ABSTRACT
To develop systems for the expression of heterologous genes in probiotic strains of Lactobacillus and Propionibacterium, we used Lactobacillus plantarum and Propionibacterium freudenreichii and a modified gene encoding cholesterol oxidase (choA) from Streptomyces sp. to generate working models. The acetyl coenzyme A carboxylase (acc) promoter derived from the acc operon of L. plantarum L137 and a previously constructed shuttle vector, pRN14, were used to construct vectors for the expression of heterologous genes in lactic acid bacteria. The concentration of cholesterol oxidase in recombinant L. plantarum carrying choA fused to the NH2-terminal region of the first open reading frame of the acc operon was 3.6 mU/mg of protein. Using the promoters from Propionibacterium, namely, P4, P8, and P138, which enabled high-level expression of choA in Escherichia coli, and a previously constructed shuttle vector pPK705, we constructed expression vectors for Propionibacterium. In recombinant P. freudenreichii subsp. shermanii IFO12426, the activities of cholesterol oxidase generated under the control of promoters P4, P8, and P138 were 1.6, 4.3, and 7.2 U/mg of protein, respectively. The expression of heterologous genes may facilitate the production of useful proteins in these economically important bacteria.
