The starch-degrading yeast Candida tsukubaensis CBS 6389 secreted amylase at high activity when grown in a medium containing soluble starch. The extracellular alpha-amylase activity was very low. The major amylase component was purified by DEAE-Sephadex A-50 chromatography and Ultrogel AcA 44 gel filtration and characterized as a glucoamylase. The enzyme proved to be a glycoprotein with a molecular weight of 56 000. The glucoamylase had a temperature optimum at 55 degrees C and displayed highest activity in a pH range of 2.4-4.8. Acarbose strongly inhibited the purified glucoamylase. Debranching activity was present as demonstrated by the release of glucose from pullulan.

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The production of extracellular amylase activity by a number of recently described amyloytic yeast species, viz. Candida homilentoma, C. silvanorum, C. tsukubaensis, Cryptococcus flavus, Leucosporidium capsuligenum, Filobasidium capsuligenum and Trichosporon pullulans, was investigated. The effects on amylase secretion of pH, different carbon sources (glucose, maltose, dextrin, soluble starch) and of various nitrogen sources [yeast nitrogen base, yeast extract, corn steep liquor (CSL)] were compared for these yeasts.