Lignin Degradation Process Research Articles

Metagenomic analysis of a top-down enriched straw biodegradation synthetic bacterial consortium (StrBsyn) facilitates anaerobic rice straw degradation

Lignocellulose is a complex and recalcitrant component of plant biomass. Traditional sources of lignocellulose-degrading microorganisms are the rumen system of herbivores and soil microorganisms, with limited studies on marine sediments. In this study, we employed a "top-down" approach to construct a straw biodegradation synthetic bacterial consortium (StrBsyn) capable of degrading lignocellulose from offshore marine sediments. It achieved 66.74% cellulose, 63.79% hemicellulose, and 42.85% lignin conversion within 30 days using 0.2% rice straws. Additionally, the maximum concentrations of total organic carbon (TOC) and total volatile fatty acids (TVFA) reached 4.66g/mL and 15.10g/L, respectively, with a significant increase in pH. β-glucosidase, xylanase, laccase, and lignin peroxidase activities were detected in StrBsyn. Metagenomic sequencing revealed a dynamic shift in the community composition and functional genes. The taxonomic assignment of these functional genes suggested the genera Clostridium, Glomeromyces, and Sedimentobacter as major contributors to carbohydrate transport, metabolism, and lignin degradation processes. This study demonstrated the significant potential of harnessing the power of marine sediment microbial communities for sustainable and efficient anaerobic lignocellulose bioconversion.

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

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

Microbial mechanisms for higher hydrogen production in anaerobic digestion at constant temperature versus gradient heating

BackgroundClean energy hydrogen (H2) produced from abundant lignocellulose is an alternative to fossil energy. As an essential influencing factor, there is a lack of comparison between constant temperatures (35, 55 and 65 °C) and gradient heating temperature (35 to 65 °C) on the H2 production regulation potential from lignocellulose-rich straw via high-solid anaerobic digestion (HS-AD). More importantly, the microbial mechanism of temperature regulating H2 accumulation needs to be investigated.ResultsConstant 65 °C led to the lowest lignin residue (1.93%) and the maximum release of cellulose and hemicellulose, and the highest H2 production (26.01 mL/g VS). H2 production at 35 and 55 °C was only 14.56 and 24.13 mL/g VS, respectively. In order to further explore the potential of ultra-high temperature (65 °C), HS-AD was performed by gradient heating conditions (35 to 65 °C). However, compared to constant 65 °C, gradient heating conditions led to higher lignin residue (2.49%) and lower H2 production (13.53 mL/g VS) than gradient heating conditions (47.98%). In addition, metagenomic analysis showed the cellulose/hemicellulose hydrolyzing bacteria and genes (mainly Thermoclostridium, and xynA, xynB, abfA, bglB and xynD), H2-producing bacteria and related genes (mainly Thermoclostridium, and nifD, nifH and nifK), and microbial movement and metabolic functions were enriched at 65 °C. However, the enrichment of two-component systems under gradient heating conditions resulted in a lack of highly-enriched ultra-high-temperature cellulose/hemicellulose hydrolyzing genera and related genes but rather enriched H2 consumption genera and genes (mainly Acetivibrio, and hyaB and hyaA) resulting in a weaker H2 production.ConclusionsThe lignin degradation process does not directly determine H2 accumulation, which was actually regulated by bacteria/genes contributing to H2 production/consumption. In addition, it is temperature that enhances the hydrolysis process of lignin rather than lignin-degrading enzymes, bacteria and genes by promoting microbial material transfer and metabolism. In terms of temperature, one of the key parameters of HS-AD for H2 production, we developed an important regulatory strategy, enriched the theoretical basis of temperature regulation for H2 production to further expanded the research horizon in this field.ABqfqNejHM5MQBNj5XnjcNVideo

Mechanism of formation H2 and CH4 by hydrolysis and alcoholysis of lignin: A density functional theory study

