Penicillium : The next emerging champion for cellulase production

Regulation of genes encoding polysaccharide-degrading enzymes in Penicillium

Penicillium fungi, including Penicillium oxalicum, can secrete a range of efficient plant-polysaccharide-degrading enzymes (PPDEs) that is very useful for sustainable bioproduction, using renewable plant biomass as feedstock. However, the low efficiency and high cost of PPDE production seriously hamper the industrialization of processes based on PPDEs. In Penicillium, the expression of PPDE genes is strictly regulated by a complex regulatory system and molecular breeding to modify this system is a promising way to improve fungal PPDE yields. In this mini-review, we present an update on recent research progress concerning PPDE distribution and function, the regulatory mechanism of PPDE biosynthesis, and molecular breeding to produce PPDE-hyperproducing Penicillium strains. This review will facilitate future development of fungal PPDE production through metabolic engineering and synthetic biology, thereby promoting PPDE industrial biorefinery applications. KEY POINTS: • This mini review summarizes PPDE distribution and function in Penicillium. • It updates progress on the regulatory mechanism of PPDE biosynthesis in Penicillium. • It updates progress on breeding of PPDE-hyperproducing Penicillium strains.

Lignocellulolytic Enzymes Production by Four Wild Filamentous Fungi for Olive Stones Valorization: Comparing Three Fermentation Regimens

Lignocellulolytic enzymes play a crucial role in efficiently converting lignocellulose into valuable platform molecules in various industries. However, they are limited by their production yields, costs, and stability. Consequently, their production by producers adapted to local environments and the choice of low-cost raw materials can address these limitations. Due to the large amounts of olive stones (OS) generated in Morocco which are still undervalued, Penicillium crustosum, Fusarium nygamai, Trichoderma capillare, and Aspergillus calidoustus, are cultivated under different fermentation techniques using this by-product as a local lignocellulosic substrate. Based on a multilevel factorial design, their potential to produce lignocellulolytic enzymes during 15 days of dark incubation was evaluated. The results revealed that P. crustosum expressed a maximum total cellulase activity of 10.9 IU/ml under sequential fermentation (SF) and 3.6 IU/ml of β-glucosidase activity under submerged fermentation (SmF). F. nygamai recorded the best laccase activity of 9 IU/ml under solid-state fermentation (SSF). Unlike T. capillare, SF was the inducive culture for the former activity with 7.6 IU/ml. A. calidoustus produced, respectively, 1,009 μg/ml of proteins and 11.5 IU/ml of endoglucanase activity as the best results achieved. Optimum cellulase production took place after the 5th day under SF, while ligninases occurred between the 9th and the 11th days under SSF. This study reports for the first time the lignocellulolytic activities of F. nygamai and A. calidoustus. Furthermore, it underlines the potential of the four fungi as biomass decomposers for environmentally-friendly applications, emphasizing the efficiency of OS as an inducing substrate for enzyme production.

Draft genome sequence data of Antarctic Penicillium sp. strain E22, from Deception Island

Here, we report the draft genome sequence and assembly of the Penicillium sp. strain E22, which was isolated from Antarctic soil of Deception Island, South Shetland Islands close to the Antarctic Peninsula. The genome was sequenced using a 2 # 250 bp paired-end method by Illumina MiSeq 6000. The genome assembly was performed using softwares implemented in the Kbase web service. The phylogenetic tree of strain E22 comparing its internal transcribed spacer (ITS) region with the other Penicillium showed high genetic similarity to Penicillium griseofulvum MN545450 and Penicillium camemberti MT530220. Draf genome of Penicillium sp. strain E22 comprises 33,653 coding sequences, with a high G + C content of 48.32% and a total size of 37,484,944 bp. This draft genome assembly version has been deposited at GenBank under accession JASJUN000000000.

Calcium signaling positively regulates cellulase translation and secretion in a Clr-2-overexpressing, catabolically derepressed strain of Penicillium funiculosum

BACKGROUND

Low-cost cellulase production is vital to sustainable second-generation biorefineries. The catabolically derepressed strain of Penicillium funiculosum NCIM1228 (PfMig188 or ∆Mig1) secretes a superior set of cellulolytic enzymes, that are most suitable for 2G biorefineries. At a 3% (w/w) load, the ∆Mig1 secretome can release > 80% of fermentable sugars from lignocellulose at a 15% (w/v) biomass load, irrespective of the type of biomass and pretreatment. The robustness of the secretome can be further increased by improving the cellulase production capacity of the fungal strain.

RESULTS

We began by identifying the transcription factor responsible for cellulase production in NCIM1228. An advanced RNA-seq screen identified three genes, clr-2, ctf1a and ctf1b; the genes were cloned under their native promoters and transformed into NCIM1228. Of the three, clr-2 overexpression led to twofold higher cellulase production than the parent strain and was thus identified as the transcriptional activator of cellulase in NCIM1228. Next, we overexpressed clr-2 in ∆Mig1 and expected an exponential increase in cellulolytic attributes accredited to the reinforced activation mechanisms, conjoint with diminished negative regulation. Although clr-2 overexpression increased the transcript levels of cellulase genes in ∆Mig1, there was no increase in cellulase yield. Even a further increase in the transcript levels of clr-2 via a stronger promoter was ineffective. However, when the CaCO3 concentration was increased to 5 g/l in the growth medium, we achieved a 1.5-fold higher activity of 6.4 FPU/ml in the ∆Mig1 strain with clr-2 overexpression. Enthused by the calcium effect, a transcriptomic screen for genes encoding Ca2+-activated kinase identified ssp1, whose overexpression could further increase cellulase yield to ~ 7.5 FPU/ml. Investigation of the mechanism revealed that calcium signaling exclusively enhances the translation and secretion of cellulase in Penicillium funiculosum.

CONCLUSIONS

Our study identifies for the first time that cellulose activates two discrete signaling events to govern cellulase transcription and posttranscriptional processes (translation, processing and secretion) in P. funiculosum NCIM1228. Whereas Clr-2, the transcriptional activator of cellulase, governs transcription, calcium signaling specifically activates cellulase translation and secretion.

