Study On Inhibition And Mechanism Of Trichoderma Viride Fermentation Broth Against Staphylococcus Aureus

Staphylococcus aureus was used as the target bacterial in this paper, the antibacterial activity, stability and mechanism of extract from Trichoderma viride fermentation broth were studied. Meanwhile, the separation, purification, identification of antibacterial material from the n-butanol extract also were studied. The studies about antibacterial activities and mechanism of Trichoderma viride fermentation broth in order to provide theoretical basis for its development and application in the field of reduction foodborne pathogens and naturel antiseptic. The results are followed:1. Using step extraction to obtain different polarity extracts from the broth and the antibacterial activity of each extract on Staphylococcus aureus were as follows: n-butanol> ethyl acetate> petroleum ether. It was found that n-butanol extract has obviously antibacterial activity on Staphylococcus aureus obviously, and the minimum inhibitory concentrations (MIC) of n-butanol extract is0.0625mg/mL. Besides, in the condition of100℃hot water treating for1h, the inhibitory rate of the fermentation broth still reach82.64%. The optimal inhibition was observed at medium pH7-8, the inhibitory rate was upper than90%.2. The elongated and rod-shaped cells of Staphylococcus aureus treated with n-butanol extract were observed by microscope. The membrane and wall integrity was indicated by determining conductivity and the releasing of macromolecules in liquid culture medium. The result showed that MBA (Maximum bactericidal concentration) n-butanol extract could impact on the membrane permeability of Staphylococcus aureus. Small molecular substances such as K+, Na+and macromolecule substances such as alkaline phosphatase (AKP), β-galactosidase, protein and soluble sugar were detected in the liquid culture medium. The n-butanol extract also reduced the activity of peroxidase and catalase in Staphylococcus aureus cells, hence the endogenous H2O2could not be broken down effectively leading to the accumulation of activity oxygen which could damage the cell wall and membrane where there are rich in lipid. Consequently, increasing the peroxidative degree of lipid.3. The n-butanol extract interfered Staphylococcus aureus utilizing nutritions such as sugar, protein and inorganic phosphorus, and seriously restrained the activity of GOT, GPT, SDH and MDH.4. Treated with the n-butanol extract for16h, the total content of proteins, the quantities of DNA and RNA were reduced.It indicated that the n-butanol extract inhibited the nucleic acid and protein synthesis.5. Two pure compounds were obtainded by thin layer chromatography. Then their chemical structures were identified by Electronic electrospray mass spectrum analysis, Infrared spectrum analysis and Nuclear Magnetic Resonance analysis, which indicated that they were pyridines compounds.The n-butanol extract from Trichoderma viride fermentation broth had significant antibacterial activity on Staphylococcus aureus, the antibacterial mechanism of the n-butanol extract are divers including changed the membrane permeability, restrained the activity of enzymes in the cells, interfered the synthesis of protein and nucleic acid, blocked the utilizing of protein, sugar and inorganic phosphorus.