The composition of accessory enzymes of Penicillium chrysogenum P33 revealed by secretome and synergistic effects with commercial cellulase on lignocellulose hydrolysis

Characterization of a rare trifunctional xylanase from endophytic fungus Chaetomium globosum and its synergistic effect with cellulase cocktail

Multifunctional xylanases present considerable potential across various sectors, including the food, chemical and biorefinery industries. Herein, a novel trifunctional xylanase Xyn1.28, identified from the lignocellulose-degrading endophytic fungus Chaetomium globosum DX-THS3, exhibits high xylanase activity (230.37 ± 2.69 U/mg) along with notable endo-glucanase activity and rare arabinofuranosidase activity, which accounted for 17-33 % and 43 % of the xylanase activity, respectively. When combined with commercial cellulase cocktail Celic CTec2 at a 1:10 activity ratio, a significant synergistic effect enhanced sugar release by 27.5 % during unpretreated corn straw degradation. Alkali-treated corn cob degradation efficiency was also improved, reducing the time to achieve maximum sugar yield by 12 h. The sugar release profiles during the initial degradation stages indicated that Xyn1.28 plays a crucial role in the initial stages of hydrolyzing biomass. Furthermore, molecular docking analysis indicated that the unique site GLN-74 may significantly influence the arabinofuranosidase activity of Xyn1.28 by forming a hydrogen bond with HIS-108. Experiments involving the mutated GLN-74 further confirmed the critical role of this site in the arabinofuranosidase activity of Xyn1.28. Overall, this rare multifunctional endo-xylanase is well-positioned to facilitate the development of efficient lignocellulose degradation systems and advance cost-effective biomass conversion.

Genomic analysis and synergistic effect with cellulase by Streptomyces thermocarboxydus 12219

In this study, we fully sequenced and analyzed the genome of strain 12219 and identified it as Streptomyces thermocarboxydus. The genome contained a single linear chromosome, 6,950,031 bp in size, with a GC content of 72.21 %. This study predicted a total of 6295 genes, including 128 glycoside hydrolase genes, 21 carbohydrate esterase genes, and 54 carbohydrate-binding module genes. When corncob was used as inducer, strain 12219 secreted cellulases and hemicellulases, with xylanase activity reaching 31.15 U/mL. During the hydrolysis of sodium hydroxide treated corn stover, a notable synergistic effect between the 12219 enzyme cocktail and commercial cellulase was observed. And the maximum degree of synergism reached 1.60. When the amount of the 12219 enzyme cocktail added to the commercial cellulase was 5 mg/g, the release of glucose, xylose, and cellobiose increased by 121.35 %, 178.58 %, and 29.33 %, respectively. These findings suggested that the 12219 enzyme cocktail held great potential for industrial applications.

Impact of straw returning on soil ecology and crop yield: A review

Several studies have demonstrated the effect of straw return on enhancing soil ecology, promoting sustainable agricultural practices, and cumulative effects on plant yield. Recent studies have focused on straw return methods and their impact on soil nutrient cycling and the overall physicochemical composition of the soil. Despite the substantial progress and successes, several research gaps in these studies require further investigations to harness the full potential of straw return. This review provides a thorough examination of straw diversity and decomposition mechanisms, the effects of straw on soil microorganisms, the interactions between cellulolytic nitrogen-fixing microbes and lignocellulose biomass, as well as nutrient mineralization, organic matter content, and their influence on plant growth and yield. This review also examined the effects of straw return on plant pathogens and its allelopathic impact on plant growth, highlighting research gaps to encourage further studies that could fully realize the potential benefits of straw return in agricultural fields for optimal plant growth.

Characterization of a novel multifunctional β-glucosidase/xylanase/feruloyl esterase and its effects on improving the quality of Longjing tea

Herein, a novel multifunctional enzyme β-glucosidase/xylanase/feruloyl esterase (GXF) was constructed by fusion of β-glucosidase and bifunctional xylanase/feruloyl esterase. The activities of β-glucosidase, xylanase, feruloyl esterase and acetyl xylan esterase displayed by GXF were 67.18 %, 49.54 %, 38.92 % and 23.54 %, respectively, higher than that of the corresponding single functional enzymes. Moreover, the GXF performed better in enhancing aroma and quality of Longjing tea than the single functional enzymes and their mixtures. After treatment with GXF, the grassy and floral odors of tea infusion were significantly improved. Moreover, GXF treatment could improve concentrations of flavonoid aglycones of myricetin, kaempferol and quercetin by 68.1-, 81.42- and 77.39-fold, respectively. In addition, GXF could accelerate the release of reducing sugars, ferulic acid and xylo-oligosaccharides by 9.48-, 8.25- and 4.11-fold, respectively. This multifunctional enzyme may have potential applications in other fields such as food production and biomass degradation.