Pretreatment of Luzhou distiller's grains for feed protein production using crude enzymes produced by a synthetic microbial consortium

Chinese distillers' grains (CDGs) have low fermentation efficiency due to the presence of lignocellulosic components, such as rice husk. In this study, a microbial consortium synthesized was used based on the "functional complementarity" principle to produce lignocellulolytic crude enzyme. The crude enzyme was used to hydrolyze CDGs. After enzymatic hydrolysis, lignocellulose was damaged to varying degrees and the crystallinity decreased. Subsequently, the feed protein was produced using yeast through two pathways. The results showed that the crude enzyme produced by the microbial consortium (comprising Trichoderma reesei, Aspergillus niger, and Penicillium) exhibited excellent enzymatic efficiency, yielding 27.88%, 19.64%, and 10.88% of reducing sugar, cellulose, and hemicellulose. The true protein content of CDGs increased by 53.49% and 48.35% through the first and second pathways, respectively. Notably, the second pathway demonstrated higher economic benefits to produce feed protein. This study provides a pathway for high-quality utilization of CDGs.

Every road leads to Rome: diverse biosynthetic regulation of plant cell wall-degrading enzymes in filamentous fungi Penicillium oxalicum and Trichoderma reesei

Cellulases and xylanases are plant cell wall-degrading enzymes (CWDEs) that are critical to sustainable bioproduction based on renewable lignocellulosic biomass to reduce carbon dioxide emission. Currently, these enzymes are mainly produced from filamentous fungi, especially Trichoderma reesei and Penicillium oxalicum. However, an in-depth comparison of these two producers has not been performed. Although both P. oxalicum and T. reesei harbor CWDE systems, they exhibit distinct features regulating the production of these enzymes, mainly through different transcriptional regulatory networks. This review presents the strikingly different modes of genome-wide regulation of cellulase and xylanase biosynthesis in P. oxalicum and T. reesei, including sugar transporters, signal transduction cascades, transcription factors, chromatin remodeling, and three-dimensional organization of chromosomes. In addition, different molecular breeding approaches employed, based on the understanding of the regulatory networks, are summarized. This review highlights the existence of very different regulatory modes leading to the efficient regulation of CWDE production in filamentous fungi, akin to the adage that "every road leads to Rome." An understanding of this divergence may help further improvements in fungal enzyme production through the metabolic engineering and synthetic biology of certain fungal species.

Profiling of the β-glucosidases identified in the genome of Penicillium funiculosum: insights from genomics, transcriptomics, proteomics, and homology-modeling studies

The enzymatic conversion of lignocellulosic biomass to bioethanol depends on efficient enzyme systems with β-glucosidase as one of the key components. In this study, we performed in-depth profiling of the various β-glucosidases present in the genome of the hypercellulolytic fungus Penicillium funiculosum using genomics, transcriptomics, proteomics, and molecular dynamics simulation approaches. Of the eight β-glucosidase genes identified in the P. funiculosum genome, three were predicted to be extracellular based on signal peptide prediction and abundance in the secretome. Among the three secreted β-glucosidases, two belonged to the GH3 family and one belonged to the GH1 family. Homology models of these proteins predicted a deep and narrow active site for the GH3 β-glucosidases (PfBgl3A and PfBgl3B) and a shallow open active site for the GH1 β-glucosidase (PfBgl1A). The enzymatic assays indicated that P. funiculosum-secreted proteins showed high β-glucosidase activities with prominent bands on the 4-methylumbelliferyl β-D-glucopyranoside zymogram. To understand the contributory effects of each of the three secreted β-glucosidases (PfBgls), the corresponding gene was deleted separately, and the effect of the deletion on the β-glucosidase activity of the secretome was examined. Although not the most abundant, PfBgl3A was found to be one of the most important β-glucosidases, as evidenced by a 42% reduction in β-glucosidase activity in the ΔPfBgl3A strain. Our results advance the understanding of the genetic and biochemical nature of all β-glucosidases produced by P. funiculosum and pave the way to design a superior biocatalyst for the hydrolysis of lignocellulosic biomass. IMPORTANCE Commercially available cellulases are primarily produced from Trichoderma reesei. However, external supplementation of the cellulase cocktail from this host with exogenous β-glucosidase is often required to achieve the desired optimal saccharification of cellulosic feedstocks. This challenge has led to the exploration of other cellulase-producing strains. The nonmodel hypercellulolytic fungus Penicillium funiculosum has been studied in recent times and identified as a promising source of industrial cellulases mainly due to its ability to produce a balanced concoction of cellulolytic enzymes, including β-glucosidases. Various genetic interventions targeted at strain improvement for cellulase production have been performed; however, the β-glucosidases of this strain have remained largely understudied. This study, therefore, reports profiling of all eight β-glucosidases of P. funiculosum via molecular and computational approaches. The results of this study provide useful insights that will establish the background for future engineering strategies to transform this fungus into an industrial workhorse.

Significance of glycans in cellulolytic enzymes for lignocellulosic biorefinery - A review

Lignocellulosic (LC) biomass is the most abundant renewable resource for mankind gravitating society towards sustainable solution for energy that can reduce the carbon footprint. The economic feasibility of 'biomass biorefinery' depends upon the efficiency cellulolytic enzymes which is the main crux. Its high production cost and low efficiencies are the major limitations, that need to be resolved. As the complexity of the genome increases, so does the complexity of the proteome, further facilitated by protein post-translational modifications (PTMs). Glycosylation is regarded the major PTMs and hardly any recent work is focused on importance of glycosylation in cellulase. By modifying protein side chains and glycans, superior cellulases with improved stability and efficiency can be obtained. Functional proteomics relies heavily on PTMs because they regulate activity, localization, and interactions with protein, lipid, nucleic acid, and cofactor molecules. O- and N- glycosylation in cellulases influences its characteristics adding positive attributes to the enzymes.

Multidisciplinary approach to the study of large-format oil paintings

Cultural heritage has become a keystone for comprehending our society, as it represents and reflects our origins, passions, beliefs and traditions. Furthermore, it provides fundamental information about specific temporary spaces, materials' availability, technology, artist's intention, and site weather conditions. Our aim was to develop a multidisciplinary approach with a main focus on investigating two Italian large-format paintings located in highly diverse environments such as the National Theater of Costa Rica. We monitored environmental conditions and quantified fungal aerial spores. Then, we determined regions of possible biodeterioration with the software MicroorganismPattern and used the software PigmentArrangement to elucidate the apparent colour of the paintings based on distribution and arrangement of the pigment crystals. Finally, we characterized eight genera of calcareous nannofossils found in the ground layers of the artwork. The former Men's Canteen at the National Theater of Costa Rica presented a mean air temperature of 23.5 [Formula: see text]C, a relative humidity of 72.7% and a concentration of CO[Formula: see text] of 570 ppm. The fungal aerial concentration was 1776 spores/m[Formula: see text]. The software MicroorganismPattern identified 32 sampling regions, out of which 11 were positive for microbial contamination. The software PigmentArrangement determined that the blue crystals (ultramarine pigment) had the shortest distances between themselves (29 [Formula: see text]m). Finally, the nanofossils identified enabled us to restrict the age of the material to a biostratigraphic interval ranging from Coniacian to Maastricthian ages. By using a multidisciplinary approach we were able to explore the diptych, suggest a set of minimally invasive perspectives in tropical environments to be used worldwide and obtain key information about the artist's artistic process, materials used along with better understand its state of conservation.

