. The samples were collected and cultured in the lignin-enriched medium. Pure isolated colonies were characterized through 16S rRNA gene sequencing. The ability of the isolates to grow and utilize aromatic monomers (veratryl and guaiacol alcohol) and decolorize lignin-like dyes (Azure B, Congo Red, Remazol Brilliant Blue R) was evaluated. Of the twenty-six (26) bacteria isolates 10 isolates, including Pseudomonas spp. (88%), Enterobacter spp. (8%), and Escherichia coli (4%) were identified as true lignin peroxidase producers. Pseudomonas aeruginosa (CP031449.2) and E. coli (LR025096.1) exhibited the highest ligninolytic activities. These isolates could potentially be exploited in the industry and wastewater treatment as effective lignin degrading agents. [ABSTRACT FROM AUTHOR]

Lignin peroxidase is one of a series of enzymes involved in lignin degradation and is secreted by white-rot fungi. However, white-rot fungi have a long growth cycle and low enzyme activity, which limits their application. An efficient and stable heterologous expression system might be the solution to overcome these critical limitations. In this study, the lignin peroxidase gene of white-rot fungus (Phanerodontia chrysosporium) was cloned and heterologously expressed in the food-grade yeast Cyberlindnera jadinii for the first time. The strain ZHMX4 expressing lignin peroxidase was constructed, and its genetic stability, enzyme activity and phenotypic analysis were evaluated. ZHMX4 retained and maintained genetic stability for up to 100 generations. Its lignin peroxidase activity reached a maximum at 96 h with 68.52 U/L. Phenotypic analysis (Biolog) showed obvious changes in the substrate metabolism of the engineered strain compared to Cyberlindnera jadinii. Thus, ZHMX4 is a food-grade genetically engineered strain with great potential for lignin degradation. This study successfully expressed lignin peroxidase in Cyberlindnera jadinii as a new approach for the biodegradation of lignin. These findings should be useful for further academic studies, industrial applications of lignin peroxidase and construction of artificial white-rot fungi. [ABSTRACT FROM AUTHOR]

The difficulty of degrading lignin is the main factor limiting the high-value conversion process of lignocellulosic biomass. The biodegradation of lignin has attracted much attention because of its strong environmental friendliness, but it still faces some dilemmas such as slow degradation rate and poor adaptability. The microbial consortia with high lignin degradation efficiency and strong environmental adaptability were obtained in our previous research. To further increase the lignin degradation efficiency, this paper proposes a composite treatment technology of steam explosion combined with microbial consortium degradation to treat three kinds of biomass. We measured the lignin degradation efficiency, selectivity value (SV) and enzymatic saccharification efficiency. The structural changes of the biomass materials and microbial consortium structure were also investigated. The experimental results showed that after 1.6 MPa steam explosion treatment, the lignin degradation efficiency of the eucalyptus root reached 35.35% on the 7th days by microbial consortium. At the same time, the lignin degradation efficiency of the bagasse and corn straw treated by steam explosion followed by microbial biotreatment was 37.61–44.24%, respectively, after only 7 days of biotreatment. The microbial consortium also showed strong selectivity degradation to lignin. The composite treatment technology can significantly improve the enzymatic saccharification efficiency. Saccharomycetales, Ralstonia and Pseudomonadaceae were the dominant microorganisms in the biomass degradation systems. It was proved that the combined treatment technology of steam explosion and microbial consortium degradation could overcome the drawbacks of traditional microbial pretreatment technology, and can facilitate the subsequent high-value conversion of lignocellulose. [ABSTRACT FROM AUTHOR]

ABSTRACT Terrestrial organic carbon such as lignin is an important component of the global marine carbon. However, the structural complexity and recalcitrant nature of lignin are deemed challenging for biodegradation. It has been speculated that bacteria play important roles in lignin degradation in the marine system. However, the extent of the involvement of marine microorganisms in lignin degradation and their contribution to the oceanic carbon cycle remains elusive. In this study, two bacterial consortia capable of degrading alkali lignin (a model compound of lignin), designated LIG-B and LIG-S, were enriched from the nearshore sediments of the East and South China Seas. Consortia LIG-B and LIG-S mainly comprised of the Proteobacteria phylum with Nitratireductor sp. (71.6%) and Halomonas sp. (91.6%), respectively. Lignin degradation was found more favorable in consortium LIG-B (max 57%) than in LIG-S (max 18%). Ligninolytic enzymes laccase (Lac), manganese peroxidase (MnP), and lignin peroxidase (LiP) capable of decomposing lignin into smaller fragments were all active in both consortia. The newly emerged low-molecular-weight aromatics, organic acids, and other lignin-derived compounds in biotreated alkali lignin also evidently showed the depolymerization of lignin by both consortia. The lignin degradation pathways reconstructed from consortium LIG-S were found to be more comprehensive compared to consortium LIG-B. It was further revealed that catabolic genes, involved in the degradation of lignin and its derivatives through multiple pathways via protocatechuate and catechol, are present not only in lignin-degrading consortia LIG-B and LIG-S but also in 783 publicly available metagenomic-assembled genomes from nine nearshore regions. IMPORTANCE Numerous terrigenous lignin-containing plant materials are constantly discharged from rivers and estuaries into the marine system. However, only low levels of terrigenous organic carbon, especially lignin, are detected in the global marine system due to the abundance of active heterotrophic microorganisms driving the carbon cycle. Simultaneously, the lack of knowledge on lignin biodegradation has hindered our understanding of the oceanic carbon cycle. Moreover, bacteria have been speculated to play important roles in the marine lignin biodegradation. Here, we enriched two bacterial consortia from nearshore sediments capable of utilizing alkali lignin for cell growth while degrading it into smaller molecules and reconstructed the lignin degradation network. In particular, this study highlights that marine microorganisms in nearshore regions mostly undergo similar pathways using protocatechuate and catechol as ring-cleavage substrates to drive lignin degradation as part of the oceanic carbon cycle, regardless of whether they are in sediments or water column.