Penicillium chrysogenum: Beyond the penicillin

Almost one century after the Sir Alexander Fleming's fortuitous discovery of penicillin and the identification of the fungal producer as Penicillium notatum, later Penicillium chrysogenum (currently reidentified as Penicillium rubens), the molecular mechanisms behind the massive production of penicillin titers by industrial strains could be considered almost fully characterized. However, this filamentous fungus is not only circumscribed to penicillin, and instead, it seems to be full of surprises, thereby producing important metabolites and providing expanded biotechnological applications. This review, in addition to summarizing the classical role of P. chrysogenum as penicillin producer, highlights its ability to generate an array of additional bioactive secondary metabolites and enzymes, together with the use of this microorganism in relevant biotechnological processes, such as bioremediation, biocontrol, production of bioactive nanoparticles and compounds with pharmaceutical interest, revalorization of agricultural and food-derived wastes or the enhancement of food industrial processes and the agricultural production.

Distinct lignocellulolytic enzymes produced by Trichoderma harzianum in response to different pretreated substrates

In order to optimize the composition of enzyme cocktail for improving the hydrolytic efficiency of lignocellulose, different substrates were tested as inducers for producing lignocellulolytic enzymes by Trichoderma harzianum EM0925 in this study. As results, ultrafine grinding or steam explosion pretreated substrates can induce T. harzianum EM0925 to secret holo lignocellulolytic enzymes; acid treated substrate can induce cellobiohydrolase; while alkali or sodium chlorite treated substrates can induce β-xylosidase specifically. Furthermore, the combination of enzyme cocktails with different hydrolysis characteristics can further improve the hydrolysis efficiency, since 100% yields of glucose and xylose were obtained simultaneously from ultrafine grinding treated corn stover at low enzyme dosage (1.2 mg proteins/g substrate). This study for the first time demonstrated an effective solution that specific-pretreated substrates can be used as inducers for specific enzyme production by T. harzianum, which provided new idea and potential strategy for the construction of highly-efficient lignocellulolytic enzyme cocktails.

Investigation of Abortiporus biennis lignocellulolytic toolbox, and the role of laccases in polystyrene degradation

White-rot basidiomycetes are the only microorganisms able to produce both hydrolytic (cellulases and hemicellulases) and oxidative (ligninolytic) enzymes for degrading all lignocellulose constituents. Their enzymatic machinery makes them ideal for the discovery of novel enzymes with desirable properties. In the present work, Abortiporus biennis, a white-rot fungus, was studied in regard to its lignocellulolytic potential. Secretomics and biochemical analyses were employed to study the strain's enzymatic arsenal, after growth in corn stover cultures and xylose-based defined media. The results revealed the presence of all the necessary enzymatic activities for complete breakdown of biomass, while the prominent role of oxidative enzymes in the lignocellulolytic strategy of the strain became evident. Two novel laccases, AbiLac1 and AbiLac2, were isolated from the culture supernatant with ion-exchange chromatography. Characterization of purified laccases revealed their ability to oxidize a wide variety of phenolic and non-phenolic substrates. AbiLac1 was found to oxidize polystyrene powder, showing high depolymerization potential, based on radical chain scission mechanism as evidenced by molecular weight decrease. The results of the present study demonstrate the biotechnological potential of the unexplored enzymatic machinery of white-rot basidiomycetes, including the design of improved lignocellulolytic cocktails, as well as the degradation and/or valorization of plastic waste materials.

Potential of lignocellulose degrading microorganisms for agricultural residue decomposition in soil: A review

Lignocellulosic crop residues (LCCRs) hold a significant share of the terrestrial biomass, estimated at 5 billion Mg per annum globally. A massive amount of these LCCRs are burnt in many countries resulting in immense environmental pollution; hence, its proper disposal in a cost-effective and eco-friendly manner is a significant challenge. Among the different options for management of LCCRs, the use of lignocellulose degrading microorganisms (LCDMOs), like fungi and bacteria, has emerged as an eco-friendly and effective way for its on-site disposal. LCDMOs achieve degradation through various mechanisms, including multiple supportive enzymes, causing oxidative attacks by which recalcitrance of lignocellulose material is reduced, paving the way to further activity by depolymerizing enzymes. This improves the physical properties of soil, recycles plant nutrients, promotes plant growth and thus helps improve productivity. Rapid and proper microbial degradation may be achieved through the correct combination of the LCDMOs, supplementing nutrients and controlling different factors affecting microbial activity in the field. The review is a critical discussion of previous studies revealing the potential of individuals or a set of LCDMOs, factors controlling the rate of degradation and the key researchable areas for better understanding of the role of these decomposers for future use.