Lignocellulolytic Biocatalysts: The Main Players Involved in Multiple Biotechnological Processes for Biomass Valorization

Human population growth, industrialization, and globalization have caused several pressures on the planet's natural resources, culminating in the severe climate and environmental crisis which we are facing. Aiming to remedy and mitigate the impact of human activities on the environment, the use of lignocellulolytic enzymes for biofuel production, food, bioremediation, and other various industries, is presented as a more sustainable alternative. These enzymes are characterized as a group of enzymes capable of breaking down lignocellulosic biomass into its different monomer units, making it accessible for bioconversion into various products and applications in the most diverse industries. Among all the organisms that produce lignocellulolytic enzymes, microorganisms are seen as the primary sources for obtaining them. Therefore, this review proposes to discuss the fundamental aspects of the enzymes forming lignocellulolytic systems and the main microorganisms used to obtain them. In addition, different possible industrial applications for these enzymes will be discussed, as well as information about their production modes and considerations about recent advances and future perspectives in research in pursuit of expanding lignocellulolytic enzyme uses at an industrial scale.

Subcritical Water Pretreatment for the Efficient Valorization of Sorghum Distillery Residue for the Biorefinery Platform

The depletion of fossil fuels is resulting in an increased energy crisis, which is leading the paradigm shift towards alternative energy resources to overcome the issue. Lignocellulosic biomass or agricultural residue could be utilized to produce energy fuel (bioethanol) as it can resolve the issue of energy crisis and reduce environmental pollution that occurs due to waste generation from agriculture and food industries. A huge amount of sorghum distillery residue (SDR) is produced during the Kaoliang liquor production process, which may cause environmental problems. Therefore, the SDR generated can be utilized to produce bioethanol to meet current energy demands and resolve environmental problems. Using a central composite experimental design, the SDR was subjected to hydrothermal pretreatment. The conditions selected for hydrothermal pretreatment are 155 °C, 170 °C, and 185 °C for 10, 30, and 50 min, respectively. Based on the analysis, 150 °C for 30 min conditions for SDR hydrothermal pretreatment were selected as no dehydration product (Furfural and HMF) was detected in the liquid phase. Therefore, the pretreated slurry obtained using hydrothermal pretreatment at 150 °C for 30 min was subjected to enzymatic hydrolysis at 5% solid loading and 15 FPU/gds. The saccharification yield obtained at 72 h was 75.05 ± 0.5%, and 5.33 g/L glucose concentration. This non-conventional way of enzymatic hydrolysis eliminates the separation and detoxification process, favoring the concept of an economical and easy operational strategy in terms of biorefinery.

Pretreatment of lignocellulosic biogas substrates by filamentous fungi

Decomposition of lignocellulosic plant biomass by four filamentous fungi was carried out to facilitate subsequent anaerobic degradation and biogas formation. Agricultural side products, wheat straw and corn stover and forestry energy plant willow chips were selected as plant biomass sources. The substrates were confronted by pure cultures of Penicillium aurantiogriseum (new isolate from rumen), Trichoderma reesei (DSM768), Gilbertella persicaria (SZMC11086) and Rhizomucor miehei (SZMC11005). In addition to total cellulolytic filter paper degradation activity, the production of endoglucanase, cellobiohydrolase, β-glucosidase enzymes were followed during the pretreatment period, which lasted for 10 days at 37 °C. The products of pretreatments were subsequently tested for mesophilic biogas production in batch reactors. All 4 strains effectively pretreated the lignocellulosic substrates albeit in varying degrees, which was related to the level of the tested hydrolytic enzyme activities. Penicillium aurantiogriseum showed outstanding hydrolytic enzyme production and highest biogas yield from the partially degraded substrates. Corn stover was the best substrate for biomass decomposition and biogas production. Scanning electron microscopy confirmed the deep penetration of fungal hyphae into the lignocellulosic substrate in all cases.

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.

Characterization of Microbial Diversity in Decayed Wood from a Spanish Forest: An Environmental Source of Industrially Relevant Microorganisms

Rotting wood is inhabited by a large diversity of bacteria, fungi, and insects with complex environmental relationships. The aim of this work was to study the composition of the microbiota (bacteria and fungi) in decaying wood from a northwest Spanish forest as a source of industrially relevant microorganisms. The analyzed forest is situated in a well-defined biogeographic area combining Mediterranean and temperate macrobioclimates. Bacterial diversity, determined by metagenome analyses, was higher than fungal heterogeneity. However, a total of 194 different cultivable bacterial isolates (mainly Bacillaceae, Streptomycetaceae, Paenibacillaceae, and Microbacteriaceae) were obtained, in contrast to 343 fungal strains (mainly Aspergillaceae, Hypocreaceae, and Coniochaetaceae). Isolates traditionally known as secondary metabolite producers, such as Actinobacteria and members of the Penicillium genus, were screened for their antimicrobial activity by the detection of antibiotic biosynthetic clusters and competitive bioassays against fungi involved in wood decay. In addition, the ability of Penicillium isolates to degrade cellulose and release ferulic acid from wood was also examined. These results present decaying wood as an ecologically rich niche and a promising source of biotechnologically interesting microorganisms.

