Rice sheath blight (ShB) caused by Rhizoctonia solani is one of the most serious diseases that threatens rice (Oryza sativa) production. However, the mechanisms of defense against ShB in rice remain largely unknown. In this study, we identified that the expression levels of β-glucanase (OsBGL) family genes sensitively respond to infection by R. solani, and OsBGLs positively regulate rice resistance to ShB. In addition, OsBGL2 colocalized with AtPDCB1 at the plasmodesmata (PD) and limited the PD permeability. The level of callose accumulation in osbgls mutants and overexpressors was examined, and OsBGLs were found contribute to callose accumulation. Taken together, these data suggest that OsBGLs can regulate the deposition of callose at the PD to reduce its permeability to defend itself against ShB. Through the identification of these genes and the elucidation of their functions, this research fills the gap in the mechanism of PD permeability in rice ShB resistance.

BACKGROUND: The combination of cellulase and lytic polysaccharide monooxygenase (LPMO) is known to boost enzymatic saccharification of cellulose. Although the synergy between cellulases (GH5, 6 or 7) and LPMOs (AA9) has been extensively studied, the interplay between other glycoside hydrolase and LPMO families remains poorly understood.
RESULTS: In this study, two cellulolytic enzyme-encoding genes SmBglu12A and SmLpmo10A from Streptomyces megaspores were identified and heterologously expressed in Escherichia coli. The recombinant SmBglu12A is a non-typical endo-β-1,4-glucanase that preferentially hydrolyzed β-1,3-1,4-glucans and slightly hydrolyzed β-1,4-glucans and belongs to GH12 family. The recombinant SmLpmo10A belongs to a C1-oxidizing cellulose-active LPMO that catalyzed the oxidation of phosphoric acid swollen cellulose to produce celloaldonic acids. Moreover, individual SmBglu12A and SmLpmo10A were both active on barley β-1,3-1,4-glucan, lichenan, sodium carboxymethyl cellulose, phosphoric acid swollen cellulose, as well as Avicel. Furthermore, the combination of SmBglu12A and SmLpmo10A enhanced enzymatic saccharification of phosphoric acid swollen cellulose by improving the native and oxidized cello-oligosaccharides yields.
CONCLUSIONS: These results proved for the first time that the AA10 LPMO was able to boost the catalytic efficiency of GH12 glycoside hydrolases on cellulosic substrates, providing another novel combination of glycoside hydrolase and LPMO for cellulose enzymatic saccharification.

Lignocellulosic biomass, which mainly consists of cellulose and hemicellulose, is the most abundant renewable biopolymer on earth. β-Glucanases are glycoside hydrolases (GHs) that hydrolyze β-glucan, one of the dominant components of the plant cell wall, into cello-oligosaccharides and glucose. Among them, endo-β-1,4-glucanase (EC 3.2.1.4), exo-glucanase/cellobiohydrolase (EC 3.2.1.91), and β-glucosidase (EC 3.2.1.21) play critical roles in the digestion of glucan-like substrates. β-Glucanases have attracted considerable interest within the scientific community due to their applications in the feed, food, and textile industries. In the past decade, there has been considerable progress in the discovery, production, and characterization of novel β-glucanases. Advances in the development of next-generation sequencing techniques, including metagenomics and metatranscriptomics, have unveiled novel β-glucanases isolated from the gastrointestinal microbiota. The study of β-glucanases is beneficial for research and development of commercial products. In this study, we review the classification, properties, and engineering of β-glucanases.

The low production of natural products (NPs) is still the critical restrictive factor in exploiting their potential large-scale applications and a barrier to isolating and identifying other meaningful products. Given that the stimulation of cell wall integrity (CWI) has become a novel strategy to modulate the production of microbial natural products, herein, exogenous β-glucanase treatment was developed as an external cell wall β-glucan stress to stimulate the fungal CWI, and then to improve the production of fungal NPs. It was found that the production of fungal NPs cercosporin and sophorolipids, biosynthesized by Cercospora sp. and Starmerella bombicola, respectively, was significantly improved by the treatment of β-glucanase under a controllable dose. Moreover, it demonstrated that β-glucanase had an ability to stimulate fungal CWI through slight fungal superficial damage, thus facilitating the secretion of NPs. We expected that this easy-operating method to stimulate fungal CWI could be feasible to improve more fungal NPs production. KEY POINTS: • Exogenous β-glucanase stimulated the fungal cell wall integrity • Changing fungal cell walls modulated natural product production • β-glucanase with potential universal effects on more fungal natural products.

High stability at acidic environment is required for 1,3-1,4-β-glucanase to function in biofuel, brewing and animal feed industries. In this study, a mesophilic β-glucanase from Bacillus terquilensis CGX 5-1 was rationally engineered through sequence alignment and surface charge engineering to improve its acidic resistance ability. Nineteen singly-site variants were constructed and Q1E, I133L and V134A variants showed better acidic stability without the compromise of catalytic property and thermostability. Furthermore, four multi-site variants were constructed and one double-site variant Q1E/I133L with better stability at acidic environment and higher catalytic property was obtained. The fluorescence spectroscopy and structural analysis showed that more surface negative charge, decreased exposure degree of residue No.1, shifted side chain direction of residue No.133 and the lower total and folding free energy might be the reason for the improvement of acidic stability of Q1E/I133L variant. The obtained Q1E/I133L variant has potential applications in industries.

