High-level production of a thermoacidophilic beta-glucosidase from Penicillium citrinum YS40-5 by solid-state fermentation with rice bran

Novel Cellulase Screening and Optimal Production from the Wood Decaying Xylariaceae: Daldinia Species

The highest cellulases production from Daldinia caldariorum 263 (D-263) was found among Daldinia eschscholzii and Daldinia childiae. Three cellulases, one xylanase and one β-glucosidase of the molecular weights 55, 43, 34, 30, and 105 kDa, respectively, were determined by zymographic sodium dodecyl sulfate polyacrylamide gel electrophoresis. From the N-terminal sequencing, the major cellulase CelA belonging to glycosyl hydrolase family 5 was determined. By following an orthogonal experiment design (L9), factors affecting the cultivation of D. caldariorum 263 are ranked as medium composition > temperature > pH ≥ FP (%). The optimum cultivation conditions for obtaining the best FPase (600 mU/ml) at 72 h are 150 rpm, 35 °C, pH 7, 0.2% soy peptone and 0.5% α-cellulose in minimal requirement medium. In comparison with Trichoderma reesei (ATCC26921) secreting 1,135 mU/ml of FPase after 6 days cultivation at pH 5, D. caldariorum 263 grew faster at 35 °C and produced the maximum FPase within 3 days at pH 7.

Production, purification, and determination of the biochemical properties of β-glucosidase in Trichoderma koningii via solid substrate fermentation

The β-glucosidase enzyme was obtained from Trichoderma koningii Oudem. NRRL 54330 under optimal conditions by solid substrate fermentation (SSF) using corn cobs as substrate. The enzyme was purified by two-step procedures, ammonium sulphate precipitation and cefarose-4B-l-tyrosine-1-naphthylamine hydrophobic interaction chromatography, followed by biochemical and kinetic characterisation. The β-glucosidase was obtained from T. koningii using ground corn cob as substrate and Na2HPO4, pH 9, as humidification medium. The optimum conditions for enzyme production by SSF were 30 °C and 6 days. The purification efficiency of the obtained β-glucosidase was calculated to be 22.56-fold with a yield of 73.51 %. In the determination of β-glucosidase activity, p-nitrophenyl-β-d-glucopyranoside (pNPG) substrate was used, and the optimum pH and temperature values at which β-glucosidase showed high activity were determined to be pH 3.0 and 75 °C. The purity of the enzyme and the presence/number of subunits were checked using two different electrophoretic methods, SDS-PAGE and NATIVE-PAGE electrophoretic methods. The K m and V max values of the purified enzyme were determined to be 0.16 mM and 2000 EU respectively. It was also found that d-(+)-glucose and δ-gluconolactone inhibitors exhibited competitive inhibition of β-glucosidase in the presence of pNPG.

Microbial production and applications of β-glucosidase-A review

β-Glucosidase exists in all areas of living organisms, and microbial β-glucosidase has become the main source of its production because of its unique physicochemical properties and the advantages of high-yield production by fermentation. With the rise of the green circular economy, the production of enzymes through the fermentation of waste as the substrate has become a popular trend. Lignocellulosic biomass is an easily accessible and sustainable feedstock that exists in nature, and the production of biofuels from lignocellulosic biomass requires the involvement of β-glucosidase. This review proposes ways to improve β-glucosidase yield and catalytic efficiency. Optimization of growth conditions and purification strategies of enzymes can increase enzyme yield, and enzyme immobilization, genetic engineering, protein engineering, and whole-cell catalysis provide solutions to enhance the catalytic efficiency and activity of β-glucosidase. Besides, the diversified industrial applications, challenges and prospects of β-glucosidase are also described.

Novel β-Glucosidase Mibgl3 from Microbacterium sp. XT11 with Oligoxanthan-Hydrolyzing Activity

The enzymatic pathway of xanthan depolymerization has been predicted previously; however, the β-glucosidase and unsaturated glucuronyl hydrolase in this system have not been cloned and characterized. This lack of knowledge hinders rational modification of xanthan and exploration of new applications. In this work, we report on the properties of Mibgl3, a xanthan-degrading enzyme isolated from Microbacterium sp. XT11. Mibgl3 exhibits typical structural features of the GH3 family but shares low sequence identity with reported GH3 enzymes. The activity of Mibgl3 can be inhibited by Cu²⁺, Fe²⁺, Zn²⁺, and glucose. Unlike most β-glucosidases, Mibgl3 can tolerate a wide pH range and is activated by high concentrations of NaCl. This improves the commercial value of Mibgl3. In particular, Mibgl3 exhibits higher substrate specificity toward oligoxanthan than other β-glucosidases. Ion chromatography, ultrahigh-performance liquid chromatography-mass spectrometry (UPLC-MS), and GC-MS results showed that Mibgl3 could effectively hydrolyze oligoxanthan to release glucose and glucuronate. Therefore, Mibgl3 might play an important role in xanthan depolymerization by functioning as hydrolase of both the xanthan backbone and sidechains. This knowledge of the enzymatic properties and hydrolysis mechanism of a β-glucosidase will be beneficial for future applications.