The extensive use of azo dyes by the global textile industry induces significant environmental and human health hazards, which makes efficient remediation crucial but also challenging. Improving dye removal efficiency will benefit the development of bioremediation techniques for textile effluents. In this study, an efficient system for azo dye (Direct Red 5B, DR5B) biodecolorization is reported, which uses the white-rot fungus Ganoderma lucidum EN2 and alkali lignin. This study suggests that the decolorization of DR5B could be effectively enhanced (from 40.34% to 95.16%) within 48 h in the presence of alkali lignin. The dye adsorption test further confirmed that the alkali-lignin-enhanced decolorization of DR5B was essentially due to biodegradation rather than physical adsorption, evaluating the role of alkali lignin in the dye biodegradation system. Moreover, the gas chromatography/mass spectrometry analysis and DR5B decolorization experiments also indicated that alkali lignin carried an excellent potential for promoting dye decolorization and displayed a significant role in improving the activity of lignin-modifying enzymes. This was mainly because of the laccase–mediator system, which was established by the induced laccase activity and lignin-derived small aromatic compounds. [ABSTRACT FROM AUTHOR]

Lignocellulosic crop waste is the world's most abundant renewable raw material. Its burning leads to the loss of an energy valuable resource and causes enormous environmental damage. An environmentally friendly and promising biotechnological process for such waste utilization is the production of mushrooms for food and medicine. However, the energy intensity of substrate preparation hinders the development of work in this direction. Another significant challenge in this field is to increase the biological efficiency of substrate processing. The purpose of our investigation was to reveal the contribution of microorganisms to solving this and other problems of mushroom cultivation based on a review of the latest scientific research on the topic. The literature from databases of Google Scholar, Scopus, and Web of Science was selected by various combinations of search queries concerning mushrooms, substrates, microbial communities, and their effects. The current state of the issue of mushrooms and microorganisms' interactions is presented. The review considers in detail the contribution of microorganisms to the substrate preparation, describes microbial communities in various phases of the mushroom cultivation process, and identifies the main groups of microorganisms associated with lignocellulose degradation, mushroom growth promotion, and protection against pathogens. The significant contribution of bacteria to mushroom cultivation is shown. The review demonstrates that the contribution of bacteria to lignin degradation in lignocellulosic substrates during mushroom cultivation is largely underestimated. In this process, various genera of the bacterial phyla Bacillota, Pseudomonadota, and Actinomycetota are involved. The correct combinations of microorganisms can provide controllability of the entire cultivation process and increase required indicators. However, expanding research in this direction is necessary to remove gaps in understanding the relationship between microorganisms and mushrooms. [ABSTRACT FROM AUTHOR]

Lignin is the most abundant source of renewable aromatic biopolymers and its valorization presents significant value for biorefinery sustainability, which promotes the utilization of renewable resources. However, it is challenging to fully convert the structurally complex, heterogeneous, and recalcitrant lignin into high-value products. The in-depth research on the lignin degradation mechanism, microbial metabolic pathways, and rational design of new systems using synthetic biology have significantly accelerated the development of lignin valorization. This review summarizes the key enzymes involved in lignin depolymerization, the mechanisms of microbial lignin conversion, and the lignin valorization application with integrated systems and synthetic biology. Current challenges and future strategies to further study lignin biodegradation and the trends of lignin valorization are also discussed. Lignin-degrading modifying enzymes/auxiliary enzymes are useful biocatalysts for lignin depolymerization. LPMOs may be involved in lignin biodegradation as lignin-degrading auxiliary enzymes, expanding our knowledge of LPMO function. The aromatics metabolic upper pathways and central pathways of bacteria are the key mechanisms for biological funneling of lignin-derived aromatics and lignin valorization. Tricarboxylic acid cycle-based lignin transformation approaches eliminate the dependence on the chassis strain's inherent metabolic features and expand the types of lignin valorization. Intelligent design and integration of lignin depolymerization, aromatic metabolic pathways, and conversion processes are effective methods of microbial lignin valorization. [ABSTRACT FROM AUTHOR]

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. [Display omitted] [ABSTRACT FROM AUTHOR]

Bio-depolymerized the lignin macromolecules into low molecular lignin-derived aromatic compounds satisfies the requirement for carbon dioxide peaking and is also one of the important ways to realize lignin valorization. Coriolopsis trogii is a kind of less reported lignin-degrading white-rot fungus. The degradability of a self-isolated C. trogii TS01 on industrial lignins, including enzymatic hydrolysis lignin (EHL) and Kraft lignin (KL), was investigated in this paper. The results indicated that EHL could be used as an efficient carbon source to promote the cell growth and ligninolytic enzyme secretion of C. trogii TS01. Compared with using 2% glucose as carbon source, 1% EHL plus 1% glucose would increase the maximum cell dry weight, laccase activity, and manganese-dependent peroxidase activity of C. trogii TS01 by 24.8%, 164.1%, and 200%, respectively. However, the cell growth and ligninolytic enzyme secretion would be significantly inhibited in the case of 1% KL plus 1% glucose used as carbon source. As a result, at the 12th day of fermentation, the degradation rates of EHL and KL were 50.6% and 5.7%, respectively. The UV and FTIR analysis indicated that after been fermented by C. trogii TS01, S-unit content in EHL was decreased by 12.5% but G-unit content was increased by 53.7%. In conclusion, the research of this paper will provide a promising solution for the valorization of enzymatic hydrolysis lignin since the high biodegradation rate of lignin and high activity of ligninolytic enzymes could be achieved simultaneously. [ABSTRACT FROM AUTHOR]

Large quantities of lignin are produced as by-streams via chemical pulping and emerging biorefinery processes. These lignins are typically waterinsoluble; however, they can be converted into a water-soluble form by chemical modifications. A novel LigniOx technology solubilizes lignin using alkali-O2 oxidation. The product can be used for bio-based dispersants. This study evaluated the biodegradability of alkali-O2 oxidized kraft, organosolv, and hydrolysis lignin. The oxidized lignins exhibited higher biodegradation in soil and in aquatic environments in comparison to a commercial kraft lignin and a commercial lignosulfonate. In soil, the biodegradabilities of oxidized lignins were 19 to 44%, whereas the reference lignins exhibited only 5 to 12% conversion to CO2. Biodegradation of the oxidized lignins and references in the aquatic environment increased in a similar order as in the soil environment, although the degradation in each sample was slightly smaller than in the soil. The improved biodegradability of the oxidized lignins was due to the altered chemical structure of lignin. Compared to the untreated lignin, the oxidized lignin contained structures formed in aromatic ring opening reactions, making the lignin more accessible to microbial degradation. In addition, the oxidized lignin contained carbon originating from small organic compounds, which are easily biodegradable. [ABSTRACT FROM AUTHOR]

The unique ability of basidiomycete white rot fungi to degrade all components of plant cell walls makes them indispensable organisms in the global carbon cycle. In this study, we analyzed the proteomes of two closely related white rot fungi, Obba rivulosa and Gelatoporia subvermispora, during eight-week cultivation on solid spruce wood. Plant cell wall degrading carbohydrate-active enzymes (CAZymes) represented approximately 5% of the total proteins in both species. A core set of orthologous plant cell wall degrading CAZymes was shared between these species on spruce suggesting a conserved plant biomass degradation approach in this clade of basidiomycete fungi. However, differences in time-dependent production of plant cell wall degrading enzymes may be due to differences among initial growth rates of these species on solid spruce wood. The obtained results provide insight into specific enzymes and enzyme sets that are produced during the degradation of solid spruce wood in these fungi. These findings expand the knowledge on enzyme production in nature-mimicking conditions and may contribute to the exploitation of white rot fungi and their enzymes for biotechnological applications. [ABSTRACT FROM AUTHOR]