Synergistic hydrolysis of filter paper by recombinant cellulase cocktails leveraging a key cellobiase, Cba2, of Cellulomonas biazotea

Cellulomonas biazotea, a Gram-positive cellulolytic bacterium isolated from soil, is capable of producing a complete cellulase complex exhibiting endoglucanase, exoglucanase, and cellobiase activities. Despite the presence of a full complement of all three types of cellulases, samples prepared from both cell lysates and culture media of C. biazotea showed only weak synergistic activities formed among the cellulase components, as reflected by their inefficient performance in filter paper hydrolysis. However, when the five previously characterized recombinant cellobiases of C. biazotea were mixed individually or in different combinations with recombinant enzyme preparations (CenA/Cex) containing an endoglucanase, CenA, and an exoglucanase, Cex, of another Cellulomonas species, C. fimi, the cellulase cocktails exhibited not only much higher but also synergistic activities in filter paper hydrolysis. Among the 5 C. biazotea cellobiases studied, Cba2 was shown to perform 2.8 to 3.8 times better than other homologous isozymes when acting individually with CenA/Cex. More noteworthy is that when Cba2 and Cba4 were added together to the reaction mixture, an even better synergistic effect was achieved. The filter paper activities resulting from Cba2 and Cba4 interacting with CenA/Cex are comparable to those obtained from some commercial fungal cellulase mixtures. To our knowledge, our results represent the first demonstration of synergistic effects on filter paper hydrolysis achieved using recombinant bacterial cellulases.

Improving saccharification of ramie stalks by synergistic effect of in-house cellulolytic enzymes consortium

The high cost of cellulase is one of the main obstacles hindering the large-scale biorefining of lignocellulosic biomass. Therefore, developing efficient method for preparation of cellulase is promising. In the present study, the production of cellulase by Trichoderma reesei, Trichoderma harzianum, and Aspergillus niger was optimized, and the synergistic effect of these cellulase on enzymatic hydrolysis of pretreated ramie stalks was also evaluated. The maximum CMCase (Carboxymethyl Cellulase) and filter paper activity (FPA) produced by T. reesei reached to 3.12 IU/mL and 0.13 IU/mL, respectively. The maximum activities of CMCase (3.68 IU/mL), FPA (0.04 IU/mL) and β-glucosidase (8.44 IU/mL) were obtained from A. niger. The results also showed that under the premise of the same FPA activity, the contribution of β-glucosidase activity to yield of reducing sugar was greater than that of CMCase. Besides, cellulase produced by T. reesei and A. niger had the best synergistic effect on enzymatic hydrolysis of pretreated ramie stalks. The highest reducing sugars yield (417 mg/g dry substrate) was achieved when enzyme cocktail was prepared at the ratio of 1:1, which was 1.36–3.35 folds higher than that of different single enzymes. The present research has provided a novel method for efficient preparation of enzymes consortium for enzymatic hydrolysis of ramie stalks.

Barley Husk Degraded by Fusarium graminearum MH1 Induced Premature Yeast Flocculation

Premature yeast flocculation (PYF) is one of the pivotal problems affecting beer flavor and production. PYF is induced by certain non-starch polysaccharides produced by the degradation of malted barley husks upon the growth of contaminated microorganisms, such as Fusarium graminearum. In this research, the formation mechanism of PYF was uncovered by investigating the secretome of F. graminearum MH1 inoculated to the barley husk. The polysaccharide extract of degraded husk was ultrafiltrated into four fractions and characterized by the minimum PYF concentration, molecular mass distribution, monosaccharide composition, and zeta potential. Among the four fractions, the high-molecular-weight polysaccharide fraction had the highest content of uronic acid and the most negative zeta potential, which contributed to the most severe PYF phenomenon. In addition, the PYF yeast showed a more negative zeta potential than the control yeast during the small-scale brewing process. This is aligned to the negatively charged polysaccharides potentially bonded to the surface of yeast cells through the calcium cation in the same fermentation system, which results in rapid flocculation and precipitation. Approximately 12% of the 214 proteins identified in the Fusarium graminearum MH1 secretome were hemicellulases, which substantially interpreted the mechanism of polysaccharides inducing PYF yeast during beer brewing.

