To improve the production of curdlan by Agrobacterium sp. A02 during fermentation, and optimize the fed-batch fermentation process.

The 3 kinds of fed-batch fermentation processes were carried out for Agrobacterium sp. during the batch fermentation process in a 15 L fermenter, including a single supplementation of carbon source after discharging the fermentation broth, continuous feeding of the culture medium after discharging, and a single supplementation of the culture medium after discharging. The effects of these processes on the production of curdlan were investigated.

The single supplementation of carbon source after discharging had the worst effect, while the continuous feeding of the culture medium had the best effect. The curdlan production obtained by continuous medium supplementation and one-time medium supplementation was 66.69 g/L and 66.51 g/L respectively. Compared with the curdlan production obtained by one-time carbon source supplementation (53.69 g/L), it increased by 23.97% and 24.31% respectively. The production intensity was all 0.69 g/(L·h), which was 23.2% higher than the one-time carbon source supplementation [0.56 g/(L·h)]. The curdlan production rate of continuous medium supplementation was 0.11 g/(h·g-cell), which was 22.2% higher than the process of one-time carbon source supplementation and one-time medium supplementation [0.09 g/(h·g-cell)]. The conversion rates of continuous medium supplementation and one-time medium supplementation were 44.31% and 40.67% respectively, which were 1.1 times and 1.0 times that of one-time carbon source supplementation (40.67%).

By comparing the 3 kinds of fed-batch fermentation processes, the fermentation process of continuous feeding of the culture medium after discharging in the middle stage of fermentation has the highest production of curdlan, production intensity, specific curdlan production rate and conversion rate, which is superior to the other 2 kinds of fermentation processes. This study provides useful information for enhancing the industrial production of curdlan.