Hydrolysis and alcoholysis are considered as viable routes for efficient degradation and recycling high-quality gas fuel of lignin. Mechanism of formation H2 and CH4 by hydrolysis and alcoholysis of various phenylic lignin model compounds were studied using density functional theory method at M06–2X/6–31++G(d,p) level. Formation H2 by eight hydrolysis reaction pathways and formation CH4 by eight alcoholysis reaction pathways were designed. The standard kinetic and thermodynamic parameters of hydrolysis and alcoholysis reaction pathways were calculated. The results show that energy barriers for hydrolysis of phenyl (p-hydroxyphenyl, guaiacyl, and syringyl) formaldehyde paths (about 270.0 kJ/mol) are higher than those for hydrolysis of phenyl (p-hydroxyphenyl, guaiacyl, and syringyl) acetaldehyde paths (about 250.0 kJ/mol). Thus, H2 is easily formed during the decomposition of phenyl (p-hydroxyphenyl, guaiacyl, and syringyl) acetaldehyde. The energy barriers for alcoholysis of phenyl (p-hydroxyphenyl, guaiacyl, and syringyl) formaldehyde paths (about 370.0 kJ/mol) are lower than those for alcoholysis of phenyl (p-hydroxyphenyl, guaiacyl, and syringyl) acetaldehyde paths (about 355.0 kJ/mol). Thus, CH4 is easily formed during the decomposition of phenyl (p-hydroxyphenyl, guaiacyl, and syringyl) acetaldehyde. In addition, temperature is the key factor in the lignin degradation process, the calculation results indicate the reaction rate increases with the increase of temperature, and the reaction in water molecular environment is better than that in methanol medium.

Insights on kraft lignin degradation in an anaerobic environment

Lignin is an aromatic macromolecule and one of the main constituents of lignocellulosic materials. Kraft lignin is generated as a residual by-product of the lignocellulosic biomass industrial process, and it might be used as a feedstock to generate low molecular weight aromatic compounds. In this study, we seek to understand and explore the potential of ruminal bacteria in the degradation of kraft lignin. We established two consortia, KLY and KL, which demonstrated significant lignin-degrading capabilities. Both consortia reached maximum growth after two days, with KLY showing a higher growth and decolorization rate. Additionally, SEM analysis revealed morphological changes in the residual lignin from both consortia, indicating significant degradation. This was further supported by FTIR spectra, which showed new bands corresponding to the C-H vibrations of guaiacyl and syringyl units, suggesting structural transformations of the lignin. Taxonomic analysis showed enrichment of the microbial community with members of the Dickeya genus. Seven metabolic pathways related to lignin metabolism were predicted for the established consortia. Both consortia were capable of consuming aromatic compounds such as 4-hydroxybenzoic acid, syringaldehyde, acetovanillone, and syringic acid, highlighting their capacity to convert aromatic compounds into commercially valuable molecules presenting antifungal activity and used as food preservatives as 4-hydroxyphenylacetic, 3-phenylacetic, and phenylacetic acids. Therefore, the microbial consortia shown in the present work are models for understanding the process of lignin degradation and consumption in bacterial anaerobic communities and developing biological processes to add value to industrial processes based on lignocellulosic biomass as feedstock.

Pengaruh Pre-Treatment Kimia dan Biologi Terhadap Produksi Biogas dari Kulit Kopi

Coffee, as a major commodity in Indonesia, produces a huge number of byproducts and residues during the processing process. Coffee wastes and byproducts produced during coffee berry processing are a major source of contamination and represent significant environmental challenges in the coffee production process. One promising alternative in utilizing coffee wastes is converting into energy source i.e, of biogas from coffee pulp. Coffee pulp has toxic components that act as a methane inhibitor; these type of biomass have a problem with the lignin degradation process, which binds cellulose and hemicellulose. The use of cow's rumen fluid for methane production from coffee pulp is still rare, particularly for rumen fluid. Chemical pretreatment was carried out using alkali-peroxide followed by rumen fluid pretreatment. The performance of biogas produced from coffee pulp (with and without pretreatment) using rumen fluid as an inoculum has been investigated. Biogas was produced in a semi-batch reactor with a working volume of 2 liters for 30 days. Removal lignin, SS, VFA, and biogas yield were measured. This study aims to determine the biogas production from coffee pulp using variation HRT 20 and 30 days. It can be concluded that chemical pretreatment of NaOH - H2O2 combination can reduce lignin up to 75.02%. The volume of biogas produced increased with chemical pretreatment and rumen fluid as compared to the substrate with only rumen pretreatment According to Gas Chromatography analysis, the methane gas obtained from chemical pretreatment and rumen with HRT 30 days is 47.93%, while the methane obtained from rumen pretreatment with HRT 30 days is 34.28%.

