Abstract:

The gene encoding multifunctional amylases OPMA-N and OPMA-G were cloned into expression vector pMA5, and  the secretory expression of multifunctional amylases OPMAN and OPMAG were achieved with the engineering strain pMA5-OPMA-N and pMA5-OPMA-G. To enhance the expression level and secretion yield of OPMAN and OPMAG, the fermentation conditions were further optimized. The results show that the optimal fermentation conditions for the expression and secretion of OPMAN were obtained in the culture medium (16%) containing 0.5% yeast extract, 0.3% urea, 1% MgSO4, at pH=6.5 and 37 ℃ for 48 h, and for the expression and secretion of OPMAG was obtained in the culture medium (32%) containing 1% starch, 0.8% yeast extract, 1% NaCl, at pH=7.0, and 37 ℃ for 36 h. Under the optimal conditions, the secretion yields of OPMAN and OPMA-G were about 45% and 58% of the total extracellular proteins, respectively and the specific activities of the secreted OPMAN and OPMA-G were 4.57 and 4.65 enzymology activity unit per mg.

Key words:  , multifunctional amylase； Bacillus subtilis； expression； fermentation； activity