Lignin, a rigid polymer composed of phenolic subunits with high molecular weight and complex structure, ranks behind only cellulose in the contribution to the biomass of plants. Therefore, lignin can be used as a new environmentally friendly resource for the industrial production of a variety of polymers, dyes and adhesives. Since laccase was found to be able to degrade lignin, increasing attention had been paid to the valorization of lignin. Research has mainly focused on the identification of lignin-degrading enzymes, which play a key role in lignin biodegradation, and the potential application of lignin degradation products. In this review, we describe the source, catalytic specificity and enzyme reaction mechanism of the four classes of the lignin-degrading enzymes so far discovered. In addition, the major pathways of lignin biodegradation and the applications of the degradative products are also discussed. Lignin-degrading bacteria or enzymes can be used in combination with chemical pretreatment for the production of value-added chemicals from lignin, providing a promising strategy for lignin valorization. [ABSTRACT FROM AUTHOR]

Lignin peroxidase (LiP), which has been studied extensively in white-rot basidiomycetes and their potential to degrade dyes from textile wastewater, plays a role in the biodegradation of lignin from pulp and paper industry wastewater, as well as agricultural waste. Lignin peroxidase (LsLiP) was successfully purified from the newly isolated Lentinus squarrosulus MPN12 with a 47.1-fold purification and a 15.7% yield. After 48 h-incubation, LsLiP was able to decolorize all tested dyes up to 92% for Acid Blue 62 (NY3), followed by Porocion Brilliant blue HGR (PB, 73.5%), Acid Blue 281 (NY5, 70.5%), Acid Blue 113 (IN13, 61%), Acid red 266 (NY7, 56%), and 34.5% for Acid red 299 (NY1), compared to the negative control with the heat-denatured enzyme. The biodegradation potential of LsLiP was further suggested by the change of lignin structure based on Fourier transform infrared (FTIR) analyses. Lignin structure was noticeably changed before and after LsLiP treatment, especially in the fingerprint regions (1600 to 1000 cm-1) and 2930 cm-1 corresponding to the stretching vibrations of various groups in lignin. Thus, LsLiP has potential application in both enzyme-based decolorization of synthetic dyes and lignin biodegradation. [ABSTRACT FROM AUTHOR]

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Abstract Background As one of the major components of lignocellulosic biomass, lignin has been considered as the most abundant renewable aromatic feedstock in the world. Comparing with thermal or catalytic strategies for lignin degradation, biological conversion is a promising approach featuring with mild conditions and diversity, and has received great attention nowadays. Results In this study, a consortium of white rot fungi composed of Lenzites betulina and Trametes versicolor was employed to enhance the ligninolytic enzyme activity of laccase (Lac) and manganese peroxidase (MnP) under microbial synergism. The maximum enzymatic activity of Lac and MnP was individually 18.06 U mL−1 and 13.58 U mL−1 along with a lignin degradation rate of 50% (wt/wt), which were achieved from batch cultivation of the consortium. The activities of Lac and MnP obtained from the consortium were both improved more than 40%, as compared with monocultures of L. betulina or T. versicolor under the same culture condition. The enhanced biodegradation performance was in accordance with the results observed from scanning electron microscope (SEM) of lignin samples before and after biodegradation, and secondary-ion mass spectrometry (SIMS). Finally, the analysis of heteronuclear single quantum coherence (HSQC) NMR and gas chromatography–mass spectrometry (GC–MS) provided a comprehensive product mapping of the lignin biodegradation, suggesting that the lignin has undergone depolymerization of the macromolecules, side-chain cleavage, and aromatic ring-opening reactions. Conclusions Our results revealed a considerable escalation on the enzymatic activity obtained in a short period from the cultivation of the L. betulina or T. versicolor due to the enhanced microbial synergistic effects, providing a potential bioconversion route for lignin utilization.

Multicomponent systems, such as laccase cooperating with other proteins in ligninase, are able to modify the chemical structure of lignin efficiently and opens the door to potential applications. Here, an in‐depth investigation of hemoglobin‐assisted laccase oxidation of soluble lignosulfonate is carried out, using a combination of UV–visible spectroscopy, isothermal titration calorimetry, gel permeation chromatography, Raman spectroscopy, 2D nuclear magnetic resonance spectroscopy, and high‐performance liquid chromatography–mass spectrometry. Intriguingly, hemoglobin enhances the exothermically oxidative process of the laccase reaction. Product characterizations suggest that hemoglobin may preferentially reduce the ratio of guaiacyl/syringyl subunits and promote phenylcoumaran formation simultaneously. The complicated interactions among hemoglobin, laccase, and lignin make a multiple‐component reaction, suggesting that Fe‐containing macromolecules have the capacity to mediate laccase based chemical modifications of lignin. [ABSTRACT FROM AUTHOR]

Lignin is an abundant plant‐based biopolymer that has found applications in a variety of industries from construction to bioethanol production. This recalcitrant branched polymer is naturally degraded by many different species of microorganisms, including fungi and bacteria. These microbial lignin degradation mechanisms provide a host of possibilities to overcome the challenges of using harmful chemicals to degrade lignin biowaste in many industries. The classes and mechanisms of different microbial lignin degradation options available in nature form the primary focus of the present review. This review first discusses the chemical building blocks of lignin and the industrial sources and applications of this multifaceted polymer. The review further places emphasis on the degradation of lignin by natural means, discussing in detail the lignin degradation activities of various fungal and bacterial species. The lignin‐degrading enzymes produced by various microbial species, specifically white‐rot fungi, brown‐rot fungi, and bacteria, are described. In the end, possible directions for future lignin biodegradation applications and research investigations have been provided. [ABSTRACT FROM AUTHOR]

