Sequential enzymatic monitoring of glucose, ethanol and glutamate in bioreactor fermentation broth containing a high salt concentration by a multi-channel flow-injection analysis method

An automated multi-channel flow-injection analysis (FIA) system was developed and its application as an on-line multi-component sensing device for bioprocess monitoring was demonstrated. For system development, an automated glucose analyzer was modified by installing a column switching valve downstream from the injector, and into each channel an immobilized enzyme (oxidase) mini-reactor was inserted. The product (hydrogen peroxide) from each enzymatic reaction was detected electrochemically. Several components (up to six) can be measured sequentially or in a programmed sequence by a computer controlling the electrical valve described above. To test the utility of the present system, the following fermentation process was utilized. Aged fish sauce was transferred into a fermenter loaded with Torulopsis versatiles immobilized beads, and the fermentation process was triggered by the addition of glucose. During the whole process, the glucose level was monitored periodically and the contents of ethanol and glutamate were measured when the glucose content dropped to a certain level. Since the unusually high salt content (17.9%) in the fermentation broth affected the measurement, an additional mini-reactor packed with an ion-exchange resin was inserted between the injector and the column switching valve to stabilize the baseline. As another novel aspect, this anion-exchange column can be used without regeneration, which is valuable for long-term use.