Isolation and characterization of a thermostable endo-beta-glucanase active on 1,3-1,4-beta-D-glucans from the aerobic fungus talaromyces emersonii CBS 814.70

Identification and Characterization of Two Novel Extracellular β-Glucanases from Chaetomium globosum against Fusarium sporotrichioides

Chaetomium globosum can inhibit the growth of fusarium by means of their extracellular proteins. Two novel β-glucanases, designated Cgglu17A and Cgglu16B, were separated from the supernatant of C. globosum W7 and verified to have the ability to hydrolyze cell walls of Fusarium sporotrichioides MLS-19. Cgglu17A (397 amino acids) was classified as glycoside hydrolase family 17 while Cgglu16B belongs to the family16 (284 amino acids). Recombinant protein Cgglu17A was successfully expressed in Escherichia coli, and the enzymes were purified by affinity chromatography. Maximum activity of Cgglu17A appeared at the pH 5.5 and temperature 50 °C, but Cgglu16B shows the maximum activity at the pH 5.0 and temperature 50 °C. Most of heavy metal ions had inhibition effect on the two enzymes, but Cgglu17A and Cgglu16B were respectively activated by Ba2+ and Mn2+. Cgglu17A exhibited high substrate specificity, almost only catalyzing the cleavage of β-1,3-glycosidic bond, in various polysaccharose, to liberate glucose. However, Cgglu16B showed high catalytic activities to both β-1,3-glycosidic and β-1,3-1,4-glycosidic bonds. Cgglu17A was an exo-glucanase, but Cgglu16B was an endo-glucanase based on hydrolytic properties assay. Both of two enzymes showed potential antifungal activity, and the synergistic effect was observed in the germination experiment of pathogenic fungus. In conclusion, Cgglu17A (exo-1,3-β-glucanase) and Cgglu16B (endo-1,3(4)-β-glucanase) were confirmed to play a key role in the process of C. globosum controlling fusarium and have potential application value on industry and agriculture for the first time.

Application of foam separation in production of β-glucanase in Pichia

β-glucanase is widely used in many fields and has great economic value and development space, but it faces the difficulties of separation and nutrient destruction in the process of industrial production. Foam separation is a simple, mild and efficient adsorption separation technique that enables efficient separation and extraction of β-glucanase. In this study, five single factors(loading volume, pH, separation gas velocity, fermentation loading concentration, surfactant concentration) of foam separation and harvest of β-glucanase produced by Pichia pastoris were studied. The best univariate condition was: 600 mL/min separation gas velocity, loading volume of 200 mL, initial enzyme concentration of 100 g/mL, surfactant concentration of 0.3 mg/mL and pH of 5. Based on the best univariate condition, the optimal separation conditions of β-glucanase were further explored, and the five-factor four-level orthogonal test was designed. From the experimental results, the best separation condition was: 600 mL/min, loading volume of 200 mL, initial enzyme concentration of 100 μg/mL, surfactant concentration of 0.5 mg/mL and pH of 5. Under this separation condition, the enrichment ratio (E) was 0.56 and the recovery rate (R) was 96.01%.

Characterization of a Thermostable Lichenase from Bacillus subtilis B110 and Its Effects on β-Glucan Hydrolysis

Lichenase is an enzyme mainly implicated in the degradation of polysaccharides in the cell walls of grains. Emerging evidence shows that a highly efficient expression of a thermostable recombinant lichenase holds considerable promise for application in the beer-brewing and animal feed industries. Herein, we cloned a lichenase gene (CelA203) from Bacillus subtilis B110 and expressed it in E. coli. This gene contains an ORF of 729 bp, encoding a protein with 242 amino acids and a calculated molecular mass of 27.3 kDa. According to the zymogram results, purified CelA203 existed in two forms, a monomer, and a tetramer, but only the tetramer had potent enzymatic activity. CelA203 remained stable over a broad pH and temperature range and retained 40% activity at 70°C for 1 h. The K_m and V_max of CelA203 towards barley β-glucan and lichenan were 3.98 mg/ml, 1017.17 U/mg, and 2.78 mg/ml, 198.24 U/mg, respectively. Furthermore, trisaccharide and tetrasaccharide were the main products obtained from CelA203-mediated hydrolysis of deactivated oat bran. These findings demonstrate a promising role for CelA203 in the production of oligosaccharides in animal feed and brewing industries.