How to Reduce Char Formation in the Lignin Degradation Process: A Review

AbstractAs the most abundant biomass resource in nature, the utilization of renewable aromatic rings contained in lignin has always been the focal point for materials science and chemistry. Many of the current lignin degradation methods need to be carried out under harsh conditions such as extremely high temperatures or high pressures. This leads to the cross‐linking reaction between lignin and depolymerization intermediates to produce solid char. The milder method also requires the use of heating, which may also lead to the polymerization of some intermediates in the reaction to form char. It has been a difficult problem for researchers to find a way to reduce the solid char. This review discusses different methods to avoid or reduce char formation and sedimentation, including thermal degradation, electrochemical catalysis, fungal degradation, and mechanochemical methods. The aim of the review is to help reduce char formation during lignin degradation and to increase the rate of lignin biomass degradation.

Lytic polysaccharide monooxygenase synergized with lignin-degrading enzymes for efficient lignin degradation

Even though the discovery of lytic polysaccharide monooxygenases (LPMOs) has fundamentally shifted our understanding of biomass degradation, most of the current studies focused on their roles in carbohydrate oxidation. However, no study demonstrated if LPMO could directly participate to the process of lignin degradation in lignin-degrading microbes. This study showed that LPMO could synergize with lignin-degrading enzymes for efficient lignin degradation in white-rot fungi. The transcriptomics analysis of fungi Irpex lacteus and Dichomitus squalens during their lignocellulosic biomass degradation processes surprisingly highlighted that LPMOs co-regulated with lignin-degrading enzymes, indicating their more versatile roles in the redox network. Biochemical analysis further confirmed that the purified LPMO from I.lacteus CD2 could use diverse electron donors to produce H2O2, drive Fenton reaction, and synergize with manganese peroxidase for lignin oxidation. The results thus indicated that LPMO might uniquely leverage the redox network toward dynamic and efficient degradation of different cell wall components.

Exoproteomic Study and Transcriptional Responses of Laccase and Ligninolytic Peroxidase Genes of White-Rot Fungus Trametes hirsuta LE-BIN 072 Grown in the Presence of Monolignol-Related Phenolic Compounds.

Being an abundant renewable source of aromatic compounds, lignin is an important component of future bio-based economy. Currently, biotechnological processing of lignin through low molecular weight compounds is one of the conceptually promising ways for its valorization. To obtain lignin fragments suitable for further inclusion into microbial metabolism, it is proposed to use a ligninolytic system of white-rot fungi, which mainly comprises laccases and peroxidases. However, laccase and peroxidase genes are almost always represented by many non-allelic copies that form multigene families within the genome of white-rot fungi, and the contributions of exact family members to the overall process of lignin degradation has not yet been determined. In this article, the response of the Trametes hirsuta LE-BIN 072 ligninolytic system to the presence of various monolignol-related phenolic compounds (veratryl alcohol, p-coumaric acid, vanillic acid, and syringic acid) in culture media was monitored at the level of gene transcription and protein secretion. By showing which isozymes contribute to the overall functioning of the ligninolytic system of the T. hirsuta LE-BIN 072, the data obtained in this study will greatly contribute to the possible application of this fungus and its ligninolytic enzymes in lignin depolymerization processes.

Lignin Promotes Mycelial Growth and Accumulation of Polyphenols and Ergosterol in Lentinula edodes.

It has been demonstrated that lignin was efficiently degraded by Lentinula edodes (L. edodes). However, the process of lignin degradation and utilization by L. edodes has not been discussed in detail. Therefore, the effects of lignin on L. edodes mycelium growth, chemical compositions, and phenolic profiles were investigated herein. It has been revealed that 0.10% lignin acted as the most effective concentration to accelerate mycelia growth, which yielded the highest biomass of 5.32 ± 0.07 g/L. Furthermore, a 0.10% concentration of lignin promoted the accumulation of phenolic compounds, especially protocatechuic acid, with peak value of 48.5 ± 1.2 μg/g. In contrast, the higher concentration of lignin (0.20%) exerted an inhibitory effect on the growth of L. edodes. Overall, the application of lignin at the optimal concentration of 0.10% could not only enhance the mycelial growth but also accumulate the phenolic acids and raise the nutritional and medical values of L. edodes.

Properties, Physiological Functions and Involvement of Basidiomycetous Alcohol Oxidase in Wood Degradation.

