Study On Extraction、Activity Determination And Application About Antimicrobial Substances From Tenebrin Molitor L.

In order to provide new experimental evidences and theoretical basis for morerational development and utilization of antimicrobial substances from Tenebriomolitor L., in this thesis, the antimicrobial substances from larvae and adults weredetermined of their inhibition activities against the common pathogenic bacteria andfungi. And also the antimicrobial substances’ antimicrobial mechanism were studiedpreliminarily, their effects of vegetable and food’s anticorrosion application werediscussed. The primary results were as follows:1The extraction of antimicrobial substance from Tenebrio molitor L.The antimicrobial substance from larvae of Tenebrio molitor L. were extractedwith10different solvents: methanol, ethanol, ethyl acetate, petroleum ether, acetone,benzene and so on. The crude extract was tested for antimicrobial activity on E.coli.The results showed that drilling method of inhibition zone and ethyl acetate were thebest measurement method and the best extraction solvent. Ultimately it was determined that the best method for induction was bacillus injection with feeding48h,through4different methods. After the induction, the antimicrobial substances wereextracted from larvae and adults of Tenebrio molitor by ethyl acetate, then the crudeextracts were separated by silica gelcolumn chromatography.2The antibacterial and antifungal activities of antimicrobial substances fromTenebrio molitor L.The antimicrobial substances were tested to study their antimicrobial activities to4species of bacteria by means of drilling method of inhibition zone and5species offungi by means of hypha growth method. The results showed that they all showedsigificant antibacterial activities against4kinds of bacteria(including G and G+): theextracts from larvae and adults had stronger antibacterial activity against E.coli than100mg/mL ampicillin, after inducing the extract from larvae had slightly strongerantibacterial activity against E.coli than adults, the diameter of inhibition zone was27.40mm. The antimicrobial substances had stronger antibacterial effect against E.coli,and good thermal stability. MIC test results showed that antimicrobial substances’MIC from larvae and adults was6.25mg/mL of0.05%Tween20dilution againstE.coli, the MIC was12.5mg/mL against Staphylococcus aureus, and the minimuminhibitory concentrations against the two bacteria had antibacterial effects. Through the determination of lethal curve of E.coli, the results showed that the antibacterialsubstances had not inhibitory effects, but the bactericidal effects.The antimicrobial substances all showed sigificant antifungal activities against5kinds of fungi: they had the best inhibitory effects when they were200mg/mL againstFusarium oxysporum in vitro (the mycelial growth inhibiting rate of larval antimicrobial substance was62.34%,60.61%for the adults), the worst inhibitory effects againstColletotrichum gloeosporioides (the mycelial growth inhibiting rate of larval antimicrobial substance was29.55%,27.27%for the adults); and antimicrobial substanceshad the lethal effects against Fusarium oxysporum.3The anticorrosion application of antimicrobial substances from Tenebriomolitor L.The experiments introduced antifungal activities using different concentrationsof antimicrobial substances against4species of pathogenic fungi in vivo, the resultsshowed that: the antimicrobial substances all showed sigificant antifungal activitiesagainst Colletotrichum gloeosporioides, Venturia pirina, Gloelsporium fructigenumBlerk, Fusarium oxysporum, and different concentrations of antimicrobial substancescould reduce the decay rate of fruits and vegetables, when the concentration was200mg/mL, the decay rate of tomatoes(compared with sterile water) decreased by34.97%,31.31%respectively, the effect was the most obvious. Inhibitory effects in vitrodecreased compared with effects in vivo, but it directly proofed the antimicrobialsubstances had inhibitory effects for fruits and vegetables’ diseases.The results of anticorrosion application showed that: the antimicrobial substances’ whole fruit preservation effect was obvious, preserving time was up to30d;antimicrobial substances with hot water for preserving fresh fruit had better effect,maximum preserving time might be extended to38d; the200mg/mL antimicrobialsubstances had stronger antiseptic effect to dried bean curds, and its shelf life wasabout10~15d.