Poria cocos mushroom is widely used as a food and an herb in East Asian and other countries due to its high nutritional value. Research has demonstrated that Poria cocos polysaccharides (PCP) are the major bioactives and possess antioxidation, anti-inflammation, immunoregulation, and other health promoting properties. However, the efficient preparation of PCP has been a challenge, particularly in large scale for industry. Herein, we investigated the biotransformation of PCP from Poria cocos, catalyzed by β-glucanase from Aspergillus niger and focused on optimizing the most four influencing parameters: Temperature, time, pH, and enzyme dosage in this study. After numerous optimizations with the assistance of response surface optimization methodology, we have established that the optimal conditions for the biotransformation PCP preparation were as following: Enzymolysis temperature 60 °C, time 120 min, pH 5.0 and enzyme dose 20 mL. Under these conditions, the extraction yield of PCP reached as high as 12.8%. In addition, the antioxidant activities of PCP were evaluated by reducing power assay and 1,1-diphenyl-2-picryl-hydrazyl, superoxide anion, and hydroxyl radicals scavenging assays. Resulting data showed that PCP presented outstanding antioxidant capacity. Thus, these findings indicate that PCP could be produced as a natural antioxidant for further development.

In this study, a strain producing β-glucanase and protease, identified as Bacillus velezensis Y1, was isolated from the manure of piglet. We attempted to produce β-glucanase and protease after optimization of various process parameters with the submerged fermentation. The effects of each factor on producing β-glucanase and protease were as follows: temperature > time > pH > loaded liquid volume. The properties of the β-glucanase showed that the most suitable reaction temperature was 65 °C and pH was 6.0. However for protease optimum reaction temperature was 50 °C, and pH was 6.0. The amplified PCR fragments of β-glucanase and protease were 1434 bp containing an open reading frame of 1413 bp encoding a protein with 444 amino acids and 1752 bp containing an open reading frame of 1521 bp encoding a protein with 506 amino acids, respectively. So, the study demonstrated a viable approach of using newly identified B. velezensis Y1 strain for the maximum yield of two industrially important enzymes.

The enrichment of β-glucan in barley significantly decreases the quality of dough and baked bread, and β-glucanase can improve dough and bread quality. Nevertheless, the mechanism by which β-glucanase improves the quality of fermented barley flour-based products is still poorly understood. The gluten microcosmic structure, molecular structure and yeast gas production capacity were investigated using Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, Scanning electron microscopy (SEM) and F3 rheological fermentation techniques. The results showed that β-Glucanase can degrade the high-molecular-weight β-glucan to low-molecular-weight oligosaccharide fragments, which reduces the viscosity of the β-glucans, promotes cross-linking between the gluten molecules, and indirectly improves the gluten network structure, thereby alleviating the negative effects of β-glucans. The β-glucosidase produced during yeast metabolism can further hydrolyse low-molecular-weight oligosaccharides into reducing sugars that can be used by yeast, increasing the carbon sources available to yeasts and the gas production capability of yeasts.

Producing heterologous enzymes in the animal digestive tract to improve feed utilization rate is a new research strategy by transgenic technology. In this study, transgenic pigs specifically expressing β-glucanase gene in the intestine were successfully produced by somatic cell nuclear transfer technology in order to improve digestibility of dietary β-glucan and absorption of nutrients. The β-glucanase activity in the intestinal juice of 4 transgenic pigs was found to be 8.59 ± 2.49 U/mL. The feeding trial results showed that the crude protein digestion of 4 transgenic pigs was significantly increased compared with that of the non-transgenic pigs. In order to investigate the inheritance of the transgene, 7 G1 transgenic pigs were successfully obtained. The β-glucanase activity in the intestinal juice of 7 G1 transgenic pigs was found to be 2.35 ± 0.72 U/mL. The feeding trial results showed the crude protein digestion and crude fat digestion were significantly higher in 7 G1 transgenic pigs than in non-transgenic pigs. Taken together, our study demonstrated that the foreign β-glucanase expressing in the intestine of the transgenic pigs could reduce the anti-nutritional effect of β-glucans in feed. In addition, β-glucanase gene could be inherited to the offsprings and maintain its physiological function. It is a promising approach to improve feed utilization by producing transgenic animals.

In order to provide an efficient way to degrade carboxymethylcellulose (CMC), three pathways were investigated: enzymolysis, combination of ultrasound pretreatment and enzymolysis, and sonoenzymolysis. Effects of these treatments on enzymatic kinetics, degradation kinetics and properties of degraded CMC were investigated. The degradation degree of CMC was increased by 18.90% and 35.73% with ultrasound pretreatment (at an intensity of 24 W/mL for 30 min) and sonoenzymolysis (at an intensity of 9 W/mL for 50 min), compared with that obtained under the traditional enzymolysis. Analysis of kinetics demonstrated that ultrasound, both pretreatment and combined with β-glucanase, could accelerate CMC degradation. Measurements of rheological properties, molecular weight and structures of CMC hydrolysates revealed that ultrasound broke the glycosidic bond of CMC chains without changing its primary structure. The sonoenzymolysis process was the most efficient method to degrade CMC, with potential to provide a way to obtain CMC with lowest molecular weight or viscosity.