Recent Developments in Industrial Mycozymes: A Current Appraisal

Fungi, being natural decomposers, are the most potent, ubiquitous and versatile sources of industrial enzymes. About 60% of market share of industrial enzymes is sourced from filamentous fungi and yeasts. Mycozymes (myco-fungus; zymes-enzymes) are playing a pivotal role in several industrial applications and a number of potential applications are in the offing. The field of mycozyme production, while maintaining the old traditional methods, has also witnessed a sea change due to advents in recombinant DNA technology, optimisation protocols, fermentation technology and systems biology. Consolidated bioprocessing of abundant lignocellulosic biomass and complex polysaccharides is being explored at an unprecedented pace and a number of mycozymes of diverse fungal origins are being explored using suitable platforms. The present review attempts to revisit the current status of various mycozymes, screening and production strategies and applications thereof.

A diverse and partially cellulolytic fungal community contributes to the diet of three species of the aquatic insect Phylloicus (Trichoptera: Calamoceratidae) in Amazonian streams

Investigations on the fungal community associated with the digestive tract (DT) of insects have provided insights into the diversity of associated microorganisms and their potential roles in the interaction with their hosts. However, most studies have focused on terrestrial insects, with few studies focusing on aquatic insects in Neotropical regions. We studied fungal taxa associated with the DT of larval stages of the aquatic shredders Phylloicus amazonas, P. elektoros and P. fenestratus in the Brazilian Amazon Forest. Filamentous fungi were isolated, purified and screened for cellulolytic activity. A total of 33 fungal taxa was identified through the combination of classical and molecular taxonomy. The genus Penicillium was the most frequent in DT of Phylloicus spp. (18.75%). The occurrence of fungal taxa among hosts was quite variable, with more than half of the associated fungi being exclusive of each host species. A significant portion of the fungal community associated with each host presented cellulolytic activity (± 50%). It was concluded that the fungal community associated with Phylloicus spp. larvae consist mainly of fungal taxa from food items, which come from riparian vegetation (whose plant species are variable) or are indigenous of the aquatic ecosystems, which is the habitat of these larvae.

Optimization of extracellular ethanol-tolerant β-glucosidase production from a newly isolated Aspergillus sp. DHE7 via solid state fermentation using jojoba meal as substrate: purification and biochemical characterization for biofuel preparation

BACKGROUND

The increasing demand and the continuous depletion in fossil fuels have persuaded researchers to investigate new sources of renewable energy. Bioethanol produced from cellulose could be a cost-effective and a viable alternative to petroleum. It is worth note that β-glucosidase plays a key role in the hydrolysis of cellulose and therefore in the production of bioethanol. This study aims to investigate a simple and standardized method for maximization of extracellular β-glucosidase production from a novel fungal isolate under solid-state fermentation using agro-industrial residues as the sole source of carbon and nitrogen. Furthermore, purification and characterization of β-glucosidase were performed to determine the conditions under which the enzyme displayed the highest performance.

RESULTS

A fungus identified genetically as a new Aspergillus sp. DHE7 was found to exhibit the highest extracellular β-glucosidase production among the sixty fungal isolates tested. Optimization of culture conditions improved the enzyme biosynthesis by 2.1-fold (174.6 ± 5.8 U/g of dry substrate) when the fungus grown for 72 h at 35 °C on jojoba meal with 60% of initial substrate moisture, pH 6.0, and an inoculum size of 2.54 × 107 spores/mL. The enzyme was purified to homogeneity through a multi-step purification process. The purified β-glucosidase is monomeric with a molecular mass of 135 kDa as revealed by the SDS-PAGE analysis. Optimum activity was observed at 60 °C and pH of 6.0, with a remarkable pH and thermal stability. The enzyme retained about 79% and 53% of its activity, after 1 h at 70 °C and 80 °C, respectively. The purified β-glucosidase hydrolysed a wide range of substrates but displaying its greater activity on p-nitrophenyl-β-D-glucopyranoside and cellobiose. The values of Km and Vmax on p-nitrophenyl β-D-glucopyranoside were 0.4 mM and 232.6 U/mL, respectively. Purified β-glucosidase displayed high catalytic activity (improved by 25%) in solutions contained ethanol up to 15%.

CONCLUSION

β-glucosidase characteristics associated with its ability to hydrolyse cellobiose, underscore its utilization in improving the quality of food and beverages. In addition, taking into consideration that the final concentration of ethanol produced by the conventional methods is about 10%, suggests its use in ethanol-containing industrial processes and in the saccharification processes for bioethanol production.