Extensive research efforts have been devoted to describing yeast alcohol oxidase (AO) and its promoter region, which is vastly applied in studies of heterologous gene expression. However, little is known about basidiomycetous AO and its physiological role in wood degradation. This review describes several alcohol oxidases from both white and brown rot fungi, highlighting their physicochemical and kinetic properties. Moreover, the review presents a detailed analysis of available AO-encoding gene promoter regions in basidiomycetous fungi with a discussion of the manipulations of culture conditions in relation to the modification of alcohol oxidase gene expression and changes in enzyme production. The analysis of reactions catalyzed by lignin-modifying enzymes (LME) and certain lignin auxiliary enzymes (LDA) elucidated the possible involvement of alcohol oxidase in the degradation of derivatives of this polymer. Combined data on lignin degradation pathways suggest that basidiomycetous AO is important in secondary reactions during lignin decomposition by wood degrading fungi. With numerous alcoholic substrates, the enzyme is probably engaged in a variety of catalytic reactions leading to the detoxification of compounds produced in lignin degradation processes and their utilization as a carbon source by fungal mycelium.

Wood decay fungi: an analysis of worldwide research

PurposeWood decay fungi are the only forms of life capable of degrading wood to its initial constituents, greatly contributing to the soil ecosystem. This study summarizes the current research status and development characteristics of global wood decay fungi research, in order to better understand their role in soils.MethodsA bibliometric analysis was applied to the literature from 1913 to 2020, based on data from the Web of Science (WOS) Core Collection. For this, various bibliometric analysis methods, R (Biblioshiny package), and VOSviewer were applied.ResultsA total of 8089 documents in this field were identified in the WOS Core Collection. The annual number of publications tended to increase, with exponential growth after 2008. Researchers in this field were mainly concentrated in North Europe, the USA, and China. Biotechnology, applied microbiology, environmental sciences, and microbiology were the most popular WOS categories. Bioresource Technology and Applied Environmental Microbiology were the top two journals with the most citations. The top three authors with the most published papers were Dai YC, Martinez AT, and Cui BK. Co-occurrence analysis of author keywords identified six clusters, mainly divided into three categories: the classification and diversity, the degradation mechanisms, and the ecological functions of wood decay fungi. Clustering results further showed that the lignin degradation process and the application of wood decay fungi in industrial production and soil contamination remediation are current research hotspots.ConclusionsWe present a comprehensive and systematic overview of research related to wood decay fungi and provide a deep perspective to understand the associated research progress. This is important for facilitating the development of a profound understanding of the contribution of wood decay fungi to soil systems and the degradation of soil contaminants.

Dopant-assisted atmospheric pressure photoionization Orbitrap mass spectrometry – An approach to molecular characterization of lignin oligomers

Lignin is the second most abundant biopolymer in nature and is considered an important renewable source of aromatic compounds. One of the most promising analytical methods for molecular characterization of lignin is Orbitrap high-resolution mass spectrometry with atmospheric pressure photoionization (APPI), proved itself in the study of lignins of various origins and their depolymerization products. In this work, the photoionization of lignin using acetone, 1,4-dioxane, and THF as solvents for the biopolymer and APPI dopants providing the generation of protonated and deprotonated molecules of lignin oligomers has been studied. The ionization conditions were optimized on the basis of the dependences of the total ion current on temperature and the flow rate of the solution into the ion source. Lignin degradation processes under APPI conditions occur mainly with the cleavage of ether β-O-4 bonds between phenylpropane structural units, demethylation (negative ion mode), as well as the loss of water and formaldehyde (positive ion mode). Negative ion mode APPI provides a higher ionization efficiency in the region of high molecular weights, however, it is characterized by an increased fragmentation of β-O-4 ether bonds compared to APPI(+) leading to a partial depolymerization of lignin in the ion source. The combination of APPI with Orbitrap high-resolution mass spectrometry allows obtaining mass spectra of coniferous and deciduous wood lignins with resolved fine structure and containing signals of up to 3000 oligomers in the mass range of 300–1800 Da. This can be used for comprehensive characterization of lignins at molecular level and tracking changes in biopolymer chemical composition in various processes.

Isolasi dan Karakterisasi Jamur Pelapuk Putih Pendegradasi Lignin dari Limbah Cair Pulp dan Kayu Lapuk Eukaliptus (Eucalyptus sp)

Lignin is an organic polymer compound that is difficult to degrade in the environment because of its very complex structure consisting of an aromatic ring group and three carbons in the side chain. This exploratory study aims to determine whether white rot fungi isolated from wastewater from eucalypt pulp and weathered wood are lignolytic and the ability of the isolates to degrade tannins as an approach in the lignin degradation process. The experimental design is divided into two stages, namely: 1) Isolation of fungi that have the ability to degrade tannins quantitatively and qualitatively as well as characterization of fungi morphologically (macroscopic and microscopic). 2) Testing the ability of superior white rot fungus isolates in degrading tannins at concentrations of 0.5%, 1%, 1.5% and 2% of tannins. The brown zone formed in white rot fungal isolates was measured the zone diameter and intensity of the brown color. The results of this study indicate that of the 29 isolates obtained, there were five superior isolates capable of degrading tannins, namely isolates LD06, LD07, BE01.3, BE01.4 and BE02.2. BE01.3 was isolated at 2% tannin concentration, the second largest diameter of the brown zone after LD06 isolate and the highest brown color intensity level three with a slightly dark brown color intensity, namely slightly blackish brown.
 Keywords: Isolation, characterization, white rot fungi, tannins, lignin degradation

