New identification of the strain Rhizopus microsporus var. oligosporus spT3 as Rhizopus microsporus var. chinensis

Abstract

The wild Rhizopus strain spT3 extracted from tempeh of Bali, Indonesia (Institute of Microbial Resources, Taichung, Taiwan) had first been identified as Rhizopus microspores var. oligosporus spT3. This strain is used to ferment soybeans, to detoxify them and improve their nutritional value. Analysis of fermented seeds showed that this strain strongly degrades numerous noxious antinutritional factors, which is unusual for R. microsporus var. oligosporus. The activity of strain spT3 on carbohydrates, compared with that of R. microsporus var. oligosporus NRRL 2710 (= CBS 338.62 = ATCC 22959 = IMI 174457 = IFO 8631 = Scholer's M140), presented differences suggesting that strain spT3 was not a R. microsporus var. oligosporus. As a matter of fact, strain spT3 hydrolyzed sucrose and raffinose, whereas R. microsporus var. oligosporus NRRL 2710 did not. A taxonomic study including morphology, growth temperature, and mating showed that the strain spT3 was similar to R. microsporus var. chinensis CBS 261.28 (= Scholer's M213).Key words: Rhizopus microsporus var. oligosporus, Rhizopus microsporus var. chinensis, Rhizopus microsporus var. rhizopodiformis, mating, carbohydrate utilization, taxonomy, scanning electron microscopy.