Background: Lignin is a complex polymer of phenyl propanoid units found in the vascular tissues of the plants as one of lignocellulose materials. Many bacteria secrete enzymes to lyse lignin, which can be essential to ease the production of bioethanol. Current research focused on the study of ligninolytic bacteria capable of producing lignin peroxidase (LiP) which can help in lignin biodegradation and bioethanol production. Ligninolytic bacterial strains were isolated and screened from the soil samples of Simlipal Biosphere Reserve (SBR), Odisha (India), for the determination of their LiP activity. Enzymatic assay and optimization for the LiP activity were performed with the most potent bacterial strain. The strain was identified by morphological, biochemical, and molecular methods. Results: In this study, a total of 16 bacteria (Simlipal ligninolytic bacteria [SLB] 1–16) were isolated from forest soils of SBR using minimal salt medium containing lignin. Out of the 16 isolates, 9 isolates showed decolourization of methylene blue dye on LB agar plates. The bacterial isolates such as SLB8, SLB9, and SLB10 were able to decolourize lignin with 15.51%, 16.80%, and 33.02%, respectively. Further enzyme assay was performed using H2O2 as substrate and methylene blue as an indicator for these three bacterial strains in lignin containing minimal salt medium where the isolate SLB10 showed the highest LiP activity (31.711 U/mg). The most potent strain, SLB10, was optimized for enhanced LiP enzyme activity using response surface methodology. In the optimized condition of pH 10.5, temperature 30 °C, H2O2 concentration 0.115 mM, and time 42 h, SLB10 showed a maximum LiP activity of 55.947 U/mg with an increase of 1.76 times from un-optimized condition. Further chemical optimization was performed, and maximum LiP activity as well as significant dye-decolourization efficiency of SLB10 has been found in bacterial growth medium supplemented individually with cellulose, yeast extract, and MnSO4. Most notably, yeast extract and MnSO4-supplemented bacterial culture medium were shown to have even higher percentage of dye decolourization compared to normal basal medium. The bacterial strain SLB10 was identified as Bacillus mycoides according to morphological, biochemical, and molecular (16S rRNA sequencing) characterization and phylogenetic tree analysis. Conclusion: Result from the present study revealed the potential of Bacillus mycoides bacterium isolated from the forest soil of SBR in producing LiP enzyme that can be evaluated further for application in lignin biodegradation and bioethanol production. Scaling up of LiP production from this potent bacterial strain could be useful in different industrial applications. [ABSTRACT FROM AUTHOR]

Dye-decolorizing peroxidases (DyPs) are heme-containing peroxidases, which have promising application in biodegradation of phenolic lignin compounds and in detoxification of dyes. In this study, the crystal structure of Bs DyP- veratryl alcohol (VA) complex delves deep into the binding of small substrate molecules within the DyP heme cavity. The biochemical analysis shows that Bs DyP oxidizes the VA with a turnover number of 0.065 s−1, followed by the oxidation of 2,6-dimethoxyphenol (DMP) and guaiacol with a comparable turnover number (k cat) of 0.07 s−1 and 0.07 s−1, respectively. Moreover, biophysical and computational studies reveal the comparable binding affinity of substrates to Bs DyP and produce lower-energy stable Bs DyP-ligand(s) complexes. All together with our previous findings, we are providing a complete structural description of substrate-binding sites in DyP. The structural insight of Bs DyP helps to modulate its engineering to enhance the activity towards the oxidation of a wide range of substrates. • The Bs DyP crystal structure has been determined in complex with veratryl alcohol. • The complex structure reveals the binding site for small substrates. • Bs DyP shows activity towards lignin model compounds. • In silico studies endorse the binding of small substrates at active site in Bs DyP. [ABSTRACT FROM AUTHOR]

The objective of this work was to optimize the culture conditions for laccase production in the presence of Kraft lignin by Fusarium oxysporum JUMAD-053, and to evaluate the biodegradation products of lignin. The fungal isolate that presented highest laccase activity had its production optimized by a statistical factorial design 3³ in 15 experimental runs. F. oxysporum presented the highest constitutive laccase titer (5.37 U/mL). Statistical factorial design demonstrated a maximum laccase titer of 9.8 U/mL when assayed against ABTS under the conditions optimized: 1.125% (w/v) yeast extract, 0.5% (w/v) Kraft lignin and 10 days of cultivation. The maximum laccase titer when assayed on DMP was 8.4 U/mL, following the conditions optimized: 1.125% yeast extract, 0.25% Kraft lignin and 7 days of cultivation. The analysis of cultures led to identification of metabolites; two being aromatic: 2,6-dimethoxy benzoic acid and sesamin; also, fumonisin and long-chain fatty acids. As a result of the study, the maximum laccase activities of 9.8 and 8.4 U/mL measured from ABTS and DMP substrates, respectively. The search shows new sources of fungal laccase for obtaining new metabolites of biodegradation from Kraft lignin in culture medium. [ABSTRACT FROM AUTHOR]

Background: As one of the major components of lignocellulosic biomass, lignin has been considered as the most abundant renewable aromatic feedstock in the world. Comparing with thermal or catalytic strategies for lignin degradation, biological conversion is a promising approach featuring with mild conditions and diversity, and has received great attention nowadays. Results: In this study, a consortium of white rot fungi composed of Lenzites betulina and Trametes versicolor was employed to enhance the ligninolytic enzyme activity of laccase (Lac) and manganese peroxidase (MnP) under microbial synergism. The maximum enzymatic activity of Lac and MnP was individually 18.06 U mL−1 and 13.58 U mL−1 along with a lignin degradation rate of 50% (wt/wt), which were achieved from batch cultivation of the consortium. The activities of Lac and MnP obtained from the consortium were both improved more than 40%, as compared with monocultures of L. betulina or T. versicolor under the same culture condition. The enhanced biodegradation performance was in accordance with the results observed from scanning electron microscope (SEM) of lignin samples before and after biodegradation, and secondary-ion mass spectrometry (SIMS). Finally, the analysis of heteronuclear single quantum coherence (HSQC) NMR and gas chromatography–mass spectrometry (GC–MS) provided a comprehensive product mapping of the lignin biodegradation, suggesting that the lignin has undergone depolymerization of the macromolecules, side-chain cleavage, and aromatic ring-opening reactions. Conclusions: Our results revealed a considerable escalation on the enzymatic activity obtained in a short period from the cultivation of the L. betulina or T. versicolor due to the enhanced microbial synergistic effects, providing a potential bioconversion route for lignin utilization. [ABSTRACT FROM AUTHOR]

