Deactivation and activation of lignocellulose degrading enzymes in the presence of laccase

Comparative analysis of Chrysoporthe cubensis exoproteomes and their specificity for saccharification of sugarcane bagasse

The phytopathogenic fungus Chrysoporthe cubensis is a relevant source of lignocellulolytic enzymes. This work aimed to compare the profile of lignocellulose-degrading proteins secreted by C. cubensis grown under semi-solid state fermentation using wheat bran (WB) and sugarcane bagasse (SB). The exoproteomes of the fungus grown in wheat bran (WBE) and sugarcane bagasse (SBE) were qualitative and quantitatively analyzed by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). Data are available via ProteomeXchange with identifier PXD046075. Label-free proteomic analysis of WBE and SBE showed that the fungus produced a spectrum of carbohydrate-active enzymes (CAZymes) with exclusive characteristics from each extract. While SBE resulted in an enzymatic profile directed towards the depolymerization of cellulose, the enzymes in WBE were more adaptable to the degradation of biomass rich in hemicellulose and other non-lignocellulosic polymers. Saccharification of alkaline pre-treated sugarcane bagasse with SBE promoted glucose release higher than commercial cocktails (8.11 g L-1), while WBE promoted the higher release of xylose (5.71 g L-1). Our results allowed an in-depth knowledge of the complex set of enzymes secreted by C. cubensis responsible for its high lignocellulolytic activity and still provided the identification of promising target proteins for biotechnological applications in the context of biorefinery.

How can vanillin improve the performance of lignocellulosic biomass conversion in an immobilized laccase microreactor system?

Gentle and effective pretreatment is necessary to produce clean lignocellulosic biomass-based fuels. Herein, inspired by the efficient lignin degradation in the foregut of termites, the microreactor system using immobilized laccase and recoverable vanillin was proposed. Firstly, the co-deposition coating of dopamine, hydrogen peroxide and copper sulfate was constructed for laccase immobilization and a high immobilization efficiency of 87.0% was obtained in 30 min. After storage for 10 days, 82.2% activity was maintained in the laccase-loaded microreactor, which is 210.0% higher than free laccase. In addition, 6% (w/w) vanillin can improve lignin degradation in the laccase-loaded microreactor without impairing laccase activity, leading to a 47.3% increment in cellulose accessibility. Finally, a high cellulose conversion rate of 88.1% can be achieved in 1 h with glucose productivity of 2.62 g L^-1 h^-1. These demonstrated that the appropriate addition of vanillin can synergize with immobilized laccase to enhance the conversion of lignocellulosic biomass.

Penicillium polonicum a new isolate obtained from Cerrado soil as a source of carbohydrate-active enzymes produced in response to sugarcane bagasse

Penicillium species have been studied as producers of plant cell wall degrading enzymes to deconstruct agricultural residues and to be applied in industrial processes. Natural environments containing decaying plant matter are ideal places for isolating fungal strains with cellulolytic and xylanolytic activities. In the present study, Cerrado soil samples were used as source of filamentous fungi able to degrade xylan and cellulose. Penicillium was the most abundant genus among the obtained xylan and carboxymethylcellulose degraders. Penicillium polonicum was one of the best enzyme producers in agar-plate assays. In addition, it secretes CMCase, Avicelase, pectinase, mannanase, and xylanase during growth in liquid media containing sugarcane bagasse as carbon source. The highest value for endo-β-1,4-xylanase activity was obtained after 4 days of growth. Xyl PP, a 20 kDa endo-β-1,4-xylanase, was purified and partially characterized. The purified enzyme presented the remarkable feature of being resistant to the lignin-derived phenolic compounds, p-coumaric and trans-ferulic acids. This feature calls for its further use in bioprocesses that use lignocellulose as feedstock. Furthermore, future work should explore its structural features which may contribute to the understanding of the relationship between its structure and resistance to phenolic compounds.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03405-x.

