Studies On Postharvest Biological And Its Application Effect Of Antagonistic Bacteria In Pepper

Postharvest diseases of fruit and vegetable is one of the main factors affecting on preservation and storage, the use of chemical agent is still the main measures recently, but unfittable does will cause residual pollution; induce drug resistance of pathogenic bacteria easily; Cause environmental pollution; Harm people’s health and so on. the healthy plants presented arge amounts of endophytes which will be a new repository as bio-control bacteria, it has a good application prospect, in terms of searching for new controlling postharvest diseases of fruits and vegetables. Take chilli as object, it was selected from healthy plants of pepper which have antagonistic effect on alternaria alternate and Colletotrichum capsici, it was identified by the morphological characteristics, physiological and biochemical reactions, and molecular biology. It was studied on the culture conditions optimization, antimicrobial active, substances separation basis of good strains of bacteria inhibiting effect of chili.1the distribution diversity of endogenous bacteria in different parts of chilli different kinds of chilli pulp.27strains endophytic bacteria and7strains fungis were isolated from stems, roots, leaves and fruit of capsicum from pepper plant,12strains were isolated from different types of pepper.3strain of endophytic fungi,5of them showed antifungal effect against the pathogens, the strain-L in bell pepper was the best antagonistic to Alternaria alternate, Colletotrichum capsici and Phytophthora capsici, the bacteriostatic diameter was27.71mm,24.8mm,19.45mm respectly. The strain-39was good antagonistic to Alternaria alternate, Colletotrichum capsici, the bacteriostatic diameter was10.45mm、6.9mm、17.82mm respectly.2the identification of strain-L and strain-39. Analysis of the characteristics of morphology, Physiology, bioehemistry and the16SrDNA, strain L was identified as a strain of Bacillus subtilis, which had99%sequence similarity with B. subtilis strain-39was identified as a strain of Rhodotorula mucilaginosa, which had99%sequence similarity with Uncultured basidiomycota genomic. strain-L and strain-39have the16SrDNA length of1452bp and539bp.3Antibacterial mechanism research ethanol sediment and absolute ethyl alcohol of strain-39fermentation was studied, The results show that75%ethanol sediment and ethyl acetate extract produced from strain-39had a good antibacterial effect on Alternaria alternata mycelial growth, spores bearing and germination, the EC50of the ethyl acetate extract is16.3531mg/L-1, the EC50of75%ethanol sediment is11.8003mg/L-1, it also had a significant inhibitory effect on the food (pepper, tomato), when the concentration of ethyl acetate extract was100mg/mL, the decay rates of peppers and tomats were reduced by51.897%and58.47%, the concentration of75%ethanol sediment was100mg/mL, the decay rates of peppers and tomats were reduced by47.51%and50.47%. Growth inhibition rate had significant difference between75%ethanol sediment and ethyl acetate extract at various pH (2-12) and different temperature treatment, it had no diference at ultraviolet treatment. Overall, this study indicates that the strain-39active substance is composed of various components.4the research on biological characteristics, the result showed that the pH value and temperature has obviously effect on the growth of the strain, strain can growth better in the range of the pH5.2-pH8.0and25℃-30℃, the optimal growth of pH and is7.2and28℃respectly, which have strong osmotic pressure at the same time, strain-L can be able to use all of the organic nitrogen source, carbon source and few unorganic nitrogen source, which explain that the strain have strong adaptability without strict requirements.5The effective impact to preserve long pepper of different varieties treated with fermented filtrated liquor of strain-L. the results of invivo and invitro tests indicated that different concentrations strain-L fermentation medium had a good antibacterial effect on A.alternate, Through the damage inoculation, strain-L fermentation medium has obvious antibacterial effect on the green pepper and red chilli, the decay rates of green peppers were declined by51.87%. compared with sterile water, decay rate of the red chilli were declined by58.54%compared with sterile water, the preservation effect on strain-L fermentation medium on different varieties of pepper had significant difference during24d storage period by noninvasive inoculation, the results showed that the strain-L fermented liquid treatment can obviously decrease the decay rate of chili postharvest in the storage period, was obviously superior to the sterile water group. After24d, the decay rate of green pepper treated with fermentation medium and preservation liquid were37.5%, 32.50%respectly, decreased by35%and40%respectively compared to sterile water group, the level of decay rates was different with fermentation medium treatment group and preservation liquid treatment between different varieties. In the storage period, the strain-L delayed the reducing sugar content, inhibit the loss of soluble solid content and soluble protein, maintain the stable color and quality structure. Strain-L fermentation liquor obtained the good storage effect in keeping the chili good commodity value, sensory quality and nutritional value.6optimization of fermentation culture conditions. Object as strain L, a novel experimental design and analysis approach named uniform design and support vector regression (UD-SVR) was proposed to optimize alternative culture medium components and fermenter conditions. The optimal formula considering9factors through3rounds of mixed level experiments was starch0.5%, glucose2%, yeast extract0.4%, CaCl21.3%, KH2PO40.1%,30℃,36h, inoculation amountl%and pH7.0. The inhibitory activity reached57.39%of10fold diluted fermented liquid,20.53%higher than the benchmark formulation of the single factor. UD-SVR is more efficient than the referencing models and has potentials to be widely used for experimental design and analysis of the prescription optimization.7purification and separation of components of fermented liquid of strain L. It was extracted by n-butyl alcohol and silica gel column chromatography and liquid chromatograph separation of the strain-L, a total of four bacteria inhibitory active component has been isolated, the spores germination inhibition rate to A alternate respectively were part5(3.213min)20.73%、16(22.618min) components27.43%、17(23.783min) group13.76%,18(27.210min) group of28.5%, It was identify the molecular weight and constitutional formula of four components by the HPLC/ESI-TOF/MS tandem mass spectrometry, respectively, and the molecular were253Da、366Da、1131Da、384.2Da, C,oH23NO6、C24H30O3/C17H30N6OS、C55H87O24、 C24H32O4. respectly. research on inhibitory activity of the strongest component17deeply, combined with mass spectrometry, IR and1H-NMR,13C-NMR, identified as aesicn compounds.