Production of a xylose-stimulated β-glucosidase and a cellulase-free thermostable xylanase by the thermophilic fungus Humicola brevis var. thermoidea under solid state fermentation

Enhanced saccharification levels of corn starch using as a strategy a novel amylolytic complex (AmyHb) from the thermophilic fungus Humicola brevis var. thermoidea in association with commercial enzyme

Amylases represent a versatile group of catalysts that are used for the saccharification of starch because they can hydrolyze the glycosidic bonds of starch molecules to release glucose, maltose, and short-chain oligosaccharides. The amylolytic complex of the thermophilic filamentous fungus Humicola brevis var. thermoidea (AmyHb) was produced, biochemically characterized, and compared with the commercial amylase Termamyl. In addition, the biotechnological application of AmyHb in starch saccharification was investigated. The highest production was achieved using a wheat bran medium at 50 °C for 5-6 days in solid-state fermentation (849.6 ± 18.2 U·g-1) without the addition of inducers. Optimum amylolytic activity occurred at pH 5.0 at 60 °C, and stability was maintained between pH 5.0 and 6.0, with thermal stability at 50-60 °C, especially in the presence of Ca2+. These results were superior to those found with Termamyl. Both enzymes were strongly inhibited by Hg2+, Cu2+, and Ag+; however, AmyHb displayed increased activity in the presence of Mn2+ and Na+. In addition, AmyHb showed greater tolerance to a wide range of ethanol concentrations. AmyHb appears to be a complex consisting of glucoamylase and α-amylase, based on its substrate specificity and TLC. The hydrolysis tests on cornstarch flour showed that the cocktail of AmyHb50% + Termamyl50% significantly increased the release of glucose and total reducing sugars (36.6%) when compared to the enzymes alone. AmyHb exhibited promising physicochemical properties and good performance with commercial amylase; therefore, this complex is a biotechnological alternative candidate for the bioprocessing of starch sources.

Heat-moisture treatment can modulate all-purpose wheat flour for short dough biscuit making: Evidences and mechanism

In view of the merits of all-purpose wheat flour (APWF) to soft wheat flour (SWF) in cost and protein supply, the feasibility of heat-moisture treatment (HMT, 19% moisture for 1 h at 60, 80 and 100 °C, respectively) to modify APWF as a substitute SWF in making short dough biscuits was explored. For underlying mechanisms, on the one hand, HMT reduced the hydration capacity of damaged starch particles by coating them with denatured proteins. On the other hand, HMT at 80 °C and 100 °C significantly denatured gluten proteins to form protein aggregates, highly weakening the gluten network in dough. These two aspects jointly conferred APWF dough with higher deformability and therefore significantly improved the qualities of biscuits. Moreover, the qualities of biscuits from APWF upon HMT-100 °C were largely comparable to that from SWF, even higher values were concluded in spread ratio, volume, specific volume and consumer acceptance.

Recombinant GH3 β-glucosidase stimulated by xylose and tolerant to furfural and 5-hydroxymethylfurfural obtained from Aspergillus nidulans

The β-glucosidase gene from Aspergillus nidulans FGSC A4 was cloned and overexpressed in the A. nidulans A773. The resulting purified β-glucosidase, named AnGH3, is a monomeric enzyme with a molecular weight of approximately 80 kDa, as confirmed by SDS-PAGE. Circular dichroism further validated its unique canonical barrel fold (β/α), a feature also observed in the 3D homology model of AnGH3. The most striking aspect of this recombinant enzyme is its robustness, as it retained 100% activity after 24 h of incubation at 45 and 50 ºC and pH 6.0. Even at 55 °C, it maintained 72% of its enzymatic activity after 6 h of incubation at the same pH. The kinetic parameters Vmax, KM, and Kcat/KM for ρ-nitrophenyl-β-D-glucopyranoside (ρNPG) and cellobiose were also determined. Using ρNPG, the enzyme demonstrated a Vmax of 212 U mg - 1, KM of 0.0607 mmol L - 1, and Kcat/KM of 4521 mmol L - 1 s - 1 when incubated at pH 6.0 and 65 °C. The KM, Vmax, and Kcat/KM using cellobiose were 2.7 mmol L - 1, 57 U mg - 1, and 27 mmol -1 s - 1, respectively. AnGH3 activity was significantly enhanced by xylose and ethanol at concentrations up to 1.5 mol L - 1 and 25%, respectively. Even in challenging conditions, at 65 °C and pH 6.0, the enzyme maintained its activity, retaining 100% and 70% of its initial activity in the presence of 200 mmol L - 1 furfural and 5-hydroxymethylfurfural (HMF), respectively. The potential of this enzyme was further demonstrated by its application in the saccharification of the forage grass Panicum maximum, where it led to a 48% increase in glucose release after 24 h. These unique characteristics, including high catalytic performance, good thermal stability in hydrolysis temperature, and tolerance to elevated concentrations of ethanol, D-xylose, furfural, and HMF, position this recombinant enzyme as a promising tool in the hydrolysis of lignocellulosic biomass as part of an efficient multi-enzyme cocktail, thereby opening new avenues in the field of biotechnology and enzymology.