Towards efficient enzymatic saccharification of pretreated lignocellulose: Enzyme inhibition by lignin-derived phenolics and recent trends in mitigation strategies

Lignocellulosic biorefinery based on its sugar-platform has been considered as an efficient strategy to replace fossil fuel-based refinery. In the bioconversion process, pretreatment is an essential step to firstly open up lignocellulose cell wall structure and enhance the accessibility of carbohydrates to hydrolytic enzymes. However, various lignin and/or carbohydrates degradation products (e.g. phenolics, 5-hydroxymethylfurfural, furfural) also generated during pretreatment, which severely inhibit the following enzymatic hydrolysis and the downstream fermentation process. Among them, the lignin derived phenolics have been considered as the most inhibitory compounds and their inhibitory effects are highly dependent on the source of biomass and the type of pretreatment strategy. Although liquid-solid separation and subsequent washing can remove the lignin derived phenolics and other inhibitors, this is undesirable in the realistic industrial application where the whole slurry of pretreated biomass need to be directly used in the hydrolysis process. This review summarizes the phenolics formation mechanism for various commonly applied pretreatment methods and discusses the key factors that affect the inhibitory effect of phenolics on cellulose hydrolysis. In addition, the recent achievements on the rational design of inhibition mitigation strategies to boost cellulose hydrolysis for sugar-platform biorefinery are also introduced. This review also provides guidance for rational design detoxification strategies to facilitate whole slurry hydrolysis which helps to realize the industrialization of lignocellulose biorefinery.

Effects of laccase and cellulase on saccharification of barley malt

Improving saccharification of barley malt is beneficial to promoting economic benefits of beer brewers, but there are few detailed reports on the application of cellulase and laccase in barley malt. So, barley malt was pretreated by cellulase and laccase, and the malt wort and brewer's spent grains were analyzed by HPLC, FTIR and SEM in this study. The concentration of malt wort was increased significantly to 8.1 (° Bx), which increased by 28.6% after barley malt was pretreated by cellulase, but laccase could not improve saccharification of barley malt. Through analysis of sugar in malt wort and cellulose and lignin components as well as physical and chemical structures of brewer's spent grains, the increase in sugar content in malt wort was mainly due to the increase in glucose because of hydrolysis of cellulose in barley malt by cellulase. Furtherly, laccase and cellulase should have a mutual inhibition when they are pretreated simultaneously.

Enzymatic synthesis of wet-resistant lignosulfonate-starch adhesives

This work describes a new method for improving the properties, mainly the wet-resistance, of starch-based adhesives using enzymatically polymerized lignosulfonates. A correlation of viscosity with molecular weight was found, allowing simple control of enzymatic polymerization of lignosulfonates. Incorporation of lignosulfonates polymerized from 29 kDa to > 4500 kDa using laccase led to a considerable increase in wet-resistance (from 15 to 20 min for the laminating glue and from 150 to 1200 min for the bag glue) while not affecting (for the laminating glue) or even improving the bonding time (from 80 to 60 s for the bag glue). Finally, the effect of active laccase in the final adhesive was investigated by enzymatic inactivation using NaN₃ before formulation of the glue, as well as by extra laccase addition. In conclusion, this study shows that enzymatically polymerized lignosulfonate is a robust strategy for improving wet resistance of starch-based adhesives.

Multifactorial effects of gluconic acid pretreatment of waste straws on enzymatic hydrolysis performance

The chemical compositions of lignin, hemicellulose and cellulose are so far unascertained to various lignocellulose in respect to effect of cellulose enzymatic hydrolysis. The novel and environment-friendly gluconic acid (GA) pretreatment technology showed impressive results on the enzymatic hydrolysis of cellulose in various agricultural straws. However, only few of the main reasons or critical issues pertaining to this reaction are known. Therefore, the novel GA pretreatment was carried out to remove hemicellulose from the three representative waste straws under different conditions. Next, for the enzymatic hydrolysis of the residual cellulose fraction in the pretreated straws, some mathematical correlations have been investigated between enzyme accessibility, hemicellulose removal rate, and cellulose crystallinity index. Both linear and nonlinear models were compared using five-parameter logic curve, four-parameter logic curve, and Deming regression. Hemicellulose removal was logically ascribed to be the trigger for cellulose saccharification efficiency during GA pretreatment of these waste straws.

