Studies On The Production, Properties Of Lipase From Aspergillus Niger By Shake-flask And Its Application On Synthesis Of Lauric Acid Monoester

Lipase, also known as triglyceride hydrolase, has hydrolysis features in water-phase system and has esterification, transesterification, aminolysis, alcoholysis and other characteristics in non-aqueous-phase system. Compared with the chemical method, it has its own advantages, such as mild reaction, improved selectivity, simple separation and purification, high yield, non toxic and so on. Therefore, the lipase becomes a research hotspot.The object of this study was a Aspergillus niger strain. The fermentation conditions and medium components had been optimized, showed that, cane sugar 3g/L, fish meal peptone 12g/L, olive oil emulsion 10g/L, MgSO₄·7H₂O 0.5g/L, K₂HPO₄·3H₂O 2.0g/L, pH 7.0, at 30℃, the yield of lipase could get 2.7U/mL.This paper also studied the enzymatic properties of Aspergillus niger lipase. The optimal pH and temperature for activity of the lipase were 7.0 and 45℃, respectively. It was stable at temperature below 60℃and in the pH range from 3.0 to 8.0. Na+, Cu²⁺ and Zn²⁺ ions less affected the activity of lipase, K+, Mg²⁺ and Ca²⁺ ions stimulated its activity, the role of Ca²⁺ ions was more obvious, whereas Mn²⁺ and Fe²⁺ ions caused inhibition. And the lipase could catalytic synthesis reaction of lauric acid and glycerol, it could be used to synthetic fatty acid glyceride.At last, Aspergillus niger lipase was applied to synthesize fatty acid monoglyceride. The lipase had strong catalytic activity and selectivity. It could catalyze the fatty acids and glycerin synthetic fatty acid glyceride in a solvent-free reaction system and the reaction process parameters was optimized. The results showed that When the ratio of glycerol to lauric acid 1:1, the lipase dosage 0.5%(W/W), the water dosage 3%(W/W)based on the reactant was employed in the reacting system, the conversion rate of lauric acid could reach 91.2% at 50℃for 12h reaction. The content of lauric acid monoglycerid was about 70% in the reacting production.