Study On Antimicrobial Substances In Fermentation Filtrate Of Bacterial Endophyte Strain011

Endophytes produce a variety of anti microbial substances and many of them are novel substances unexploited.As a germoplasm resource pool, they have a brilliant prospect of study and practical utilization. Considered as safer and non-contamination biocontrol reagents,they have a promising utilization potential in agriculture and food quality and safty controling. In this study, based on Strain Oll as experimental materials, the antimicrobial activity of fermentation products was investigated and viability in bio-control was also studied. Furthermore, fermentaion conditions were tested to gain understanding of the optimum medium recipe and fermentaion conditions, underlying large-scale fermentation. In addition, the anti-microbial substances were isolated and indentifed via mass spectrography which gave rise to indentification of the structure. The results are displayed as below:1.Results of plate perforation method to test anti-microbial activity showed the ferment was inhibitive to8fungal phytopathogens, among which the Alternaria sonali was most sensitive to it, with width of5.5mm of the inhibition band. Microscopy showed the ferment caused hyphae and spores abnormality. Analysis of the spores germination rate revealed that minimum inhibition concentration (MIC) of ferment was30%, half effective inhibition concentration was9.64%. The activity was relatively therma stable, with95%activity remained after exposed to100℃for lh, acid-tolerant and insensitive to ultraviolet (UV), with no obvious activity change after exposed to acid pH2.0or UV radiation at30cm for120min, respectively.2. The single factor test and orthogonal design experiments were also employed to study the optimal liquid media compositions and fermentation conditions of the strain. The optimal medium compositions include sucrose5g/L, yeast extract27g/L, NaCl4g/L. The optimal fermentation parameters were48h,33℃, inoculum volume3%, medium volume80mL/250mL, rotation speed220r/min and initial pH7.0. Under this condition, the specific density of the011strain reached0.812, The inhibition zone of011strain ferments were6.7mm, compared before optimization OD6800.608, The inhibition zone of011strain ferments5.3mm, has been significantly improved. 3.Ferment of Strain011was pre-processed and purified by High Performance Liquid Chromatography (HPLC) primarily, and three bioactive ingredients were obtained, named8,9,10respectively. The inhibition zone of antimicrobial agent gradient8、9、10against Phytophthora sonali are2.2mm,2.8mm and3.8mm. NO10ingredient was further purified via HPLC and6ingredients were obtained, named A, B, C, D, E, F respectively. Bacteriostatic effect of active components are100%,100%,100%,100%,97.80%,5.66%. The subsequent Mass Chromatography (MS) analysis determined the molecular weight of E as664Da.