Constructing Marine Bacterial Metabolic Chassis for Potential Biorefinery of Red Algal Biomass and Agaropectin Wastes

초록

Marine red algal biomass is a promising feedstock forsustainableproduction of value-added chemicals. However, the major constituentsof red algal biomass, such as agar and carrageenan, are not easilyassimilated by most industrial metabolic chassis developed to date.Synthetic biology offers a solution by utilizing nonmodel organismsas metabolic chassis for consolidated biological processes. In thisstudy, the marine heterotrophic bacterium Pseudoalteromonasatlantica T6c was harnessed as a metabolic chassisto produce value-added chemicals from the affordable red algal galactansor agaropectin, a byproduct of industrial agarose production. To constructa heterologous gene expression device in P. atlantica T6c, promoters related to agar metabolism were screened from thedifferentially expressed genes using RNA-Seq analysis. The expressiondevice was built and tested with selected promoters fused to a reportergene and tuned by incorporation of a cognate repressor predicted fromthe agar-specific polysaccharide utilization locus. The feasibilityof the marine bacterial metabolic chassis was examined by introducingthe biosynthetic gene clusters of beta-carotene and violacein.Our results demonstrate that the metabolic chassis platform enablesdirect conversion of low-cost red algal galactans or industrial wasteagaropectin into valuable bioactive pigments without any pretreatmentof biomass. The developed marine bacterial chassis could potentiallybe used in a biorefinery framework to produce value-added chemicalsfrom marine algal galactans.

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