Lignocellulose degradation for the bioeconomy: The potential of enzyme synergies between xylanases, ferulic acid esterase and laccase for the production of arabinoxylo-oligosaccharides

The success of establishing bioeconomies replacing current economies based on fossil resources largely depends on our ability to degrade recalcitrant lignocellulosic biomass. This study explores the potential of employing various enzymes acting synergistically on previously pretreated agricultural side streams (corn bran, oat hull, soluble and insoluble oat bran). Degrees of synergy (oligosaccharide yield obtained with the enzyme combination divided by the sum of yields obtained with individual enzymes) of up to 88 were obtained. Combinations of a ferulic acid esterase and xylanases resulted in synergy on all substrates, while a laccase and xylanases only acted synergistically on the more recalcitrant substrates. Synergy between different xylanases (glycoside hydrolase (GH) families 5 and 11) was observed particularly on oat hulls, producing a yield of 57%. The synergistic ability of the enzymes was found to be partly due to the increased enzyme stability when in combination with the substrates.

Enhanced lignin biodegradation by consortium of white rot fungi: microbial synergistic effects and product mapping

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.

Enzymatic utilization of oil and lignocellulosic biomass using halophilic marine bacteria Micrococcus luteus and Pseudoalteromonas peptidolytica

In this study, hydrolytic and oxidative activities of enzymes isolated from halophilic microbes were characterized and applied for biomass utilization. First, lipase from Micrococcus luteus, and peroxidase and laccase from Pseudoalteromonas phenolica and Pseudoalteromonas peptidolytica were selected and their catalytic activities were determined, respectively. The M. luteus lipase encoding gene was synthesized after codon-optimization and could be successfully expressed in Escherichia coli with the assist of the Tif chaperone protein. The purified enzyme showed 119.13 ± 7.18 and 34.42 ± 5.91 U/mL of lipase and esterase activities, respectively. Moreover, the M. luteus lipase was applied for hydrolysis of the triglycerides mixture, which resulted in 182.9 ± 11.1 mg/L/h of glycerol productivity. Next, peroxidase and laccase activities of P. phenolica and P. peptidolytica were determined, and extracellular enzymes of P. peptidolytica was applied for lignocellulosic biomass degradation, which resulted in 91.9 μg glucose/mg lignocellulose of production yields. Finally, the hydrolytic and oxidative activities of the enzymes from halophilic microbes could be further utilized for biomass treatment and biochemical production.

Secretomic insight into the biomass hydrolysis potential of the phytopathogenic fungus Chrysoporthe cubensis

The phytopathogenic fungus Chrysoporthe cubensis has a great capacity to produce highly efficient enzymes for the hydrolysis of lignocellulosic biomass. The bioinfosecretome of C. cubensis was identified by computational predictions of secreted proteins combined with protein analysis using 1D-LC-MS/MS. The in silico secretome predicted 562 putative genes capable of encoding secreted proteins, including 273 CAZymes. Proteomics analysis confirmed the existence of 313 proteins, including 137 CAZymes classified as Glycosyl Hydrolases (GH), Polysaccharide Lyases (PL), Carbohydrate Esterases (CE) and Auxiliary Activities enzymes (AA), which indicates the presence of classical and oxidative cellulolytic mechanisms. The enzymes diversity in the extract shows fungal versatility to act in complex biomasses. This study provides an insight into the lignocellulose-degradation mechanisms by C. cubensis and allows the identification of the enzymes that are potentially useful in improving industrial process of bioconversion of lignocellulose. SIGNIFICANCE: Chrysoporthe cubensis is an important deadly canker pathogen of commercially cultivated Eucalyptus species. The effective depolymerisation of the recalcitrant plant cell wall performed by this fungus is closely related to its high potential of lignocellulolytic enzymes secretion. Since the degradation of biomass occurs in nature almost exclusively by enzyme secretion systems, it is reasonable to suggest that the identification of C. cubensis lignocellulolytic enzymes is relevant in contributing to new sustainable alternatives for industrial solutions. As far as we know, this work is the first accurate proteomic evaluation of the enzymes secreted by this species of fungus. The integration of the gel-based proteomic approach, the bioinformatic prediction of the secretome and the analyses of enzymatic activity are powerful tools in the evaluation of biotechnological potential of C. cubensis in producing carbohydrate-active enzymes. In addition, analysis of the C. cubensis secretome grown in wheat bran draws attention to this plant pathogen and its extracellular enzymatic machinery, especially regarding the identification of promising new enzymes for industrial applications. The results from this work allowed for explanation and reinforce previous research that revealed C. cubensis as a strong candidate to produce enzymes to hydrolyse sugarcane bagasse and similar substrates.

