Lactic acid production through cell-recycle repeated-batch bioreactor

Area of Science:

• Biotechnology
• Microbial Fermentation
• Biochemical Engineering

Background:

• Nitrogen sources critically influence microbial cell growth and metabolite production.
• Yeast extract is a potent nitrogen source for lactic acid fermentation, but its high concentration increases production costs.

Purpose of the Study:

• To investigate the impact of various nitrogen sources on lactic acid fermentation.
• To optimize yeast extract dosage for cost-effective lactic acid production.
• To evaluate a repeated-batch fermentation with cell recycling for enhanced efficiency.

Main Methods:

• Screening of nitrogen sources for optimal cell growth and lactic acid yield.
• Determining optimal yeast extract concentrations for batch fermentation.
• Implementing a repeated-batch fermentation strategy with Enterococcus faecalis RKY1 and cell recycling.

Main Results:

• Yeast extract significantly improved cell growth and lactic acid productivity.
• Optimal yeast extract concentrations were identified for maximizing yield and productivity in batch mode.
• Repeated-batch fermentation with cell recycling achieved comparable lactic acid concentrations (92-94 g/L) and productivity (6.03-6.20 g/[L x h]) using only 26% of the yeast extract required for conventional batch processes.
• Long-term operational stability was demonstrated.

Conclusions:

• Yeast extract is a highly effective nitrogen source for lactic acid fermentation.
• Repeated-batch fermentation with cell recycling offers a cost-effective and efficient alternative to conventional batch processes by significantly reducing nitrogen source requirements.
• This optimized approach maintains high lactic acid yield and productivity while ensuring process stability.