Screening Of Antagonistic Bacteria For C.Gloeosporioides And Effects Of Its Fermentation On Fresh-keeping Of Postharvest Capsicum

Except for water loss and chiling injury,the loss caused by pathogenic fungi and decay bacteria accounted for about 50%-90% of total loss during the process of preservation of the postharvest capsicum. Postharvest disease of fruits and vegetables is main factors which affect the preservation and storage. The study found postharvest disease of capsicum mainly include C.gloeosporioides, Stemphylium botryosum, Erwinia carotovor, BotrytisCinerea. Per,phytophthora capsici. The incidence of C.gloeosporioides is the highest, at 40.0%. The use of antistaling agents is still the main measures to reduce the disease during the process of preservation of the postharvest capsicum recently,but continuous use is easy to induce drug resistance of pathogenic bacteria and the residual pollution caused by the high dosage damages people's health, Searching more effective and safe measure to reduce papper postharvest diseases attractted much attention.There are large amounts of endophytes can be used to reduce the plants disease in healthy plants. Screening of antagonistic bacteria from endophytes have a good application prospect in terms of researching for new controlling postharvest diseases of capsicum. For this aim, A C.gloeosporioides antagonistic bacteria P5 was isolated from capsicum fruit.lt was identified as Bacillus subtilis on the basis of morphological characters, physiological and biochemical property together with the sequence analysis of 16S rDNA. And the physical and chemical properties of the crude fermentation extract were assayed with C.gloeosporioides as indicative bacteria. The liquid fermentation medium and fermentation conditions were optimized by single factor method and response surface Box-Behnken design as well. In addition the effects of the crude fermentation extract on fresh-keeping of Postharvest capsicum was also analyzed. The main conclusions are as follows:1. A C.gloeosporioides antagonistic bacteria P5 was isolated from capsicum fruit.It was identified as Bacillus subtilis on the basis of morphological characters, physiological and biochemical property together with the sequence analysis of 16S rDNA.2. The physical and chemical properties of the crude fermentation extract were assayed with C.gloeosporioides as indicative bacteria. In addition the effects of the crude fermentation extract on fresh-keeping of Postharvest capsicum was also analyzed.The crude fermentation extract was very stable within the test range from 40? to 100? under pH 8.0, but with 85% original activity after treated at 121 ? for 30min; it showed no change from pH 5.5 to pH 9.5 under room temperature; it remained 89.87% of the initial activities under UV irradiation for 12 h.3.The liquid fermentation medium and fermentation conditions were optimized by single factor method and response surface Box-Behnken design. The optimal fermentation conditions were initial pH 7.0, temperature 28 ?, fermentation time 48 h, medium capacity 110 mL/250 mL,inoculation rate 3%, and rotate speed 180 r·min^-1. The optimum medium was 20 g·L^-1 glucose,9 g·L^-1 yeast extract,4 g·L^-1 CaCl₂. Inhibitory activity of P5 crude fermentation extract increased to 38.55% from 22.65%.4. The crude fermentation extract, compared with control treatment, had better effects on fresh-keeping of Postharvest capsicum and it could effectively reduce loss rate and decay rate, inhibit decreasing of content of titratable acidity, contents of the vitamin C, total carbohydrate and chlorophyll.