Abstract Background The white rot fungus Phlebia radiata, a type species of the genus Phlebia, is an efficient decomposer of plant cell wall polysaccharides, modifier of softwood and hardwood lignin, and is able to produce ethanol from various waste lignocellulose substrates. Thus, P. radiata is a promising organism for biotechnological applications aiming at sustainable utilization of plant biomass. Here we report the genome sequence of P. radiata isolate 79 originally isolated from decayed alder wood in South Finland. To better understand the evolution of wood decay mechanisms in this fungus and the Polyporales phlebioid clade, gene content and clustering of genes encoding specific carbohydrate-active enzymes (CAZymes) in seven closely related fungal species was investigated. In addition, other genes encoding proteins reflecting the fungal lifestyle including peptidases, transporters, small secreted proteins and genes involved in secondary metabolism were identified in the genome assembly of P. radiata. Results The PACBio sequenced nuclear genome of P. radiata was assembled to 93 contigs with 72X sequencing coverage and annotated, revealing a dense genome of 40.4 Mbp with approximately 14 082 predicted protein-coding genes. According to functional annotation, the genome harbors 209 glycoside hydrolase, 27 carbohydrate esterase, 8 polysaccharide lyase, and over 70 auxiliary redox enzyme-encoding genes. Comparisons with the genomes of other phlebioid fungi revealed shared and specific properties among the species with seemingly similar saprobic wood-decay lifestyles. Clustering of especially GH10 and AA9 enzyme-encoding genes according to genomic localization was discovered to be conserved among the phlebioid species. In P. radiata genome, a rich repertoire of genes involved in the production of secondary metabolites was recognized. In addition, 49 genes encoding predicted ABC proteins were identified in P. radiata genome together with 336 genes encoding peptidases, and 430 genes encoding small secreted proteins. Conclusions The genome assembly of P. radiata contains wide array of carbohydrate polymer attacking CAZyme and oxidoreductase genes in a composition identifiable for phlebioid white rot lifestyle in wood decomposition, and may thus serve as reference for further studies. Comparative genomics also contributed to enlightening fungal decay mechanisms in conversion and cycling of recalcitrant organic carbon in the forest ecosystems.

The unique ability of basidiomycete white rot fungi to degrade all components of plant cell walls makes them indispensable organisms in the global carbon cycle. In this study, we analyzed the proteomes of two closely related white rot fungi, Obba rivulosa and Gelatoporia subvermispora, during eight-week cultivation on solid spruce wood. Plant cell wall degrading carbohydrate-active enzymes (CAZymes) represented approximately 5% of the total proteins in both species. A core set of orthologous plant cell wall degrading CAZymes was shared between these species on spruce suggesting a conserved plant biomass degradation approach in this clade of basidiomycete fungi. However, differences in time-dependent production of plant cell wall degrading enzymes may be due to differences among initial growth rates of these species on solid spruce wood. The obtained results provide insight into specific enzymes and enzyme sets that are produced during the degradation of solid spruce wood in these fungi. These findings expand the knowledge on enzyme production in nature-mimicking conditions and may contribute to the exploitation of white rot fungi and their enzymes for biotechnological applications.

Lignin bio-valorization is an emerging field of applied biotechnology and has not yet been studied at low temperatures. Paraburkholderia aromaticivorans AR20-38 was examined for its potential to degrade six selected lignin monomers (syringic acid, p-coumaric acid, 4-hydroxybenzoic acid, ferulic acid, vanillic acid, benzoic acid) from different upper funneling aromatic pathways. The strain degraded four of these compounds at 10°C, 20°C, and 30°C; syringic acid and vanillic acid were not utilized as sole carbon source. The degradation of 5 mM and 10 mM ferulic acid was accompanied by the stable accumulation of high amounts of the value-added product vanillic acid (85–89% molar yield; 760 and 1540 mg l−1, respectively) over the whole temperature range tested. The presence of essential genes required for reactions in the upper funneling pathways was confirmed in the genome. This is the first report on biodegradation of lignin monomers and the stable vanillic acid production at low and moderate temperatures by P. aromaticivorans. Key points: • Paraburkholderia aromaticivorans AR20-38 successfully degrades four lignin monomers. • Successful degradation study at low (10°C) and moderate temperatures (20–30°C). • Biotechnological value: high yield of vanillic acid produced from ferulic acid. [ABSTRACT FROM AUTHOR]

Abstract Background The white rot fungus Irpex lacteus exhibits a great potential in biopretreatment of lignocellulose as well as in biodegradation of xenobiotic compounds by extracellular ligninolytic enzymes. Among these enzymes, the possible involvement of dye-decolorizing peroxidase (DyP) in lignin degradation is not clear yet. Results Based on the extracellular enzyme activities and secretome analysis, I. lacteus CD2 produced DyPs as the main ligninolytic enzymes when grown in Kirk’s medium supplemented with lignin. Further transcriptome analysis revealed that induced transcription of genes encoding DyPs was accompanied by the increased expression of transcripts for H2O2-generating enzymes such as alcohol oxidase, pyranose 2-oxidase, and glyoxal oxidases. Meanwhile, accumulation of transcripts for glycoside hydrolase and protease was observed, in agreement with abundant proteins. Moreover, the biochemical analysis of IlDyP2 and IlDyP1 confirmed that DyPs were able to catalyze the oxidation of typical peroxidases substrates ABTS, phenolic lignin compounds DMP, and guaiacol as well as non-phenolic lignin compound, veratryl alcohol. More importantly, IlDyP1 enhanced catalytic activity for veratryl alcohol oxidation in the presence of mediator 1-hydroxybenzotriazole, which was similar to the laccase/1-hydroxybenzotriazole system. Conclusions The results proved for the first time that DyPs depolymerized lignin individually, combining catalytic features of different peroxidases on the functional level. Therefore, DyPs may be considered an important part of ligninolytic system in wood-decaying fungi.

Syringate and vanillate are the major metabolites of lignin biodegradation. In Sphingobium sp. strain SYK-6, syringate is O demethylated to gallate by consecutive reactions catalyzed by DesA and LigM, and vanillate is O demethylated to protocatechuate by a reaction catalyzed by LigM. The gallate ring is cleaved by DesB, and protocatechuate is catabolized via the protocatechuate 4,5-cleavage pathway. The transcriptions of desA, ligM, and desB are induced by syringate and vanillate, while those of ligM and desB are negatively regulated by the MarR-type transcriptional regulator DesR, which is not involved in desA regulation. Here, we clarified the regulatory system for desA transcription by analyzing the IclR-type transcriptional regulator desX, located downstream of desA. Quantitative reverse transcription (RT)-PCR analyses of a desX mutant indicated that the transcription of desA was negatively regulated by DesX. In contrast, DesX was not involved in the regulation of ligM and desB. The ferulate catabolism genes (ferBA), under the control of a MarR-type transcriptional regulator, FerC, are located upstream of desA. RT-PCR analyses suggested that the ferB-ferA-SLG_25010-desA gene cluster consists of the ferBA operon and the SLG_25010-desA operon. Promoter assays revealed that a syringateand vanillate-inducible promoter is located upstream of SLG_25010. Purified DesX bound to this promoter region, which overlaps an 18-bp inverted-repeat sequence that appears to be essential for the DNA binding of DesX. Syringate and vanillate inhibited the DNA binding of DesX, indicating that the compounds are effector molecules of DesX. [ABSTRACT FROM AUTHOR]