A novel mechanism of β-glucosidase stimulation through a monosaccharide binding-induced conformational change

It is urgent the transition from a fossil fuel-based economy to a sustainable bioeconomy based on bioconversion technologies using renewable plant biomass feedstocks to produce high chemicals, bioplastics, and biofuels. β-Glucosidases are key enzymes responsible for degrading the plant cell wall polymers, as they cleave glucan-based oligo- and polysaccharides to generate glucose. Monosaccharide-tolerant or -stimulated β-glucosidases have been reported in the past decade. Here, we describe a novel mechanism of β-glucosidase stimulation by glucose and xylose. The glycoside hydrolase 1 family β-glucosidase from Thermotoga petrophila (TpBgl1) displays a typical glucose stimulation mechanism based on an increased V_max and decreased K_m in response to glucose. Through molecular docking and dynamics analyses, we mapped putative monosaccharide binding regions (BRs) on the surface of TpBgl1. Our results indicate that after interaction with glucose or xylose at BR1 site, an adjacent loop region assumes an extended conformation, which increases the entrance to the TpBgl1 active site, improving product formation. Biochemical assays with TpBgl1 BR1 mutants, TpBgl1^D49A/Y410A and TpBgl1^D49K/Y410H, resulted in decreasing and abolishing monosaccharide stimulation, respectively. These mutations also impaired the BR1 looping extension responsible for monosaccharide stimulation. This study provides a molecular basis for the rational design of β-glucosidases for biotechnological applications.

First Insights into the Microbiome of a Mangrove Tree Reveal Significant Differences in Taxonomic and Functional Composition among Plant and Soil Compartments

Mangrove forest trees play important ecological functions at the interface between terrestrial and marine ecosystems. However, despite playing crucial roles in plant health and productivity, there is little information on microbiomes of the tree species in mangrove ecosystems. Thus, in this study we aimed to characterize the microbiome in soil (rhizosphere) and plant (root, stem, and leaf endosphere) compartments of the widely distributed mangrove tree Rhizophora stylosa. Surprisingly, bacterial operational taxonomic units (OTUs) were only confidently detected in rhizosphere soil, while fungal OTUs were detected in all soil and plant compartments. The major detected bacterial phyla were affiliated to Proteobacteria, Actinobacteria, Planctomycetes, and Chloroflexi. Several nitrogen-fixing bacterial OTUs were detected, and the presence of nitrogen-fixing bacteria was confirmed by nifH gene based-PCR in all rhizosphere soil samples, indicating their involvement in N acquisition in the focal mangrove ecosystem. We detected taxonomically (54 families, 83 genera) and functionally diverse fungi in the R. stylosa mycobiome. Ascomycota (mainly Dothideomycetes, Eurotiomycetes, Sordariomycetes) were most diverse in the mycobiome, accounting for 86% of total detected fungal OTUs. We found significant differences in fungal taxonomic and functional community composition among the soil and plant compartments. We also detected significant differences in fungal OTU richness (p < 0.002) and community composition (p < 0.001) among plant compartments. The results provide the first information on the microbiome of rhizosphere soil to leaf compartments of mangrove trees and associated indications of ecological functions in mangrove ecosystems.

Isolation of Penicillium citrinum from Roots of Clerodendron cyrtophyllum and Application in Biosynthesis of Aglycone Isoflavones from Soybean Waste Fermentation

Soybeans offer an abundant source of isoflavones, which confer useful bioactivities when existing in aglycone forms. The conversion of isoflavones into aglycones via fermentation of soybean products is often realized by β-glucosidase, an enzyme produced by fungi. In this study, a filamentous fungus, Clerodendron cyrtophyllum, was isolated from root of Clerodendron cyrtophyllum Turcz, which was able to produce the highest activity of β-glucosidase up to 33.72 U/mL at 144 h during fermentation on Potato Dextrose Broth (PDB). The obtained fungus was grown on isoflavones-rich soybean extract to produce genistein and daidzein, achieving the conversion rate of 98.7%. Genistein and daidzein were isolated and purified by column chromatography using hexane/acetone (29:1/1:1), reaching purities of over 90% of total isoflavones, as identified and determined by TLC, LC-MS/MS, and 1H and 13C NMR spectroscopy. These results imply that the isolated P. citrinum is a potential fungal strain for industrial-scale production of genistein and daidzein from isoflavones-containing soybean extracts. These products may serve as potential raw materials for manufacture of functional foods that are based on aglycones.

Cloning, purification, and characterization of GH3 β-glucosidase, MtBgl85, from Microbulbifer thermotolerans DAU221

Background

β-Glucosidases have attracted considerable attention due to their important roles in various biotechnological processes such as cellulose degradation to make energy and hydrolysis of isoflavone. Microbulbifer thermotolerans (M. thermotolerans) is isolated from deep-sea sediment and has not been researched much yet. As a potential candidate for a variety of biotechnological industries, β-glucosidases from the novel bacterial species should be researched extensively.

