L-lactic acid production by Bacillus subtilis MUR1

Area of Science:

• Microbiology
• Biotechnology
• Industrial Fermentation

Background:

• Lactic acid (LA) is a valuable organic acid with broad industrial applications.
• Developing efficient microbial strains for high-yield LA production is crucial for sustainable manufacturing.
• Bacillus subtilis is a well-characterized bacterium with potential for metabolic engineering.

Purpose of the Study:

• To characterize the novel Bacillus subtilis MUR1 strain for lactic acid production.
• To optimize fermentation conditions for enhanced L-lactic acid (L-LA) yield and productivity.
• To evaluate the feasibility of using alternative nutrient sources in the production medium.

Main Methods:

• Fermentation of Bacillus subtilis MUR1 in various culture conditions (batch and fed-batch).
• Optimization of initial glucose concentration in fed-batch cultures.
• Analysis of L-LA concentration, substrate conversion yield, and production rate.
• Medium formulation adjustments using corn steep liquor as a partial replacement for yeast extract.

Main Results:

• Bacillus subtilis MUR1 demonstrated high L-LA production: 99.3 g/l in 12 h and 183.2 g/l in 52 h.
• Achieved a high substrate conversion yield of 98.5% and a maximum L-LA production rate of 16.1 g/l/h.
• Fed-batch culture with an initial 30 g/l glucose concentration yielded the highest L-LA concentration and productivity.
• Corn steep liquor effectively replaced part of the yeast extract in the production medium.

Conclusions:

• Bacillus subtilis MUR1 is a highly promising strain for industrial lactic acid production.
• Optimized fed-batch fermentation strategies significantly improve L-LA yield and productivity.
• The use of corn steep liquor offers a cost-effective alternative for medium formulation in L-LA biosynthesis.