Direct conversion of cassava starch into single cell oil by co-cultures of the oleaginous yeast Rhodosporidium toruloides and immobilized amylases-producing yeast Saccharomycopsis fibuligera

Abstract

Some strains of Rhodosporidium toruloides can produce high concentrations of single cell oil. However, this oleaginous yeast does not produce amylases. Cells of the amylase-producing yeast Saccharomycopsis fibuligera A11-c were immobilized using polyvinyl alcohol. The immobilized yeast could produce 325 U/ml of amylase activity within 72 h of incubation. These amylases hydrolyzed cassava starch and the resulting product was converted into single cell oil by R. toruloides 21167. In a 2-l co-culture bioreactor, a single cell oil yield (64.9% w/w) from a cell mass of R. toruloides 21167 (20.1 g/l) were produced from cassava starch (6.0% w/v). Over 96% of the fatty acids produced were C16:0, C18:0, C18:1 and C18:2, useful for conversion into biodiesel.