Advances and Challenges in Biocatalysts Application for High Solid-Loading of Biomass for 2nd Generation Bio-Ethanol Production

Growth in population and thereby increased industrialization to meet its requirement, has elevated significantly the demand for energy resources. Depletion of fossil fuel and environmental sustainability issues encouraged the exploration of alternative renewable eco-friendly fuel resources. Among major alternative fuels, bio-ethanol produced from lignocellulosic biomass is the most popular one. Lignocellulosic biomass is the most abundant renewable resource which is ubiquitous on our planet. All the plant biomass is lignocellulosic which is composed of cellulose, hemicellulose and lignin, intricately linked to each other. Filamentous fungi are known to secrete a plethora of biomass hydrolyzing enzymes. Mostly these enzymes are inducible, hence the fungi secrete them economically which causes challenges in their hyperproduction. Biomass’s complicated structure also throws challenges for which pre-treatments of biomass are necessary to make the biomass amorphous to be accessible for the enzymes to act on it. The enzymatic hydrolysis of biomass is the most sustainable way for fermentable sugar generation to convert into ethanol. To have sufficient ethanol concentration in the broth for efficient distillation, high solid loading ~<20% of biomass is desirable and is the crux of the whole technology. High solid loading offers several benefits including a high concentration of sugars in broth, low equipment sizing, saving cost on infrastructure, etc. Along with the benefits, several challenges also emerged simultaneously, like issues of mass transfer, low reaction rate due to water constrains in, high inhibitor concentration, non-productive binding of enzyme lignin, etc. This article will give an insight into the challenges for cellulase action on cellulosic biomass at a high solid loading of biomass and its probable solutions.

Consolidated bioprocessing of lignocellulosic biomass: Technological advances and challenges

Consolidated bioprocessing (CBP) is characterized by a single-step production of value-added compounds directly from biomass in a single vessel. This strategy has the capacity to revolutionize the whole biorefinery concept as it can significantly reduce the infrastructure input and use of chemicals for various processing steps which can make it economically and environmentally benign. Although the proof of concept has been firmly established in the past, commercialization has been limited due to the low conversion efficiency of the technology. Either a native single microbe, genetically modified microbe or a consortium can be employed. The major challenge in developing a cost-effective and feasible CBP process is the recognition of bifunctional catalysts combining the capability to use the substrates and transform them into value-added products with high efficiency. This article presents an in-depth analysis of the current developments in CBP around the globe and the possibilities of advancements in the future.

Analysis of carbohydrate-active enzymes and sugar transporters in Penicillium echinulatum: A genome-wide comparative study of the fungal lignocellulolytic system

Penicillium echinulatum 2HH is an ascomycete well known for its production of cellulolytic enzymes. Understanding lignocellulolytic and sugar uptake systems is essential to obtain efficient fungi strains for the production of bioethanol. In this study we performed a genome-wide functional annotation of carbohydrate-active enzymes and sugar transporters involved in the lignocellulolytic system of P. echinulatum 2HH and S1M29 strains (wildtype and mutant, respectively) and eleven related fungi. Additionally, signal peptide and orthology prediction were carried out. We encountered a diverse assortment of cellulolytic enzymes in P. echinulatum, especially in terms of β-glucosidases and endoglucanases. Other enzymes required for the breakdown of cellulosic biomass were also found, including cellobiohydrolases, lytic cellulose monooxygenases and cellobiose dehydrogenases. The S1M29 mutant, which is known to produce an increased cellulase activity, and the 2HH wild type strain of P. echinulatum did not show significant differences between their enzymatic repertoire. Nevertheless, we unveiled an amino acid substitution for a predicted intracellular β-glucosidase of the mutant, which might contribute to hyperexpression of cellulases through a cellodextrin induction pathway. Most of the P. echinulatum enzymes presented orthologs in P. oxalicum 114-2, supporting the presence of highly similar cellulolytic mechanisms and a close phylogenetic relationship between these fungi. A phylogenetic analysis of intracellular β-glucosidases and sugar transporters allowed us to identify several proteins potentially involved in the accumulation of intracellular cellodextrins. These may prove valuable targets in the genetic engineering of P. echinulatum focused on industrial cellulases production. Our study marks an important step in characterizing and understanding the molecular mechanisms employed by P. echinulatum in the enzymatic hydrolysis of lignocellulosic biomass.

Production Optimization and Biochemical Characterization of Cellulase from Geobacillus sp. KP43 Isolated from Hot Spring Water of Nepal

This study is aimed at isolating and identifying a thermophilic cellulolytic bacterium from hot spring water and characterizing thermostable cellulase produced by the isolate. Enrichment and culture of water sample was used for isolation of bacterial strains and an isolate with highest cellulase activity was chosen for the production, partial purification, and biochemical characterization of the enzyme. Different staining techniques, enzymatic tests, and 16s ribosomal DNA (16s rDNA) gene sequencing were used for the identification of the isolate. The cellulase producing isolate was Gram positive, motile, and sporulated rod-shaped bacterium growing optimally between 55°C and 65°C. Based on partial 16s rDNA sequence analysis, the isolate was identified as Geobacillus sp. and was designated as Geobacillus sp. KP43. The cellulase enzyme production condition was optimized, and the product was partially purified and biochemically characterized. Optimum cellulase production was observed in 1% carboxymethyl cellulose (CMC) at 55°C. The molecular weight of the enzyme was found to be approximately 66 kDa on 12% SDS-PAGE analysis. Biochemical characterization of partially purified enzyme revealed the temperature optimum of 70°C and activity over a wide pH range. Further, cellulase activity was markedly stimulated by metal ion Fe^2+. Apart from cellulases, the isolate also depicted good xylanase, cellobiase, and amylase activities. Thermophilic growth with a variety of extracellular enzyme activities at elevated temperature as well as in a wide pH range showed that the isolated bacteria, Geobacillus sp. KP43, can withstand the harsh environmental condition, which makes this organism suitable for enzyme production for various biotechnological and industrial applications.

Penicillium Ochrochloron RLS11 Secretome Containing Carbohydrate-Active Enzymes Improves Commercial Enzyme Mixtures During Sugarcane Straw Saccharification

Filamentous fungi are prolific producers of carbohydrate-active enzymes (CAZymes) and important agents that carry out plant cell wall degradation in natural environments. The number of fungal species is frequently reported in the millions range, with a huge diversity and genetic variability, reflecting on a vast repertoire of CAZymes that these organisms can produce. In this study, we evaluated the ability of previously selected ascomycete and basidiomycete fungi to produce plant cell wall-degrading enzyme (PCWDE) activities and the potential of the culture supernatants to increase the efficiency of the Cellic® CTec2/HTec2 for steam-exploded sugarcane straw saccharification. The culture supernatant of Penicillium ochrochloron RLS11 showed a promising supplementation effect on Cellic® CTec2/HTec2, and we conducted the whole-genome sequencing and proteomic analysis for this fungus. The size of the assembled genome was 38.06 Mbp, and a total of 12,015 protein-coding genes were identified. The repertoire of PCWDE-coding genes was comparatively high among Penicillium spp. and showed an expansion in important cellulases and xylanases families, such as GH3, GH6, GH7, and GH11. The proteomic analysis indicated cellulases that probably enhanced the biomass saccharification performance of the Cellic® CTec2/HTec2, which included enzymes from GH3, GH6, and GH7 families.

