苏云金杆菌低成本固体发酵培养基的研制

苏云金杆菌(Bacillus thuringiensis,简称Bt)是一类对多种害虫有效的病原微生物。为降低该菌产品制剂的生产成本,以北方常见的玉米芯粉、棉粕、豆粕等农产品下脚料为培养基质,研究了对多种鳞翅目、双翅目害虫具有特异杀虫活性的Bt菌株CYZ-4的固体发酵培养基配方。经对培养基的初始含水量、p H值等单因素试验发现,培养基初始含水量为70%、p H值为8.2时,玉米芯固体发酵培养基的产孢量达到最大;当玉米芯粉与棉粕质量比为5∶5和6∶4,与豆粕质量比为6∶4或7∶3时,发酵效果优于其他组合,产物孢子浓度在9.3×109个/g以上;复合固体发酵培养基基础配方中,玉米芯粉、棉粕、豆粕质量分数分别为19.1%、7.2%、3.6%时发酵Bt的效果最好。培养基3种成分及p H值的L9(34)正交试验结果表明,将玉米芯粉、豆粕、棉粕按质量分数分别为16.0%、6.7%、7.2%的比例混合,添加0.075%KH2PO4、0.05%Mg SO4、0.035%Ca CO3,调节初始含水量为70%、p H值为8.2,按4%的接种量接种,30℃下培养6 d,菌株的产孢量最大,达到1.80×1010个/g。该固体发酵培养基配方成本低,发酵条件简单,适于以药肥撒施毒土方式施用防治鳞翅目和双翅目地下害虫。

Development of Low-cost Solid Fermentation Medium of Bacillus thuringiensis

Bacillus thuringiensis ( Bt) is a biological insecticide used widely. This paper proposes to study the solid fermentation of Bt CYZ-4 strain,which has specific insecticidal activity to Lepidoptera and Diptera. In order to reduce production costs,some agricultural products such as corncob powder,cottonseed meal and soybean meal were used as culture medium. The single factor experiments showed that the amount of spores was improved most under the treatment of corncob powder with the initial water content of 70%and pH value of 8. 2. When the mass ratio of corncob powder and cottonseed meal was 5:5 or 6:4,and that of corncob powder and soybean meal was 6:4 or 7:3,the fermentation effects were better than others, with the product spore concentration more than 9. 3 × 109 cells/g. In composite solid fermentation base formulation,the optimum composition was 19. 1% of corncob powder,7. 2% of cottonseed meal, and 3. 6% of soybean meal. The optimum culture medium composition and pH value were obtained through the orthogonal design. The results showed that the optimum fermentation conditions were as follows: the medium contained 16. 0% corncob powder, 7. 2% cottonseed meal, 6. 7% soybean meal, 0. 075%KH2 PO4,0. 05% MgSO4,and 0. 035% CaCO3,with 70% of the initial moisture content and pH value of 8. 2,the inoculums amount was 4%,and the strain was cultivated at 30 ℃ for 6 d. Under these condi-tions,the maximum spore yield reached 1. 80 × 1010 cells/g,which was higher than that under the initial fermentation level. The solid fermentation medium had low cost and simple fermentation conditions,also easy for use in the field.