Methods

β-Glucosidase, MtBgl85, from M. thermotolerans DAU221 was purified by His-tag affinity chromatography and confirmed by SDS-PAGE and zymogram. Its biochemical and physiological properties, such as effects of temperature, pH, metal ions, and organic solvents, substrate specificity, and isoflavone hydrolysis, were investigated.

Results

M. thermotolerans DAU221 showed β-glucosidase activity in a marine broth plate containing 0.1% esculin and 0.25% ammonium iron (III) citrate. The β-glucosidase gene, mtbgl85, was isolated from the whole genome sequence of M. thermotolerans DAU221. The β-glucosidase gene was 2,319 bp and encoded 772 amino acids. The deduced amino acid sequence had a 43% identity with OaBGL84 from Olleya aquimaris and 35% and 32% identity with to CfBgl3A and CfBgl3C from Cellulomonas fimi among bacterial glycosyl hydrolase family 3, respectively. The optimal temperature of MtBgl85 was 50 °C and the optimum pH was 7.0. MtBgl85 activity was strongly reduced in the presence of Hg²⁺ and Cu²⁺ ions. As a result of measuring the activity at various concentrations of NaCl, it was confirmed that the activity was maintained up to the concentration of 1 M, but gradually decreased with increasing concentration. MtBgl85 showed higher enzyme stability at non-polar solvents (high Log P_ow) than polar solvents (low Log P_ow). The hydrolyzed products of isoflavone glycosides and arbutin were analyzed by HPLC.

Microbial Beta Glucosidase Enzymes: Recent Advances in Biomass Conversation for Biofuels Application

The biomass to biofuels production process is green, sustainable, and an advanced technique to resolve the current environmental issues generated from fossil fuels. The production of biofuels from biomass is an enzyme mediated process, wherein β-glucosidase (BGL) enzymes play a key role in biomass hydrolysis by producing monomeric sugars from cellulose-based oligosaccharides. However, the production and availability of these enzymes realize their major role to increase the overall production cost of biomass to biofuels production technology. Therefore, the present review is focused on evaluating the production and efficiency of β-glucosidase enzymes in the bioconversion of cellulosic biomass for biofuel production at an industrial scale, providing its mechanism and classification. The application of BGL enzymes in the biomass conversion process has been discussed along with the recent developments and existing issues. Moreover, the production and development of microbial BGL enzymes have been explained in detail, along with the recent advancements made in the field. Finally, current hurdles and future suggestions have been provided for the future developments. This review is likely to set a benchmark in the area of cost effective BGL enzyme production, specifically in the biorefinery area.

Penicillium citrinum UFV1 β-glucosidases: purification, characterization, and application for biomass saccharification

BACKGROUND

β-Glucosidases are components of the cellulase system, a family of enzymes that hydrolyze the β-1,4 linkages of cellulose. These proteins have been extensively studied due to the possibility of their use in various biotechnological processes. They have different affinities for substrates (depending on their source) and their activities can be used for saccharification of different types of biomass. In this context, the properties and the synergistic capacity of β-glucosidases from different organisms, to supplement the available commercial cellulase cocktails, need a comprehensive evaluation.

RESULTS

Two β-glucosidases belonging to GH3 family were secreted by Penicillium citrinum UFV. PcβGlu1 (241 kDa) and PcβGlu2 (95 kDa) presented acidic and thermo-tolerant characteristics. PcβGlu1 showed Michaelis-Menten kinetics for all substrates tested with K_m values ranging from 0.09 ± 0.01 (laminarin) to 1.7 ± 0.1 mM (cellobiose, C2) and k_cat values ranging from 0.143 ± 0.005 (laminarin) to 8.0 ± 0.2 s^-1 (laminaribiose, Lb). PcβGlu2 showed substrate inhibition for 4-methylumbelliferyl-β-d-glucopyranoside (MUβGlu), p-nitrophenyl-β-d-glucopyranoside (pNPβGlu), cellodextrins (C3, C4, and C5), N-octil-β-d-glucopyranoside, and laminaribiose, with K_m values ranging from 0.014 ± 0.001 (MUβGlu) to 0.64 ± 0.06 mM (C2) and k_cat values ranging from 0.49 ± 0.01 (gentiobiose) to 1.5 ± 0.2 s^-1 (C4). Inhibition constants (K_i) for PcβGlu2 substrate inhibition ranged from 0.69 ± 0.07 (MUβGlu) to 10 ± 1 mM (Lb). Glucose and cellobiose are competitive inhibitors of PcβGlu1 and PcβGlu2 when pNPβGlu is used as a substrate. For PcβGlu1 inhibition, K_i = 1.89 ± 0.08 mM (glucose) and K_i = 3.8 ± 0.1 mM (cellobiose); for PcβGlu2, K_i = 0.83 ± 0.05 mM (glucose) and K_i = 0.95 ± 0.07 mM (cellobiose). The enzymes were tested for saccharification of different biomasses, individually or supplementing a Trichoderma reesei commercial cellulose preparation. PcβGlu2 was able to hydrolyze banana pseudostem and coconut fiber with the same efficiency as the T. reesei cocktail, showing significant synergistic properties with T. reesei enzymes in the hydrolysis of these alternative biomasses.