A recently characterized cytochrome P450 isozyme GcoA activates lignin components through a selective O‐demethylation or alternatively an acetal formation reaction. These are important reactions in biotechnology and, because lignin is readily available; it being the main component in plant cell walls. In this work we present a density functional theory study on a large active site model of GcoA to investigate syringol activation by an iron(IV)‐oxo heme cation radical oxidant (Compound I) leading to hemiacetal and acetal products. Several substrate‐binding positions were tested and full energy landscapes calculated. The study shows that substrate positioning determines the product distributions. Thus, with the phenol group pointing away from the heme, an O‐demethylation is predicted, whereas an initial hydrogen‐atom abstraction of the weak phenolic O‐H group would trigger a pathway leading to ring‐closure to form acetal products. Predictions on how to engineer P450 GcoA to get more selective product distributions are given. [ABSTRACT FROM AUTHOR]

The production of adhesive from sugar cane bagasse was performed in this study. The goal of this investigation was optimization of wallpaper adhesive production from sugar cane bagasse cellulose by experiments which were designed by full factorial method and carried out in a lab scale reactor with variations in reaction condition such as temperature, catalyst and feed concentration. The analysis of the results showed that the amount and quality of produced wallpaper adhesive is related to reaction condition. The investigation results showed that the optimum condition for removal of lignin from sugar cane bagasse is occurred at ammonia solution concentration of 30 percent and temperature of 150 centigrade. Production of water soluble carbohydrate was carried out by hydrolysis of deligninificated sugarcane in sulfuric acid solution at concentrations of 72 up to 68 percent and controlled temperatures from 20 to 25 centigrade. The results of quality investigations showed that the optimum glue formulation is occurred at carbohydrate concentration of 3 percent and borax concentration of 0.2 percent. [ABSTRACT FROM AUTHOR]

Degradation of most of the lignocellulose-rich agricultural residue in the cold regions of China is limited due to the cold climate. Lignin is the main component of lignocellulose, and the effective degradation of lignin is one of the most crucial processes in degrading lignocellulose. Psychrotrophic lignin-degrading bacteria and cold adapted ligninolytic enzymes have promising potential for the degradation and transformation of lignin, which are conducive to the resource utilization of lignocelluloses and energy-saving production under cold conditions. In this study, a newly psychrotrophic bacterial strain, Arthrobacter sp. C2, was isolated. The optimal enzyme activity conditions and lignin degradation pathways of C2 were investigated using sodium lignin sulfonate as substrate. The optimal conditions for enzyme activity included an initial pH of 6.74, a temperature of 14.9 °C, an incubation time of 6.87 days, and an inoculum size of 2.24%. Under the optimal conditions, the lignin peroxidase and manganese peroxidase activities and the degradation rate reached 29.8 U/L, 56.4 U/L and 40.1%, respectively. The biodegradation products including acids, phenols, aldehydes and alcohols were analyzed by gas chromatography–mass spectrometry and Fourier transform infrared spectroscopy. Further, the potential degradation pathways were proposed according to the results obtained in this study and those presented in the relevant literature. This study not only provides valuable psychrotrophic strain resources for the sustainable utilization of lignocellulose in cold regions, but also supplies potential application options for energy-saving production of useful chemicals using cold adapted enzymes. [ABSTRACT FROM AUTHOR]

Acetylated lignin (AL) can improve compatibility with commercial plastic polymers compared to existing lignin and can be used as an effective additive for eco-friendly biocomposites. For this reason, AL can be effectively incorporated into polylactic acid (PLA)-based biocomposites, but its biodegradation properties have not been investigated. In this study, biodegradation experiments were performed under mesophilic and thermophilic conditions to determine the effect of AL addition on the biodegradation characteristics of PLA-based biocomposites. As a result, the PLA-based biocomposite showed a faster biodegradation rate in a thermophilic composting environment, which is higher than the glass transition temperature of PLA, compared to a mesophilic environment. 16S rDNA sequencing results showed that differences in microbial communities depending on mesophilic and thermophilic environments strongly affected the biodegradation rate of lignin/PLA biocomposites. Importantly, the addition of AL can effectively delay the thermophilic biodegradation of PLA biocomposites. As a result of tracking the changes in physicochemical properties according to the biodegradation period in a thermophilic composting environment, the main biodegradation mechanism of AL/PLA biocomposite hydrolysis. It proceeded with cleavage of the PLA molecular chain, preferential biodegradation of the amorphous region, and additional biodegradation of the crystalline region. Above all, adding AL can be proposed as an effective additive because it can minimize the decline in the mechanical properties of PLA and delay the biodegradation rate more effectively compared to existing kraft lignin (KL). [ABSTRACT FROM AUTHOR]

The greatest limitation to utilization of maize stover by ruminants as a feed is the high concentration of lignin, which limits fibre digestibility. However, ruminants can effectively utilize maize stover if its nutritive value is improved using white rot fungal species. This study was designed to determine optimal bio-physical conditions for mycelial growth and select the most ideal fungal species and pre-treatment options for improving nutritive value of maize stover. Four popular edible Pleurotus fungal species (viz. Pleurotus florida, Pleurotus ostreatus, Pleurotus sajor caju and Pleurotus pulmonarius) were subjected to varying temperatures, pH levels, hydrogen peroxide (H2O2) concentration and illumination to establish the extent of mycelial growth rate. Inclusion of H2O2 was used to determine optimal levels for preservation and prevention of contamination from other indigenous microbiota. Effects of pre-treatment options on chemical composition and nutritive value of maize stover were also examined. Mycelial growth rate of Pleurotus species on potato dextrose agar (PDA) varied (P

Abstract Lignocellulose is a promising sustainable alternative fuel and its decomposition is critical for the formation of sediment organic matter. The lignin of lignocellulose limits the access of enzymes to cellulose and slows down the decomposition. Therefore, the development of efficient microbial consortia to deconstruct lignin is of great interest. In this study, a 715-day in situ experiment was performed to investigate the degradation process of macrophyte Phragmites australis debris at different depths of sediments (up to 38 cm) in a eutrophic lake. Although litter mass degradation showed an obvious decreasing tendency as the depth increased, the efficiency of lignin degradation in subsurface sediments was significance higher than that in surface sediments (p < 0.05). Pyrosequencing analysis showed that the subsurface sediments contained the specific anaerobic bacteria (genus Sulfuricurvum , Clostridium and Treponema) and anaerobic fungi (phylum Chytridiomycota and Rozellomycota). These anaerobic microbes well adapted to the degradation of recalcitrant organic matter, and led to the increasing activity of lignin biodegradation in subsurface sediments. This work could help improve our understanding of lignin biodegradation and develop a potential biotechnology for efficient biofuel production. Highlights • A in situ experiment was studied the litter degradation in sediments (up to 38 cm). • Removal efficiencies of litter mass were decreased as increasing sediments depths. • Removal efficiencies of lignin were increased as increasing sediments depths. • Anoxia inhibits cellulose enzyme activity but promotes lignin enzyme activity. • Specific anaerobic microbes led to improved lignin removal in deep sediments. [ABSTRACT FROM AUTHOR]