A review on global perspectives of sustainable development in bioenergy generation

Over the last few decades, the globe has much relied on fossil fuels; however, environmental concerns forced the World to look at biofuel as an alternative for stable economic development. Biofuel also facilitates national energy security maintenance and reduces environmental complications. The present study is focused on an in-depth analysis of bioenergy policy measures undertaken by various federal agencies of different countries in order to shed light on the bottlenecks that impede biofuel's growth as a sustainable and alternative fuel. An in-depth assessment of feedstock utilization, blending targets, and policy assistance schemes have been thoroughly reviewed. In addition, the potential of commercial firms for the production of bioenergy is highlighted in order to grasp the current bioenergy market scenario better. Finally, the article is concluded with the viewpoints of the authors to address the standing issues of global bioenergy generation.

Engineering interventions in industrial filamentous fungal cell factories for biomass valorization

Filamentous fungi possess versatile capabilities for synthesizing a variety of valuable bio compounds, including enzymes, organic acids and small molecule secondary metabolites. The advancements of genetic and metabolic engineering techniques and the availability of sequenced genomes discovered their potential as expression hosts for recombinant protein production. Remarkably, plant-biomass degrading filamentous fungi show the unique capability to decompose lignocellulose, an extremely recalcitrant biopolymer. The basic biochemical approaches have motivated several industrial processes for lignocellulose biomass valorisation into fermentable sugars and other biochemical for biofuels, biomolecules, and biomaterials. The review gives insight into current trends in engineering filamentous fungi for enzymes, fuels, and chemicals from lignocellulose biomass. This review describes the variety of enzymes and compounds that filamentous fungi produce, engineering of filamentous fungi for biomass valorisation with a special focus on lignocellulolytic enzymes and other bulk chemicals.

Nanotechnology-assisted production of value-added biopotent energy-yielding products from lignocellulosic biomass refinery - A review

The need to develop sustainable alternatives for pretreatment and hydrolysis of lignocellulosic biomass (LCB) is a massive concern in the industrial sector today. Breaking down of LCB yields sugars and fuel in the bulk scale. If explored under nanotechnology, LCB can be refined to yield high-performance fuel sources. The toxicity and cost of conventional methods can be reduced by applying nanoparticles (NPs) in refining LCB. Immobilization of enzymes onto NPs or used in conjugation with nanomaterials would instill specific and eco-friendly options for hydrolyzing LCB. Nanomaterials increase the proficiency, reusability, and stability of enzymes. Notably, magnetic NPs have bagged their place in the downstream processing of LCB effluents due to their efficient separation and cost-effectiveness. The current review highlights the role of nanotechnology and its particles in refining LCB into various commercial precursors and value-added products. The relationship between nanotechnology and LCB refinery is portrayed effectively in the present study.

Sustainable green approach to synthesize Fe3O4/α-Fe2O3 nanocomposite using waste pulp of Syzygium cumini and its application in functional stability of microbial cellulases

Synthesis of nanomaterials following green routes have drawn much attention in recent years due to the low cost, easy and eco-friendly approaches involved therein. Therefore, the current study is focused towards the synthesis of Fe₃O₄/α-Fe₂O₃ nanocomposite using waste pulp of Jamun (Syzygium cumini) and iron nitrate as the precursor of iron in an eco-friendly way. The synthesized Fe₃O₄/α-Fe₂O₃ nanocomposite has been extensively characterized through numerous techniques to explore the physicochemical properties, including X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, Ultraviolet-Vis spectroscopy, field emission scanning electron microscope, high resolution transmission electron microscope and vibrating sample magnetometer. Further, efficiency of the Fe₃O₄/α-Fe₂O₃ nanocomposite has been evaluated to improve the incubation temperature, thermal/pH stability of the crude cellulase enzymes obtained from the lab isolate fungal strain Cladosporium cladosporioides NS2 via solid state fermentation. It is found that the presence of 0.5% Fe₃O₄/α-Fe₂O₃ nanocomposite showed optimum incubation temperature and thermal stability in the long temperature range of 50–60 °C for 15 h along with improved pH stability in the range of pH 3.5–6.0. The presented study may have potential application in bioconversion of waste biomass at high temperature and broad pH range.

Lytic Polysaccharide Monooxygenase from Talaromyces amestolkiae with an Enigmatic Linker-like Region: The Role of This Enzyme on Cellulose Saccharification

The first lytic polysaccharide monooxygenase (LPMO) detected in the genome of the widespread ascomycete Talaromyces amestolkiae (TamAA9A) has been successfully expressed in Pichia pastoris and characterized. Molecular modeling of TamAA9A showed a structure similar to those from other AA9 LPMOs. Although fungal LPMOs belonging to the genera Penicillium or Talaromyces have not been analyzed in terms of regioselectivity, phylogenetic analyses suggested C1/C4 oxidation which was confirmed by HPAEC. To ascertain the function of a C-terminal linker-like region present in the wild-type sequence of the LPMO, two variants of the wild-type enzyme, one without this sequence and one with an additional C-terminal carbohydrate binding domain (CBM), were designed. The three enzymes (native, without linker and chimeric variant with a CBM) were purified in two chromatographic steps and were thermostable and active in the presence of H2O2. The transition midpoint temperature of the wild-type LPMO (Tm = 67.7 °C) and its variant with only the catalytic domain (Tm = 67.6 °C) showed the highest thermostability, whereas the presence of a CBM reduced it (Tm = 57.8 °C) and indicates an adverse effect on the enzyme structure. Besides, the potential of the different T. amestolkiae LPMO variants for their application in the saccharification of cellulosic and lignocellulosic materials was corroborated.