Thermostable Cellulases / Xylanases From Thermophilic and Hyperthermophilic Microorganisms: Current Perspective

The bioconversion of lignocellulose into monosaccharides is critical for ensuring the continual manufacturing of biofuels and value-added bioproducts. Enzymatic degradation, which has a high yield, low energy consumption, and enhanced selectivity, could be the most efficient and environmentally friendly technique for converting complex lignocellulose polymers to fermentable monosaccharides, and it is expected to make cellulases and xylanases the most demanded industrial enzymes. The widespread nature of thermophilic microorganisms allows them to proliferate on a variety of substrates and release substantial quantities of cellulases and xylanases, which makes them a great source of thermostable enzymes. The most significant breakthrough of lignocellulolytic enzymes lies in lignocellulose-deconstruction by enzymatic depolymerization of holocellulose into simple monosaccharides. However, commercially valuable thermostable cellulases and xylanases are challenging to produce in high enough quantities. Thus, the present review aims at giving an overview of the most recent thermostable cellulases and xylanases isolated from thermophilic and hyperthermophilic microbes. The emphasis is on recent advancements in manufacturing these enzymes in other mesophilic host and enhancement of catalytic activity as well as thermostability of thermophilic cellulases and xylanases, using genetic engineering as a promising and efficient technology for its economic production. Additionally, the biotechnological applications of thermostable cellulases and xylanases of thermophiles were also discussed.

A trimodular family 16 glycoside hydrolase from the cellulosome of Ruminococcus flavefaciens displays highly specific licheninase (EC 3.2.1.73) activity

Cellulosomes are highly complex cell-bound multi-enzymatic nanomachines used by anaerobes to break down plant carbohydrates. The genome sequence of Ruminococcus flavefaciens revealed a remarkably diverse cellulosome composed of more than 200 cellulosomal enzymes. Here we provide a detailed biochemical characterization of a highly elaborate R. flavefaciens cellulosomal enzyme containing an N-terminal dockerin module, which anchors the enzyme into the multi-enzyme complex through binding of cohesins located in non-catalytic cell-bound scaffoldins, and three tandemly repeated family 16 glycoside hydrolase (GH16) catalytic domains. The DNA sequence encoding the three homologous catalytic domains was cloned and hyper-expressed in Escherichia coli BL21 (DE3) cells. SDS-PAGE analysis of purified His₆ tag containing RfGH16_21 showed a single soluble protein of molecular size ~89 kDa, which was in agreement with the theoretical size, 89.3 kDa. The enzyme RfGH16_21 exhibited activity over a wide pH range (pH 5.0-8.0) and a broad temperature range (50-70 °C), displaying maximum activity at an optimum pH of 7.0 and optimum temperature of 55 °C. Substrate specificity analysis of RfGH16_21 revealed maximum activity against barley β-d-glucan (257 U mg^-1) followed by lichenan (247 U mg^-1), but did not show significant activity towards other tested polysaccharides, suggesting that it is specifically a β-1,3-1,4-endoglucanase. TLC analysis revealed that RfGH16_21 hydrolyses barley β-d-glucan to cellotriose, cellotetraose and a higher degree of polymerization of gluco-oligosaccharides indicating an endo-acting catalytic mechanism. This study revealed a fairly high, active and thermostable bacterial endo-glucanase which may find considerable biotechnological potentials.

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.

A novel bifunctional glucanase exhibiting high production of glucose and cellobiose from rumen bacterium

Herbivores gastrointestinal microbiota is of tremendous interest for mining novel lignocellulosic enzymes for bioprocessing. We previously reported a set of potential carbohydrate-active enzymes from the metatranscriptome of the Hu sheep rumen microbiome. In this study, we isolated and heterologously expressed two novel glucanase genes, Cel5A-h38 and Cel5A-h49, finding that both recombinant enzymes showed the optimum temperatures of 50 °C. Substrate-specificity determination revealed that Cel5A-h38 was exclusively active in the presence of mixed-linked glucans, such as barley β-glucan and Icelandic moss lichenan, whereas Cel5A-h49 (EC 3.2.1.4) exhibited a wider substrate spectrum. Surprisingly, Cel5A-h38 initially released only cellotriose from lichenan and further converted it into an equivalent amount of glucose and cellobiose, suggesting a dual-function as both endo-β-1,3-1,4-glucanase (EC 3.2.1.73) and exo-cellobiohydrolase (EC 3.2.1.91). Additionally, we performed enzymatic hydrolysis of sheepgrass (Leymus chinensis) and rice (Orysa sativa) straw using Cel5A-h38, revealing liberation of 1.91 ± 0.30 mmol/mL and 2.03 ± 0.09 mmol/mL reducing sugars, respectively, including high concentrations of glucose and cellobiose. These results provided new insights into glucanase activity and lay a foundation for bioconversion of lignocellulosic biomass.

