Study On The Characteristics Of Lipase Produced By Lactic Acid Bacteria And Its Application In Mutton Fermented Sausage

Lactic acid bacteria(53)of different species deposited in the laboratory were used as research strains to screen and identify strains with strong enzyme-producing ability and excellent biological characteristics.The single factor and Box-Behnken response surface method were used to optimize the enzyme production conditions,the crude enzymatic properties and the expression of lipase functional gene were determined,The strain TR1-1-3 was used as a starter to produce mutton fermented sausage,Which was to explore the effect of lactic acid bacteria producing lipase on fat decomposition and fatty acid content in mutton fermented sausage.The result showed that a strain Lactobacillus helveticus-TR1-1-3 of lipase with high lipase activity and good fermentation characteristics was screened.The enzyme production capacity of the strain could be improved by optimizing the culture conditions.The optimal conditions were determined by single factor and Box-Behnken response surface to be 2%inoculation,36?,pH=5.84,48h,Under these conditions,the enzyme activity was 10.92 U/mL,which was higher than before optimization.The metal ions Fe2+ and Mn2+activated the enzyme production,while Ca2+,Mg2+,Cu2+ have different degrees of inhibition.The lipase produced by this strain has a degrading effect on medium,short-chain,long-chain ester substrates and the degradation effect on p-nitrophenol palmitate(C16)was better.The optimum reaction temperature of the enzyme was35?,the stability in 30??55? was better,it was moderately heat-resistant and mild lipase,the optimum reaction pH was 7,the stability at pH 5.5?9.0 was better,it was a neutral lipase and has a wide pH adaptation range.The expression of lipase gene was positive correlation of the enzyme activity of different species of lactic acid bacteria,the expression of Lactobacillus helveticus strain lipase gene was significantly higher(P<0.05)than the Pediococcus pentrea,and the expression of the same high-lipase activity strain was higher than the lipase-free strain.The strain TR1-1-3 was used as a starter to produce mutton fermented sausage.The TR1-1-3 group had better acid production performance,rapidly reduced the fermentation pH and Aw,improved sausage color,reduced nitrite residue,improvement of safety and has effect on fat oxidation,During the maturity period,the content of long-chain fatty acids and saturated fatty acids in the high-activity group increased significantly,the content of myristic acid was significantly higher than that in other experimental groups(P<0.05),while the content of monounsaturated and polyunsaturated fatty acids was higher in the storage period.Moreover It could be seen that the lipase produced by lactic acid bacteria has a weak decomposition ability to fat,which could reduce the fat content,promoted the release of free fatty acids,increased the content of long-chain fatty acids,saturated fatty acids and polyunsaturated fatty acids,which improved the quality and flavor characteristics of sausage.