Homolactic fermentation from glucose and cellobiose using Bacillus subtilis.

Area of Science:

• Biotechnology
• Microbial Fermentation
• Biochemical Engineering

Background:

• Biodegradable plastics are derived from polylactate, a polymer of lactic acid.
• Lactic acid can be produced from renewable resources by microorganisms like Bacillus subtilis.
• B. subtilis secretes enzymes capable of hydrolyzing lignocellulosic biomass into usable compounds.

Purpose of the Study:

• To investigate the potential of Bacillus subtilis for L-lactate production from cellobiose and glucose.
• To develop a robust fermentation process for high-yield L-lactate production.

Main Methods:

• Fermentation of cellobiose and glucose by wild-type and genetically modified B. subtilis strains.
• Generation of a B. subtilis CH1 alsS- strain to eliminate 2,3-butanediol production.
• Optimization of fermentation conditions in mineral media supplemented with yeast extract.

Main Results:

• B. subtilis fermented cellobiose to L-lactate with 82% theoretical yield under non-aerated conditions.
• The B. subtilis CH1 alsS- strain achieved a 15% increase in L-lactate yield from glucose compared to the parental strain.
• The modified strain produced 105 g/L of L-lactate with 95% yield and 99.5% optical purity from 10% glucose.

Conclusions:

• Bacillus subtilis demonstrates significant potential for L-lactate production due to its cellobiose utilization and osmotic stress resistance.
• A robust fermentation process for L-lactate production can be developed using engineered B. subtilis strains.