Optimization Of Conditions For Liquid And Solid-State Fermentation Of Antagonistic Strain B. Subtilis SQR9

Environmental-friendly biological control represents an alternative for protection of plants against soil-borne diseases. Since direct application of antagonistic microbial culture to control soil-borne plant diseases is not effective. It is proved that a combination of antagonists with suitable mature compost are more efficient in inhibiting soil-borne disease than using single antagonistic microbes or compost alone. After years of effort in our laboratory, a Bacillus subtilis strain SQR9screened in our laboratory showed excellent activity against soil-borne fungi and bacterial diseases. In this study, fermentation conditions and the anti-fungal activity of SQR9were tested systematically. The main results of this work were as following:(1) The best carbon and nitrogen sources for SQR9growth in liquid fermentation were maltose and peptone respectively. The best media was:1%maltose,3%peptone, and0.15%NaCl by the orthogonal experiment. The optimized culture conditions were as follows:37℃, the initial pH7.0,60ml of medium in a250ml flask,2%of the inoculant,72h of incubation time and180rpm of shaking speed. Under this optimized conditions, the SQR9number and diameter of inhibition zone against Fusarium oxysporum f. sp. Cucumerinum could reach to9.57×109CFU·mL-1and23.5mm.(2) The optimum fermentation parameters of SQR9in rapeseed meal compost were obtained as follows:10%of inoculant,0%of wheat bran supplementation,40%of initial moisture content, fermentation temperature of37℃, and once three days of turning over. Under this optimized conditions, the SQR9number and sopre number could reach to2.91×1O8CFU·-g-1and2.54×1O8CFU·g-1respectively.(3) The optimum fermentation parameters of SQR9in cow manure compost were obtained as follows:10%of inoculant,15%of wheat bran supplementation,60%of initial moisture content, fermentation temperature of37℃, and once a day of turning over. Under this optimized conditions, the SQR9number and sopre number could reach to9.07×109CFU·g-1and8.03×109CFU·g-1respectively.(4) The optimum fermentation parameters of SQR9in pig slurry organic fertilizer were obtained as follows:10%of inoculant,5%of wheat bran supplementation,60%of initial moisture content, fermentation temperature of37℃, and once a day of turning over. Under this optimized conditions, the SQR9number and sopre number could reach to1.54×109CFU·g-1and1.26×109CFU·g-1respectively.(5) The optimum fermentation parameters of SQR9fermentation in Chinese medicinal herb residue compost were obtained as follows:10%of inoculant,15%of wheat bran supplementation,65%of initial moisture content, fermentation temperature of37℃, and once a day of turning over. Under this optimized conditions, the SQR9number and sopre number could reach to1.20×1011CFU·g-1and1.97×1010CFU·g-1respectively.(6) The optimum proportion of four organic composts for SQR9fermentation was determined as follows by orthogonal test:Chinese medicinal herb residue compost:cow manure compost:pig slurry organic fertilizer:rapeseed meal compost was40:6:0:8, in which the number of SQR9cells could be as high as1.97×1010CFU·g-1.(7) The seed germination indexes of most bio-organic fertilizer were more than76%. The mixed bio-organic fertilizer and Chinese medicine residue bio-organic fertilizer were less toxic. High quality bio-organic fertilizer could be produced with certain agricultural waste under suitable fermentation condition.