Cloning and expression of amyE gene from Bacillus subtilis in Zymomonas mobilis and direct production of ethanol from soluble starch

Two proven secretion signal zmo130 and zmo331 native to Zymomonas mobilis were fused to the N terminal of alpha-amylase from Bacillus subtilis and transformed into 5 different strains of Z. mobilis separately. It was found that the signal zmo130 could direct the extracellular secretion of the expressed alpha-amylase with high activity, but zmo331 could not. Fermentation experiments demonstrated that the recombinant Z. mobilis CICC 10225(p130A) exhibited the highest level of ethanol production, which is nearly 50% of the theoretical yield of ethanol from soluble starch, but another recombinant Z. mobilis ATCC 31821(p130A) took the shortest fermentation time of approximately 3 days, with the second high level of ethanol yield. The recombined strains in our study could be an important target for the following genetic engineering of next amylase in order to hydrolyze starch completely.