Leaf litter lignin degradation in response to understory vegetation removal in a Masson pine plantation

AbstractUnderstory vegetation changes, caused by forestry management, can alter the litter species composition and microclimate in situ, which while profoundly influence litter lignin degradation processes, is seldom investigated. To reveal the effects of these changes, understory vegetation in plots was treated as follows: no understory vegetation removal; only shrub removal; only herb removal; and, both shrub and herb removal. Single‐ and mixed‐species litterbags (1.0 mm mesh with uncut leaf litter) matching the treated vegetation characteristics (complied with a 7:2:1 air‐dried mass ratio for the litter form trees, shrubs, and herbs) were placed on the floor. After 2 years, 5.9% (single‐tree litter in the plots with shrub removal) to 41.4% (mixture in the plots with no understory vegetation removal) of the initial lignin content was degraded among litterbag types and plot treatments. Incidence of nonadditive effects was reduced, and the nonadditive lignin degradation rate varied but remained low among plot treatments when understory vegetation was removed. In all plot treatments, lignin degradation rate was higher in single‐shrub or single‐herb litter than in single‐tree litter (at least 9.7% ± 1.2% for the deviation). Mixtures in the plots, with no understory vegetation removal, exhibited a greater lignin degradation rate than that of the litter mixtures in the other plots. Path analysis indicated that microbial biomass nitrogen, average temperature, and lignin concentration were positively correlated with lignin degradation rate. Therefore, in addition to the litter species composition, alterations in microclimate as a result of understory vegetation changes can be a key factor that influence lignin degradation rate.

Bio-Pulping of Bagasse As The Material For Paper Making Using Different Species of White Rot Fungi and Incubation Time

The Biopulping is defined as the biological process of lignin degradation by utilizing microorganisms that produce some enzymes. A microorganism which widely known in the degradation of lignin and cellulose is a group of white-rot fungi. The aims for this research to know the most effective white rot fungi species of G.lucidum, P.tuber-regium, and T.versicolor in the degradation of lignin and cellulose with different incubation time on bagasse substrate. The effectivity of biopulping indicated by the highest degradation of lignin concentration and the lowest degradation of cellulose concentration. This study used an experimental design with Completely Randomized design with a two factorial pattern. The independent variable of this study is white rot fungi species and incubation time while the dependent variable is the concentration of lignin and cellulose. The main parameter was the concentration of lignin and cellulose, supporting parameters were pH, weight loss of substrate and mycelial growth. The result showed the degradation of lignin and cellulose in all treatment. The best degradation of lignin and cellulose showed by species T.versicolor and P.tuber-regium within 30 days of incubation

Lignin degradation in cooking with active oxygen and solid Alkali process: A mechanism study

Non-phenol structure in lignin is difficult to be degraded under alkaline conditions, thus limiting the delignification efficacy in many pretreatment technologies. Intriguingly, the non-phenol structures can be degraded into low-molecular-weight products in cooking with active oxygen and solid alkali process. Herein, model compounds were adopted to investigate the degradation mechanism of lignin non-phenol structure under same conditions. Two pathways of converting the non-phenol structure to degradable structures are found: 1) After the Cα-Cβ bond cleavage at the lignin side chain, the benzoic structure intermediates are degraded; 2) After hydrolysis of the aryl-ether bond, the phenol structure intermediates are then degraded. Moreover, the degradation of the phenol structure intermediates will further promote the hydrolysis of the ether bonds, thus resulting in the improvement in the delignification process. This work describes a novel pathway in lignin oxidation degradation and helps to understand the chemistry of lignin degradation process in related alkaline oxidation pretreatment technologies.

