THE UTILIZATION OF FLAVONOID COMPOUNDS BY YEASTS AND YEAST-LIKE FUNGI

Abstract

Three hundred cultures of yeasts and yeast-like fungi were tested for their ability to metabolize flavonoid compounds. Rutin, quercitrin, taxifolin, and naringin were used by strains of Pullularia and by the asporogenous yeasts Cryptococcus albidus and Cryptococcus diffluens. Catechin and 5, 7-dihydroxyiso-flavone were not used by any of the cultures tested.The utilization of flavonoid compounds was dependent upon the nutritional complexity of the medium used. When a complex organic nitrogen source was used in the medium, not only were quercetin glycosides metabolized at a faster rate but yeasts, which were inactive on a synthetic medium, utilized varying amounts of the glycosides. The aglycone quercetin was utilized only in the presence of organic nitrogen compounds. Culture filtrates were inactive but cell-free extracts of a Pullularia sp. and of strains of C. albidus and C. diffluens degraded rutin, in the presence of air, to glucose, rhamnose, protocatechuic acid, phloroglucinol carboxylic acid, and carbon monoxide. The metabolism of flavonol glycosides by yeasts is discussed as a taxonomic characteristic and the pathway used is compared to the known microbiological routes for the utilization of these compounds.