Combined whole cell wall analysis and streamlined in silico carbohydrate-active enzyme discovery to improve biocatalytic conversion of agricultural crop residues

The production of biofuels as an efficient source of renewable energy has received considerable attention due to increasing energy demands and regulatory incentives to reduce greenhouse gas emissions. Second-generation biofuel feedstocks, including agricultural crop residues generated on-farm during annual harvests, are abundant, inexpensive, and sustainable. Unlike first-generation feedstocks, which are enriched in easily fermentable carbohydrates, crop residue cell walls are highly resistant to saccharification, fermentation, and valorization. Crop residues contain recalcitrant polysaccharides, including cellulose, hemicelluloses, pectins, and lignin and lignin-carbohydrate complexes. In addition, their cell walls can vary in linkage structure and monosaccharide composition between plant sources. Characterization of total cell wall structure, including high-resolution analyses of saccharide composition, linkage, and complex structures using chromatography-based methods, nuclear magnetic resonance, -omics, and antibody glycome profiling, provides critical insight into the fine chemistry of feedstock cell walls. Furthermore, improving both the catalytic potential of microbial communities that populate biodigester reactors and the efficiency of pre-treatments used in bioethanol production may improve bioconversion rates and yields. Toward this end, knowledge and characterization of carbohydrate-active enzymes (CAZymes) involved in dynamic biomass deconstruction is pivotal. Here we overview the use of common "-omics"-based methods for the study of lignocellulose-metabolizing communities and microorganisms, as well as methods for annotation and discovery of CAZymes, and accurate prediction of CAZyme function. Emerging approaches for analysis of large datasets, including metagenome-assembled genomes, are also discussed. Using complementary glycomic and meta-omic methods to characterize agricultural residues and the microbial communities that digest them provides promising streams of research to maximize value and energy extraction from crop waste streams.

Transcriptional analysis of the lichenase-like gene cel12A of the filamentous fungus Stachybotrys atra BP-A and its relevance for lignocellulose depolymerization

To rationally optimize the production of industrial enzymes by molecular means requires previous knowledge of the regulatory circuits controlling the expression of the corresponding genes. The genus Stachybotrys is an outstanding producer of cellulose-degrading enzymes. Previous studies isolated and characterized the lichenase-like/non-typical cellulase Cel12A of S. atra (AKA S. chartarum) belonging to glycosyl hydrolase family 12 (GH12). In this study, we used RT-qPCR to determine the pattern of expression of cel12A under different carbon sources and initial ambient pH. Among the carbon sources examined, rice straw triggered a greater increase in the expression of cel12A than 1% lactose or 0.1% glucose, indicating specific induction by rice straw. In contrast, cel12A was repressed in the presence of glucose even when combined with this inducer. The proximity of 2 adjacent 5'-CTGGGGTCTGGGG-3' CreA consensus target sites to the translational start site of cel12A strongly suggests that the carbon catabolite repression observed is directly mediated by CreA. Ambient pH did not have a significant effect on cel12A expression. These findings present new knowledge on transcriptional regulatory networks in Stachybotrys associated with cellulose/hemicellulose depolymerization. Rational engineering of CreA to remove CCR could constitute a novel strategy for improving the production of Cel12A.

Sources, Extraction and Biomedical Properties of Polysaccharides

In the recent era, bioactive compounds from plants have received great attention because of their vital health-related activities, such as antimicrobial activity, antioxidant activity, anticoagulant activity, anti-diabetic activity, UV protection, antiviral activity, hypoglycemia, etc. Previous studies have already shown that polysaccharides found in plants are not likely to be toxic. Based on these inspirational comments, most research focused on the isolation, identification, and bioactivities of polysaccharides. A large number of biologically active polysaccharides have been isolated with varying structural and biological activities. In this review, a comprehensive summary is provided of the recent developments in the physical and chemical properties as well as biological activities of polysaccharides from a number of important natural sources, such as wheat bran, orange peel, barely, fungi, algae, lichen, etc. This review also focused on biomedical applications of polysaccharides. The contents presented in this review will be useful as a reference for future research as well as for the extraction and application of these bioactive polysaccharides as a therapeutic agent.

Fungal β-1,3-1,4-glucanases: production, proprieties and biotechnological applications

β-1,3-1,4-glucanases (or lichenases; EC 3.2.1.73) comprise one of the main enzymes used in industry during recent decades. These enzymes hydrolyze β-glucans containing β-1,3 and β-1,4 linkages, such as cereal β-glucans and lichenan. The β-1,3-1,4-glucanases are produced by a variety of bacteria, fungi, plants and animals. A large number of microbial β-1,3-1,4-glucanases have potential application in industrial processes, such as feed, food and detergent industries. The present review summarizes the available studies with respect to β-1,3-1,4-glucanases production conditions, enzyme biochemical properties and potential industrial application. © 2018 Society of Chemical Industry.

Metagenomic analysis of uncultured microorganisms and their enzymatic attributes

Although second generation biofuel technology is a sustainable route for bioethanol production it is not currently a robust technology because of certain hindrances viz., unavailability of potential enzyme resources, low efficiency of enzymes and restricted availability of potent enzymes that work under harsh conditions in industrial processes. Therefore, bioprospecting of extremophilic microorganisms using metagenomics is a promising alternative to discover novel microbes and enzymes with efficient tolerance to unfavourable conditions and thus could revolutionize the energy sector. Metagenomics a recent field in "omics" technology enables the genomic study of uncultured microorganisms with the goal of better understanding microbial dynamics. Metagenomics in conjunction with NextGen Sequencing technology facilitates the sequencing of microbial DNA directly from environmental samples and has expanded, and transformed our knowledge of the microbial world. However, filtering the meaningful information from the millions of genomic sequences offers a serious challenge to bioinformaticians. The current review holds the opinion tool 'know- how' to unravel the secrets of nature while expediting the bio-industrial world. We also discuss the novel biocatalytic agents discovered through metagenomics and how bioengineering plays a pivotal role to enhance their efficiency.

