High cell density continuous fermentation for L-lactic acid production from cane molasses.

Area of Science:

• Biotechnology
• Industrial Microbiology
• Biochemical Engineering

Background:

• Lactic acid (LA) production commonly uses glucose or lactose with yeast extract (YE).
• High production costs are associated with sugar, nitrogen, and vitamin supplementation.
• Molasses, a sugar industry by-product, offers a cost-effective alternative feedstock.

Purpose of the Study:

• To investigate the feasibility of producing lactic acid from molasses supplemented with yeast extract.
• To optimize lactic acid production using a continuous-flow, high-cell-density (HCD) bioreactor with cell recycling.

Main Methods:

• Utilized a 1L continuous-flow HCD bioreactor with external membrane microfiltration for cell recycling.
• Employed *Lactobacillus delbrueckii* NCIM 2025 for lactic acid fermentation.
• Supplemented cane molasses with 1 g/L yeast extract.

Main Results:

• Achieved a high lactic acid yield of 0.95-0.98 g/g from approximately 100 g sugars/L.
• Obtained volumetric lactic acid productivities ranging from 4.3-27.6 g/L/h at dilution rates of 0.04-0.36 h⁻¹.
• Demonstrated comparable productivity to glucose-based production with YE supplementation.

Conclusions:

• Cane molasses is a cost-effective and viable feedstock for lactic acid production.
• The HCD bioreactor system with cell recycling enables efficient lactic acid fermentation from molasses.
• Utilizing molasses significantly impacts the economics of industrial lactic acid production.