Fungal Lignocellulose Utilisation Strategies from a Bioenergetic Perspective: Quantification of Related Functional Traits Using Biocalorimetry

In the present study, we investigated whether a non-invasive metabolic heat flux analysis could serve the determination of the functional traits in free-living saprotrophic decomposer fungi and aid the prediction of fungal influences on ecosystem processes. For this, seven fungi, including ascomycete, basidiomycete, and zygomycete species, were investigated in a standardised laboratory environment, employing wheat straw as a globally relevant lignocellulosic substrate. Our study demonstrates that biocalorimetry can be employed successfully to determine growth-related fungal activity parameters, such as apparent maximum growth rates (AMGR), cultivation times until the observable onset of fungal growth at AMGR (tAMGR), quotients formed from the AMGR and tAMGR (herein referred to as competitive growth potential, CGP), and heat yield coefficients (YQ/X), the latter indicating the degree of resource investment into fungal biomass versus other functional attributes. These parameters seem suitable to link fungal potentials for biomass production to corresponding ecological strategies employed during resource utilisation, and therefore may be considered as fungal life history traits. A close connection exists between the CGP and YQ/X values, which suggests an interpretation that relates to fungal life history strategies.

Production of cellulosic ethanol and value-added products from corn fiber

Corn fiber, a by-product from the corn processing industry, mainly composed of residual starch, cellulose, and hemicelluloses, is a promising raw material for producing cellulosic ethanol and value-added products due to its abundant reserves and low costs of collection and transportation. Now, several technologies for the production of cellulosic ethanol from corn fiber have been reported, such as the D3MAX process, Cellerate™ process, etc., and part of the technologies have also been used in industrial production in the United States. The ethanol yields range from 64 to 91% of the theoretical maximum, depending on different production processes. Because of the multicomponent of corn fiber and the complex structures highly substituted by a variety of side chains in hemicelluloses of corn fiber, however, there are many challenges in cellulosic ethanol production from corn fiber, such as the low conversion of hemicelluloses to fermentable sugars in enzymatic hydrolysis, high production of inhibitors during pretreatment, etc. Some technologies, including an effective pretreatment process for minimizing inhibitors production and maximizing fermentable sugars recovery, production of enzyme preparations with suitable protein compositions, and the engineering of microorganisms capable of fermenting hexose and pentose in hydrolysates and inhibitors tolerance, etc., need to be further developed. The process integration of cellulosic ethanol and value-added products also needs to be developed to improve the economic benefits of the whole process. This review summarizes the status and progresses of cellulosic ethanol production and potential value-added products from corn fiber and presents some challenges in this field at present.

The transcription factor ZmMYB69 represses lignin biosynthesis by activating ZmMYB31/42 expression in maize

A MYB family transcription factor ZmMYB69 is a transcriptional activator at the upper level of ZmMYB31 and ZmMYB42 in the hierarchical network that controls lignin biosynthesis in maize.

Biochemical characterization of an engineered bifunctional xylanase/feruloyl esterase and its synergistic effects with cellulase on lignocellulose hydrolysis

Herein, the xylanase and feruloyl esterase domains of the xylanase/feruloyl esterase bifunctional enzyme (Xyn-Fae) from Prevotella ruminicola 23 were identified using N- and C-terminal truncation mutagenesis. In addition, a novel and more efficient xylanase/feruloyl esterase bifunctional enzyme XynII-Fae was constructed, and its synergistic action with a commercial cellulase for lignocellulose hydrolysis was studied. When 40% cellulase was replaced by XynII-Fae, the production of reducing sugars increased by 65% than that with the cellulase alone, and the conversions of xylan and glucan were increased by 125.1% and 54.3%, respectively. When 80% cellulase was substituted by XynII-Fae, up to 43.5 μg/mL ferulic acid and 418.7 μg/mL acetic acid were obtained. The XynII-Fae could also accelerate the hydrolysis of wheat straw and sugarcane bagasse with commercial cellulase. These results indicated that the synergistic action of XynII-Fae with cellulase could dramatically improve the hydrolysis efficiency of lignocellulose, showing the great potential for industrial applications.

