Heterologous expression and characterization of a cold-adapted endo-1,4−β−glucanase gene from Bellamya chinensis laeta

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.

Novel cold-adapted raw-starch digesting α-amylases from Eisenia fetida: Gene cloning, expression, and characterization

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There have been few reports about gene cloning and expression of α-amylases from E. fetida.

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Ef-Amy I and II were shown to 89% identity of amino acid sequences.

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The catalytically important residues of α-amylase of GH family 13 were conserved in Ef-amy I and II.

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The substrate specificities of rEf-Amy I and II were dissimilar.

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It found that rEf-Amy I and II could be possible use for simultaneous saccharification and fermentation process.

We identified the raw-starch-digesting α-amylase genes a earthworm Eisenia fetid α amylase I and II (Ef-Amy I and Ef-Amy II). Each gene consists of 1,530 base pairs (bp) that encode proteins of 510 amino acids, as indicated by the corresponding mRNA sequences. Ef-Amy I and II showed an 89% amino acid identity. The amino acid sequences of Ef-Amy I and II were similar to those of the α-amylases from porcine pancreas, human pancreas, Tenebrio molitor, Oryctolagus cuniculus, and Xenopus (Silurana) tropicalis. Each gene encoding mature Ef-Amy I and II was expressed in the GS115 strain of Pichia pastoris. The molecular masses of the recombinant Ef-Amy I and II were 57 kDa each, and catalytically important residues of α-amylases of the GH family 13 were conserved in both proteins. These amylases exhibited raw-starch-digesting activity at 4 °C. The substrate specificities of rEf-Amy I and II were dissimilar. rEf-Amy I and II were shown to be active even in 40% ethanol, 4 M NaCl, and 4 M KCl.