CONCLUSIONS

The β-glucosidases from P. citrinum UFV1 present different enzymatic properties from each other and might have potential application in several biotechnological processes, such as hydrolysis of different types of biomass.

Cultural conditions optimization for production of β-galactosidase from Bacillus licheniformis ATCC 12759 under solid-state fermentation

Objective:

The aim of this work was to study the optimal cultivation conditions for β-galactosidase production byBacillus licheniformisATCC 12759.

Materials and methods:

The screening of β-galactosidase production fromB. licheniformisATCC 12759 was performed by solid state fermentation method on media rich with rice bran (RB). Different factors were tested for the optimization of β-galactosidase production.

Results:

Certain fermentation parameters involving incubation time, incubation temperature, inoculum level, moisture content, initial pH, agitation speed, size of fermentation medium and optimum temperature of β-galactosidase activity were studied separately. Maximal amount of β-galactosidase production was obtained when solid-state fermentation (SSF) was carried out using RB, having inoculum level 35%, moisture content of 20%, initial pH 7.5 at 37°C for 48 h.

Conclusion:

Results indicated that optimal fermentation conditions play a key role in the maximum production of β-galactosidase fromB. licheniformisATCC 12759. This study shows the potential of the studied enzymes to be promoting candidates for the degradation of lactose and production of important bioproducts.

Impact of pH regulation on multicopper oxidase production and swarming motility in the bacterium Proteus hauseri ZMd44

Proteus hauseri ZMd44, a biodecolorizing bacterium, has been known to produce electricity and multicopper oxidase (Mco-laccase) under copper induction. However, optimization and regulation of production have not been explored. This study is the first attempt to evaluate several parameters on biomass and Mco-laccase production of P. hauseri ZMd44. Through orthogonal experiments with Taguchi's L9, it was found that P. hauseri ZMd44 was sensitive to pH value. The cells grew relatively quickly at pH 7, thus the biomass and Mco-laccase production reached 1.66 g/L and 1043.6 U/L, respectively. Higher pH values also influenced the swarming motility, which is an important characteristic of P. hauseri ZMd44 that affects urinary tract infection. The swarming circle and the diameter of the swarm, represented by the motility velocity, were found to be more controlled after 24 h of growth at pH 6. The swarming ability of P. hauseri was completely inhibited by the addition of 3 mM copper or zinc ions. Therefore, the Mco-laccase and swarming motility could be controlled by regulating pH and ion content.

Enhanced alkaline cellulases production by the thermohalophilic Aspergillus terreus AUMC 10138 mutated by physical and chemical mutagens using corn stover as substrate

A thermohalophilic fungus, Aspergillus terreus AUMC 10138, isolated from the Wadi El-Natrun soda lakes in northern Egypt was exposed successively to gamma and UV-radiation (physical mutagens) and ethyl methan-sulfonate (EMS; chemical mutagen) to enhance alkaline cellulase production under solid state fermentation (SSF) conditions. The effects of different carbon sources, initial moisture, incubation temperature, initial pH, incubation period, inoculum levels and different concentrations of NaCl on production of alkaline filter paper activity (FPase), carboxymethyl cellulase (CMCase) and β-glucosidase by the wild-type and mutant strains of A. terreus were evaluated under SSF. The optimum conditions for maximum production of FPase, CMCase and β-glucosidase were found to be the corn stover: moisture ratio of 1:3(w/v), temperature 45 °C, pH range, 9.0–11.0, and fermentation for 4, 4 and 7 day, respectively. Inoculum levels of 30% for β-glucosidase and 40% for FPase, CMCase gave the higher cellulase production by the wild-type and mutant strains, respectively. Higher production of all three enzymes was obtained at a 5% NaCl. Under the optimized conditions, the mutant strain A. terreus M-17 produced FPase (729 U/g), CMCase (1,783 U/g), and β-glucosidase (342 U/g), which is, 1.85, 1.97 and 2.31-fold higher than the wild-type strain. Our results confirmed that mutant strain M-17 could be a promising alkaline cellulase enzyme producer employing lignocellulosics especially corn stover.

