β-glucosidase from thermophilic fungus Thermoascus crustaceus: production and industrial potential

Cloning, heterologous expression and characterization of β-glucosidase deriving from Moniliophthora perniciosa (Stahel) Aime and Phillips Mora

Β-glucosidase (BGLs) act synergistically with endoglucanases and exoglucanases and then are of great interest for biomass conversion into bioethanol. Thus, the aim of the current study is to produce a recombinant β-glycosidase from Moniliophtora perniciosa expressed in Escherichia coli cells. Enzyme coding sequence expression was confirmed through Sanger sequencing after using wheat bran (WB) and carboxymethylcellulose (CMC) as fungal growth media. Synthetic gene betaglyc-GH1 with optimized codons for E. coli expression was cloned in pET-28a. β-glucosidase recombinant (GH1chimera) was purified using a nickel column and its identity was confirmed through mass spectrometry. The recombinant enzyme presented an apparent molecular mass of 53.23 kDa on SDS-PAGE. Recombinant β-glucosidase has shown hydrolytic activity using p-nitrophenyl-β-D-glycopyranoside (pNPG) as substrate and maximum activity at pH 4.6 and 65 °C. Thus, the results indicate that the application of the GH1chimera in the hydrolysis of lignocellulosic materials to obtain glucose monomers can be efficient.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-04128-x.

Application of Immobilized β-Glucosidase from Candida boidinii in the Hydrolysis of Delignified Sugarcane Bagasse

Candida boidinii is a methylotrophic yeast with wide geographical distribution. In the present study, the microorganism was isolated from the Bahian semiarid and the enzymatic extract containing β-glucosidase was obtained through submerged fermentation. Response surface methodology was employed to optimize of fermentation medium. The higher production of β-glucosidase was obtained after 71 h of fermentation in an optimized medium composed of 3.35% glucose, 1.78% yeast extract and 1% peptone. The optimum pH and temperature of enzymatic activity were 6.8 (citrate-phosphate buffer) and 71.7 °C, respectively. Salts tested (10 mM) CaCl2, Na2SO4 and ZnSO4 promotes the increase of 91%, 45% and 80% of activity, respectively. The enzyme retained 64% ± 2.3 of its initial activity after 1 h heating at 90 °C. The production of reducing sugars was 95.94% after 24 h of hydrolysis and, with the addition of metal ions, this value increased more than 2 times. Among the supports analyzed for immobilization, chitosan showed higher residual activity during reuse. The immobilized enzyme showed higher activity at 60 °C with pH 6 and preserved almost 100% of the initial activity after 30 min at 70 °C.

Lignocellulolytic extremozymes and their biotechnological applications

Lignocellulolytic enzymes are used in different industrial and environmental processes. The rigorous operating circumstances of these industries, however, might prevent these enzymes from performing as intended. On the other side, extremozymes are enzymes produced by extremophiles that can function in extremely acidic or basic; hot or cold; under high or low salinity conditions. These severe conditions might denature the normal enzymes that are produced by mesophilic microorganisms. The increased stability of these enzymes has been contributed to a number of conformational modifications in their structures. These modifications may result from a few amino acid substitutions, an improved hydrophobic core, the existence of extra ion pairs and salt bridges, an increase in compactness, or an increase in positively charged amino acids. These enzymes are the best option for industrial and bioremediation activities that must be carried out under difficult conditions due to their improved stability. The review, therefore, discusses lignocellulolytic extremozymes, their structure and mechanisms along with industrial and biotechnological applications.

