The production of lipid from the hydrolyzate of the steam pretreated substrates

Nine oleaginous yeasts (Trichosporon oleaginosus, two Lipomyces starkeyi L. tetrasporus, L. spencer-martinsiae, Rhodotorula glutinis, Rhodotorula graminis, Rhodosporidium toruloides, Yarrowia lipolytica), which show potential for producing biodiesel, were assessed for growth and lipid production when they were grown on the hemicellulose-rich, water-soluble fraction after SO₂ catalyzed steam pretreatment of biomass. The influence of potential inhibitors, such as furfural and 5-hydorxymethy furfural (HMF) that were produced during the SO₂ steam pretreatment inhibited growth (OD₆₀₀) and glucose consumption to various extents. Growth of T. oleaginosus reached 20.0 (OD₆₀₀)after 6 days while R. graminis and R. glutinis reached an OD_{600 of} 16.3 and 15.0 after 6 days, respectively. However, R. toruloides and Y. lipolytica did not grow well in the presence of furfural and HMF. Five of the strains (L. starkeyi, T. oleaginosus, L. spencer-martinsiae, R. graminis, R. glutinis) consumed more than 85% of glucose in the presence of furfural and HMF. When the carbon source within the media was changed from glucose to a mixture of glucose and xylose, the OD₆₀₀ of both R. graminis and R. glutinis reached 16.0 after 6 days. L. starkeyi consumed more than 95% of the sugars within the medium and R. graminis and R. glutinis consumed 74.5% and 82.5% of the sugars, respectively. This initial screening showed that some oleaginous yeasts were able to directly grow on biomass derived sugars without the need for a detoxification step.