Characterisation of a Novel Acetyl Xylan Esterase (BaAXE) Screened from the Gut Microbiota of the Common Black Slug (Arion ater)

Acetyl xylan esterases (AXEs) are enzymes capable of hydrolysing the acetyl bonds in acetylated xylan, allowing for enhanced activity of backbone-depolymerizing enzymes. Bioprospecting novel AXE is essential in designing enzyme cocktails with desired characteristics targeting the complete breakdown of lignocellulose. In this article, we report the characterisation of a novel AXE identified as Gene_id_40363 in the metagenomic library analysed from the gut microbiota of the common black slug. The conserved domain description was identified with an NCBI BLASTp search using the translated nucleotide sequence as a query. The activity of the recombinant enzyme was tested on various synthetic substrates and acetylated substrates. The protein sequence matched the conserved domain described as putative hydrolase and aligned closely to an uncharacterized esterase from Buttiauxella agrestis, hence the designation as BaAXE. BaAXE showed low sequence similarity among characterized CE family proteins with an available 3D structure. BaAXE was active on 4-nitrophenyl acetate, reporting a specific activity of 78.12 U/mg and a Km value of 0.43 mM. The enzyme showed optimal activity at 40 °C and pH 8 and showed high thermal stability, retaining over 40% activity after 2 h of incubation from 40 °C to 100 °C. BaAXE hydrolysed acetyl bonds, releasing acetic acid from acetylated xylan and β-D-glucose pentaacetate. BaAXE has great potential for biotechnological applications harnessing its unique characteristics. In addition, this proves the possibility of bioprospecting novel enzymes from understudied environments.

Fungal glycosyl hydrolases for sustainable plant biomass valorization: Talaromyces amestolkiae as a model fungus

As the main decomposers and recyclers in nature, fungi secrete complex mixtures of extracellular enzymes for degradation of plant biomass, which is essential for mobilization of the organic carbon fixed by the photosynthesis in vegetal cells. Biotechnology can emulate the closed natural biological cycles, using lignocellulosic biomass as a renewable resource and lignocellulolytic fungal enzymes as catalysts to sustainably produce consumer goods. Cellulose and hemicellulose are the major polysaccharides on Earth, and the main enzymes involved in their hydrolytic depolymerization are cellulases (endoglucanases, cellobiohydrolases, and β-glucosidases) and hemicellulases (mainly endoxylanases and β-xylosidases). This work will focus on the enzymes secreted by the filamentous ascomycete Talaromyces amestolkiae and on some of their biotechnological applications. Their excellent hydrolytic activity was demonstrated by the partial degradation of xylans to prebiotic oligosaccharides by the endoxylanase XynN, or by the saccharification of lignocellulosic wastes to monosaccharides (fermentable to ethanol) either by the whole secretomes or by isolated enzymes used as supplements of commercial cocktails. However, apart from their expected hydrolytic activity, some of the β-glycosidases produced by this strain catalyze the transfer of a sugar molecule to specific aglycons by transglycosylation. As the synthesis of customized glycoconjugates is a major goal for biocatalysis, mutant variants of the β-xyloxidase BxTW1 and the ß-glucosidases BGL-1 and BGL-2 were obtained by directed mutagenesis, substantially improving the regioselective production yields of bioactive glycosides since they showed reduced or null hydrolytic activity.

Cellulose induced protein 1 (Cip1) from Trichoderma reesei enhances the enzymatic hydrolysis of pretreated lignocellulose

Background

Trichoderma reesei is currently the main strain for the commercial production of cellulase. Cellulose induced protein 1 (Cip1) is one of the most abundant proteins in extracellular proteins of T. reesei. Reported literatures about Cip1 mainly focused on the regulation of Cip1 and its possible enzyme activities, but the effect of Cip1 on the enzymatic hydrolysis of lignocellulose and possible mechanism have not still been reported.

Results

In this study, Cip1 from T. reesei was cloned, expressed and purified, and its effects on enzymatic hydrolysis of several different pretreated lignocellulose were investigated. It was found that Cip1 could promote the enzymatic hydrolysis of pretreated lignocellulose, and the promoting effect was significantly better than that of bovine serum albumin (BSA). And especially for the lignocellulosic substrate with high lignin content such as liquid hot water pretreated corn stover and corncob residue, the promoting effect of Cip1 was even better than that of the commercial cellulase when adding equal amount protein. It was also showed that the metal ions Zn²⁺ and Cu²⁺ influenced the promoting effect on enzymatic hydrolysis. The Cip1 protein had no lyase activity, but it could destroy the crystal structure of cellulose and reduce the non-productive adsorption of cellulase on lignin, which partly interpreted the promoting effect of Cip1 on enzymatic hydrolysis of lignocellulose.

Conclusion

The Cip1 from T. reesei could significantly promote the enzymatic hydrolysis of pretreated lignocellulose, and the promotion of Cip1 was even higher than that of commercial cellulase in the enzymatic hydrolysis of the substrates with high lignin content. This study will help us to better optimize cellulase to improve its ability to degrade lignocellulose, thereby reducing the cost of enzymes required for enzymatic hydrolysis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-021-01625-z.