Role and significance of lytic polysaccharide monooxygenases (LPMOs) in lignocellulose deconstruction

Lytic polysaccharide monooxygenases (LPMOs) emerged a decade ago and have been described as biomass deconstruction boosters as they play an extremely important role in unravelling the enzymatic biomass hydrolysis scheme. These are oxidative enzymes requiring partners to donate electrons during catalytic action on cellulose backbone. Commercial cellulase preparations are mostly from the robust fungal sources, hence LPMOs from fungi (AA9) have been discussed. Characterisation of LPMOs suffers due to multiple complications which has been discussed and challenges in detection of LPMOs in secretomes has also been highlighted. This review focuses on the significance of LPMOs on biomass hydrolysis due to which it has become a key component of cellulolytic cocktail available commercially for biomass deconstruction and its routine analysis challenge has also been discussed. It has also outlined a few key points that help in expressing catalytic active recombinant AA9 LPMOs.

Cellulose-deconstruction potential of nano-biocatalytic systems: A strategic drive from designing to sustainable applications of immobilized cellulases

Nanostructured materials along with an added value of polymers-based support carriers have gained high interest and considered ideal for enzyme immobilization. The recently emerged nanoscience interface in the form of nanostructured materials combined with immobilized-enzyme-based bio-catalysis has now become research and development frontiers in advance and applied bio-catalysis engineering. With the involvement of nanoscience, various polymers have been thoroughly developed and exploited to nanostructured engineer constructs as ideal support carriers/matrices. Such nanotechnologically engineered support carriers/matrix possesses unique structural, physicochemical, and functional attributes which equilibrate principal factors and strengthen the biocatalysts efficacy for multipurpose applications. In addition, nano-supported catalysts are potential alternatives that can outstrip several limitations of conventional biocatalysts, such as reduced catalytic efficacy and turnover, low mass transfer efficiency, instability during the reaction, and most importantly, partial, or complete inhibition/deactivation. In this context, engineering robust and highly efficient biocatalysts is an industrially relevant prerequisite. This review comprehensively covered various biopolymers and nanostructured materials, including silica, hybrid nanoflower, nanotubes or nanofibers, nanomembranes, graphene oxide nanoparticles, metal-oxide frameworks, and magnetic nanoparticles as robust matrices for cellulase immobilization. The work is further enriched by spotlighting applied and industrially relevant considerations of nano-immobilized cellulases. For instance, owing to the cellulose-deconstruction features of nano-immobilized cellulases, the applications like lignocellulosic biomass conversion into industrially useful products or biofuels, improved paper sheet density and pulp beat in paper and pulp industry, fruit juice clarification in food industry are evident examples of cellulases, thereof are discussed in this work.

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.

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.

Production of a β-Glucosidase-Rich Cocktail from Talaromyces amestolkiae Using Raw Glycerol: Its Role for Lignocellulose Waste Valorization

As β-glucosidases represent the major bottleneck for the industrial degradation of plant biomass, great efforts are being devoted to discover both novel and robust versions of these enzymes, as well as to develop efficient and inexpensive ways to produce them. In this work, raw glycerol from chemical production of biodiesel was tested as carbon source for the fungus Talaromyces amestolkiae with the aim of producing enzyme β-glucosidase-enriched cocktails. Approximately 11 U/mL β-glucosidase was detected in these cultures, constituting the major cellulolytic activity. Proteomic analysis showed BGL-3 as the most abundant protein and the main β-glucosidase. This crude enzyme was successfully used to supplement a basal commercial cellulolytic cocktail (Celluclast 1.5 L) for saccharification of pretreated wheat straw, corroborating that even hardly exploitable industrial wastes, such as glycerol, can be used as secondary raw materials to produce valuable enzymatic preparations in a framework of the circular economy.

Hemicellulases from Penicillium and Talaromyces for lignocellulosic biomass valorization: A review

The term hemicellulose groups different polysaccharides with heterogeneous structures, mannans, xyloglucans, mixed-linkage β-glucans and xylans, which differ in their backbone and branches, and in the type and distribution of glycosidic linkages. The enzymatic degradation of these complex polymers requires the concerted action of multiple hemicellulases and auxiliary enzymes. Most commercial enzymes are produced by Trichoderma and Aspergillus species, but recent studies have disclosed Penicillium and Talaromyces as promising sources of hemicellulases. In this review, we summarize the current knowledge on the hemicellulolytic system of these genera, and the role of hemicellulases in the disruption and synthesis of glycosidic bonds. In both cases, the enzymes from Penicillium and Talaromyces represent an interesting alternative for valorization of lignocellulosic biomass in the current framework of circular economy.

Role of psychrotrophic fungal strains in accelerating and enhancing the maturity of pig manure composting under low-temperature conditions

This study investigatedthe effects of applying psychrotrophic cellulose-degrading fungion cellulase production, fungal community structure, and maturity of pig manure (PM) compost under low-temperature conditions. Three psychrotrophic fungal strains were isolated and identified, and after the cold-active cellulase production conditions were optimized, they were inoculated into PM compost. While the control (CK) compost temperature failed to reachthe thermophilic stage, the inoculated compost temperature reached it within 3 days and was maintained for up to 17 days. Fungal inoculants improved fungal community structure at the end of composting, as suggested by network analysis. Principal component analysis revealed that the germination index (GI), total phosphorus (TP), total potassium (TK), and total nitrogen (TN) were the most influential physicochemical parameters affecting compost maturity. The results of the compost products reflected the suitability of the compost as a fertilizer. This study indicated that newly identified strains positively impacted composting at low temperatures.

Improving β-glucosidase and xylanase production in a combination of waste substrate from domestic wastewater treatment system and agriculture residues

Cellulase and hemicellulase activities are considered to the major bottlenecks in the lignocellulosic biorefinery process, especially in an enzyme cocktail lacking β-glucosidase (BGL) and xylanase (XYL). In view of this issue, higher levels of BGL and XYL activities were obtained in the presence of wastewater and activated sludge as an induction medium mixed with 5% of rice straw by Hypocrea sp. W₆₃. The analysis of the ionic content showed that a relatively low sludge dose could enhance the production of BGL and XYL. Most importantly, compared to a medium using freshwater, the proportion of 1:10 sludge to wastewater, which contained nutrient elements, led to 3.4-fold BGL and 3.7-fold XYL production improvements. This research describes the reuse of substrates that are largely and continuously generated from domestic wastewater treatment systems and agriculture residues, which consequently leads to the development of a simultaneous enzyme production process for sustainable biorefinery practices.