Grazing promoted soil microbial functional genes for regulating C and N cycling in alpine meadow of the Qinghai-Tibetan Plateau

Microbial functional genes can reflect the nutrient cycle activities in soil, because they encode various enzymes involved in the material cycle. Therefore, the gene abundance variation can reveal the impact of interference on the material cycle of grassland. To study the cycle of carbon (C), nitrogen (N) and phosphorus (P) between plant and soil in grassland under different grazing regimes, we investigated the soil microbial functional genes related to C, N, and P cycling by high-throughput quantitative PCR and 16S rRNA-based Illumina sequencing analysis under grazing exclusion (GE), rotational grazing (RG), and continuous grazing (CG) in alpine meadow of the Qinghai-Tibetan Plateau, where climate is characterized by little rain and low temperature, and grassland is very sensitive to grazing. The results showed at the early grazing period, C fixtion (rbcL, korA, and frdA) and lignin degradation (abfA, xylA, exg, lig, exoPG, chiA, and glx) processes were slower under GE; CH4 metabolism (mcrA) was faster under CG; RG and CG improved the denitrification process (narG); RG slowed down organic-P mineralization (phoD). At the late grazing period, C fixation (accA and frdA) and degradation (mnp, apu, and amyA) processes were slower under GE; CH4 metabolism (pmoA and mxa) was faster under CG; RG and CG improved the ammonia-oxidizing (amoA2), nitrification (hao), and denitrification (nirS3 and nirK1) processes. The majority of the genes involved in C, N, and P cycling decreased, the C, N and P content in plant leaf decreased, while that of soil increased from early to late grazing period. No matter grazing or not, there were negative relationships between genes and soil nutrients, and positive relationships between genes and plant nutrients, implying a trade-off between plant nutrients and soil nutrients along the grazing time. The genes responsible for regulating C and N cycling were increased under grazing, implying that reasonable grazing is beneficial to the nutrients cycling of grassland.

Microstructure and physico-chemical transformation of some common woods from Cameroon during drying

The influence of drying on the microstructure, physical and chemical properties of some tropical wood species has been investigated using thermogravimetric analysis, differential scanning calorimetric (DSC), FTIR-ATR spectroscopy, mercury intrusion porosimetry (MIP) and environmental scanning electron microscopy (ESEM) analysis. Eleven tropical species were used in this study. Results showed that the common Cameroonian wood species can be grouped into three classes: Ga (lightwood) with cross-linking fibers having high volume of macropores, density in the range 0.2–0.4 g cm−3 and high lignin content; Gb (medium dense) with unidirectional fibers packing, density around 0.6 g cm−3 and Gc group showing high densification of unidirectional fibers and low porosity justifying the density > 0.8 g cm−3. Both the Gb an Gc groups have less significant lignin content. A relatively high rate of drying for Ga with respect to low drying rate for Gc was observed in direct relation with their porosity of ~ 72 Vol% and ~ 36 Vol%, respectively. LTF and WG showed similar cumulative pore volume (0.44 mL g−1) with different pore size distribution: 28% and 22% of macropores, 39% and 60% of mesopores and 33% and 18% micropores, respectively. Thermal analysis revealed that lightwoods have the highest amounts of residues and lower thermal stability of chemical components than dense woods. It has been found that the degradation process of hemicellulose, cellulose and lignin occurs mainly at about 200–300 °C, 300–350 °C and 350–500 °C, respectively. The group Ga with low drying rate, a low cycle of reproduction, a high volume of porosity together with large pore sizes appeared promising candidates for the design of ecological, environmental and sustainable management policy of wood transformation in developing countries and even worldwide.

A highly active carboxylic acid reductase from Mycobacterium abscessus for biocatalytic reduction of vanillic acid to vanillin

Vanillin is a value added compound used in wide range of areas including food, beverage, fragrance and pharmaceutical. It can be produced by reduction of vanillic acid, a by-product in lignin degradation processes or a competing component in the metabolic pathways in biological vanillin production. The reduction process is energetically disadvantageous due to the high activation energy in the reaction coordinates, but can be overcome by an enzymatic strategy using carboxylic acid reductases (CARs). In this study, fourteen CARs heterologously expressed in Escherichia coli were tested for vanillic acid reduction, of which a CAR from Mycobacterium abscessus B1MLD7 gene, as a result, was selected for the highest activity. The selected CAR exhibited 8.6-fold higher in vitro activity than that of the CAR from Nocardia iowensis Q6RKB1, previously reported to have the highest activity in vanillic acid reduction. The effect of substrate concentration and reducing power supply on the biocatalytic reaction has been investigated to enhance the yield while minimizing the by-product formation, resulting in 2.86 g L−1 of vanillin production in the whole cell biocatalytic reaction. The sequential and structural analyses of the enzyme with molecular modeling also have been carried out to discuss the catalytic characteristics of the enzyme.