Studies On Lipid Production By The Marine Yeast Rhodotorula Mucilaginosa TJY15a

In the past years, biodiesel, which is a renewable, biodegradable, and nontoxic fuel has received increasing attention because of the environmental pollution and energy crisis world wide.The raw materials for biodiesel production are vegetable oil and waste oil at present. However, the high material price of vegetable oil and waste oil led to the high production cost of biodiesel production. So to find cheep materials is very important for the biodiesel industrialization. It has been well documented that single cell oils are produced by some oleaginous microorganisms, such as yeast, fungi, bacteria, and microalgae.In general, yeast and molds can accumulate much more lipids than bacteria and microalgae. With the rapid expansion of biodiesel, microbial oils might become one of potential oil feed stocks for biodiesel production in the future.771 yeast strains isolated from different marine environments were screened for their ability to produce single cell oils. Among them, a total of 7 yeast strains were found to produce high lipid, and the yeast strain TJY15a which was identified to be Rhodotorula mucilaginosa was found to produce the highes level of lipid. The optimal medium components and growth conditions for lipid production by strain TJY15a were studied using "one-variable-at-a-time" method. The results showed that the optimal medium components for the highest lipid production by strain TJY15a were glucose 6.0%(w/v),yeast extract,0.86%,KH2PO40.7%,Na2HPO4 0.25%,MgSO4·7H2O0.15%,CaCl20.015%,FeCl3·6H2O 0.015%,ZnSO4-7H2O 0.002%,MnSO4·H2O 0.006%,(NH4)2SO4 0.05%,and initial pH 6.2.The optimal growth conditions were shaking speed 180 rpm, temperature 28℃.Under these conditions, the biomass and lipid can reach 17.9 g/L and 49.6%, respectively.Hydrolysate of cassava starch was used as the carbon sources for lipid production by this yeast strain. The cells containing 52.9%(w/w) of lipid was obtained during the fed-batch cultivation and the biomass reached 21.8 g/L.The fatty acids from R.mucilaginosa TJY15a were mainly composed of palmitic acid (C16:0), palmitoleic acid (C16:1),stearic acid (C18:0), oleic acid (C18:1) and linolenic acid (C18.2), suggesting that the fatty acids could be used as feedstock for biodiesel production.The fed-batch fermentation for lipid production from hydrolysate of cassava starch by R.mucilaginosa TJY15a was investigated in 2 L fermentor. The experimental results showed that at the end of the fed-batch cultivation the biomass and lipid reached 24.0 g/L and 52.5%,respectively.