Aims: Soil biosolarization (SBS) is a pest control technology that includes the incorporation of organic matter into soil prior to solarization. The objective of this study was to measure the impact of the initial soil microbiome on the temporal evolution of genes encoding lignocellulose‐degrading enzymes during SBS. Methods and Results: Soil biosolarization field experiments were completed using green waste (GW) as a soil amendment and in the presence and absence of compost activating inoculum. Samples were collected over time and at two different soil depths for measurement of the microbial community and the predicted lignocellulosic‐degrading microbiome. Compost inoculum had a significant positive effect on several predicted genes encoding enzymes involved in cellulose, hemicellulose and lignin degradation. These included beta‐glucosidase, endo‐1,3(4)‐beta‐glucanase, alpha‐galactosidase and laccase. Conclusion: Amendment of micro‐organisms found in compost to soil prior to SBS enhanced the degradation potential of cellulose, hemicellulose and lignin found in GW. Significance and Impact of the Study: The type of organic matter amended and its biotransformation by soil micro‐organisms impact the efficacy of SBS. The results suggest that co‐amending highly recalcitrant biomass with micro‐organisms found in compost improves biomass conversion during SBS. [ABSTRACT FROM AUTHOR]

Degradation characteristics of kraft lignin were investigated during peracetic acid (PAA) treatment at room temperature. PAA was prepared by direct mixing of acetic acid (AA) and hydrogen peroxide (HP) at different ratios. At a ratio of AA to HP of 1:1.5 (v/v), undissolved lignin content was the lowest (34.7%). Lignin-derived compounds that were produced from the initial lignin after PAA treatment were detected in the liquid fraction (EA extracts) in small quantities (< below 0.1% of initial lignin), while their species were different depending on mix ratio. It was found that degradation behavior depends on not only PAA, but also HP concentrations. Meanwhile, the lignin-derived products of EA extracts in liquid fractions showed decreased molecular weight and polydispersity compared with the initial lignin. As reaction severity increased, amounts of low-molecular weight lignin in liquid fractions increased. At room temperature, different lignin degradation behavior can be induced by controlling the mix ratio of AA and HP. [ABSTRACT FROM AUTHOR]

Abstract Lignin is currently an under-used material of the pulping and cellulosic ethanol production plants. The first and foremost objective in dealing with lignin is to augment the use of this aromatic compound and financial profitability of lignin-based processes. Of particular interests are lignin oxidation and depolymerization methods that harvest either the aromatic subunits of polymers or monomeric/oligomeric aromatic products used as platform chemicals. In this context, many studies have focused on the catalytic processes in which a nitroxyl catalyst, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), was employed to oxidize hydroxyl groups in lignin structure and selectively depolymerize lignin via cleavage of the ether and C C bonds. In discussing the advanced studies especially over the last decade on the oxidation of lignin models with TEMPO catalyst systems, this review provides a description of promising methods that can be employed for authentic lignin conversion. In the present review, a particular emphasis is dedicated to the proposed mechanisms for the oxidation of lignin and lignin models. [ABSTRACT FROM AUTHOR]

Highlights • Lignin (L) precipitated by HCl from its black liquor was used in the reactions. • L was modified by formaldehyde or tetraethyl orthosilicate (TEOS). • L and modified lignins were used as macroinitiator for ROP of caprolactone. • Low cost bio- based thermoplastics were successfully prepared. • L precipitation process had a significant effect on the copolymer structure. Abstract Lignin is the second most abundant biopolymer after cellulose. Due to its biodegradability and availability, lignin is a suitable replacement for the conventional polyol. Modification of lignin enhances its reactivity and dispersion in the polymer- based materials in order to prepare low cost lignin- based thermoplastics as an alternative for petroleum- based thermoplastics. In this study, unmodified lignin and lignin modified with silica particles and formaldehyde were used as a polyol macroinitiator for ring opening polymerization (ROP) of ε-caprolactone (CL) monomer. As a determining parameter of the polymer chain length, the molar ratio of CL to hydroxyl groups (OH) of macroinitiator was set at 5.5 or 22 for all copolymers. Decrease in the OH peak intensity and the enhancement of carbonyl peak intensity were observed in the FTIR spectra, indicating progress of the reaction between lignin or modified lignins and CL. Compared to the macroinitiators, changes in the morphology of the graft copolymers were identified by SEM. The chain structure, chain length of the grafted polycaprolactone (PCL) onto the lignin or modified lignin and percentage of the free PCL were determined using NMR analyses. Thermal properties of the synthesized lignin- based thermoplastics were investigated by DSC and TGA analyses. By decreasing the CL/OH ratio from 22 to 5.5, melt temperatures (T m) and degree of crystallinity (X c) descended from 57 °C and 70% to 55 °C and 57%, respectively. [ABSTRACT FROM AUTHOR]

Highlights • SE assist chemistry method could positively affect biomass digestibility. • SE-2.4 MPa-5%NH 3 ·H 2 O followed by EH could give 73.22% of biomass digestibility for CS. • CS rich in G- and S-monomers showed relatively high biomass saccharification. • High content of H-monomer exhibited a certain inhibitory effect in sugar release. Abstract In this study, the fermentable sugar released from cotton stalk (CS), which were pretreated by instant catapult steam explosion (SE) combined with different concentrations of strong monobasic acid (HCl), weak monobasic acid (CH 3 COOH), strong monobasic alkali (NaOH) and weak monobasic alkali (NH 3 ·H 2 O), followed by hydrolysis in cellulase/xylanase mixed enzyme solutions, were comparably investigated. The highest yield of 73.22% of fermentable sugar yield was obtained in SE-2.4 MPa-5%NH 3 ·H 2 O treated CS substrates, which was 5.14 times higher than that from enzymatic hydrolysis (EH) of raw CS. Furthermore, evaluation of monolignins content (H, G, S) in different CS samples suggested that substrates rich in guaiacyl (G) and syringyl (S) would generate a higher efficiency of enzymatic saccharification. Therefore, the slight genetic modification of monolignins for cotton stalk might be a potential way to enhance biomass degradation and transformation. [ABSTRACT FROM AUTHOR]