Catalytic properties of amylases produced by Cunninghamella echinulata and Rhizopus microsporus

The present work aimed to characterize and compare the catalytic properties of amylases from Cunninghamella echinulata and Rhizopus microsporus. The highest production of amylase by C. echinulata, 234.94 U g-1 of dry substrate (or 23.49 U mL-1), was obtained using wheat bran as a substrate, with 50-55% initial moisture and kept at 28 °C for 48 h. The highest production of amylases by R. microsporus, 224.85 U g-1 of dry substrate (or 22.48 U mL-1), was obtained cultivating wheat bran with 65% initial moisture at 45 °C for 24 h. The optimal activity of the amylases was observed at pH 5.0 at 60 °C for C. echinulata enzymes and at pH 4.5 at 65 °C for R. microsporus. The amylases produced by C. echinulata were stable at pH 4.0-8.0, while the R. microsporus enzymes were stable at pH 4.0-10.0. The amylases produced by C. echinulata remained stable for 1 h at 50 °C and the R. microsporus amylases maintained catalytic activity for 1 h at 55 °C. The enzymatic extracts of both fungi hydrolyzed starches from different plant sources and showed potential for liquefaction of starch, however the amylolytic complex of C. echinulata exhibited greater saccharifying potential.

A review on applications of β-glucosidase in food, brewery, pharmaceutical and cosmetic industries

β-glucosidases hydrolyse glycosidic bonds to release non-reducing terminal glucosyl residues from glycosides and oligosaccharides via catalytic mechanisms. It is very well known that the β-glucosidase enzyme is used in biorefineries for cellulose degradation, where β-glucosidases is the rate-limiting enzyme for the final glucose production from cellobiose. The β-glucosidase enzyme is used as a catalyst in other industrial sectors, including pharmaceuticals, breweries, dairy, and food processing. With the aid of β-glucosidase enzymes, cyanogenic glycosides and plant glycosides are transformed into sugar moiety and aglycones. These aglycone compounds are employed as aromatic compounds in the food processing and brewing industries. They are also used as medications and dietary supplements based on their pharmacological qualities. Applications of aglycones and the microbiological sources of β-glucosidase in aglycone production have been discussed in this review.

Improving the catalytic activity of β-glucosidase from Coniophora puteana via semi-rational design for efficient biomass cellulose degradation

In order to improve the degradation activity of β-glucosidase (CpBgl) from Coniophora puteana, the structural modification was conducted. The enzyme activity of mutants CpBgl-Q20C and CpBgl-A240S was increased by 65.75% and 58.58%, respectively. These mutants exhibited maximum activity under the same conditions as wild-type CpBgl (65 ℃ and pH 5.0), slightly improved stabilities compared that of the wild-type, and remarkably enhanced activities in the presence of Mn²⁺ or Fe²⁺. The V_max of CpBgl-Q20C and CpBgl-A240S was increased to 138.18 and 125.14 μmol/mg/min, respectively, from 81.34 μmol/mg/min of the wild-type, and the catalysis efficiency (k_cat/K_m) of CpBgl-Q20C (335.79 min^-1/mM) and CpBgl-A240S (281.51 min^-1/mM) was significantly improved compared with that of the wild-type (149.12 min^-1/mM). When the mutant CpBgl-Q20C were used in the practical degradation of different biomasses, the glucose yields of filter paper, corncob residue, and fungi mycelia residue were increased by 17.68%, 25.10%, and 20.37%, respectively. The spatial locations of the mutation residues in the architecture of CpBgl and their unique roles in the enzyme-substrate binding and catalytic efficiency were probed in this work. These results laid a foundation for evolution of other glycoside hydrolases and the industrial bio-degradation of cellulosic biomass in nature.

Effects of Mixed Adding Crude Extracts of β-Glucosidases from Three Different Non-Saccharomyces Yeast Strains on the Quality of Cabernet Sauvignon Wines

The aim of this study was to investigate the effects of crude extracts of β-glucosidase from Issatchenkia terricola SLY-4, Pichia kudriavzevii F2-24 and Metschnikowia pulcherrima HX-13 (termed as SLY-4E, F2-24E and HX-13E) on the flavor complexity and typicality of Cabernet Sauvignon wines. The grape must was fermented using Saccharomyces cerevisiae with single or mixed SLY-4E, F2-24E and HX-13E. The physicochemical characteristics, volatile aroma compounds, total anthocyanins and sensory attributes of the wines were determined. Adding SLY-4E, F2-24E and HX-13E in wines resulted in a decrease in the anthocyanin content, total acids and volatile acids in wines but an increase in the content of terpenes, benzene derivatives, higher alcohols and esters, which may enhance wine sensory qualities and result in loss of wine color. Different adding strategies of β-glucosidase led to a variety of effects on wine aroma. S/H/F-Ew significantly increased the content of benzene derivatives, higher alcohols and long-chain fatty acid esters, which enhanced the fruity and floral flavor of wines. F2-24E significantly increased the content of short- and medium-chain fatty acid esters, acetate esters and carbonyl compounds. The results indicated that the mixed addition of non-Saccharomyces crude extracts and co-fermentation with S. cerevisiae could further improve wine flavor quality.

