An efficient chemoenzymatic approach to produce galactose from red macroalgae biomass and its valorization

Marine biomass is receiving much attention as the third-generation feedstock owing to its advantages over terrestrial biomass. Red macroalgae have an impressive high carbohydrate content, with galactose as the most abundant monosaccharide. However, the technology for producing galactose with a high yield and its valorization is not yet available. This study described an efficient chemoenzymatic approach toward upgrading of red macroalgae (Gelidium amansii) into value-added products (taking galactonic acid as an example). With the aid of microwave-assisted maleic acid pretreatment, galactose was obtained with an excellent yield of 92.7%. Various inhibitors were simultaneously generated and their inhibition effects on biocatalysis were overcame by genetic and bioprocess engineering. Finally, the galactose in the hydrolysate was converted into galactonic acid with a yield of 100% by engineered Pseudomonas putida. This approach can be easily expanded to other galactose derived products and promotes green development of marine biomass biorefinery.