An aerobic, Gram-negative, non-sporulating, motile, rod-shaped and lignin-degrading bacterial strain, Pseudomonas sp. CCA1, was isolated from leaf soil collected in Japan. This strain grew at 20-45 °C (optimum 20 °C), at pH 5.0-10.0 (optimum pH 5.0), and in the presence of 2% NaCl. Its major cellular fatty acids were C16:0 and summed feature 8 (C18:1ω6c and/or C18:1ω7c). The predominant quinone system was ubiquinone-9. Comparative 16S rRNA gene sequence analysis showed that Pseudomonas sp. CCA1 was related most closely to P. citronellolis NBRC 103043T (98.9%), but multilocus sequence analysis based on fragments of the atpD, gyrA, gyrB and rpoB gene sequences showed strain CCA1 to branch separately from its most closely related Pseudomonas type strains. DNA-DNA hybridization values between Pseudomonas sp. CCA1 and type strains of closely related Pseudomonas species were less than 53%. Based on its phenotypic, chemotaxonomic and phylogenetic features, we propose that Pseudomonas sp. CCA1 represents a novel species within the genus Pseudomonas, for which the name Pseudomonas humi sp. nov. is proposed. The type strain is CCA1 (= HUT 8136T = TBRC 8616T). [ABSTRACT FROM AUTHOR]

Symbiotic bacteria in the termite gut system may play an important role in lignin degradation that can assist the subsequent saccharification process. Pseudocitrobacter anthropi MP-4, which is capable of degrading lignin components and rapidly growing on various lignin analogue dyes, was successfully screened from the gut of a wood-feeding termite Microtermes pakistanicus. Further decolorization tests with this strain showed that the strain MP-4 potentially produced some relevant extracellular enzymes to participate in lignin degradation. The removal rate of chemical oxygen demand by this strain was recorded as high as 52.1% when it was incubated in a mineral-salt medium with lignin as the sole carbon source. For the degrading process of MP-4 on lignin, it was proposed through a series of evaluations by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and pyrolysis gas chromatography/mass spectroscopy, that the lignin degradation mechanism of the strain MP-4 would primarily include the cleavage of various chemical linkages and the demethylation reactions. This resulted in a change in the S/G ratio and the disappearance of the biphenyl structure in the lignin components. Thus, these findings suggested that the strain MP-4 uniquely presented an attractive capability to deconstruct lignin components from biomass, which may be potentially valuable for a future industrial exploration. [ABSTRACT FROM AUTHOR]

A strain of Bacillus bacteria, which was able to increase the molecular weight (M) of black liquor (BL) lignin through polymerization, enabling the subsequent industrial use of lignin, was isolated and characterized. This study is believed to be the first time that actual bacteria cells, rather than pure laccase, have been used to polymerize BL lignin. Black liquor is a toxic waste product from the pulp and paper industry that contains lignin. However, the M of lignin is too low for commercial use. The bacteria performed two processes. First, the bacteria produced laccase, which degraded lignin into low M aromatic compounds (LMWACs). Second, the laccase transformed the LMWACs into quinone intermediates, which polymerized and became high M lignin. Five bacterial strains were isolated from a pulp mill, and the best strain was selected. The optimum growing conditions and BL concentration were determined. The optimum growth conditions when using pure lignin were 1 g/L lignin, 5 g/L urea, and 35 °C. When using BL instead of pure lignin, the optimum concentration was 2% BL (v/v). This information could help develop effective industrial utilization of BL lignin. [ABSTRACT FROM AUTHOR]

The capacities of white rot fungal treatments to degrade lignocellulose and further to improve the rumen degradability were examined in two kinds of corn stover (CAU3138 and ZN01). A total of seven fungi were evaluated according to their growth rates and selective values (SV) on both stovers under 28 °C for 28 days. Then, three selected fungi were evaluated by their in vitro gas production (IVGP) as a measure of rumen fermentation capacity. The results showed that Irpex lacteus, Pleurotus ostreatus, and Pleurotus cystidiosus had high speeds of colonization and high SV on both stovers. The IVGP of the ZN01 treated with any of the three fungi was lower than that of the raw stover, and the IVGP of the CAU3138 treated with P. ostreatus and P. cystidiosus had no significant change (P > 0.05). However, the IVGP of the CAU3138 treated with I. lacteus was significantly increased (P < 0.05) and further increased as the treatment time was prolonged. This study indicated that SV was not always a good predictor for the performance of the fungus. Here, I. lacteus performed best, regarding fungal growth and IVGP of the CAU3138. [ABSTRACT FROM AUTHOR]

The separation of lignin from the black liquor generated during alkaline pulping is reviewed in this article with an emphasis on chemistry. Based on published accounts, the precipitation of lignin from spent pulping liquor by addition of acids can be understood based on dissociation equilibria of weak acid groups, which affects the solubility behavior of lignin-related chemical species. Solubility issues also govern lignin separation technologies based on ultrafiltration membranes; reduction in membrane permeability is often affected by conditions leading to decreased solubility of lignin decomposition products and the presence of colloidal matter. Advances in understanding of such phenomena have potential to enable higher-value uses of black liquor components, including biorefinery options, alternative ways to recover the chemicals used to cook pulp, and debottlenecking of kraft recovery processes. [ABSTRACT FROM AUTHOR]

Abstract Soil carbon (C) and nitrogen (N) availability depend on the breakdown of soil polymers such as lignin, chitin, and protein that represent the major fraction of soil C and N but are too large for immediate uptake by plants and microorganisms. Microorganisms may adjust the production of enzymes targeting different polymers to optimize the balance between C and N availability and demand, and for instance increase the depolymerization of N-rich compounds when C availability is high and N availability low ("microbial N mining"). Such a mechanism could mitigate plant N limitation but also lie behind a stimulation of soil respiration frequently observed in the vicinity of plant roots ("priming effect"). We here compared the effect of increased C and N availability on the depolymerization of native bulk soil organic matter (SOM), and of 13C-enriched lignin, chitin, and protein added to the same soil in two complementary ten day microcosm incubation experiments. A significant reduction of chitin depolymerization (described by the recovery of chitin-derived C in the sum of dissolved organic, microbial and respired C) upon N addition indicated that chitin was degraded to serve as a microbial N source under low-N conditions and replaced in the presence of an immediately available alternative. Protein and lignin depolymerization in contrast were not affected by N addition. Carbon addition enhanced microbial N demand and SOM decomposition rates, but significantly reduced lignin, chitin, and protein depolymerization. Our findings contrast the hypothesis of increased microbial N mining as a key driver behind the priming effect and rather suggest that C addition promoted the mobilization of other soil C pools that replaced lignin, chitin, and protein as microbial C sources, for instance by releasing soil compounds from mineral bonds. We conclude that SOM decomposition is interactively controlled by multiple mechanisms including the balance between C vs N availability. Disentangling these controls will be crucial for understanding C and N cycling on an ecosystem scale. Highlights • Low N and high C availability might boost soil N-polymer breakdown ("N mining"). • N mining might thus lie behind higher soil respiration near plant roots ("priming"). • We tested the effect of C and N input on the degradation of SOM and added polymers. • C input increased SOM degradation but reduced that of chitin, lignin and protein. • Our findings challenge the hypothesis of N mining as a key driver of priming. [ABSTRACT FROM AUTHOR]