Study On Obtaining Oils By Fungi Treating Sweet Potato Starch Processing Waste Water

Bio-diesel oil was one of the most important liquid and renewable energy resources. But bio-diesel oil was not used broadly because of many disadvantages such as high cost from animal and plant oils. The main components of microbial oils were triglycerides, which were similar to animal and plant oils. There were advantages of oils produced by microbes, such as short period, low cost, not affected by weather etc. Supplying cheaper oil resource by microbes for bio-diesel oil was becoming a hot research field.The paper studied on microbial oils production by fungi growing in sweet potato starch processing waste water, which could reduce the material cost. Meanwhile, it was benefit for the environment as the COD was also reduced. Four kinds of waste water manufacturing technics were compared; The components and content of waste water varied with different batches. The COD was 20000~60000mg/L, total saccharide was 5%~10%, and pH was 4.0~6.0. So the waste water could be utilized easily.By culturing in waste water, the strain named FR7 which could produce oil higher was obtained from 15 microorganisms(separation,purification,screening from the earth samples gathered from coast to coast by the lab). FR7 was identified as Cunninghamella echinulata by Microbiology Institute of Science of China.The nutritional and environmental conditions were studied, and the optimum condition was including: The best fermentation conditions were C/N=70, NaAc2g/L, KH2PO42g/L, MgSO4 2g/L, pH 5.0~7.0, culturing 11d. The removing rate of COD could be 87%, and the rate of oil content in mycelium was 58%.GC analysis indicated that the main components of oils produced by FR7 contained C16:0(19.5646%), C18:0(8.8003%), C18:1(47.8803%), C18:2(13.8263%), C18:3(6.2547%). The esterification invert rate was 78.4% by alkaline catalyzing method.Additionally, the modality of FR7 mycelium in PDY which influenced the fermentation results could remain floccule by addition of 0.2%(NH4)2SO4 in culture medium. The oils could be synthesized ahead of time when NaAc and FeSO4 were added to the culture medium.The more times FR7 reproduced, the worse fermentation results were. So the rejuvenation of FR7 was essential after a period of time. As components of waste water of different batches varied, the fermentation results varied.The paper studied on microbial oils producing from sweet potato starch processing waste water for the first time, including waste water analysis, comparison of oils producing ability, nutritional and environmental technics, GC analysis, and oils esterification. The paper made a foundation for supplying cheaper oil resource by microbes for bio-diesel oil.