Assessment of cellulolytic microorganisms in soils of Nevados Park, Colombia

A systematized survey was conducted to find soil-borne microbes that degrade cellulose in soils from unique ecosystems, such as the Superpáramo, Páramo, and the High Andean Forest in the Nevados National Natural Park (NNNP), Colombia. These high mountain ecosystems represent extreme environments, such as high levels of solar radiation, low atmospheric pressure, and extreme daily changes in temperature. Cellulolytic activity of the microorganisms was evaluated using qualitative tests, such as growth in selective media followed by staining with congo red and iodine, and quantitative tests to determine the activity of endoglucanase, β-glucosidase, exoglucanase, and total cellulase. Microorganisms were identified using molecular markers, such as the 16S rRNA gene for bacteria and the internal transcribed spacer region (ITS) of ribosomal DNA for fungi. Multivariate statistical analysis (MVA) was used to select microorganisms with high cellulolytic capacity. A total of 108 microorganisms were isolated from the soils and, in general, the enzymatic activities of fungi were higher than those of bacteria. Our results also found that none of the organisms studied were able to degrade all the components of the cellulose and it is therefore suggested that a combination of bacteria and/or fungi with various enzymatic activities be used to obtain high total cellulolytic activity. This study gives an overview of the potential microorganism that could be used for cellulose degradation in various biotechnological applications and for sustainable agricultural waste treatment.

Production of Sporotrichum thermophile xylanase by solid state fermentation utilizing deoiled Jatropha curcas seed cake and its application in xylooligosachharide synthesis

De-oiled Jatropha curcas seed cake, a plentiful by-product of biodiesel industry was used as substrate for the production of a useful xylanase from Sporotrichum thermophile in solid state fermentation. Under the optimized conditions, 1025U xylanase/g (deoiled seed cake) was produced. The xylanase exhibited half life of 4h at 45°C and 71.44min at 50°C respectively. It was stable in a broad pH range of 7.0-11.0. Km and Vmax were 12.54mg/ml and 454.5U/ml/min respectively. S. thermophile xylanase is an endoxylanase free of exoxylanase activity, hence advantageous for xylan hydrolysis to produce xylooligosachharides. Hydrolysis of oat spelt xylan by S. thermophile xylanase yielded 73% xylotetraose, 15.4% xylotriose and 10% xylobiose. The S. thermophile endoxylanase thus seem potentially useful in the food industries.

Conversion of biomass-derived oligosaccharides into lipids

BACKGROUND

Oligocelluloses and oligoxyloses are partially hydrolyzed products from lignocellulosic biomass hydrolysis. Biomass hydrolysates usually contain monosaccharides as well as various amounts of oligosaccharides. To utilize biomass hydrolysates more efficiently, it is important to identify microorganisms capable of converting biomass-derived oligosaccharides into biofuels or biochemicals.

RESULTS

We have demonstrated that the oleaginous yeast Cryptococcus curvatus can utilize either oligocelluloses or oligoxyloses as sole carbon sources for microbial lipid production. When oligocelluloses were used, lipid content and lipid coefficient were 35.9% and 0.20 g/g consumed sugar, respectively. When oligoxyloses were used, lipid coefficient was 0.17 g/g consumed sugar. Ion chromatography analysis showed oligocelluloses with a degree of polymerization from 2 to 9 were assimilated. Our data suggested that these oligosaccharides were transported into cells and then hydrolyzed by cytoplasmic enzymes. Further analysis indicated that these enzymes were inducible by oligocelluloses. Lipid production on cellulose by C. curvatus using the simultaneous saccharification and lipid production process in the absence of cellobiase achieved essentially identical results to that in the presence of cellobiase, suggesting that oligocelluloses generated in situ were utilized with high efficiency. This study has provided inspiring information for oligosaccharides utilization, which should facilitate biorefinery based on lignocellulosic biomass.

CONCLUSIONS

C. curvatus can directly utilize biomass-derived oligosaccharides. Oligocelluloses are transported into the cells and then hydrolyzed by cytoplasmic enzymes. A simultaneous saccharification and lipid production process can be conducted without oligocelluloses accumulation in the absence of cellobiase by C. curvatus, which could reduce the enzyme costs.

Valorization of cereal based biorefinery byproducts: reality and expectations

The growth of the biobased economy will lead to an increase in new biorefinery activities. All biorefineries face the regular challenges of efficiently and economically treating their effluent to be compatible with local discharge requirements and to minimize net water consumption. The amount of wastes resulting from biorefineries industry is exponentially growing. The valorization of such wastes has drawn considerable attention with respect to resources with an observable economic and environmental concern. This has been a promising field which shows great prospective toward byproduct usage and increasing value obtained from the biorefinery. However, full-scale realization of biorefinery wastes valorization is not straightforward because several microbiological, technological and economic challenges need to be resolved. In this review we considered valorization options for cereals based biorefineries wastes while identifying their challenges and exploring the opportunities for future process.