Simultaneous manipulation of transcriptional regulator CxrC and translational elongation factor eEF1A enhances the production of plant-biomass-degrading enzymes of Penicillium oxalicum

Genetic engineering is an efficient approach to improve fungal bioproducts, but the specific targets are limited. In this study, it was found that the key transcription repressor CxrC of Penicillium oxalicum could physically interact with the translational elongation factor eEF1A that positively regulated the production of plant-biomass-degrading enzymes by the fungus under Avicel induction. Simultaneously deletion of the cxrC and overexpression of the eEF1A in the strain Δku70 resulted in 55.4%-314.6% higher production of cellulase, xylanase and raw-starch-degrading enzymes than that of the start strain Δku70. Transcript abundance of the genes encoding predominant cellulases, xylanases and raw-starch-degrading enzymes were significantly upregulated in the mutant ΔcxrC::eEF1A. The ΔcxrC::eEF1A enhanced saccharification efficiency of raw cassava flour by 9.3%-15.5% at early-middle stage of hydrolysis in comparison with Δku70. The obtained knowledges expanded the sources used as effective targets for increased production of plant-biomass-degrading enzymes by fungi.

Fungal cellulases: protein engineering and post-translational modifications

Enzymatic degradation of lignocelluloses into fermentable sugars to produce biofuels and other biomaterials is critical for environmentally sustainable development and energy resource supply. However, there are problems in enzymatic cellulose hydrolysis, such as the complex cellulase composition, low degradation efficiency, high production cost, and post-translational modifications (PTMs), all of which are closely related to specific characteristics of cellulases that remain unclear. These problems hinder the practical application of cellulases. Due to the rapid development of computer technology in recent years, computer-aided protein engineering is being widely used, which also brings new opportunities for the development of cellulases. Especially in recent years, a large number of studies have reported on the application of computer-aided protein engineering in the development of cellulases; however, these articles have not been systematically reviewed. This article focused on the aspect of protein engineering and PTMs of fungal cellulases. In this manuscript, the latest literatures and the distribution of potential sites of cellulases for engineering have been systematically summarized, which provide reference for further improvement of cellulase properties. KEY POINTS: •Rational design based on virtual mutagenesis can improve cellulase properties. •Modifying protein side chains and glycans helps obtain superior cellulases. •N-terminal glutamine-pyroglutamate conversion stabilizes fungal cellulases.

Improvement of cellulase and xylanase production in Penicillium oxalicum under solid-state fermentation by flippase recombination enzyme/ recognition target-mediated genetic engineering of transcription repressors

Penicillium oxalicum has received increasing attention as a potential cellulase-producer. In this study, a copper-controlled flippase recombination enzyme/recognition target (FLP/FRT)-mediated recombination system was constructed in P. oxalicum, to overcome limited availability of antibiotic resistance markers. Using this system, two crucial transcription repressor genes atf1 and cxrC for the production of cellulase and xylanase under solid-state fermentation (SSF) were simultaneously deleted, thereby leading to 2.4- to 29.1-fold higher cellulase and 78.9% to 130.8% higher xylanase production than the parental strain under SSF, respectively. Glucose and xylose released from hydrolysis of pretreated sugarcane bagasse achieved 10.6%-13.5% improvement by using the crude enzymes from the engineered strain Δatf1ΔcxrC::flp under SSF in comparison with that of the parental strain. Consequently, these results provide a feasible strategy for improved cellulase and xylanase production by filamentous fungi.