Mucoraceous moulds involved in the commercial fermentation of Sufu Pehtze

Sufu is a fermented cheese-like soybean product in China and Vietnam, obtained by fungal solid-state fermentation of soybean curd (tofu), which results in moulded tofu or 'pehtze'. The final product sufu is obtained by maturing pehtze in a brine containing alcohol and salt during a period of several months. The present report deals with the identity and phylogenetic relationships of mould starter cultures used for the preparation of pehtze. Starter cultures used in commercial pehtze fermentation were obtained from factories located in several provinces of China and Vietnam, isolated from their pehtze and some were obtained from culture collections. They were identified as Actinomucor repens, Actinomucor taiwanensis, Mucor circinelloides, Mocur hiemalis, Mocur racemosus, and Rhizopus microsporus var. microsporus. Phylogenetic relations based on sequencing of genomic DNA of these starters and of relevant control strains from collections indicate that the genera Mucor, Actinomucor and Rhizopus form distinct and homogenous clusters, with Mucor and Actinomucor showing a slightly closer relationship with each other than with Rhizopus.