Expression and biochemical characterization of a multifunctional glycosidase from the thermophilic Bacillus licheniformis SR01

A gene (gkdA) (741 bp) encoding a putative protein of 247 amino acids was cloned from the Bacillus licheniformis SR01. The protein was expressed in Escherichia coli BL21 with a molecular mass estimated by SDS-PAGE of approximately 28.03 kDa and showed a calculating isoelectric point (pI) of 6.42. Structure analysis and function identification showed that the enzyme was a multifunctional glycosidase. Its specific activity was 0.013 U/μg. The recombinant glycosidase showed a maximum activity at 50°C and pH 7.0. It was very stable below 90°C and may have heat activation at higher temperatures. The relative residual activity was still more than 80% after 120 min at pH 5.0-10.0. The enzyme activity was inhibited by Cu²⁺, Fe²⁺, Ca²⁺, Mg²⁺, Co²⁺, Li⁺, SDS and EDTA, activated by Ca²⁺, and not affected by Mn²⁺ and K⁺. Under simulated stomach, and in vitro intestine, conditions, the enzyme retained 80%, and more than 100%, activity, respectively, after incubation for 90 min. The excellent properties of this enzyme, specifically its thermal stability and multifunctional abilities, give it potential application in the field of feed processing and other high-temperature processing industries.

Improvement of the thermostability and catalytic efficiency of a highly active β-glucanase from Talaromyces leycettanus JCM12802 by optimizing residual charge-charge interactions

BACKGROUND

β-Glucanase is one of the most extensively used biocatalysts in biofuel, food and animal feed industries. However, the poor thermostability and low catalytic efficiency of most reported β-glucanases limit their applications. Currently, two strategies are used to overcome these bottlenecks, i.e., mining for novel enzymes from extremophiles and engineering existing enzymes.

RESULTS

A novel endo-β-1,3-1,4-glucanase of GH16 (Tlglu16A) from the thermophilic fungus Talaromyces leycettanus JCM12802 was produced in Pichia pastoris and characterized. For potential industrial applications, recombinant TlGlu16A exhibits favorable enzymatic properties over most reported glucanases, i.e., remarkable stability over a wide pH range from 1.0 to 10.0 and superior activity on glucan substrates (up to 15,197 U/mg). The only weakness of TlGlu16A is the thermolability at 65 °C and higher. To improve the thermostability, the enzyme thermal stability system was then used to engineer TlGlu16A through optimization of residual charge-charge interactions. Eleven mutants were constructed and compared to the wild-type TlGlu16A. Four mutants, H58D, E134R, D235G and D296K, showed longer half-life time at 80 °C (31, 7, 25, 22 vs. 0.5 min), and two mutants, D235G and D296K, had greater specific activities (158.2 and 122.2 %, respectively) and catalytic efficiencies (k cat/K m, 170 and 114 %, respectively).

CONCLUSIONS

The engineered TlGlu16A has great application potentials from the perspectives of enzyme yield and properties. Its thermostability and activity were apparently improved in the engineered enzymes through charge optimization. This study spans the genetic, functional and structural fields, and provides a combination of gene mining and protein engineering approaches for the systematic improvement of enzyme performance.

Engineering of a thermostable β-1,3-1,4-glucanase from Bacillus altitudinis YC-9 to improve its catalytic efficiency

BACKGROUND

Error-prone polymerase chain reaction (PCR) is frequently used in directed evolution of enzymes to modify their quality. In this study, error-prone PCR was used to improve the catalytic efficiency of β-1,3-1,4-glucanase from Bacillus altitudinis YC-9.

RESULTS

By screening, the mutant Glu-3060 with higher activity was selected among 5000 transformants. After induction with isopropyl β-D-1-thiogalactopyranoside (IPTG), the activity of the mutant Glu-3060 reached 474.6 U mL(-1), resulting in a 48.6% increment of the parent enzyme activity. Research on the characterization of the mutated enzyme showed the optimal pH of the mutated enzyme to be 5.0, which is lower than the parent enzyme, but thermal stability was almost the same between them. Sequence analysis of the mutated enzyme revealed that three amino acids were changed compared with the parent enzyme, including K142N, Q203L and N214D.

CONCLUSION

The three-dimensional structure predicted by SWISS-MODEL of the mutated enzyme Glu-3060 showed that the substitution of three amino acids had an effect on the catalytic activity, stability and optimal pH of the enzyme, through changing the charge properties or electron density, forming secondary keys, the acidity of the amino acids and the side chain group. The sum effects of all the factors were increased activity of the mutated enzyme and decreased optimal pH, while the same thermostability was maintained, thereby increasing the suitability of the enzyme for industrial use.

