Nisin Production by Immobilized Microbial Cell Culture during Batch and Fed-Batch Fermentations with Various pH Profiles

Abstract

In this study, nisin production has been enhanced by using batch and fed-batch fermentation with calcium-alginate immobilized cell culture. Due to the inhibitory effects of original phosphate rich growth medium on the immobilizing beads, an altered complex growth medium for nisin production was used. Various pH profiles were evaluated for both batch and fed-batch fermentations. For batch fermentations, a 2.1 fold higher nisin activity was obtained by allowing the pH to drop freely after 4 hrs of fermentation at constant pH. A periodic pH profile exhibited a detrimental effect on nisin production during batch fermentations. For fed-batch fermentations, a 2.9 fold higher nisin activity was obtained by allowing the pH to remain at pH of 6.8. Approximately the same maximum concentration, 3300 IU/ml, of nisin was observed when the best pH profile for batch and fed batch experiments were compared. The results also showed that immobilized cell culture can be used in order to improve nisin fermentation for both batch and fed-batch fermentation.