柑橘砂皮病菌生防菌的筛选及其发酵条件优化

Screening and optimization of fermentation conditions for antagonistic bacteria to Diaporthe citri

以柑橘砂皮病菌为靶标菌株,采用平板对峙法从土壤中分离到的227株细菌中获得4株对柑橘砂皮病菌有明显抑制活性的菌株,其中Y2菌株发酵液稀释5倍和10倍后,对柑橘砂皮病菌菌丝生长的抑制率分别为69.85%、61.76%。生理生化测定与16S r RNA基因序列分析结合,确定Y2菌株为短小芽孢杆菌(Bacillus pumilus)。Y2菌株培养的最佳氮源和最佳碳源分别为蛋白胨和可溶性淀粉,最佳发酵温度28℃,转速180 r/min。Y2菌株产生的抑菌活性物质经80℃高温处理和强酸、强碱处理,活性明显下降。

For screening antagonistic bacteria to control citrus melanose, 227 strains were isolated from soil collected in Hunan with gradient dilution method. Four strains showed obvious antagonistic effects to Diaporthe citri by using agar plate dual culture, and strain Y2 was finally screened out because its fermented filtrates diluted 5 times and 10 times could inhibition growth of mycelia by 69.85% and 61.76%, respectively. Morphological, physiological and biochemical characteristics and analysis of 16 S r DNA sequence confirmed that strain Y2 is Bacillus pumilus. The optimum nitrogen source and carbon source of strain Y2 were soluble starch and peptone, respectively and the optimum fermentation conditions for strain Y2 include temperature at 28 ℃ and the rotation speed at 180 r/min. Under high temperature（80 ℃）, strong acid and strong alkali conditions, the activity of the bacteriostatic substances produced by strain Y2 decreased significantly.