High-level production of β-1,3-1,4-glucanase by Rhizomucor miehei under solid-state fermentation and its potential application in the brewing industry

AIMS

To improve the β-1,3-1,4-glucanase production by Rhizomucor miehei under solid-state fermentation (SSF) for industrial application.

METHODS AND RESULTS

The fermentation conditions for β-1,3-1,4-glucanase production by R. miehei CAU432 under SSF were optimized using a 'one-factor-at-a-time' method. Under the optimized fermentation conditions, viz. oatmeal (0·45-0·9 mm) as sole carbon source, 5% (w/w) peptone as sole nitrogen source, initial moisture of 80% (w/w), initial culture pH of 5·0, incubation temperature of 50°C and incubation time of 6 days, the highest β-1,3-1,4-glucanase activity of 20,025 U g(-1) dry substrate was achieved, which represents the highest yield for β-1,3-1,4-glucanase production ever reported. The crude enzyme was extracted and purified to homogeneity with a purification fold of 4·6 and a recovery yield of 9·0%. The addition of the purified β-1,3-1,4-glucanase in mash obviously reduced its filtration time (24·6%) and viscosity (2·61%).

CONCLUSIONS

The optimal fermentation conditions for maximal β-1,3-1,4-glucanase production under SSF was obtained, and the enzyme was suitable for application in the malting process.

SIGNIFICANCE AND IMPACT OF THE STUDY

The high production yield and excellent capability of the enzyme may enable it great potential in industries, especially in brewing industry.

Purification and characterization of a novel alkaline β-1,3-1,4-glucanase (lichenase) from thermophilic fungus Malbranchea cinnamomea

A novel alkaline β-1,3-1,4-glucanase (McLic1) from a thermophilic fungus, Malbranchea cinnamomea, was purified and biochemically characterized. McLic1 was purified to homogeneity with a purification fold of 3.1 and a recovery yield of 3.7 %. The purified enzyme was most active at pH 10.0 and 55 °C, and exhibited a wide range of pH stability (pH 4.0–10.0). McLic1 displayed strict substrate specificity for barley β-glucan, oat β-glucan and lichenan, but did not show activity towards other tested polysaccharides and synthetic p-nitrophenyl derivates, suggesting that it is a specific β-1,3-1,4-glucanase. The K  m values for barley β-glucan, oat β-glucan and lichenan were determined to be 0.69, 1.11 and 0.63 mg mL−1, respectively. Moreover, the enzyme was stable in various non ionic surfactants, oxidizing agents and several commercial detergents. Thus, the alkaline β-1,3-1,4-glucanase may have potential in industrial applications, such as detergent, paper and pulp industries.

Purification and characterization of a novel lichenase from Bacillus licheniformis GZ-2

A novel lichenase from Bacillus licheniformis GZ-2 was purified to homogeneity by two steps ion-exchange chromatography with a specific activity of 8231.3 U/mg. The purified enzyme showed as a single protein band with a molecular mass of 25 kDa. The optimum pH and temperature for the enzyme activity were 6.5 and 60 °C, respectively. The enzyme exhibited strict specificity for β-1,3-1,4-d-glucans. The kinetic parameters Km and Vmax were 5.11 mg/mL and 2097 µmol/Min/mg for lichenan and 7.42 mg/mL and 1440 µmol/Min/mg for barley β-glucan. Compared to most of the reported β-1,3-1,4-glucanases (lichenase), the activity of the purified enzyme for lichenan was much higher than that for barley β-glucan. The main products of β-glucan hydrolyzed by the lichenase were cellubiosyltriose (DP3) and cellutriosyltraose (DP4). The lichenase gene from B. licheniformis GZ-2 was cloned and sequenced. The open reading frame of gene gz-2 contained 642 bp coding for a 214 amino acid mature protein. The gene was cloned into an expression vector pET 28a and expressed in Escherichia coli BL21. The activity in cell lysate supernatant was 137.9 U/mg.

Microbacterium oxydans, a novel alginate- and laminarin-degrading bacterium for the reutilization of brown-seaweed waste

There is a growing demand for the efficient treatment of seaweed waste. We identified six bacterial strains from the marine environment for the reutilization of brown-seaweed waste, and the most potentially useful strain, Microbacterium oxydans, was chosen and further investigated. Plate assays indicated that this bacterial isolate possessed both alginate lyase and laminarinase activities. The optimal inoculum size, pH, temperature and substrate concentration for the degradation of brown-seaweed polysaccharides by the isolate were as follows: 20% (v v(-1)), pH 6.0, 37 °C, and 5 g L(-1) for alginate and 20% (v v(-1)), pH 6.0, 30 °C, and 10 g L(-1) for laminarin, respectively. During 6 d in culture under the optimal conditions, the isolate produced 0.17 g L(-1) of reducing sugars from alginate with 11.0 U mL(-1) of maximal alginate lyase activity, and 5.11 and 2.88 g L(-1) of reducing sugars and glucose from laminarin, respectively. In particular, a fair amount of laminarin was degraded to glucose (28.8%) due to the isolate's exolytic laminarinase activity. As a result, the reutilization of brown-seaweed waste by this isolate appears to be possible for the production of reducing sugars as a valuable resource. This is the first study to directly demonstrate the ability of M. oxydans to degrade both alginate and laminarin.

