Application of a microtitre reader system to the screening of inulinase nulinase-producing yeasts

Abstract

Fourteen strains of yeast from genera Kluyveromyces, Candida, Debaryomyces and Schizosaccharomyces were investigated for inulinase production. In the first stage, the microtitre reader system SLT was used for the determination of enzyme activity and the evaluation of cellular growth. Different culture conditions were tested and four strains of Kluyveromyces were selected on the basis of enzyme activity and growth capacity at low pH and high temperature: K. marxianus CBS 6397, DSM 70792, ATCC 36907 and IZ 619. These strains were tested in greater volume using pH 4.0, 45°C and inulin (10 g/l) as selection conditions. On the basis of results obtained, the strain K. marxianus ATCC 36907 was selected for inulinase production. Enzyme stability at low pH (4.0) as well as high temperature (50°C) for 10, 30 and 60 min was also evaluated, but no significant difference in enzyme activity was observed. It could be demonstrated that the microtitre reader system is an excellent method for the screening of microorganisms.