Secretory expression of Rhizopus oryzae α-amylase in <i>Kluyveromyces lactis</i>

Abstract

Kluyveromyces lactis is a non-conventional yeast species extensively used in the expression of heterologous genes. In this study, a genetically modified K. lactis with high-level expression of α- amylase from Rhizopus oryzae was obtained, which could successfully hydrolyze and use starch for growth very well. Shake flask fermentation indicated that, the recombinant yeast was able to produce the α-amylase at considerable secretion levels using a variety of carbon sources. The highest level of amylase expression was 22.4 U/ml when cultivated at 30°C and pH 7.0 in the presence of galactose. Moreover, it was shown that the recombinant yeast, which could efficiently degrade starch, yielded a final biomass of 12.25 g/l with enzyme activity of 11 U/ml in the culture medium using 20 g soluble starch/l as the sole carbon source.

Key words: Kluyveromyces lactis, α-amylase, secretion, starch, fermentation.