Rasamsonia pulvericola sp. nov., isolated from house dust

In the course of a global survey of the indoor mycobiota, we sampled and analysed settled dust from 87 buildings from 14 countries, using both a modified dilution-to-extinction method and 454-pyrosequencing. Rasamsonia is a recently established genus including thermotolerant or thermophilic species, five of which have been isolated from humans, including the emerging pathogen R. argillacea. A new species, R. pulvericola, was recovered from one residence in Songkhla, Thailand, and is morphologically characterised and compared phylogenetically with other members of the genus. Rasamsonia pulvericola forms a clade with R. brevistipitata and shares morphological characters such as usually biverticillate and never terverticillate conidiophores, and subglobose to ellipsoidal conidia. It has a lower maximum growth temperature and is the first mesophilic species added to the genus. The ITS sequence of R. pulvericola was not detected in the 454-pyrosequencing data for Thailand or other countries, but a similar ITS sequence was detected in Micronesia, probably representing another undescribed Rasamsonia species.

Purification, characterization, and heterologous expression of a thermostable β-1,3-1,4-glucanase from Bacillus altitudinis YC-9

Purification, characterization, gene cloning, and heterologous expression in Escherichia coli of a thermostable β-1,3-1,4-glucanase from Bacillus altitudinis YC-9 have been investigated in this paper. The donor strain B. altitudinis YC-9 was isolated from spring silt. The native enzyme was purified by ammonium sulfate precipitation, diethylaminoethyl-cellulose anion exchange chromatography, and Sephadex G-100 gel filtration. The purified β-1,3-1,4-glucanase was observed to be stable at 60 °C and retain more than 90% activity when incubated for 2 h at 60 °C and remain about 75% and 44% activity after incubating at 70 °C and 80 °C for 10 min, respectively. Acidity and temperature optimal for this enzyme was pH 6 and 65 °C. The open reading frame of the enzyme gene was measured to be 732 bp encoding 243 amino acids, with a predicted molecular weight of 27.47 kDa. The gene sequence of β-1,3-1,4-glucanase showed a homology of 98% with that of Bacillus licheniformis. After being expressed in E. coli BL21, active recombinant enzyme was detected both in the supernatants of the culture and the cell lysate, with the activity of 102.7 and 216.7 U/mL, respectively. The supernatants of the culture were used to purify the recombinant enzyme. The purified recombinant enzyme was characterized to show almost the same properties to the wild enzyme, except that the specific activity of the recombinant enzyme reached 5392.7 U/mg, which was higher than those ever reported β-1,3-1,4-glucanase from Bacillus strains. The thermal stability and high activity make this enzyme broad prospect for industry application. This is the first report on β-1,3-1,4-glucanase produced by B. altitudinis.

Purification and characterization of a novel β-1,3-1,4-glucanase (lichenase) from thermophilic Rhizomucor miehei with high specific activity and its gene sequence

Production, purification, and characterization of a novel β-1,3-1,4-glucanase (lichenase) from thermophilic Rhizomucor miehei CAU432 were investigated. High-level extracellular β-1,3-1,4-glucanase production of 6230 U/mL was obtained when oat flour (3%, w/v) was used as a carbon source at 50 °C. The crude enzyme was purified to homogeneity with a specific activity of 28818 U/mg. The molecular weight of purified enzyme was estimated to be 35.4 kDa and 33.7 kDa by SDS-PAGE and gel filtration, respectively. The optimal pH and temperature of the enzyme were pH 5.5 and 60 °C, respectively. The K(m) values of purified β-1,3-1,4-glucanase for barley β-glucan and lichenan were 2.0 mM and 1.4 mM, respectively. Furthermore, the gene (RmLic16A) encoding the β-1,3-1,4-glucanase was cloned and its deduced amino acid sequence showed the highest identity (50%) to characterized β-1,3-1,4-glucanase from Paecilomyces thermophila. The high-level production and biochemical properties of the enzyme enable its potential industrial applications.