Steam Explosion Pretreatment of Beechwood. Part 2: Quantification of Cellulase Inhibitors and Their Effect on Avicel Hydrolysis

Biomass pretreatment is a mandatory step for the biochemical conversion of lignocellulose to chemicals. During pretreatment, soluble compounds are released into the prehydrolyzate that inhibit the enzymatic hydrolysis step. In this work, we investigated how the reaction conditions in steam explosion pretreatment of beechwood (severity: 3.0–5.25; temperature: 160–230 °C) influence the resulting amounts of different inhibitors. Furthermore, we quantified the extent of enzyme inhibition during enzymatic hydrolysis of Avicel in the presence of the prehydrolyzates. The amounts of phenolics, HMF, acetic acid and formic acid increased with increasing pretreatment severities and maximal quantities of 21.6, 8.3, 43.7 and 10.9 mg/gbeechwood, respectively, were measured at the highest severity. In contrast, the furfural concentration peaked at a temperature of 200 °C and a severity of 4.75. The presence of the prehydrolyzates in enzymatic hydrolysis of Avicel lowered the glucose yields by 5–26%. Mainly, the amount of phenolics and xylose and xylooligomers contributed to the reduced yield. As the maximal amounts of these two inhibitors can be found at different conditions, a wide range of pretreatment severities led to severely inhibiting prehydrolyzates. This study may provide guidelines when choosing optimal pretreatment conditions for whole slurry enzymatic hydrolysis.

Inhibition kinetics of acetosyringone on xylanase in hydrolysis of hemicellulose

Many phenolic compounds, derived from lignin during the pretreatment of lignocellulosic biomass, could obviously inhibit the activity of cellulolytic and hemicellulolytic enzymes. Acetosyringone (AS) is one of the phenolic compounds produced from lignin degradation. In this study, we investigated the inhibitory effects of AS on xylanase activity through kinetic experiments. The results showed that AS could obviously inhibit the activity of xylanase in a reversible and noncompetitive binding manner (up to 50% activity loss). Inhibitory kinetics and constants of xylanase on AS were conducted by the HCH-1 model (β = 0.0090 ± 0.0009 mM^-1). Furthermore, intrinsic and 8-anilino-1-naphthalenesulfonic (ANS)-binding fluorescence results showed that the tertiary structure of AS-mediated xylanase was altered. These findings provide new insights into the role of AS in xylanase activity. Our results also suggest that AS was an inhibitor of xylanase and targeting AS was a potential strategy to increase xylose production.

Review on pulp and paper activated sludge pretreatment, inhibitory effects and detoxification strategies for biovalorization

Biovalorization of pulp and paper activated sludge to value-added products could be an effective alternative to traditional sludge management methods, which tend to pose serious environmental issues. Since pulp and paper activated sludge consists of microbial biomass, cellulose, hemicellulose and lignin and thus, could be subjected to different hydrolysis methods to solubilize sludge solids and release simple sugars to form value-added products by the microbial fermentation process. Hence, different sludge hydrolysis methods have been summarized in this review paper. However, hydrolysis of lignocellulosic materials generates variety of toxic compounds during hydrolysis and causes detrimental effects. Therefore, different toxic compounds and their impact on microorganisms, cellulolytic enzymes and fermentation process have been discussed in detail and recent strategies to counteract the problems of inhibitors have also been briefly explained.

Magnetic biochar derived from biosolids via hydrothermal carbonization: Enzyme immobilization, immobilized-enzyme kinetics, environmental toxicity

