Influencing Factors In Molasses Fermentation By R. GLUTINIS And M. CIRCINELLOIDES For Microbial Oil Production

Now, many countries dedicate to study new clean renewable energy to solve the problem of the energy shortage and the environmental deterioration. People focus their attentions on the alternate energy-biodiesel, because it is renewable and persistent. But the lack of materials limit the further development of biodiesel. The microbial oil produced by the metabolic process of algae and fungus is a feasible approach to supply raw material for biodiesel. To study how the factors affect the capability in grease synthesis and accumulation of Rhodotorula glutinis and Mucor circinelloides, we use the molasses as the substrate to ferment for microbial oil.The results of the batch cultures with R. glutinis indicated that a dry-cell yield of 2.42 g/L and a grease yield of 0.8 g/L were obtained after fermenting for 132 h with an initial COD concentration 11000~13000 mg/L, culture volume 50 mL, pH 6.5, inoculum concentration 20%, temperature 30℃and swing at 160 r/min. And the COD removal could reach 62.3%. The feed-batch fermentation with R. glutinis was investigated. The biomass and lipid can reach 3.64 g/L and 1.31 g/L while adding glucose (10 g/L) in the medium at 48 h during fermentation.The results of the batch cultures with M. circinelloide showed that a dry-cell yield of 1.33 g/L and a grease yield of 0.21 g/L were obtained after fermenting for 100 h with an initial COD concentration 11000~13000 mg/L, culture volume 50 mL, pH 6.0, inoculum concentration 20%, temperature 30℃and swing at 160 r/min. And the COD removal could reach 39%. Considering the feed-batch fermentation with M. circinelloides, the results indicated that the biomass and lipid growed invisibly. According to the curve of R. glutinis and M. circinelloide, the oil accumulation lags behind the cell multiplication.Finally, we studied the mixed culture of R. glutinis and M. circinelloides. The result showed that the biomass and the COD removal of the mixed culture growed remarkably. The biomass and the COD removal could reach 2.72 g/L and 74.5% when the mixing ratio was 10:1. And the grease yield can reach 0.81 g/L when the mixing ratio was 20:1.The main composition of the oil is 9-Hexadecenoic acid, Hexadecanoic acid, 9,12-Octadecadienoic acid, 9-Octadecenoic acid, Octadecanoic acid and so on.