Harnessing microbial wealth for lignocellulose biomass valorization through secretomics: a review

The recalcitrance of lignocellulosic biomass is a major constraint to its high-value use at industrial scale. In nature, microbes play a crucial role in biomass degradation, nutrient recycling and ecosystem functioning. Therefore, the use of microbes is an attractive way to transform biomass to produce clean energy and high-value compounds. The microbial degradation of lignocelluloses is a complex process which is dependent upon multiple secreted enzymes and their synergistic activities. The availability of the cutting edge proteomics and highly sensitive mass spectrometry tools make possible for researchers to probe the secretome of microbes and microbial consortia grown on different lignocelluloses for the identification of hydrolytic enzymes of industrial interest and their substrate-dependent expression. This review summarizes the role of secretomics in identifying enzymes involved in lignocelluloses deconstruction, the development of enzyme cocktails and the construction of synthetic microbial consortia for biomass valorization, providing our perspectives to address the current challenges.

Current understanding of the inhibition factors and their mechanism of action for the lignocellulosic biomass hydrolysis

Biorefining of lignocellulosic biomass is a relatively new concept but it has strong potential to develop and partially replace the fossil derived fuels and myriad of value products to subsequently reduce the greenhouse gas emissions. However, the energy and cost intensive process of releasing the entrapped fermentable sugars is a major challenge for its commercialization. Various factors playing a detrimental role during enzymatic hydrolysis of biomass are inherent recalcitrance of lignocellulosic biomass, expensive enzymes, sub-optimal enzyme composition, lack of synergistic activity and enzyme inhibition caused by various inhibitors. The current study investigated the mechanism of enzyme inhibition during lignocellulosic biomass saccharification especially at high solid loadings. These inhibition factors are categorized into physio-chemical factors, water-soluble and -insoluble enzyme inhibitors, oligomers and enzyme-lignin binding. Furthermore, different approaches are proposed to alleviate the challenges and improve the enzymatic hydrolysis efficiency such as supplementation with surfactants, synergistic catalytic/non-catalytic proteins, and bioprocess modifications.

An In Vitro Evaluation of the Biocidal Effect of Oregano and Cloves’ Volatile Compounds against Microorganisms Colonizing an Oil Painting—A Pioneer Study

In this study, the biocidal activity of two plant derivatives (oregano and cloves’ essential oils—EOs) was evaluated, as a potential innovative and eco-friendly cleaning method for canvas paintings. The object of the study was the oil painting on canvas entitled “Studio di nudo” (Giovanni Maria Mossa, 1921), showing stains caused by microorganisms. The research focused on: (1) isolation and identification of microorganisms associated with discolorations on the obverse and reverse sides of the canvas; (2) evaluation of biocidal activity of selected EOs against fungal and bacterial collections. The phylogenetic identification was conducted with both cultivation and molecular methods. The canvas was mainly colonized by Penicillium, Aspergillus, and Cephaloteca fungal genera and by bacteria of the Bacillus genus. To evaluate the biocidal effect of the EOs’ volatile components only, an antibiogram assay (agar disc diffusion method) and a customized assay (named the contactless test) were conducted. Tested EOs showed antimicrobial activity on fungi and bacteria. However, compared to cloves, oregano EO exhibited a better inhibition activity both in contact and contactless tests. The work is pioneering for the use of EOs’ volatile compounds against oil painting biodeteriogens, and gives insights into possible extended, innovative and eco-friendly cleaning methods for painting control procedures.

The functioning of a novel protein, Swollenin, in promoting the lignocellulose degradation capacity of Trichoderma guizhouense NJAU4742 from a proteomic perspective

The functioning of a novel auxiliary enzyme, TgSWO from Trichoderma guizhouense NJAU4742, was investigated based on the proteomic analysis of wild-type (WT), knockout (KO) and overexpression (OE) treatments. The results showed that the cellulase and hemicellulase activities of OE and WT were significantly higher than those of KO. Simultaneously, tandem mass tag (TMT) analysis results indicated that cellulases and hemicellulases were significantly upregulated in OE, especially hydrophobin (HFB, A1A105805.1) and endo-β-1,4-glucanases (A1A101831.1), with ratios of 43.73 and 9.88, respectively, compared with WT. The synergistic effect of TgSWO on cellulases increased the reducing sugar content by 1.45 times in KO + TgSWO (1.8 mg) compared with KO, and there was no significant difference between KO + TgSWO (1.2 mg) and WT. This study elucidated the function of TgSWO in promoting the lignocellulose degradation capacity of NAJU4742, which provides new insights into the efficient conversion of lignocellulose.