Magnetic and nonmagnetic biochar (MBC & BC) were produced from biosolids under hydrothermal conditions and characterized in order to understand surface chemistry impacts on enzyme immobilization and activity. Peak surface pore size of MBC was 180 nm and that of BC was 17 nm. Despite similar surface area (≈ 49 m²/g) MBC immobilized more laccase (99 mg/g) than biochar (31 mg/g). For horseradish peroxidase (HRP), the two biochars had similar immobilization capacity (≈ 65 mg/g). Laccase and HRP on MBC had 47.1 and 18.0% higher specific activity than on BC, respectively. The matrix activity of MBC-laccase (33.3 U/mg support) was 3.7-fold higher than BC-laccase (8.8 U/mg support) and higher than the same amount of free laccase (30.2 U) at pH 3.0 (P < 0.05). Although MBC had its own peroxide oxidation activity (104.1 and 165.9 U/mg biochar at pHs 5&6) this only accounted for 16.7 and 20.4% of the total MBC-H RP activity respectively. After 10 wash cycles, MBC still retained 79.3% and 60.3% of laccase and HRP activity, respectively. Additionally, MBC had lower acute toxicity, suggesting that it is relative benign from an environmental perspective.

Effect of Lignin Content on Cellulolytic Saccharification of Liquid Hot Water Pretreated Sugarcane Bagasse

Lignin contributes to the rigid structure of the plant cell wall and is partially responsible for the recalcitrance of lignocellulosic materials to enzymatic digestion. Overcoming this recalcitrance is one the most critical issues in a sugar-flat form process. This study addresses the effect of low lignin sugarcane bagasse on enzymatic hydrolysis after liquid hot water pretreatment at 190 °C and 20 min (severity factor: 3.95). The hydrolysis of bagasse from a sugarcane line selected for a relatively low lignin content, gave an 89.7% yield of cellulose conversion to glucose at 40 FPU/g glucan versus a 68.3% yield from a comparably treated bagasse from the high lignin bred line. A lower enzyme loading of 5 FPU/g glucan (equivalent to 3.2 FPU/g total solids) resulted in 31.4% and 21.9% conversion yields, respectively, for low and high lignin samples, suggesting the significance of lignin content in the saccharification process. Further increases in the enzymatic conversion of cellulose to glucose were achieved when the bagasse sample was pre-incubated with a lignin blocking agent, e.g., bovine serum albumin (50 mg BSA/g glucan) at 50 °C for 1 h prior to an actual saccharification. In this work, we have demonstrated that even relatively small differences in lignin content can result in considerably increased sugar production, which supports the dissimilarity of bagasse lignin content and its effects on cellulose digestibility. The increased glucose yields with the addition of BSA helped to decrease the inhibition of non-productive absorption of cellulose enzymes onto lignin and solid residual lignin fractions.

Development of sequential and simultaneous bacterial cultures to hydrolyse and detoxify wood pre-hydrolysate for enhanced acetone-butanol-ethanol (ABE) production

The use of microorganisms is a promising option for an eco-efficient and successful conversion of hardwood hemicelluloses to biofuels. The focus of this work is the treatment of hemicellulosic pre-hydrolysate by flocculation, followed by simultaneous or separate detoxification with Ureibacillus thermosphaericus and Cupriavidus taiwanensis co-culture, and hydrolysis with Paenibacillus campinasensis. A reduction of phenolic compounds was achieved mainly after flocculation, applied as a first detoxification step, but no increase in sugars concentration was observed. The ABE fermentation of the hydrolysate obtained from the simultaneous hydrolysis and detoxification produced 6.8 g L^-1 of butanol after 116 h, which was higher than that generated with xylose synthetic medium. The higher biofuel concentration in the hydrolysate is attributed to the existence of carbon sources, other than xylose.

Optimization of conditions for the production of lignocellulolytic enzymes by Sphingobacterium sp. ksn-11 utilizing agro-wastes under submerged condition

The present work was aimed at studying the production of lignocellulolytic enzymes, namely cellulase, xylanase, pectinase, mannanase, and laccase by a newly isolated bacterium Sphingobacterium sp. ksn-11, utilizing various agro-residues as a substrate under submerged conditions. The production of lignocellulolytic enzymes was found to be maximum at the loading of 10%(w/v) agro-residues. The enzyme secretion was enhanced by two-fold at 2 mM CaCO_3, optimum pH 7, and temperature 40°. The Field Emission Gun-Scanning Electron Microscope (FEG-SEM) results have shown the degradative effect of lignocellulases; cellulase, xylanase, mannanase, pectinase, and laccase on corn husk with 3.55 U/ml, 79.22 U/ml, 12.43 U/ml, 64.66 U/ml, and 21.12 U/ml of activity, respectively. The hydrolyzed corn husk found to be good adsorbent for polyphenols released during hydrolysis of corn husk providing suitable conditions for stability of lignocellulases. Sphingobacterium sp. ksn is proved to be a promising candidate for lignocellulolytic enzymes in view of demand for enzymes in the biofuel industry.

