Catalytic efficiency diversification of duplicate β-1,3-1,4-glucanases from Neocallimastix patriciarum J11

Purification, characterization, immobilization and applications of an enzybiotic β-1,3-1,4-glucanase produced from halotolerant marine Halomonas meridiana ES021

Extracellular β-1,3-1,4-glucanase-producing strain Halomonas meridiana ES021 was isolated from Gabal El-Zeit off shore, Red Sea, Egypt. The Extracellular enzyme was partially purified by precipitation with 75% acetone followed by anion exchange chromatography on DEAE-cellulose, where a single protein band was determined with molecular mass of approximately 72 kDa. The Km value was 0.62 mg β-1,3-1,4-glucan/mL and Vmax value was 7936 U/mg protein. The maximum activity for the purified enzyme was observed at 40 °C, pH 5.0, and after 10 min of the reaction. β-1,3-1,4-glucanase showed strong antibacterial effect against Bacillus subtilis, Streptococcus agalactiae and Vibrio damsela. It also showed antifungal effect against Penicillium sp. followed by Aspergillus niger. No toxicity was observed when tested on Artemia salina. Semi-purified β-1,3-1,4-glucanase was noticed to be effective in clarification of different juices at different pH values and different time intervals. The maximum clarification yields were 51.61% and 66.67% on mango juice at 40 °C and pH 5.3 for 2 and 4 h, respectively. To our knowledge, this is the first report of β-1,3-1,4-glucanase enzyme from halotolerant Halomonas species.

Functional Characterization of the Novel Laminaripentaose-Producing β-1,3-Glucanase MoGluB and Its Biocontrol of Magnaporthe oryzae

Fungal cell wall synthesizing enzymes or remodeling enzymes represent key factors for the interaction of plant pathogen and antifungal agents, which are regarded as potential biocontrol agents. In this study, a novel endo-β-1,3-glucanase from Magnaporthe oryzae was expressed and characterized. The expression of MoGluB was significantly upregulated after 2 days of liquid culture and 48 h after infection, indicating that it may be involved in cell wall reconstitution. Purified MoGluB exhibited high activity on insoluble β-glucans, with a specific activity of 8.18 U/mg toward yeast glucan at pH 9.0 and 50 °C. MoGluB hydrolyzed pachymaran and yeast glucan into oligosaccharides dominated by laminaripentaose, suggesting that it is an endo-β-1,3-glucanase. Incubation of 8 μg of MoGluB with 10⁶ spores/mL resulted in the inhibition of conidial germination and appressorium formation of M. oryzae, illustrating effective biocontrol activity. Hydrolysates of pachymaran induced the expression of defense genes restricting M. oryzae infection in rice plants, indicating an immunostimulatory effect of MoGluB hydrolysates.

A Novel Digestive GH16 β-1,3(4)-Glucanase from the Fungus-Growing Termite Macrotermes barneyi

β-1,3-glucanases are the main digestive enzymes of plant and fungal cell wall. Transcriptomic analysis of the fungus-growing termite Macrotermes barneyi revealed a high expression of a predicted β-1,3(4)-glucanase (Mbbgl) transcript in termite gut. Here, we described the cDNA cloning, heterologous expression, and enzyme characterization of Mbbgl. Sequence analysis and RT-PCR results showed that Mbbgl is a termite-origin GH16 β-1,3(4)-glucanase. The recombinant enzyme showed the highest activity towards laminarin and was active optimally at 50 °C, pH 5.5. The enzyme displayed endo/exo β-1,3(4)-glucanase activities. Moreover, Mbbgl had weak transglycosylation activity. The results indicate that Mbbgl is an endogenous digestive β-1,3(4)-glucanase, which contributes to the decomposition of plant biomass and fungal hyphae. Additionally, the multiple activities, pH, and ion stabilities make Mbbgl a potential candidate for application in the food industry.

