氧载体对鞘氨醇单胞菌合成威兰胶的影响

Effects of Oxygen Carrier on the Biosynthesis of Welan Gum by Sphingomonas sp.ATCC 31555

鞘氨醇单胞菌(Sphingomonas sp.ATCC 31555)发酵生产威兰胶的过程中,因发酵液黏度逐渐增加,系统供氧不足,导致威兰胶产率较低。为改善发酵系统供氧情况,提高威兰胶产率,利用实验研究添加氧载体对威兰胶发酵的影响,并通过补加的方式提高威兰胶产率。结果表明:添加甘油对威兰胶产率变化没有影响,添加十二烷、正己烷以及H2O2能在一定范围内提高威兰胶产率,其中H2O2效果最佳;通过单因素实验优化H2O2的添加时间和浓度,结果当8 h添加15 mmol/L的H2O2时威兰胶产率达到最大,同时葡萄糖利用率得到较大的提高。在最优的时间附近保持H2O2总量(15 mmol/L)不变,在发酵4、8、12 h分别添加H2O25 mol/L时,产率达到1.91%,相对于空白组提高了30.02%。发酵72 h后,实验组仍能观察到部分形态正常的细胞,延长发酵周期至84 h,威兰胶产率提高至1.99%,较72h提高4.21%。5 L发酵罐扩大培养,威兰胶产率达到2.09%,明显高于摇瓶发酵(1.99%)。

In welan gum fermentation process by Sphingomonas sp.ATCC 31555,the level of dissolved oxygen drops with the viscosity of broth increasing,leading to the reduced yield of welan gum.To improve the oxygen concentration in the fermentation system and increase welan gum yield the addition of oxygen carrier was studied and multiple adding methods were used.Glycerin had no significance on welan gum yield,while dodecane,n-hexane,H2O2 could increase the yield of welan gum to a certain degree,and H2O2 was the best oxygen carrier.Optimizing adding concentration and time of H2O2 with one-factor experimental design were 15 mmol / L at the 8 h in fermentation,and Glucose utilization increased at the same time.In addition,1.91% of welan gum was obtained when adding 5 mmol / L H2O2 at the 4,8,12 h keeping the total amount(15 mmol / L) of adding H2O2 constant,increased 30.02% comparing with the blank group.Moreover,a small amount of complete cells could be observed in the experimental group at 72 h fermentation,when extended the fermentation period to the 84 h,1.99% of welan gum was obtained,increased 4.21% comparing with the group of 72 h in fermentation.5 L fermentation of expand training had welan yield 2.09%,higher than shake flask experiment results.