Strain Hd-010 Anti-pepper Root Rot Activity Product Of Fermentation Conditions,

Strain HD-010 was a Streptomyces sp which possessd antagonistic activity to Fusarium soloni caused pepper root rot. It was isolated and screened from the cultivated soil in Heilongjiang province by the key laboratory of microbiology of Heilongjiang University. For its potential biocontrol application in agriculture, the One-factor-at-a-time experiment and response surface optimization methodology was adopted to optimize the fermentation medium and conditions of the strain aiming to enhance its the antagonistic activity.The initial fermentation medium was screened from several candidate priscription. That was composed of glucose 20g/L, cane sugar 25g/L, soybean meal 50g/L, NaCl 4g/L, CaCO₃ 3g/L, K₂HPO₄ 0.2g/L, pH 7.0. While the fermentation conditions were consisted of as follows: inoculum size 2%, temperature at 28℃culture, medium loadage 30ml/250ml, rotation rate 180r/min and fermented 120h.The optimal culture medium and fermentation conditions of strain HD-010 for producing antifungal material was studied by single factor experiment. The results indicated that the optimum carbon source and nitrogen source were glucose and maize meal, respectively, otherwise Ca2+and Na+ were the significant metallic ions which could significantly effect the antagonistic activety of the fermentation liquid. According to the result of single factor experiment, four remarkable factors were obtained by using the Plackett-Burman experiment design. The factors were glucose, cane sugar, maize meal and inoculum size. Moreover, the central composite design were used to study effect of the three former factors. The follow regression model equation and optimized medium were obtained according to regression analysis of the data from uniform design experiment: Y=55.20-1.59A-1.77B+7.89C+0.68AB-2.72AC-4.82BC+1.05A2-0.96B2-5.68C2 (A was glucose, B was cane sugar, C was maize meal, Y was the response value or valence value of antimicrobial activity material).Occording to the model equation the optimum culture medium was analysised and designed with the Design-Expert 7.1.3 software, which was composed of glucose 10g/L, cane sugar 10.2g/L, maize meal 25.8g/L, NaCl 1g/L, CaCO₃ 1g/L, pH8.0, inoculum size 6%, temperature28℃culture medium loadage 30ml/250ml, rotation rate 250r/min and fermentation time 120h.The theory forecast titer value of this prescription was 66.22AU/mL. However the practical titer of the fermentation liquid was up to 71.38AU/mL. The result indicated that the forecast precision achieves 92.78% and the observations value fit the theory model nicely, and regression model was reliable. Compared with the primitive condition the yield of strain HD-010 has been increased 55.28%.