Ethanol production from the oleaginous yeast Trichosporon fermentans

The yeast Trichosporon fermentans is considered to be a good candidate for the accumulation of single cell oil. During this work the strain T. fermentans CBS 439.83 has been evaluated for SCO accumulation when cultivated on a mixture of sucrose, glucose and fructose in the presence of invertase to facilitate the uptake of sucrose. It was observed that with increasing initial sugar concentration, a quantity of ethanol (which was confirmed by both HPLC-RI and GC-FID analysis) was produced under aerobic conditions, which reached even 25 g/L when cultivated on 200 g/L initial sugars. At 40 g/L, almost no ethanol was observed. As the cultivation proceded, ethanol was consumed by the yeast. Subsequently the ability of the yeast to ferment glucose to ethanol under anaerobic conditions was evaluated. The effect of the addition of organic or inorganic nitrogen source, as well as their concentration was evaluated and found that a combination of yeast extract and peptone was more favorable than di-ammonium phosphate, whereas an increased concentration of them (of 5 g/L each) yielded to an ethanol production of 43.4 g/L from 100 g/L glucose. Subsequently the effect of the initial pH on ethanol production and productivity was evaluated. Ethanol tolerance of the yeast at the optimal cultivation conditions was also estimated. Finally, the ability of the yeast to be utilized as fermenting microorganisms on enzymaticaly liquefied wheat straw stalks was investigated.