Study Of Microbial Lipase And Its Application On The Biodiesel Production

Biodiesel is a fuel consisted of the alkyl monoesters of fatty acids from vegetable oils or animal fats. Biodiesel is received increasing attention as an alternative, non-toxic, biodegradable and renewable diesel fuel. Production of biodiesel can be catalyzed by chemical or by lipase and the later has more advantages. Microbial strains producing high-activity lipases were isolated and mutanted; the immobilization process of lipase was studied and experiments on the biodiesel production catalyzed by chemical and lipase were performed. The results were listed as follow:1)More than forty microbial strains producing high-activity lipases including over ten bacteria, ten moulds and several yeasts, were isolated from oily soils. Mould X-28 with high lipase activity was mutated with ultraviolet and mycostatin. The mutant with the highest lipase activity was isolated and named X-281. The lipase activity of X-281 was increased 229% higher than the parent strains and remained the same level after several generations. 2)The optimal conditions for enzyme production and properties of X-281 were studied systematically. Lipase secreted by X-281 is alkaline enzyme, and its activity remained steadily in higher temperature.3)The immobilization of lipase with diatomite powder as the carrier by means of absorption method was studied. The results of the optimal conditions for immobilization are that pH value was 7.6; the optimal dosage of diatomite: lipase (mass ratio) was 8:1; temperature ranged within 30-35℃. The activity of immobilized lipase under optimal condition was 4680U/g. The properties of immobilized lipase were studied systematically. The results showed that optimal reaction temperature, pH value were 35℃ and 8.5, respectively; it could retain 50% of activity at 4℃ after one month and a half.4)Preparation of biodiesel by transesterification from edible soybean oil catalyzed by alkali was discussed. It was found that methanol concentration, catalyst concentration, reaction time, reaction temperature and stir condition had effects on the yield of biodiesel. 94% biodiesel yield was achieved under the optimal conditions.5)Immobilized Lipase was used to catalyze transesterification reaction in order to produce biodiesel. The effects of the methanol toxicity, temperature, solvent amount and pretreatment of substrate were studied and the component of production was analyzed. The results showed that the transesterification degree under the optimal parameters and process could be reached 91%.