Enhanced D-lactic acid production from renewable resources using engineered Lactobacillus plantarum

Area of Science:

• Biotechnology
• Microbial Engineering
• Polymer Science

Background:

• D-lactic acid is a key monomer for producing poly-D-lactic acid (PDLA).
• PDLA is essential for creating heat-resistant stereocomplex polylactic acid.
• Efficient utilization of biomass-derived sugars is crucial for cost-effective D-lactic acid production.

Purpose of the Study:

• To develop a recombinant strain for cost-effective D-lactic acid production from biomass sugars.
• To engineer Lactobacillus plantarum for efficient assimilation of xylose.
• To optimize fermentation conditions using cost-effective medium components.

Main Methods:

• Cloning xylose-assimilating genes (xylose isomerase and xylulokinase) into Lactobacillus plantarum.
• Developing a recombinant strain (L. plantarum NCIMB 8826 ∆ldhL1-pLEM-xylAB).
• Utilizing response surface methodology for medium optimization and fed-batch fermentation.

Main Results:

• The engineered strain produced D-lactic acid (>99% optical purity) from xylose with a yield of 0.53 g/g.
• Simultaneous utilization of glucose and xylose yielded 47.2 g/L D-lactic acid.
• Fed-batch fermentation using corn stover and soybean meal extract yielded 61.4 g/L D-lactic acid with a 0.77 g/g yield.

Conclusions:

• Engineered Lactobacillus plantarum efficiently produces high-purity D-lactic acid from biomass-derived sugars.
• Optimized fermentation using agricultural byproducts significantly enhances D-lactic acid yield.
• This approach offers a sustainable and cost-effective route for producing biodegradable plastics.