Low-Cost Cellulase-Hemicellulase Mixture Secreted by Trichoderma harzianum EM0925 with Complete Saccharification Efficacy of Lignocellulose

Fermentable sugars are important intermediate products in the conversion of lignocellulosic biomass to biofuels and other value-added bio-products. The main bottlenecks limiting the production of fermentable sugars from lignocellulosic biomass are the high cost and the low saccharification efficiency of degradation enzymes. Herein, we report the secretome of Trichoderma harzianum EM0925 under induction of lignocellulose. Numerously and quantitatively balanced cellulases and hemicellulases, especially high levels of glycosidases, could be secreted by T. harzianum EM0925. Compared with the commercial enzyme preparations, the T. harzianum EM0925 enzyme cocktail presented significantly higher lignocellulolytic enzyme activities and hydrolysis efficiency against lignocellulosic biomass. Moreover, 100% yields of glucose and xylose were obtained simultaneously from ultrafine grinding and alkali pretreated corn stover. These findings demonstrate a natural cellulases and hemicellulases mixture for complete conversion of biomass polysaccharide, suggesting T. harzianum EM0925 enzymes have great potential for industrial applications.

The boosting effect of recombinant hemicellulases on the enzymatic hydrolysis of steam-treated sugarcane bagasse

To increase the efficiency of enzyme cocktails in deconstructing cellulose and hemicelluloses present in the plant cell wall, a combination of enzymes with complementary activities is required. Xylan is the main hemicellulose component of energy crops and for its complete hydrolysis a system consisting of several enzymes acting cooperatively, including endoxylanases (XYN), β-xylosidases (XYL) and α-l-arabinofuranosidases (ABF) is necessary. The current work aimed at evaluating the effect of recombinant hemicellulolytic enzymes on the enzymatic hydrolysis of steam-exploded sugarcane bagasse (SEB). One recombinant endoxylanase (HXYN2) and one recombinant β-xylosidase (HXYLA) from Humicola grisea var thermoidea, together with an α-l-arabinofuranosidase (AFB3) from Penicillium pupurogenum, all produced in Pichia pastoris, were used to formulate an efficient enzyme mixture for SEB hydrolysis using a 2³ Central Composite Rotatable Design (CCRD). The most potent enzyme for SEB hydrolysis was ABF3. Subsequently, the optimal enzyme mixture was used in combination with commercial cellulases (Accellerase 1500), either simultaneously or in sequential experiments. The supplementation of Accellerase 1500 with hemicellulases enhanced the glucose yield from SEB hydrolysis by 14.6%, but this effect could be raised to 50% when hemicellulases were added prior to hydrolysis with commercial cellulases. These results were supported by scanning electron microscopy, which revealed the effect of enzymatic hydrolysis on SEB fibers. Our results show the potential of complementary enzyme activities to improve enzymatic hydrolysis of SEB, thus improving the efficiency of the hydrolytic process.

Cooperation of hydrolysis modes among xylanases reveals the mechanism of hemicellulose hydrolysis by Penicillium chrysogenum P33

Background

Xylanases randomly cleave the internal β-1,4-glycosidic bonds in the xylan backbone and are grouped into different families in the carbohydrate-active enzyme (CAZy) database. Although multiple xylanases are detected in single strains of many filamentous fungi, no study has been reported on the composition, synergistic effect, and mode of action in a complete set of xylanases secreted by the same microorganism.

Results

All three xylanases secreted by Penicillium chrysogenum P33 were expressed and characterized. The enzymes Xyl1 and Xyl3 belong to the GH10 family and Xyl3 contains a CBM1 domain at its C-terminal, whereas Xyl2 belongs to the GH11 family. The optimal temperature/pH values were 35 °C/6.0, 50 °C/5.0 and 55 °C/6.0 for Xyl1, Xyl2, and Xyl3, respectively. The three xylanases exhibited synergistic effects, with the maximum synergy observed between Xyl3 and Xyl2, which are from different families. The synergy between xylanases could also improve the hydrolysis of cellulase (C), with the maximum amount of reducing sugars (5.68 mg/mL) observed using the combination of C + Xyl2 + Xyl3. Although the enzymatic activity of Xyl1 toward xylan was low, it was shown to be capable of hydrolyzing xylooligosaccharides into xylose. Xyl2 was shown to hydrolyze xylan to long-chain xylooligosaccharides, whereas Xyl3 hydrolyzed xylan to xylooligosaccharides with a lower degree of polymerization.

