Batch and Continuous Lactic Acid Fermentation Based on A Multi-Substrate Approach.

Area of Science:

• Biotechnology
• Industrial Microbiology
• Sustainable Chemistry

Background:

• The bioeconomy emphasizes utilizing waste materials for biobased chemical production.
• Efficient bioprocesses are crucial for sustainable chemical manufacturing.

Purpose of the Study:

• To evaluate continuous L-lactic acid production from diverse renewable substrates using a multi-substrate strategy.
• To assess the performance of *Bacillus coagulans* A534 in continuous fermentation.

Main Methods:

• Continuous fermentation experiments using *Bacillus coagulans* A534.
• Testing of multiple renewable substrates: acid whey, sugar beet molasses, sugar beet, alfalfa press green juice, and tapioca starch.
• Comparison with standard medium conditions.

Main Results:

• *Bacillus coagulans* A534 successfully metabolized all tested renewable substrates in continuous mode.
• Highest productivity of 10.34 g·L⁻¹·h⁻¹ achieved with sugar beet molasses.
• Lactic acid to sugar conversion yield reached 0.86 g·g⁻¹ with molasses.

Conclusions:

• Continuous L-lactic acid production is feasible and efficient across various renewable substrates.
• The multi-substrate capability of *Bacillus coagulans* offers significant advantages for biobased chemical manufacturing.
• This approach supports the utilization of industrial residues and waste materials in the bioeconomy.