Functional Analysis of a Highly Active β-Glucanase from Bispora sp. MEY-1 Using Its C-terminally Truncated Mutant

A β-1,3-1,4-glucanase-encoding gene, Bisglu16B, was identified in Bispora sp. MEY-1. The deduced BisGlu16B consists of an N-terminal signal peptide, a catalytic module of glycoside hydrolase family 16 (GH16), and a C-terminal serine/proline-rich module. After expression in Pichia pastoris GS115, the purified recombinant BisGlu16B showed maximal activity at pH 4.0 and 55 °C and had broad substrate specificity (β-1,3-/β-1,4-mixed, β-1,3-, β-1,4-, and β-1,6-linked glucan, and β-1,4-mannan). The enzyme possessed high specific activities toward barley β-glucan (34 700 U·mg^-1), lichenan (23 900 U·mg^-1), and laminarin (9 000 U·mg^-1). After removing the C-terminal module, the truncated mutant, BisGlu16B-ΔC, retained similar enzymatic properties to the wild type but displayed significantly enhanced activities (up to 2.5-fold). Functional and structural analyses indicated that the C-terminal module plays a key role in the substrate binding of BisGlu16B. This study provided an excellent candidate glucanase for industrial purposes and revealed the functions of a C-terminal serine/proline-rich region.

A highly active beta-glucanase from a new strain of rumen fungus Orpinomyces sp.Y102 exhibits cellobiohydrolase and cellotriohydrolase activities

A new strain of rumen fungus was isolated from Bos taurus, identified and designated Orpinomyces sp.Y102. A clone, celC7, isolated from the cDNA library of Orpinomyces sp.Y102, was predicted to encode a protein containing a signal peptide (Residues 1-17), an N-terminal dockerin-containing domain, and a C-terminal cellobiohydrolase catalytic domain of glycoside hydrolase family 6. CelC7 was insoluble when expressed in Escherichia coli. Deletion of 17 or 105 residues from the N-terminus significantly improved its solubility. The resulting enzymes, CelC7(-17) and CelC7(-105), were highly active to β-glucan substrates and were stable between pH 5.0 and 11.0. CelC7(-105) worked as an exocellulase releasing cellobiose and cellotriose from acid-swollen Avicel and cellooligosaccharides, and displayed a Vmax of 6321.64μmole/min/mg and a Km of 2.18mg/ml to barley β-glucan. Further, the crude extract of CelC7(-105) facilitated ethanol fermentation from cellulose. Thus, CelC7(-105) is a good candidate for industrial applications such as biofuel production.

Molecular evolution of glycoside hydrolase genes in the Western corn rootworm (Diabrotica virgifera virgifera)

Cellulose is an important nutritional resource for a number of insect herbivores. Digestion of cellulose and other polysaccharides in plant-based diets requires several types of enzymes including a number of glycoside hydrolase (GH) families. In a previous study, we showed that a single GH45 gene is present in the midgut tissue of the western corn rootworm, Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae). However, the presence of multiple enzymes was also suggested by the lack of a significant biological response when the expression of the gene was silenced by RNA interference. In order to clarify the repertoire of cellulose-degrading enzymes and related GH family proteins in D. v. virgifera, we performed next-generation sequencing and assembled transcriptomes from the tissue of three different developmental stages (eggs, neonates, and third instar larvae). Results of this study revealed the presence of seventy-eight genes that potentially encode GH enzymes belonging to eight families (GH45, GH48, GH28, GH16, GH31, GH27, GH5, and GH1). The numbers of GH45 and GH28 genes identified in D. v. virgifera are among the largest in insects where these genes have been identified. Three GH family genes (GH45, GH48, and GH28) are found almost exclusively in two coleopteran superfamilies (Chrysomeloidea and Curculionoidea) among insects, indicating the possibility of their acquisitions by horizontal gene transfer rather than simple vertical transmission from ancestral lineages of insects. Acquisition of GH genes by horizontal gene transfers and subsequent lineage-specific GH gene expansion appear to have played important roles for phytophagous beetles in specializing on particular groups of host plants and in the case of D. v. virgifera, its close association with maize.