Production of lipid from starch by a nitrogen-controlled mixed culture of Saccharomycopsis fibuliger and Rhodosporidium toruloides

Summary Production of lipid from starch in a two-component mixed culture in a fed batch process was studied. Saccharomycopsis fibuliger was used as the amylolytic microorganism and Rhodosporidium toruloides, which does not grow on starch, as the lipid producer. The concentration of nitrogen can be used as an external regulator of growth and competition in this process. The total biomass concentration decreased and the relative amount of Rh. toruloides increased with decreasing initial concentration of nitrogen in the medium. The highest lipid concentration (9.7 g·l^-1), highest overall lipid production rate (0.15 g·l^-1·h^-1) and highest concentration of lipid in biomass (36.5%) were obtained in cultures with an initial nitrogen concentration of 0.5 g·l^-1. Compared to monocultures of Lipomyces starkeyi and Aspergillus oryzae on starch, the mixed culture showed slightly lower conversion of starch to lipid but was superior in the final lipid concentration and the overall lipid production rate.