Expression of novel β-glucanase Cel12A from Stachybotrys atra in bacterial and fungal hosts

β-glucanase Cel12A from Stachybotrys atra has been cloned and expressed in Aspergillus niger. The purified enzyme showed high activity of β-1,3-1,4-mixed glucans, was also active on carboxymethylcellulose (CMC), while it did not hydrolyze crystalline cellulose or β-1,3 glucans as laminarin. Cel12A showed a marked substrate preference for β-1,3-1,4 glucans, showing maximum activity on barley β-glucans (27.69 U mg(-1)) while the activity on CMC was much lower (0.51 U mg(-1)). Analysis by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), isoelectric focussing (IEF), and zymography showed the recombinant enzyme has apparent molecular weight of 24 kDa and a pI of 8.2. Optimal temperature and pH for enzyme activity were 50°C and pH 6.5. Thin layer chromatography analysis showed that major hydrolysis products from barley β-glucan and lichean were 3-O-β-cellotriosyl-D-glucose and 3-O-β-cellobiosyl-D-glucose, while glucose and cellobiose were released in smaller amounts. The amino acid sequence deduced from cel12A revealed that it is a single domain enzyme belonging to the GH12 family, a family that contains several endoglucanases with substrate preference for β-1,3-1,4 glucans. We believe that S. atra Cel12A should be considered as a lichenase-like or nontypical endoglucanase.

Production, purification and characterization of a thermostable β-1,3-glucanase (laminarinase) produced by Moniliophthora perniciosa

The enzyme glucanase from Moniliophthora perniciosa was produced in liquid medium and purified from the culture supernatant. A multivariate statistical approach (Response Surface Methodology - RSM) was employed to evaluate the effect of variables, including inducer (yeast extract) and fermentation time, on secreted glucanase activities M. perniciosa detected in the culture medium. The crude enzyme present in the supernatant was purified in two steps: precipitation with ammonium sulfate (70%) and gel filtration chromatography on Sephacryl S-200. The best inducer and fermentation time for glucanase activities were 5.9 g L-1 and 13 days, respectively. The results revealed three different isoforms (GLUI, GLUII and GLUIII) with purification factors of 4.33, 1.86 and 3.03, respectively. The partially purified enzymatic extract showed an optimum pH of 5.0 and an optimum temperature of 40°C. The enzymatic activity increased in the presence of KCl at all concentrations studied. The glucanase activity was highest in the presence of 0.2 M NaCl. The enzyme showed high thermal stability, losing only 10.20% of its specific activity after 40 minutes of incubation at 90°C. A purified enzyme with relatively good thermostability that is stable at low pH might be used in future industrial applications.

Characterisation of a Talaromyces emersonii thermostable enzyme cocktail with applications in wheat dough rheology

In this paper, we report new sequence data for secreted thermostable fungal enzymes from the un-sequenced xylanolytic filamentous fungus Talaromyces emersonii and reveal novel insights on the potential role of enzymes relevant as wheat dough improvers. The presence of known and de novo enzyme sequences were confirmed through NanoLC-ESI-MS/MS and resultant peptide sequences were identified using SWISS PROT databases. The de novo protein sequences were assigned identity based on homology to known fungal proteins. Other proteins were assigned function based on the limited T. emersonii genome coverage. This approach allowed the identification of enzymes with relevance as wheat dough improvers. Rheological examination of wheat dough and wheat flour components treated with the thermostable fungal enzyme cocktail revealed structural alterations that can be extrapolated to the baking process. Thermoactive amylolytic, xylanolytic, glucanolytic, proteolytic and lipolytic enzyme activities were observed. Previously characterized T. emersonii enzymes present included; β-glucosidase, xylan-1,4-β-xyloxidase, acetylxylan esterase, acid trehalase, avenacinase, cellobiohydrolase and endo-glucanase. De novo sequence analysis confirmed peptides as being; α-glucosidase, endo-1,4-β-xylanase, endo-arabinase, endo-glucanase, exo-β-1,3-glucanase, glucanase/cellulase, endopeptidase and lipase/acylhydrolase. Rheology tests using wheat dough and fractioned wheat flour components in conjunction with T. emersonii enzymes show the role of these novel biocatalysts in altering properties of wheat substrates. Enzyme treated wheat flour fractions showed the effects of particular enzymes on appropriate substrates. This proteomic approach combined with rheological characterization is the first such report to the authors' knowledge.

Production of minicellulosomes for the enhanced hydrolysis of cellulosic substrates by recombinant Corynebacterium glutamicum

Although cellulosic materials of plant origin are the most abundant utilizable biomass resource, the amino acid-producing organism Corynebacterium glutamicum can not utilize these materials. Here we report the engineering of a C. glutamicum strain expressing functional minicellulosomes containing chimeric endoglucanase E bound to miniCbpA from Clostridium cellulovorans that can hydrolyze cellulosic materials. The chimeric endoglucanase E consists of the endoglucanase E catalytic backbone of Clostridium thermocellum fused with the endoglucanase B dockerin domain of C. cellulovorans. The resulting strain degraded cellulose efficiently by substrate targeting via the carbohydrate binding module. The assembly of minicellulosomes increased the activity against carboxymethyl cellulose approximately 2.8-fold compared with that for the corresponding enzymes alone. This is the first report of the formation of Clostridium minicellulosomes by C. glutamicum. The development of C. glutamicum strain that is capable of more effective cellulose hydrolysis brings about a realization of consolidated bioprocessing for the utilization of cellulosic biomass.