Role and significance of beta-glucosidases in the hydrolysis of cellulose for bioethanol production

One of the major challenges in the bioconversion of lignocellulosic biomass into liquid biofuels includes the search for a glucose tolerant beta-gulucosidase. Beta-glucosidase is the key enzyme component present in cellulase and completes the final step during cellulose hydrolysis by converting the cellobiose to glucose. This reaction is always under control as it gets inhibited by its product glucose. It is a major bottleneck in the efficient biomass conversion by cellulase. To circumvent this problem several strategies have been adopted which we have discussed in the article along with its production strategies and general properties. It plays a very significant role in bioethanol production from biomass through enzymatic route. Hence several amendments took place in the commercial preparation of cellulase for biomass hydrolysis, which contains higher and improved beta-glucosidase for efficient biomass conversion. This article presents beta-glucosidase as the key component for bioethanol from biomass through enzymatic route.

Characterization of a β-glucosidase with transgalactosylation capacity from the zygomycete Rhizomucor miehei

An extracellular β-glucosidase from the zygomycete Rhizomucor miehei NRRL 5282 cultivated in a wheat bran-based solid state fermentation system was characterized. The purified enzyme exhibited an optimum temperature of 68-70 °C and pH of 5.0. It efficiently hydrolyzed oligosaccharides having β-(1→4) glycosidic linkages and exhibited some β- and α-galactosidase activity. The V(max) for p-nitrophenyl-β-d-glucopyranoside and cellobiose was 468.2 and 115.5 U/mg, respectively, while the K(m) was 0.12 mM for both substrates. The enzyme had transglucosylation and transgalactosylation activities resulting in the formation of glycosides from cellobiose, lactose and ethanol. The enzyme increased the amounts of free phenolic antioxidants in sour cherry pomace indicating that its hydrolyzing activity could potentially be applicable to improve the bioavailability of these compounds.

Overexpression of an exotic thermotolerant β-glucosidase in trichoderma reesei and its significant increase in cellulolytic activity and saccharification of barley straw

Background

Trichoderma reesei is a widely used industrial strain for cellulase production, but its low yield of β-glucosidase has prevented its industrial value. In the hydrolysis process of cellulolytic residues by T. reesei, a disaccharide known as cellobiose is produced and accumulates, which inhibits further cellulases production. This problem can be solved by adding β-glucosidase, which hydrolyzes cellobiose to glucose for fermentation. It is, therefore, of high vvalue to construct T. reesei strains which can produce sufficient β-glucosidase and other hydrolytic enzymes, especially when those enzymes are capable of tolerating extreme conditions such as high temperature and acidic or alkali pH.

Results

We successfully engineered a thermostable β-glucosidase gene from the fungus Periconia sp. into the genome of T. reesei QM9414 strain. The engineered T. reesei strain showed about 10.5-fold (23.9 IU/mg) higher β-glucosidase activity compared to the parent strain (2.2 IU/mg) after 24 h of incubation. The transformants also showed very high total cellulase activity (about 39.0 FPU/mg) at 24 h of incubation whereas the parent strain almost did not show any total cellulase activity at 24 h of incubation. The recombinant β-glucosidase showed to be thermotolerant and remains fully active after two-hour incubation at temperatures as high as 60°C. Additionally, it showed to be active at a wide pH range and maintains about 88% of its maximal activity after four-hour incubation at 25°C in a pH range from 3.0 to 9.0. Enzymatic hydrolysis assay using untreated, NaOH, or Organosolv pretreated barley straw as well as microcrystalline cellulose showed that the transformed T. reesei strains released more reducing sugars compared to the parental strain.

Conclusions

The recombinant T. reesei overexpressing Periconia sp. β-glucosidase in this study showed higher β-glucosidase and total cellulase activities within a shorter incubation time (24 h) as well as higher hydrolysis activity using biomass residues. These features suggest that the transformants can be used for β-glucosidase production as well as improving the biomass conversion using cellulases.

Characterization of a thermostable β-glucosidase from Aspergillus fumigatus Z5, and its functional expression in Pichia pastoris X33

BACKGROUND

Recently, the increased demand of energy has strongly stimulated the research on the conversion of lignocellulosic biomass into reducing sugars for the subsequent production, and β-glucosidases have been the focus because of their important roles in a variety fundamental biological processes and the synthesis of useful β-glucosides. Although the β-glucosidases of different sources have been investigated, the amount of β-glucosidases are insufficient for effective conversion of cellulose. The goal of this work was to search for new resources of β-glucosidases, which was thermostable and with high catalytic efficiency.

