STABLE PRODUCTION OF HUMAN GASTRIC LIPASE BY CHROMOSOMAL INTEGRATION IN THE FISSION YEAST SCHIZOSACCHAROMYCES-POMBE

Strains of the fission yeast Schizosaccharomyces pombe have been const ructed containing single or multiple chromosomally integrated copies o f an expression cassette for production of human gastric lipase. Integ rant strains of S. pombe secrete active lipase and are stable for lipa se production over a minimum of 50 generations in non-selective media. Lipase activity levels for integrant strains containing up to three t andem copies of the expression cassette are strongly correlated with c opy number of the cassette in both complete and minimal media. Lipase activity is higher in complete medium than in minimal medium. Strains carrying three chromosomally integrated expression cassette copies can be grown without selection in complete medium and are capable of sign ificantly higher lipase activities than strains containing the express ion cassette on a multicopy plasmid.