产胞外多糖的苏云金芽孢杆菌的筛选及发酵工艺优化

Screening of an extracellular polysaccharides producing Bacillus thuringiensis strain and its fermentation optimization

微生物胞外多糖(exopolysaccharidess,EPS)因其生产周期短等优点具有潜在的应用价值。该文从纳豆中筛选出1株高产EPS的菌株并鉴定该菌株为苏云金芽孢杆菌(Bacillus thuringiensi)。为提高其EPS产量,通过对发酵培养基的组分和发酵培养条件进行单因素试验,然后采用Plackett-Burman(PB)设计对9个因素的重要性进行评判,从中选出3个重要影响因素进行Box-Benhnken实验设计优化得到最终的最佳培养方案:葡萄糖22.6 g/L,黄豆饼粉9.3 g/L,玉米浆2.0 g/L,K_(2)HPO_(4)0.5 g/L,NaH_(2)PO_(4)1.5 g/L,MgSO_(4)1.5 g/L,MnCl_(2)0.05 g/L,初始pH 7.5,装液量70 mL,温度为34℃,接种量为6%。与初始发酵工艺相比,EPS产量提高了133.3%。经7 L发酵罐放大验证后,EPS产量增加至6.56 g/L,与摇瓶水平相比,EPS产量提高了123.1%,并且已初步探索该EPS具有纳豆激酶活性。有望成为合成药物的潜在来源。

Microbial exopolysaccharides(EPS)has potential application value due to its short production cycle and other advantages.In this paper,a strain with high yield of EPS was screened from natto and identified as Bacillus thuringiensi.To improve its EPS production,the fermentation medium and fermentation conditions of strain were optimized by single-factor experiments.The Plackett-Burman(PB)design was used to evaluate the importance of nine factors,and three important factors were selected.Box-Benhnken experimental design was used to get the final optimal culture:22.6 g/L glucose,9.3 g/L soybean meal,2.0 g/L corn syrup,0.5 g/L K_(2)HPO_(4),1.5 g/L NaH_(2)PO_(4),1.5 g/L MgSO_(4),0.05 g/L MnCl_(2),pH 7.5,loading volume 70 mL,34℃,inoculum size of 6%.Compared with the initial fermentation process,the EPS production increased by 133.33%.Using 7 L fermenter to amplify and verify,the yield of EPS increased to 6.56 g/L.Compared with the shake flask level,the EPS production increased by 123.1%and the EPS had nattokinase activity.It is expected to become a potential source of synthetic drugs.