中文摘要：

为了进一步提高氧化葡萄糖杆菌右旋糖酐糊精酶的产量，在3L发酵罐水平上考察了pH（3．5—6．0）对菌体生长和产酶的影响。基于不同pH发酵过程中菌体生长及产物合成的变化，确定了pH两阶段控制策略，即0-6h时控制pH5．0，6h后将pH调至4．0。通过采用这一优化策略，右旋糖酐糊精酶酶活有了较大的提高，可达4．03U／mL，比不控制pH模式下提高了38．5％，是摇瓶水平的12．5倍，同时发酵时间从47h缩短为15h。

英文摘要：

In order to enhance the yield of dextran dextrinase （DDase） produced by Gluconobacter oxydans DSM 2003, the effects ofpH from 3.5 to 6 on cell growth and DDase activity were investigated in a 3 L fermentor. Based on time courses of cell growth and DDase activity, we developed a two-stage pH control strategy, in which pH was controlled at 5.0 for the first 6 h and then 4.0 for remaining time. Under the optimized strategy, the production of DDase had a significant improvement. Moreover, the maximal DDase activity reached 4.03 U/mL, 38.5% and 1 147% more than that from the strategy with-out pH control and in the 250 mL shake flasks, respectively. Meanwhile, the fermentation time of DDase in the fermentor was also shortened from 47 h to 15 h compared to that in 250 mL shake flasks.