Synergistic Action of a Lytic Polysaccharide Monooxygenase and a Cellobiohydrolase from Penicillium funiculosum in Cellulose Saccharification under High-Level Substrate Loading

Lytic polysaccharide monooxygenases (LPMOs) are crucial industrial enzymes required in the biorefinery industry as well as in the natural carbon cycle. These enzymes, known to catalyze the oxidative cleavage of glycosidic bonds, are produced by numerous bacterial and fungal species to assist in the degradation of cellulosic biomass. In this study, we annotated and performed structural analysis of an uncharacterized LPMO from Penicillium funiculosum (PfLPMO9) based on computational methods in an attempt to understand the behavior of this enzyme in biomass degradation. PfLPMO9 exhibited 75% and 36% sequence identities with LPMOs from Thermoascus aurantiacus (TaLPMO9A) and Lentinus similis (LsLPMO9A), respectively. Furthermore, multiple fungal genetic manipulation tools were employed to simultaneously overexpress LPMO and cellobiohydrolase I (CBH1) in a catabolite-derepressed strain of Penicillium funiculosum, PfMig1⁸⁸ (an engineered variant of P. funiculosum), to improve its saccharification performance toward acid-pretreated wheat straw (PWS) at 20% substrate loading. The resulting transformants showed improved LPMO and CBH1 expression at both the transcriptional and translational levels, with ∼200% and ∼66% increases in ascorbate-induced LPMO and Avicelase activities, respectively. While the secretome of PfMig⁸⁸ overexpressing LPMO or CBH1 increased the saccharification of PWS by 6% or 13%, respectively, over the secretome of PfMig1⁸⁸ at the same protein concentration, the simultaneous overexpression of these two genes led to a 20% increase in saccharification efficiency over that observed with PfMig1⁸⁸, which accounted for 82% saccharification of PWS under 20% substrate loading.IMPORTANCE The enzymatic hydrolysis of cellulosic biomass by cellulases continues to be a significant bottleneck in the development of second-generation biobased industries. While increasing efforts are being made to obtain indigenous cellulases for biomass hydrolysis, the high production cost of this enzyme remains a crucial challenge affecting its wide availability for the efficient utilization of cellulosic materials. This is because it is challenging to obtain an enzymatic cocktail with balanced activity from a single host. This report describes the annotation and structural analysis of an uncharacterized lytic polysaccharide monooxygenase (LPMO) gene in Penicillium funiculosum and its impact on biomass deconstruction upon overexpression in a catabolite-derepressed strain of P. funiculosum Cellobiohydrolase I (CBH1), which is the most important enzyme produced by many cellulolytic fungi for the saccharification of crystalline cellulose, was further overexpressed simultaneously with LPMO. The resulting secretome was analyzed for enhanced LPMO and exocellulase activities and the corresponding improvement in saccharification performance (by ∼20%) under high-level substrate loading using a minimal amount of protein.

Gene Regulatory Networks of Penicillium echinulatum 2HH and Penicillium oxalicum 114-2 Inferred by a Computational Biology Approach

Penicillium echinulatum 2HH and Penicillium oxalicum 114-2 are well-known cellulase fungal producers. However, few studies addressing global mechanisms for gene regulation of these two important organisms are available so far. A recent finding that the 2HH wild-type is closely related to P. oxalicum leads to a combined study of these two species. Firstly, we provide a global gene regulatory network for P. echinulatum 2HH and P. oxalicum 114-2, based on TF-TG orthology relationships, considering three related species with well-known regulatory interactions combined with TFBSs prediction. The network was then analyzed in terms of topology, identifying TFs as hubs, and modules. Based on this approach, we explore numerous identified modules, such as the expression of cellulolytic and xylanolytic systems, where XlnR plays a key role in positive regulation of the xylanolytic system. It also regulates positively the cellulolytic system by acting indirectly through the cellodextrin induction system. This remarkable finding suggests that the XlnR-dependent cellulolytic and xylanolytic regulatory systems are probably conserved in both P. echinulatum and P. oxalicum. Finally, we explore the functional congruency on the genes clustered in terms of communities, where the genes related to cellular nitrogen, compound metabolic process and macromolecule metabolic process were the most abundant. Therefore, our approach allows us to confer a degree of accuracy regarding the existence of each inferred interaction.

Screening of biological activities of fungi associated with pistachio bark beetle, Chaetoptelius vestitus (Coleoptera, Curculionidae), infesting pistachio cultivations in Tunisia

AIMS

In this study, we aimed to explore the enzymatic diversity, the entomopathogenic and the antimicrobial potentialities of fungi associated with the pistachio bark beetle, Chaetoptelius vestitus.

METHODS AND RESULTS

A total of 40 isolates were screened for enzymatic diversity. Most of them, 92·5%, were able to produce at least two of the screened enzymes. Pathogenic assays performed on C. vestitus showed a high entomopathogenic activity of the isolates Ata_io_1 (A. tamarii), Fve_io_1 (F. verticillioides), Tpi_io_1 (T. pinophilus), Pal_io_1 (P. album), Pbi_io_2 (Penicillium bilaiae) and Pch_io_1 (P. chrysogenum), as based on mean mortality of C. vestitus. A screening of antimicrobial activity using well diffusion method showed that the isolates Tro_io_1 (T. pinophilus), Tat_io_1 (T. atroroseus) and Pch_io_1 (P. chrysogenum) presented the highest antibacterial activity. Furthermore, Mgu_io_1 (M. guilliermondii), Asc_io_1 (A. sclerotiorum), Ata_io_1 (A. tamarii), G. lavendula (Gla_io_1), Pva_io_1 (P. variotii), Pul_io_1 (P. ulaiense), Tat_io_1 (T. atroroseus) and Tro_io_1 (T. roseum) were active against at least two of the three tested fungal phytopathogens.

CONCLUSIONS

Fungal isolates representing entomopathogenic activity and a broad spectrum of antimicrobial activities can be considered as promising resources for biological pistachio trees protection.

SIGNIFICANCE AND IMPACT OF THE STUDY

Fungi associated with C. vestitus were investigated for detecting their potential biotechnological applications.

