Journal of Fermentation and Bioengineering, Vol.84, No.5, 421-427, 1997
Enhancement of rice alpha-amylase production in recombinant Yarrowia lipolytica
The productivity of recombinant rice alpha-amylase, a glycosylated protein with a molecular weight of 45 kDa, was improved by using a recombinant Yarrowia lipolytica strain harboring an integrative vector, pXOS103-In. While proteose peptone was found to be a good induer for the expression of alpha-amylase, ammonium sulfate was not. The optimal pH and specific growth rate for alpha-amylase production were 6.8 and 0.1 h(-1), respectively. The concentration of proteose peptone affected alpha-amylase expression when glycerol was used as a carbon source. The optimal ratio of glycerol to proteose peptone was found to be 2.5 for the fed-batch process. In a controlled fed-batch culture, addition of ammonium sulfate by pulse feeding in the production phase caused repression, but alpha-amylase production resumed after the residual ammonium ion was depleted. When recombinant Y. lipolytica was grown in a controlled fed-batch culture in 1.5-l fermentor, using the bioprocess control strategy developed in this work, a 28-fold increase in alpha-amylase productivity was obtained (350 mg/l) as compared with that in a batch culture (12 mg/l). Practically all the alpha-amylase produced was secreted into the medium; only a negligible amount of intracellular alpha-amylase was detected. Our bioprocess control strategy developed for a fed-batch culture using a recombinant Y. lipolytica strain can be applied to the overproduction of other recombinant proteins.