Enhanced hydrolysis of lignocellulosic biomass with doping of a highly thermostable recombinant laccase

A highly thermostable laccase from Geobacillus sp. strain WSUCF1 was cloned into Escherichia coli (E. coli) using pRham N-His SUMO expression system. The thermostable laccase with a molecular weight ~30 kDa had a t_1/2 (pH 6.0) of 120 h at 50 °C. The homology modelling for laccase structure showed the presence of Cu active centers with His and Cys residues involved in the active site and ligand binding activity of the enzyme, respectively. The K_m, V_max, K_cat and K_cat/K_m values of the purified enzyme with ABTS were found to be 0.146 mM, 1.52 U/mg, 1037 s^-1 and 7102.7 s^-1 mM^-1, respectively. The doping of recombinant WSUCF1 laccase to commercial enzyme cocktails Accellerase® 1500 and Cellic CTec2 improved the hydrolysis of untreated, alkali and acid treated corn stover by 1.31-2.28 times and bagasse by 1.32-2.02 times. Further, in-house enzyme cocktails with laccase hydrolyzed untreated, alkali and acid treated bagasse and gave 1.44, 1.1, and 0.92 folds higher sugar, respectively, when compared with Accellerase 1500. The results suggested that thermostable laccase can aid in the improved hydrolysis of lignocellulosic biomass.

Mapping the Secretome and Its N-Linked Glycosylation of Pleurotus eryngii and Pleurotus ostreatus Grown on Hemp Stalks

Our previous research showed that Pleurotus eryngii and Pleurotus ostreatus were effective fungi for pretreatment of industrial hemp stalks to improve enzymatic saccharification. The secretomes of these two fungi were analyzed to search for the effective enzyme cocktails degrading hemp lignin during the pretreatment process. In total, 169 and 155 proteins were identified in Pleurotus eryngii and Pleurotus ostreatus, respectively, and 50% of the proteins involved in lignocellulose degradation were CAZymes. Because most of the extracellular proteins secreted by fungi are glycosylated proteins, the N-linked glycosylation of enzymes could be mapped. In total, 27 and 24 N-glycosylated peptides were detected in Pleurotus eryngii and Pleurotus ostreatus secretomes, respectively. N-Glycosylated peptides of laccase, GH92, exoglucanase, phenol oxidase, α-galactosidase, carboxylic ester hydrolase, and pectin lyase were identified. Deglycosylation could decrease enzymatic saccharification of hemp stalks. The activities of laccase, α-galactosidase, and phenol oxidase and the thermal stability of laccase were reduced after deglycosylation.

The initial soil microbiota impacts the potential for lignocellulose degradation during soil solarization

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.

Development of co-immobilized tri-enzyme biocatalytic system for one-pot pretreatment of four different perennial lignocellulosic biomass and evaluation of their bioethanol production potential

Today, many researchers are focusing on research for alternative promising energy sources and sustainable technology for bioethanol production to meet the increasing global energy demand. Here, we develop a novel one-pot pretreatment technology by co-immobilizing laccase, cellulase and β-glucosidase to act as a tri-enzyme biocatalyst for evaluating the bioethanol production potential of four sustainable lignocellulosic biomasses viz., Typha angustifolia, Arundo donax, Saccharum arundinaceum, and Ipomoea carnea. The co-immobilized enzyme system was more stable at different temperatures and at longer storage, compared to free enzyme. During enzymatic saccharification, Saccharum arundinaceum showed higher total reducing sugar of 205 ± 3.73 mg/g when compared to other biomass. The highest percentage of bioethanol yield of 63.43 ± 9.35% was obtained with Ipomoea carnea. The effects of co-immobilized tri-enzyme biocatalyst on the biomasses were evaluated. The results revealed that the co-immobilized tri-enzyme biocatalyst could act as effective one-pot pretreatment for the production of bioethanol from lignocellulosic biomass.