A multi-step chromatographic strategy to purify three fungal endo-β-glucanases

Fungi and fungal enzymes have traditionally occupied a central role in biotechnology. Understanding the biochemical properties of the variety of enzymes produced by these eukaryotes has been an area of research interest for decades and again more recently due to global interest in greener bio-production technologies. Purification of an individual enzyme allows its unique biochemical and functional properties to be determined, can provide key information as to the role of individual biocatalysts within a complex enzyme system, and can inform both protein engineering and enzyme production strategies in the development of novel green technologies based on fungal biocatalysts. Many enzymes of current biotechnological interest are secreted by fungi into the extracellular culture medium. These crude enzyme mixtures are typically complex, multi-component, and generally also contain other non-enzymatic proteins and secondary metabolites. In this chapter, we describe a multi-step chromatographic strategy required to isolate three new endo-β-glucanases (denoted EG V, EG VI, and EG VII) with activity against cereal mixed-linkage β-glucans from the thermophilic fungus Talaromyces emersonii. This work also illustrates the challenges frequently involved in isolating individual extracellular fungal proteins in general.

Purification of exo-1,3-beta-glucanase, a new extracellular glucanolytic enzyme from Talaromyces emersonii

The moderately thermophilic aerobic ascomycete Talaromyces emersonii secretes, under selected growth conditions, several β-glucan hydrolases including an exo-1,3-β-glucanase. This enzyme was purified to apparent homogeneity in order to characterise its biochemical properties and investigate hydrolysis of different β-glucans, including laminaran, a 1,3-β-glucan from brown algae. The native enzyme is monomeric with a molecular mass of ~40 kDa and a pI value of 4.3, and is active over broad ranges of pH and temperature, with optimum activity observed at pH 5.4 and 65 °C. At pH 5.0, the enzyme displays strict specificity for laminaran (apparent K(m) 1.66 mg mL⁻¹; V(max) 7.69 IU mL⁻¹) and laminari-oligosaccharides and did not yield activity against 1,4-β-glucans, 1,3;1,4-β-glucans or 4-nitrophenyl- and methylumbelliferyl-β-D: -glucopyranosides. Analysis of hydrolysis products formed during time-course hydrolysis of laminaran by high-performance anion exchange chromatography with pulsed amperometric detection revealed a strict exo mode of action, with glucose being the sole reaction product even at the initial stages of hydrolysis. The T. emersonii exo-1,3-β-glucanase was inhibited by glucono-δ-lactone (K(i) 1.25 mM) but at significantly higher concentrations than typically inhibitory for exo-glycosidases such as β-glucosidase. 'De novo' sequence analysis of the purified enzyme suggests that it belongs to family GH5 of the glycosyl hydrolase superfamily. The results clearly show that the exo-1,3-β-glucanase is yet another novel enzyme present in the β-glucanolytic enzyme system of T. emersonii.

Xylose reductase from the thermophilic fungus Talaromyces emersonii: cloning and heterologous expression of the native gene (Texr) and a double mutant (TexrK271R + N273D) with altered coenzyme specificity

Xylose reductase is involved in the first step of the fungal pentose catabolic pathway. The gene encoding xylose reductase (Texr) was isolated from the thermophilic fungus Talaromyces emersonii, expressed in Escherichia coli and purified to homogeneity. Texr encodes a 320 amino acid protein with a molecular weight of 36 kDa, which exhibited high sequence identity with other xylose reductase sequences and was shown to be a member of the aldoketoreductase (AKR) superfamily with a preference for reduced nicotinamide adenine dinucleotide phosphate (NADPH) as coenzyme. Given the potential application of xylose reductase enzymes that preferentially utilize the reduced form of nicotinamide adenine dinucleotide (NADH) rather than NADPH in the fermentation of five carbon sugars by genetically engineered microorganisms, the coenzyme selectivity of TeXR was altered by site-directed mutagenesis. The TeXR K271R+N273D double mutant displayed an altered coenzyme preference with a 16-fold improvement in NADH utilization relative to the wild type and therefore has the potential to reduce redox imbalance of xylose fermentation in recombinant S. cerevisiae strains. Expression of Texr was shown to be inducible by the same carbon sources responsible for the induction of genes encoding enzymes relevant to lignocellulose hydrolysis, suggesting a coordinated expression of intracellular and extracellular enzymes relevant to hydrolysis and metabolism of pentose sugars in T. emersonii in adaptation to its natural habitat. This indicates a potential advantage in survival and response to a nutrient-poor environment.

Thermostable enzymes as biocatalysts in the biofuel industry

Lignocellulose is the most abundant carbohydrate source in nature and represents an ideal renewable energy source. Thermostable enzymes that hydrolyze lignocellulose to its component sugars have significant advantages for improving the conversion rate of biomass over their mesophilic counterparts. We review here the recent literature on the development and use of thermostable enzymes for the depolymerization of lignocellulosic feedstocks for biofuel production. Furthermore, we discuss the protein structure, mechanisms of thermostability, and specific strategies that can be used to improve the thermal stability of lignocellulosic biocatalysts.