The Screening Of Oleaginous Yeasts And The Oil Production Characteristics In The Using Of Glucose And Xylose

With the emphasis on the energy crisis, the biodiesel industry has developed rapidly, and the study of microbial oil is inevitably promoted. As a direct source of microbial lipid synthesis, carbon has been concerned and researched widely. Because it is rich in amount, inexpensive and fermentable after hydrolysis, lignocellulosic biomass has easily become a key concern as renewable resource. And the hydrolysis products of lignocellulosic biomass are mainly glucose and xylose. Therefore, based on two-stage fermentation model, oil-producing characteristics of 3 typical oleaginous yeasts(Trichosporon laibachii, Rhodosporidium toruloides and Lipomyces starkeyi) are studied by using glucose, xylose and a mixture of both in different initial concentrations, in order to provide theoretical basis for the further use of cellulose. The results include the following:(1) Six oleaginous yeasts are screened with one has a high oil content. From the 26S rRNA gene analysis, the high oil content strain has the highest similarity with Trichosporon laibachii, so the strain is named Trichosporon laibachii IEM-14. Trichosporon laibachii IEM-14 can use glucose, xylose and the mixture for oil production. For the oil content can reach 82.74% and have an average value of around 50%, Trichosporon laibachii can be identified as excellent oleaginous microorganisms according to the definition.(2) Under glucose condition, the strain IEM-14 has the best oil production characteristics in 0.6mol/L initial sugar concentration. Oil production characteristics are similar in xylose and mixture as carbon source, with maximum oil yield and oil yield coefficient both in the initial concentration of 0.4mol/L. Through comparing the oil-producing properties in three carbon conditions, glucose is best for Trichosporon laibachii to grow, and xylose is good for the oil accumulation and the mixture residing therebetween.(3) Rhodosporidium toruloides has the similar oil production characteristics in glucose and xylose conditions, and maximum oil yield coefficients are both obtained in 0.4mol/L initial sugar concentration, 21.62% and 11.44% respectively. The oil contents both show an increasing trend witn the increase of these two initial carbon concentration, indicating that these two simple sugars can promote the oil synthesis of Rhodosporidium toruloides. Compared with the monosaccharide, the mixed sugar is more suitable for the oil production of Rhodosporidium toruloides, and the maximum oil yield coefficient 25.06% is obtained at a low initial concentration 0.2mol/L.(4) Lipomyces starkeyi has the best oil production characteristics with the overall highest oil content and a maximum oil yield of 19.67% in 0.4mol/L. The variation tendencies of oil content and oil yield coefficient under glucose are consistent with xylose, but the overall level is relatively low. The mixed sugar is more conducive to the growth of this strain.(5) In the three carbon sources, Trichosporon laibachii IEM-14 has better oil production capacity than both Rhodosporidium toruloides and Lipomyces starkeyi. Under conditions of glucose and mixed with sugar, Rhodosporidium toruloides has better oil production capacity than Lipomyces starkeyi. However, oil production capacity of Lipomyces starkeyi is higher when under conditions of xylose.