Heterologous expression and enhanced production of β-1,4-glucanase of Bacillus halodurans C-125 in Escherichia coli

Saccharide mapping as an extraordinary method on characterization and identification of plant and fungi polysaccharides: A review

Saccharide mapping was a promising scheme to unveil the mystery of polysaccharide structure by analysis of the fragments generated from polysaccharide decomposition process. However, saccharide mapping was not widely applied in the polysaccharide analysis for lacking of systematic introduction. In this review, a detailed description of the establishment process of saccharide mapping, the pros and cons of downstream technologies, an overview of the application of saccharide mapping, and practical strategies were summarized. With the updating of the available downstream technologies, saccharide mapping had been expanding its scope of application to various kinds of polysaccharides. The process of saccharide mapping analysis included polysaccharides degradation and hydrolysates analysis, and the degradation process was no longer limited to acid hydrolysis. Some downstream technologies were convenient for rapid qualitative analysis, while others could achieve quantitative analysis. For the more detailed structure information could be provided by saccharide mapping, it was possible to improve the quality control of polysaccharides during preparation and application. This review filled the blank of basic information about saccharide mapping and was helpful for the establishment of a professional workflow for the saccharide mapping application to promote the deep study of polysaccharide structure.

Expression and characterization of β-1,3-1,4-glucanase of Aspergillus usamii in Escherichia coli and its application in sourdough bread making

A β-1,3-1,4-glucanase gene (Auglu12A) from Aspergillus usamii was successfully expressed in Escherichia coli BL21(DE3). The recombinant enzyme, reAuglu12A was efficiently purified using the one-step nickel-nitrilotriacetic acid affinity chromatography. The specific activity of reAuglu12A was 694.8 U/mg, with an optimal temperature of 55°C and pH of 5.0. The reAuglu12A exhibited stability at temperatures up to 60°C and within the pH range of 4.0-5.5. The reAuglu12A hydrolytic activity was increased in the presence of metal ions, especially K+ and Na+ , whereas it exhibited a Km and Vmax of 8.35 mg/mL and 1254.02 µmol/min/mg, respectively, toward barley β-glucan at pH 5.0 and 55°C. The addition of reAuglu12A significantly increased the specific volume (p < 0.05) and reduced crumb firmness and chewiness (p < 0.05) of wheat-barley sourdough bread during a 7-day storage period compared to the control. Overall, the quality of wheat-barley sourdough bread was improved after incorporation of reAuglu12A (especially at 3000 U/300 g). These changes were attributed to the synergistic effect of acidification by sourdough and its metabolites which provided a conducive environment for the optimal action of reAuglu12A in the degradation of β-glucans of barley flour in sourdough. This stabilized the dough structure, thereby enhancing the quality, texture, and shelf life of the bread. These findings suggest that reAuglu12A holds promise as a candidate for β-glucanase application in the baking industry.

Biochemical Characterization of Novel GH6 Endoglucanase from Myxococcus sp. B6-1 and Its Effects on Agricultural Straws Saccharification

Cellulase has been widely used in many industrial fields, such as feed and food industry, because it can hydrolyze cellulose to oligosaccharides with a lower degree of polymerization. Endo-β-1,4-glucanase is a critical speed-limiting cellulase in the saccharification process. In this study, endo-β-1,4-glucanase gene (CelA257) from Myxococcus sp. B6-1 was cloned and expressed in Escherichia coli. CelA257 contained carbohydrate-binding module (CBM) 4-9 and glycosyl hydrolase (GH) family 6 domain that shares 54.7% identity with endoglucanase from Streptomyces halstedii. The recombinant enzyme exhibited optimal activity at pH 6.5 and 50 °C and was stable over a broad pH (6-9.5) range and temperature < 50 °C. CelA257 exhibited broad substrate specificity to barley β-glucan, lichenin, CMC, chitosan, laminarin, avicel, and phosphoric acid swollen cellulose (PASC). CelA257 degraded both cellotetrose (G₄) and cellppentaose (G₅) to cellobiose (G₂) and cellotriose (G₃). Adding CelA257 increased the release of reducing sugars in crop straw powers, including wheat straw (0.18 mg/mL), rape straw (0.42 mg/mL), rice straw (0.16 mg/mL), peanut straw (0.16 mg/mL), and corn straw (0.61 mg/mL). This study provides a potential additive in biomass saccharification applications.

Molecular and biochemical characterization of a recombinant endoglucanase rCKT3eng, from an extreme halophilic Haloarcula sp. strain CKT3

Halophilic cellulases are indispensable enzymes of heavy industrial processes as resistant biocatalysts due to high level activity at extreme conditions. In this study, crude cellulase from an extreme halophilic Haloarcula sp. CKT3 was characterized. Then, recombinant expression of putative endo-1,4-β-glucanase gene, of CKT3 strain, in E. coli BL21(DE3) was performed with the aim of obtaining highly pure, active and robust industrial enzyme for such industrial aplications. The crude cellulase had optimal activity (16.9 U/mg) at 70 °C, pH 7.0 and 4 M NaCl exhibiting good thermostability, high pH and halotolerance. Indeed, it is very stable in water-insoluble organic solvents with log P_o/w ≥ 2.13 and highly resistant to SDS (10%). Recombinant CKT3eng has a molecular weight of 36.9 kDa and 99% aminoacid identity to endo-l,4-β-D-glucanase from Haloarcula argentinensis. Its 3D structure was predicted using Phyre2 and I-TASSER. rCKT3eng enzyme provided 31.6 U/mg activity at optimal 50 °C, pH 7.0 and 3 M NaCl. In addition to its quite similar stability values and resistance to organic solvents and SDS, rCKT3eng has superiority over crude enzyme with 1.87-fold higher specific activity. Therefore, rCKT3eng offers a promising enzyme for industrial use with its valuable activity and stability in extreme conditions.