Bioconversion of Raw Starch to SCP by Coculture of Cryptococcus aerius and Saccharomyces cerevisiae

Simultaneous degradation and conversion of unhydrolysed wheat starch to high protein content SCP by monoculture of an isolated amylolytic yeast, Cryptococcus aerius and co-culture of Cryptococcus aerius and Saccharomyces cerevisiae was investigated. Amylolytic activity, starch degradation rate, biomass and protein content of biomass increased several fold in coculture versus the monoculture due to the synergistic metabolic interactions between the two species. Under optimal condition, in monoculture of C. aerius 10.02 g L 1 biomass produced after about 78 h with 27.8% protein content and >84% efficiency; while with optimal ratio of C. aerius to S.cerevisiae (5% v/v:5% v/v) the cultivation was improved totally. In coculture, total cultivation time decreased to 58 h with about 94% efficiency in biomass production, while biomass and total cellular crude protein of biomass increased from 10.02 to 11.22 g L 1 and 27 to 44.2%, respectively. These results indicate that simultaneous degradation of raw starch to SCP can be conducted efficiently by using coculture of the amylolytic yeast, C. aerius and a nonamylolytic yeast, S. cerevisiae.