Protein surface engineering of endoglucanase Penicillium verruculosum for improvement in thermostability and stability in the presence of 1-butyl-3-methylimidazolium chloride ionic liquid

Thermostability and stability in ionic liquids are essential properties of cellulases that are applied in industrial processes of bioconversion. Engineering of protein surface of endoglucanase II from Penicillium verruculosum was used to improve the enzyme thermostability and stability in 1-butyl-3-methylimidazolium chloride ([Bmim]Cl). The engineering was based on analysis of the protein surface topography and enhanced by multiple sequence alignment and ΔΔG calculations. In the case of the thermostability, half-life time was improved in 1.3-1.6 times at 70 °C and 1.2-1.4 times at 80 °C. In the case of the stability in [Bmim]Cl, the residual activity after 72 h of incubation in the presence of [Bmim]Cl (50 g/L, 50 °C, pH 4.5) was 1.7-1.9 times greater for the tailored enzyme. The yield of reducing sugars after enzymatic hydrolysis of aspen wood pretreated with [Bmim]Cl was 10-20% higher with the tailored endoglucanase.

Microbial dynamics for lignocellulosic waste bioconversion and its importance with modern circular economy, challenges and future perspectives

An extensive use of microbial dynamics for utilizing the lignocellulosic wastes has been attributed to their efficiency in bioenergy and bioproducts development as a cost effective high nutritional value. The integration of lignocellulosic waste into the circular economy can scaleup the sustainable bioproducts and bioenergy development. In this review paper, the aim is to describe the existing research efforts on organic lignocellulosic waste, cellulase producing microbes, their potential enzyme, modern circular economy with associated challenges and future perspectives. Presently, it has been reviewed that microbial cellulases have provided treasure bioproducts visions into industrial bioproducts marvels unveiled through lignocellulosic waste cutting-edge microbial explorations. Furthermore, the review focused on new insights of the growing circular economy of lignocellulosic waste used for many bioproducts and bioenergy dealings and explored the emergent lignocellulosic biorefinery approaches which could then be applied to review industrial-scale sustainable economic models for upgraded bioproducts and other production associated problems.

Designing a cellulolytic enzyme cocktail for the efficient and economical conversion of lignocellulosic biomass to biofuels

Concerns about dwindling fossil fuels and their unfavorable environmental impacts shifted the global focus towards the development of biofuels from lignocellulosic feedstocks. The structure of this biomass is very complex due to which variety of enzymes (cellulolytic, hemicellulolytic, auxiliary/AA9) and proteins (e.g. swollenin) required for efficient deconstruction. Major impediments in large-scale commercial production of cellulosic ethanol are the cost of cellulases and inability of any single microorganism to produce all cellulolytic components in sufficient titers. In the recent past, various methods for reducing the enzyme cost during cellulosic ethanol production have been attempted. These include designing optimal synergistic enzyme blends/cocktail, having certain ratios of enzymes from different microbial sources, for efficient hydrolysis of pretreated biomass. However, the mechanisms underlying the development, strategies for production and evaluation of optimal cellulolytic cocktails still remain unclear. This article aims to explore the technical and economic benefits of using cellulolytic enzyme cocktail, basic enzymatic and non-enzymatic components required for its development and various strategies employed for efficient cellulolytic cocktail preparation. Consideration was also given to the ways of evaluation of commercially available and in-house developed cocktails. Discussion about commercially available cellulolytic cocktails, current challenges and possible avenues in the development of cellulolytic cocktails included.

Designing cellulolytic enzyme systems for biorefinery: From nature to application

Cellulolytic enzymes play a key role on conversion of lignocellulosic plant biomass to biofuels and biochemicals in sugar platform biorefineries. In this review, we survey composite carbohydrate-active enzymes (CAZymes) among groups of cellulolytic fungi and bacteria that exist under aerobic and anaerobic conditions. Recent advances in designing effective cellulase mixtures are described, starting from the most complex microbial consortium-based enzyme preparations, to single-origin enzymes derived from intensively studied cellulase producers such as Trichoderma reesei, Talaromyces cellulolyticus, and Penicellium funiculosum, and the simplest minimal enzyme systems comprising selected sets of mono-component enzymes tailor-made for specific lignocellulosic substrates. We provide a comprehensive update on studies in developing high-performance cellulases for biorefineries.

Thermostable cellulases: Current status and perspectives

It is envisaged that the utilization of lignocellulosic biomass for ethanol production for transport sector, would make cellulases the most demanded industrial enzyme. The greatest potential of cellulolytic enzymes lies in ethanol production from biomass by enzymatic hydrolysis of cellulose but low thermostability and low titer of cellulase production resulting into high cost of the enzyme which is the major set-back. A number of research groups are working on cellulase to improve its thermostability so as to be able to perform hydrolysis at elevated temperatures which would eventually increase the efficiency of cellulose hydrolysis. The technologies developed from lignocellulosic biomass via cellulose hydrolysis promise environmental and economical sustainability in the long run along with non-dependence on nonrenewable energy source. This review deals with the important sources of thermostable cellulases, mechanism, its regulation, strategies to enhance the thermostability further with respect to its importance for biofuel applications.

A screening approach for assessing lytic polysaccharide monooxygenase activity in fungal strains

BACKGROUND

Efforts to develop efficient lignocellulose-degrading enzymatic preparations have led to the relatively recent discovery of a new class of novel cellulase boosters, termed lytic polysaccharide monoxygenases (LPMOs). These enzymes are copper-dependent metalloenzymes that initiate the biomass deconstruction process and subsequently work together with cellulases, hemicellulases, and other accessory enzymes to enhance their hydrolytic action. Given their wide distribution and diversity, screening and isolation of potent LPMOs from natural fungal diversity may provide an important avenue for increasing the efficiency of cellulases and thereby decreasing cellulosic ethanol production costs. However, methods for quick screening and detection are still not widely available. In this article, a simple and sensitive method is described by combining nonhydrolytic activity enhancement followed by LC-MS-based quantitation of LPMOs.

RESULTS

In this study, a screening approach has been developed for the detection of nonhydrolytic cellulase-enhancing enzymes in crude fungal supernatants. With the application of a saturating benchmark cocktail of Celluclast 1.5L, fungal isolates were selected which had the capability of hydrolyzing pretreated rice straw by their synergistic enzyme fractions. Subsequently, these fungal extracts along with an LPMO-enriched commercial enzyme were investigated for their ability to produce Type I LPMO activity. An LC-MS-based methodology was applied to quantitate gluconic acid in enzymatic hydrolysates as an indirect measurement of Type I LPMO activity.

CONCLUSION

The present study describes an LC-MS-based separation method to detect and quantitate LPMO activity in a commercial enzyme. This method was also applied to screen fungal extracts. The developed screening strategy has enabled detection of LPMO activity in two industrially important Penicillium strains.