Bioconversion Of Kitchen Waste To Surfactin By Bacillus Amyloliquefaciens HM 618

Surfactin is a kind of lipopeptide biosurfactant,which possess antibacterial,antiviral,anti-mycoplasma physiological activity,and superior ability to decrease surface tention.Surfactin was extensively used in biomedicine,food and cosmetics industry,petroleum exploitation,and other fields.However,expensive raw material cost and low yield inhibit its large-scale industrial production.Kitchen wastes were selected as the source of carbon to produce surfactin,which was a feasible way to reduce production cost.This work adopted two strategies to pretreat kitchen waste:（1）the exogenous addition of commercial enzymes;（2）the construction of an artificial mixed bacteria system.The main results were as follows:（1）At first,we optimized the enzymatic hydrolysis conditions using univariate analysis.The results demonstrated that p H in a neutral range was beneficial to generate surfactin,and the optimal p H of cellulase and lipase was 5.0 and 8.0,respectively.When pre-treatment of kitchen waste with compound enzymes,the p H was set to 7.5.The optimal enzyme dosage for amylase,proteases,cellulases,lipases,glycosidase are400 U.g^-1,4 U.g^-1,160 U.g^-1,720 U.g^-1,and 200 U.g^-1 respectively.Amylase,protease,and cellulase pretreated group obtained the maximum surfactin yield at 50℃.（2）When kitchen wastes pretreated by single enzyme,lipase pretreated group obtained maximum yield was 62.905 mg.gds^-1.When pretreated by compound enzymes,the yield was 75.707 mg.gds^-1,which higher than that of any single enzyme pretreatment group.（3）Under three different mixed bacterial systems:HM 618 co-cultured with lipase-producing fungus Aspergillus nidulan obtained highest yield of surfactin was65.404 mg.gds^-1,which higher than that of the lipase pretreatment group alone,which showed the feasibility of enzyme producers replacing commercial enzymes.（4）Surfactin will suppress the growth of Rhizoctonia solani and Botrytis cinereal.The LC-MS identified surfactin contain three homologues:C13 surfactin、C14 surfactin、C15 surfactin,in addition to surfactin,iturin were also detected,but fengycin was not detected.