Proteolytic and Lipolytic Activities of Psychrophilic and Psychrotrophic Yeasts Isolated from Chilled Household Foods and Raw Seafoods

Abstract

Proteolytic and lipolytic activities of 2 psychrophilic yeast species and 31 psychrotrophic yeast species isolated from 5 kinds of chilled foods, such as potato or macaroni salad, Chinese dumplings and raw seafoods (sea urchin roe, sliced tuna, hen clam feet), were investigated under various incubation conditions. Proteolytic activity was determined by use of YM agar plus 1% skim milk. Lipolytic activity was determined by use of butterfat in Crossley's agar and beef fat in Gorodkowa agar (Eijkman's method). These 3 kinds of agar plates were incubated for 2 weeks at 5, 15 and 25°C, respectively.The yeasts which demonstrated proteolytic activity under the conditions of incubation for one week at 5, 15 and 25°C, respectively, were 21.2, 18.2 and 15.2% of the 33 species of yeasts tested. The yeasts which demonstrated lipolytic (butterfat) activity under the same conditions of incubation amounted to 30.3, 60.6 and 54.5% of the total, respectively. It was generally found that lipolytic activity was higher than proteolytic activity.Proteolytic and/or lipolyic yeast species were widely distributed among the genera Candida, Cryptococcus, Debaryomyces, Leucosporidium, Rhodotorula, and Trichosporon. Candida sake, C. guilliermondii, C. lambica and C. solani exhibited proteolytic activity when incubated at 5°C within one week. Candida parapsilosis, C. santamariae and C. zeylanoides showed lipolytic activity under the incubation condition. Leucosporidium gelidum, Candida lipolytica and Trichosporon pullulans showed both proteolytic and lipolytic activities at 5°C within 4 days. Strain U1, a yeastlike organism resembling Aureobasidium pullulans showed both activities at 15°C within 2 days, and Rhodotorula aurantiaca, Rh. graminis and Trichosporon cutaneum showed both activities at 15°C within 2 weeks.