Assay of cellulose 1,4-β-cellobiosidase activity in soil

As the most abundant biopolymer on earth, cellulose undergoes degradation by a diverse set of enzymes with varying specificities that act in synergism. An assay protocol was developed to detect and quantify activity of cellulose 1,4-β-cellobiosidase (EC 3.2.1.91) in soil. The optimum pH and temperature for β-cellobiosidase activity were approximately pH 5.5 and 60 °C, respectively. In the tested six soils, the Michaelis constants (Km) ranged from 0.08 to 0.51 mM, and maximum velocity (Vmax) ranged from 71.5 to 318.1 μmol kg soil-1 h-1. The temperature coefficient (Q10) ranged from 1.72 to 1.99 at non-denaturing temperatures from 10 to 50 °C, and the activation energy (Ea) ranged from 42.5 to 53.7 kJ mol-1. The assay procedure provided reproducible results with a coefficient of variance ≤4.7% and demonstrated a limit of quantification (LOQ) of 50.9 μmol p-nitrophenol release kg-1 soil h-1 for β-cellobiosidase activity in soil. Notably, the developed assay protocol offers reproducibility and precision comparable to bench-scale assays while reducing costs associated with reagents, supplies, and labor.

Production, characteristics, and biotechnological applications of microbial xylanases

Microbial xylanases have gathered great attention due to their biotechnological potential at industrial scale for many processes. A variety of lignocellulosic materials, such as sugarcane bagasse, rice straw, rice bran, wheat straw, wheat bran, corn cob, and ragi bran, are used for xylanase production which also solved the great issue of solid waste management. Both solid-state and submerged fermentation have been used for xylanase production controlled by various physical and nutritional parameters. Majority of xylanases have optimum pH in the range of 4.0-9.0 with optimum temperature at 30-60 °C. For biochemical, molecular studies and also for successful application in industries, purification and characterization of xylanase have been carried out using various appropriate techniques. Cloning and genetic engineering are used for commercial-level production of xylanase, to meet specific economic viability and industrial needs. Microbial xylanases are used in various biotechnological applications like biofuel production, pulp and paper industry, baking and brewing industry, food and feed industry, and deinking of waste paper. This review describes production, characteristics, and biotechnological applications of microbial xylanases.

A Chrysoporthe cubensis enzyme cocktail produced from a low-cost carbon source with high biomass hydrolysis efficiency

Low cost and high efficiency cellulolytic cocktails can consolidate lignocellulosic ethanol technologies. Sugarcane bagasse (SCB) is a low cost agro-industrial residue, and its use as a carbon source can reduce the costs of fungi cultivation for enzyme production. Chrysoporthe cubensis grown under solid state fermentation (SSF) with wheat bran has potential to produce efficient enzymatic extracts for SCB saccharification. This fungus was grown under submersed fermentation (SmF) and SSF with in natura SCB, pretreated with acid or alkali and with others carbon sources. In natura SCB induced the highest carboxymethylcellulase (CMCase), xylanase, β-xylosidase, α-galactosidase and mannanase activities by C. cubensis under SSF. In natura and washed SCB, inducers of enzyme production under SSF, did not induce high cellulases and hemicellulases production by C. cubensis in SmF. The C. cubensis enzymatic extract produced under SSF with in natura SCB as a carbon source was more efficient for lignocelulolic biomass hydrolysis than extracts produced under SSF with wheat bran and commercial cellulolytic extract. Chrysoporthe cubensis showed high potential for cellulases and hemicellulases production, especially when grown under SSF with in natura SCB as carbon source.

