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

• Published in: ACS synthetic biology Vol. 12; no. 6; pp. 1782 - 1793
• Main Authors: Pathiraja, Duleepa, Park, Byeonghyeok, Kim, Bogun, Stougaard, Peter, Choi, In-Geol
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 16-06-2023
• Subjects: value-added chemicals; marine heterotrophic bacteria; metabolic chassis; red algal biomass; bioconversion; Pseudoalteromonas atlantica T6c
• ISSN: 2161-5063; 2161-5063
• DOI: 10.1021/acssynbio.3c00063

Marine red algal biomass is a promising feedstock for sustainable production of value-added chemicals. However, the major constituents of red algal biomass, such as agar and carrageenan, are not easily assimilated by most industrial metabolic chassis developed to date. Synthetic biology offers a solution by utilizing nonmodel organisms as metabolic chassis for consolidated biological processes. In this study, the marine heterotrophic bacterium Pseudoalteromonas atlantica T6c was harnessed as a metabolic chassis to produce value-added chemicals from the affordable red algal galactans or agaropectin, a byproduct of industrial agarose production. To construct a heterologous gene expression device in P. atlantica T6c, promoters related to agar metabolism were screened from the differentially expressed genes using RNA-Seq analysis. The expression device was built and tested with selected promoters fused to a reporter gene and tuned by incorporation of a cognate repressor predicted from the agar-specific polysaccharide utilization locus. The feasibility of the marine bacterial metabolic chassis was examined by introducing the biosynthetic gene clusters of β-carotene and violacein. Our results demonstrate that the metabolic chassis platform enables direct conversion of low-cost red algal galactans or industrial waste agaropectin into valuable bioactive pigments without any pretreatment of biomass. The developed marine bacterial chassis could potentially be used in a biorefinery framework to produce value-added chemicals from marine algal galactans.