RESULTS

In this study, a thermostable native β-glucosidase (nBgl3), which is secreted by the lignocellulose-decomposing fungus Aspergillus fumigatus Z5, was purified to electrophoretic homogeneity. Internal sequences of nBgl3 were obtained by LC-MS/MS, and its encoding gene, bgl3, was cloned based on the peptide sequences obtained from the LC-MS/MS results. bgl3 contains an open reading frame (ORF) of 2622 bp and encodes a protein with a predicted molecular weight of 91.47 kDa; amino acid sequence analysis of the deduced protein indicated that nBgl3 is a member of the glycoside hydrolase family 3. A recombinant β-glucosidase (rBgl3) was obtained by the functional expression of bgl3 in Pichia pastoris X33. Several biochemical properties of purified nBgl3 and rBgl3 were determined - both enzymes showed optimal activity at pH 6.0 and 60°C, and they were stable for a pH range of 4-7 and a temperature range of 50 to 70°C. Of the substrates tested, nBgl3 and rBgl3 displayed the highest activity toward 4-Nitrophenyl-β-D-glucopyranoside (pNPG), with specific activities of 103.5 ± 7.1 and 101.7 ± 5.2 U mg-1, respectively. However, these enzymes were inactive toward carboxymethyl cellulose, lactose and xylan.

CONCLUSIONS

An native β-glucosidase nBgl3 was purified to electrophoretic homogeneity from the crude extract of A. fumigatus Z5. The gene bgl3 was cloned based on the internal sequences of nBgl3 obtained from the LC-MS/MS results, and the gene bgl3 was expressed in Pichia pastoris X33. The results of various biochemical properties of two enzymes including specific activity, pH stability, thermostability, and kinetic properties (Km and Vmax) indicated that they had no significant differences.

Cost analysis in laccase production

In this paper the cost of producing the enzyme laccase by the white-rot fungus Trametes pubescens under both submerged (SmF) and solid-state fermentation (SSF) conditions was studied. The fungus was cultured using more than 45 culture medium compositions. The cost of production was estimated by analyzing the cost of the culture medium, the cost of equipment and the operating costs. The cost of the culture medium represented, in all cases, the highest contribution to the total cost, while, the cost of equipment was significantly low, representing less than 2% of the total costs. The cultivation under SSF conditions presented a final cost 50-fold lower than the one obtained when culturing under SmF conditions at flask scale. In addition, the laccase production under SSF conditions in tray bioreactors reduced the final cost 4-fold compared to the one obtained under SSF conditions at flask scale, obtaining a final price of 0.04 cent €/U.

Decolorization of adsorbed textile dyes by developed consortium of Pseudomonas sp. SUK1 and Aspergillus ochraceus NCIM-1146 under solid state fermentation

The objective of this study was to develop consortium using Pseudomonas sp. SUK1 and Aspergillus ochraceus NCIM-1146 to decolorize adsorbed dyes from textile effluent wastewater under solid state fermentation. Among various agricultural wastes rice bran showed dye adsorption up to 90, 62 and 80% from textile dye reactive navy blue HE2R (RNB HE2R) solution, mixture of textile dyes and textile industry wastewater, respectively. Pseudomonas sp. SUK1 and A. ochraceus NCIM-1146 showed 62 and 38% decolorization of RNB HE2R adsorbed on rice bran in 24h under solid state fermentation. However, the consortium of Pseudomonas sp. SUK1 and A. ochraceus NCIM-1146 (consortium-PA) showed 80% decolorization in 24h. The consortium-PA showed effective ADMI removal ratio of adsorbed dyes from textile industry wastewater (77%), mixture of textile dyes (82%) and chemical precipitate of textile dye effluent (CPTDE) (86%). Secretion of extracellular enzymes such as laccase, azoreductase, tyrosinase and NADH-DCIP reductase and their significant induction in the presence of adsorbed dye suggests their role in the decolorization of RNB HE2R. GCMS and HPLC analysis of product suggests the different fates of biodegradation of RNB HE2R when used Pseudomonas sp. SUK1, A. ochraceus NCIM-1146 and consortium PA.

Dynamic synergistic effect on Trichoderma reesei cellulases by novel β-glucosidases from Taiwanese fungi

Dynamic synergistic effects in cellulosic bioconversion have been revealed between Trichoderma reesei cellulases and β-glucosidases (BGLs) from six Taiwanese fungi. A high level of synergy (8.9-fold) was observed with the addition of Chaetomella raphigera BGL to T. reesei cellulases. In addition, the C. raphigera BGL possessed the highest activity (V(max)/K(m)=46.6 U/mg mM) and lowest glucose inhibition (Ki=4.6mM) with the substrate 4-nitrophenyl β-d-glucopyranoside. For the natural cellobiose substrate, however, the previously isolated Aspergillus niger BGL Novo-188 had the highest V(max)/K(m) (0.72 U/mg mM) and lowest Ki (59.5mM). The demonstrated dynamic synergistic effects between some BGLs and the T. reesei cellulase system suggest that BGLs not only prevent the inhibition by cellobiose, but also enhance activities of endo- and exo-cellulases in cellulosic bioconversion. Comparisons of kinetic parameters and synergism analyses between BGLs and T. reesei cellulases can be used for further optimization of the cellulosic bioconversion process.