The thermophilic biomass-degrading fungus Thielavia terrestris Co3Bag1 produces a hyperthermophilic and thermostable β-1,4-xylanase with exo- and endo-activity

A hyperthermophilic and thermostable xylanase of 82 kDa (TtXynA) was purified from the culture supernatant of T. terrestris Co3Bag1, grown on carboxymethyl cellulose (CMC), and characterized biochemically. TtXynA showed optimal xylanolytic activity at pH 5.5 and at 85 °C, and retained more than 90% of its activity at a broad pH range (4.5-10). The enzyme is highly thermostable with a half-life of 23.1 days at 65 °C, and active in the presence of several metal ions. Circular dichroism spectra strongly suggest the enzyme gains secondary structures when temperature increases. TtXynA displayed higher substrate affinity and higher catalytic efficiency towards beechwood xylan than towards birchwood xylan, oat-spelt xylan, and CMC. According to its final hydrolysis products, TtXynA displays endo-/exo-activity, yielded xylobiose, an unknown oligosaccharide containing about five residues of xylose and a small amount of xylose on beechwood xylan. Finally, this report represents the description of the first fungal hyperthermophilic xylanase which is produced by T. terrestris Co3Bag1. Since TtXynA displays relevant biochemical properties, it may be a suitable candidate for biotechnological applications carried out at high temperatures, like the enzymatic pretreatment of plant biomass for the production of bioethanol.

Characterization of a novel β-glucosidase from Gongronella sp. W5 and its application in the hydrolysis of soybean isoflavone glycosides

A novel β-glucosidase named BglW5 from Gongronella sp. was isolated, purified, and characterized for the first time. Under solid state fermentation, the yield of BglW5 was 49.9 U/g fermented medium. BglW5 was stable over a wide pH range of 3.0-8.5 and retained more than 50% of its maximal activity after incubation at 25 °C for 96 h. The half-lives of BglW5 were 20 h at 60 °C, and 1 h at 70 °C. The activity of BglW5 was stimulated by xylose and fructose at concentrations up to 500 mM, with maximal stimulatory effect of 1.6-fold and 2.2-fold, respectively. BglW5 converted isoflavone glycosides to aglycones, with a hydrolysis rate of 96.2% for daidzin and 96.7% for genistin. The productivities were 1.5 mmol L(-1) h(-1) for daidzein and 1.23 mmol L(-1) h(-1) for genistein, respectively. These features suggest that BglW5 has great application potential in the hydrolysis of soybean isoflavone glycosides.

Improvement of cellulase and xylanase production by solid-state fermentation of Stachybotrys microspora

The current study investigated the production of cellulases and xylanases from the rare fungus Stachybotrys microspora under solid-state fermentation (SSF) on wheat bran (WB). A comparison of both activities was first performed in submerged cultures using various concentrations of WB, glucose, and cellulose as substrates. The maximal activity of β-glucosidases and xylanases was obtained with 2% and 4% WB, respectively, whereas cellulose yielded the highest endoglucanase production. The SSF conditions were therefore consequently optimized. A moisture content of 70% gave the most significant levels of enzyme production. Inoculation by spores led to better results than by preculture, with 10(5) spores per gram of dried matter as the best inoculum dose for all activities tested. Interestingly, the WB-based medium need not to be supplemented by an exogeneous nitrogen source. Considering the richness of S. microspora secreted proteins as lytic hydrolases, the crude extracellular enzyme extracts were successfully tested in two different biotechnological fields: protoplasting of fungi and subsequent extraction of their DNA, paper pulp hydrolysis to produce fermentable sugars.

Optimization of β-glucosidase, β-xylosidase and xylanase production by Colletotrichum graminicola under solid-state fermentation and application in raw sugarcane trash saccharification

Efficient, low-cost enzymatic hydrolysis of lignocellulosic residues is essential for cost-effective production of bioethanol. The production of β-glucosidase, β-xylosidase and xylanase by Colletotrichum graminicola was optimized using Response Surface Methodology (RSM). Maximal production occurred in wheat bran. Sugarcane trash, peanut hulls and corncob enhanced β-glucosidase, β-xylosidase and xylanase production, respectively. Maximal levels after optimization reached 159.3 ± 12.7 U g⁻¹, 128.1 ± 6.4 U g⁻¹ and 378.1 ± 23.3 U g⁻¹, respectively, but the enzymes were produced simultaneously at good levels under culture conditions optimized for each one of them. Optima of pH and temperature were 5.0 and 65 °C for the three enzymes, which maintained full activity for 72 h at 50 °C and for 120 min at 60 °C (β-glucosidase) or 65 °C (β-xylosidase and xylanase). Mixed with Trichoderma reesei cellulases, C. graminicola crude extract hydrolyzed raw sugarcane trash with glucose yield of 33.1% after 48 h, demonstrating good potential to compose efficient cocktails for lignocellulosic materials hydrolysis.