Highly efficient polyhydroxyalkanoate production from lignin using genetically engineered Halomonas sp. Y3.

[Display omitted] • Halomonas sp. Y3 secreted laccase through Tat and Type I secretion system. • Biodesign of a highly efficient laccase secretion apparatus. • Heterologous expression of laccase achieved enzyme activity of 184 U/mL. • Up to 55 % lignin was degraded by the engineered strain Y3_05. • Co-transformation of Y3_05 and Y3_08 produced 740 and 1314 mg/L from lignin and APL. Lignin degradation represents a significant challenge in biological valorization, but it is suffering from insufficiency, putting barriers to efficient lignin conversion. Herein, the study first develops a highly efficient laccase secretion apparatus, enabling high enzyme activity of 184 U/mL, complementing the biochemical limits on lignin depolymerization well in Halomonas sp. Y3. Further engineering of PHA biosynthesis produces a significantly high PHA titer of 286, 742, and 868 mg/L from alkaline lignin, catechol, and protocatechuate, respectively. The integration of laccase-secretion and PHA production modules enables a record titer of 693 and 1209 mg/L in converting lignin and lignin-containing stream to PHA, respectively. The titer is improved furtherly to 740 and 1314 mg/L by developing a non-sterilized fermentation. This study advances a cheaper and greener production of valuable chemicals from lignin by constructing a biosynthetic platform for PHA production and provides novel insight into the lignin conversion by extremophilic microbes. [ABSTRACT FROM AUTHOR]