High Improvement in Lactic Acid Productivity by New Alkaliphilic Bacterium Using Repeated Batch Fermentation...

Area of Science:

• Biotechnology
• Microbiology
• Biochemical Engineering

Background:

• Optically pure lactic acid (LA) is a valuable platform chemical with diverse industrial applications.
• Cost-effective production of LA is crucial for industrial development and biotechnological advancements.

Purpose of the Study:

• To isolate and identify an alkaliphilic bacterium capable of efficient lactic acid production.
• To optimize fermentation conditions (pH, temperature) and strategies for enhanced lactic acid yield and productivity.

Main Methods:

• Isolation and characterization of alkaliphilic lactic acid bacteria, with identification via API 50 CHL and 16S rRNA gene sequencing.
• Fermentation experiments including batch, multipulse fed-batch, and repeated fermentation strategies.
• Optimization of pH, temperature, and glucose concentration for lactic acid production.

Main Results:

• An alkaliphilic strain, identified as *Enterococcus hirae* BoM 1-2, was selected for its efficient L-lactic acid production at pH 9.0 and 40°C.
• Batch fermentation yielded up to 96.0 g L^-1 LA, while multipulse fed-batch achieved 180.6 g L^-1.
• Repeated fermentation strategies, particularly with gradual glucose increase, dramatically enhanced LA productivity up to 39.9 g L^-1h^-1 (18-fold increase).

Conclusions:

• *Enterococcus hirae* BoM 1-2 is a promising strain for high-yield lactic acid production under alkaline conditions.
• Repeated fermentation coupled with optimized glucose feeding is a highly effective strategy for significantly boosting lactic acid volumetric productivity.
• The findings offer a pathway for cost-effective and efficient industrial-scale lactic acid manufacturing.