Valorization of lignin-derived compounds into poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by engineered Halomonas...

Area of Science:

• Biotechnology and Metabolic Engineering
• Polymer Science
• Microbial Fermentation

Background:

• Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a promising biopolyester with high potential but faces challenges due to high production costs associated with the propionate-dependent pathway.
• Lignin-derived compounds (LDCs) represent an abundant and sustainable feedstock, but their efficient conversion into valuable bioproducts like PHBV remains a significant hurdle.
• Developing cost-effective and environmentally friendly methods for PHBV synthesis is crucial for its widespread industrial application.

Purpose of the Study:

• To engineer Halomonas sp. Y3 for the efficient production of PHBV from various LDCs without the need for propionate supplementation.
• To enhance PHBV yield and tailor its composition by reconstructing aromatic compound catabolism pathways.
• To integrate laccase-secretion and PHBV production modules for improved PHBV synthesis directly from lignin.

Main Methods:

• Genetic engineering of Halomonas sp. Y3 by overexpressing threonine synthesis to enable PHBV production without propionate.
• Rational design and reconstruction of aromatic compound catabolism pathways to enhance the assimilation of diverse LDCs (syringyl, guaiacyl, p-hydroxyphenyl-type).
• Integration of laccase-secretion and PHBV production modules within the engineered strain for direct lignin valorization.

Main Results:

• The engineered strain achieved PHBV production without propionate, with a 3-hydroxyvalerate (3HV) proportion up to 7.89 mol%, comparable to commercial PHBV.
• The strain efficiently assimilated S-, G-, and H-type LDCs, producing PHBV at levels of 449 mg/L, 488 mg/L, and 716 mg/L, respectively, with high yields (up to 71.6 g/g).
• The integrated laccase-secretion and PHBV production system yielded 425.84 mg/L of PHBV with a 6.38 mol% 3HV proportion, demonstrating direct lignin valorization.

Conclusions:

• The engineered Halomonas sp. Y3 provides an efficient and sustainable platform for PHBV production from a variety of LDCs, overcoming the limitations of the propionate-dependent pathway.
• The metabolic engineering strategies employed significantly enhance PHBV yield and broaden the substrate range, paving the way for cost-effective biopolyester manufacturing.
• This study demonstrates a viable approach for lignin valorization into high-value bioplastics, contributing to a circular bioeconomy.