Conclusions

Synergistic effect exists among different xylanases, and it was higher between xylanases from different families. The cooperation of hydrolysis modes comprised the primary mechanism for the observed synergy between different xylanases. This study demonstrated, for the first time, that the hydrolysates of GH11 xylanases can be further hydrolyzed by GH10 xylanases, but not vice versa.

Bioethanol production from waste lignocelluloses: A review on microbial degradation potential

Tremendous explosion of population has led to about 200% increment of total energy consumptions in last twenty-five years. Apart from conventional fossil fuel as limited energy source, alternative non-conventional sources are being explored worldwide to cater the energy requirement. Lignocellulosic biomass conversion for biofuel production is an important alternative energy source due to its abundance in nature and creating less harmful impacts on the environment in comparison to the coal or petroleum-based sources. However, lignocellulose biopolymer, the building block of plants, is a recalcitrant substance and difficult to break into desirable products. Commonly used chemical and physical methods for pretreating the substrate are having several limitations. Whereas, utilizing microbial potential to hydrolyse the biomass is an interesting area of research. Because of the complexity of substrate, several enzymes are required that can act synergistically to hydrolyse the biopolymer producing components like bioethanol or other energy substances. Exploring a range of microorganisms, like bacteria, fungi, yeast etc. that utilizes lignocelluloses for their energy through enzymatic breaking down the biomass, is one of the options. Scientists are working upon designing organisms through genetic engineering tools to integrate desired enzymes into a single organism (like bacterial cell). Studies on designer cellulosomes and bacteria consortia development relating consolidated bioprocessing are exciting to overcome the issue of appropriate lignocellulose digestions. This review encompasses up to date information on recent developments for effective microbial degradation processes of lignocelluloses for improved utilization to produce biofuel (bioethanol in particular) from the most plentiful substances of our planet.

Structural and functional characterisation of xylanase purified from Penicillium chrysogenum produced in response to raw agricultural waste

Commercial interest in plant cell wall degrading enzymes (PCWDE) is motivated by their potential for energy or bioproduct generation that reduced dependency on non-renewable (fossil-derived) feedstock. Therefore, underlying work analysed the Penicillium chrysogenum isolate for PCWDE production by employing different biomass as a carbon source. Among the produced enzymes, three xylanase isoforms were observed in the culture filtrate containing sugarcane bagasse. Xylanase (PcX1) presenting 35 kDa molecular mass was purified by gel filtration and anion exchange chromatography. Unfolding was probed and analysed using fluorescence, circular dichroism and enzyme assay methods. Secondary structure contents were estimated by circular dichroism 45% α-helix and 10% β-sheet, consistent with the 3D structure predicted by homology. PcX1 optimally active at pH 5.0 and 30 °C, presenting t_1/2 19 h at 30 °C and 6 h at 40 °C. Thermodynamic parameters/melting temperature 51.4 °C confirmed the PcX1 stability at pH 5.0. PcX1 have a higher affinity for oat spelt xylan, K_M 1.2 mg·mL^-1, in comparison to birchwood xylan K_M 29.86 mg·mL^-1, activity was inhibited by Cu⁺² and activated by Zn⁺². PcX1 exhibited significant tolerance for vanillin, trans-ferulic acid, ρ-coumaric acid, syringaldehyde and 4-hydroxybenzoic acid, activity slightly inhibited (17%) by gallic and tannic acid.

Prospecting of soybean hulls as an inducer carbon source for the cellulase production

Cellulases constitute an enzymatic complex involved in the cellulose hydrolysis β-1, 4-glycosidic linkages to release of glucose. Therefore, its application to degrade agro-industrial residues becomes relevant, since glucose is a product of industrial interest, aiming at its conversion into biocommodity production (e.g., enzymes, bioethanol and other value-added biochemicals). Thus, in natura Soybean hulls as well as fractions obtained from its alkaline, autohydrolysis and organosolv pretreatments were used as carbon sources in submerged fermentation processes to evaluate the cellulase-inducing capacity using a Penicillium sp. strain. Results showed an inductive effect on the production of 0.130 and 0.066 U/mL for CMCase and FPase, respectively, using 1% of the in natura residue. Regarding the fraction obtained from soybean hulls pretreated by autohydrolysis and organosolv, avicelase and β-Glucosidase displayed a production of 0.200 and 0.550 U/mL, respectively. Therefore, the use of pretreated Soybean hull revealed its potential as an alternative carbon source for the cellulase production, which may contribute significantly to biotechnological purposes by adding value to an agro-industrial residue.