Repeated Batch Fermentation Using Immobilized Cells: A Superior Alternative to Fed-Batch Processes-A Comparative Study with Zymomonas mobilis as a Model Organism

Bio-based production has gained a much of research interest for meeting the global chemical and energy demands. Enhanced process productivity and yield are of the utmost concern when it comes to producing cost- efficient bioproducts. This study compares different fermentation strategies to gain higher ethanol productivity from glucose fermentation using Zymomonas mobilis as model organism. Batch, fed-batch, and repeated batch fermentation using immobilize cells were evaluated in their performance to better produce ethanol from synthetic glucose. In fed-batch operation, a total of ۱۴۰ g/L of glucose was fermented in a stepwise feeding method, the maximum ethanol titer of ۶۵.۷ g/L with a volumetric productivity of ۲.۹۸ g/L/h was observed and ethanol yield of ۰.۴۷ g/g was obtained which corresponds to fermentation efficiency of ۹۲%. Repeated batch process using immobilized cells out performed fed-batch mode. Zymomonas mobilis cells immobilized in alginate beads were used for glucose fermentation for four consecutive cycles without any signs of cell leakage. Ethanol yield was maintained steady from ۰.۴۹ g/g in the first cycle to ۰.۴۸ g/g in the fourth cycle. Volumetric productivity of ۱۰.۸۱ g/L/h which was ۲.۵۳ times higher than observed in the first cycle was recorded after the completion of fourth cycle. The study suggests the use of immobilized cell systems in a repeated batch process as a potent strategy to achieve high cell density that would decrease the fermentation time, thereby increasing the process productivity.

کلیدواژه ها:

Immobilized ، Zymomonas mobilis ، Volumetric Productivity ، Bio-products ، Bio-economy