Construction of Saccharomyces cerevisiae with secretive α-amylase activity and low production of ethyl carbamate

In order to construct Saccharomyces cerevisiae with α-amylase activity and low production of ethyl carbamate (EC). The expression vectors containing promotor sequence of ADH1 and ADH2 and α-amylase encoding sequence of Saccharomycopsis fibuligera were constructed, respectively. The α-amylase expression vectors were transformed into SΔcar1 and the positive recombinants were screened. The results indicated that the positive recombinants with α-amylase activity and reduced ethyl carbamate (EC)production were constructed and named SΔcar1/A1and SΔcar1/A2, respectively. In solid and liquid medium, α-amylase expression of SΔcar1/A1 was induced by glucose. Meanwhile, with the increasing of glucose concentration, the α-amylase expression was increased. However, the α-amylase of SΔcar1/A2 could be expressed without glucose and it could be feedback-inhibited by glucose. The results indicated α-amylase expression of SΔcar1/A2 was increased by low glucose concentration and reduced by high glucose concentration, although its expression was higher in the presence of glucose than without glucose. In conclusion, the ability of SΔcar1/A2 to produce α-amylase and hydrolyze starch was higher than SΔcar1/A1.In view of those, the SΔcar1/A2 could be used to ferment the materials containing starch. However, further research should be carried out about the condition of enzyme expression, catalyzing and fermentation.