Production of microbial lipids by oleaginous microorganisms

Biodiesel is derived from triglycerides or free fatty acid by transesterification with short chain alcohols. Biodiesel is a renewable, biodegradable and nontoxic fuel. Biodiesel is similar to petro-diesel in combustion properties. Currently varied plant oils, animal fats and waste cooking oils are usually adopted as feedstocks for biodiesel production. But the high cost of these feedstocks has become a rising problem for large-scale biodiesel production. Microorganisms, such as fungi, bacteria and microalge that can accumulate lipids more than 20 % of their biomass are defined as oleaginous species. In the study, lipid production capabilities of Candida lipolytica and Rhodotorula glutinis were investigated in batch and two stage fermentation systems. The effects of various operational parameters, namely amount of yeast (1, 3 and 5 % v/v), incubation time, temperature (20-40°C), initial pH (4-7) of the medium, agitation speed (50-200 rpm) on the lipid production were determined. In order to increase lipid production in yeasts various substances such as cheese whey, glucose, NH4Cl, (NH4)2SO4 and molasses were added to the media. The highest lipid accumulation was found at pH 5, 30°C, 150 rpm on the fourth day. The extraction of lipid content was carried out according to the modified Bligh and Dyer method. In the batch system the maximum lipid content of C. lipolytica and R. glutinis were 29.35±4.58 % and 29.53±0.46 %, respectively. The highest lipid content ratio (41.6±0.1 %) was obtained by C. lipolytica in the two stage fermentation system. The extracted lipids were transesterified by a base catalyst. The methyl esters were analyzed by using gas chromotography-mass spectrometer. The biodiesel yields of C. lipolytica and R. glutinis were 79 % and 80.65 %, respectively. The fatty acid compositions of lipids were determined to be appropriate for the production of biodiesel which contains mainly palmitic acids, oleic acids and stearic acids. KEYWORDS: Candida lipolytica, Rhodotorula glutinis, lipid, biodiesel, two stage fermentation system, cheese whey.