Study On Antibacterial Substances Separated From Musca Domestica Larvae And Their Protective Agents

Housefly has been regarded as a kind of common resource insects.It has been used for producing low cost protein feed,the extensions of its potential value are far from satisfaction.With its unique immune system,housefly larvae can coexist with different bacteria without being infected.According to related study,there are variety of antibacterial substances in the body of housefly larvae,including all kinds of antimicrobial peptides and chitosan.These antibacterial substances not only have broad-spectrum antimicrobial effects on bacteria and fungi,but also can kill viruses,protozoans,even tumor cells.These antibacterial substances are quite subtle in molecular mass and very stable.It is acknowledged that these antibacterial substances can perforate the cell membrane.How to develop and proper using of housefly larvae have been a hot research area in recent years.As there are variety of antibacterial substance in the body of housefly larvae,it is difficult to purify single antimicrobial component from housefly larvae,and the single antimicrobial component can lead to decrease of the antibacterial effect.The purpose of this study was aimed to prepare of composite antibacterial substance from housefly larvae.Firstly,acetic acid was used as solven and extracting solution was heated to remove the unstable proteins.Following by 10 kDa ultrafiltration of extracting solution,the composite antibacterial concentrate in the retentate was obtained.Compared with lyophilization,ultrafiltration could improve concentration of soluble proteinin the retentate significantly.Retentate of ultrafiltration contained large amounts of protein,but in the permeate,the concentration of protein was extremely low.Gel filtration chromatography showed that majority of antimicrobial substances in retentate were protein components,and the antimicrobial substances in permeate were non-protein.Comparing with the antimicrobial substances in retentate,antimicrobial substances in permeate had a more broader range of antibacterial activity.Temperature stability and pH stability from permeate and retentate,minimum inhibitory protein concentration of antimicrobial substances from retentate,suitable protective agent and their shelf life were further investigated.Results showed antimicrobial substances from permeate had better temperature capability and acid and alkali resistance than that from permeate.And antimicrobial substances from permeate had more killing effect against G+bacteria than against G-bacteria.The antimicrobial substances from retentate with 2%Trehalose and 5%Glycerin as protective agents at 4 degree centigrade had a relatively long shelf life.In comparison,antimicrobial substances from permeate with 5%Trehalose and 2%Glycerinas protective agents at 4 degree centigrade had a relatively long shelf life.