Agar Metabolism of the New Marine Bacterium Cellulophaga Lytica W5C and Its Potential Use in Marine Biomass Conversions

Marine macroalgae, considered as third generation biomass, are a promising feedstock source for the production of various biofuels and fine chemicals. Red macroalgae, in particular, contains agarose as one of its main components. This polysaccharide accounts for up to 52 dry weight percent in Gelidium amansii. Agarose is made up of alternating units of D-galactose and 3,6-anhydro-L-galactose (L-AHG). Because of the high carbohydrate content of red macroalgae, specifically the fermentable D-galactose, it is a viable resource of sugars. The products of agarose hydrolysis are also known to have medical and pharmaceutical effects. Due to the potential of red macroalgae as biomass resource, studies on organisms capable of degrading agar or agarose have steadily increased in the past years. Moreover, researchers have also begun to elucidate the metabolic pathway for the rare sugar, L-AHG. In this study, an agar-degrading bacterium designated as W5C, was isolated from marine red macroalgae, Palmaria sp., collected from the seashore of Yeosu, South Korea. Preliminary characterization identified the bacterium as Gram-negative, catalase- and gelatinase-positive, and oxidase- and amylase-negative. Based on 16S rRNA sequencing and phylogenetic analysis, strain W5C belonged to the Cellulophaga genus and is highly related to Cellulophaga lytica. Full genome sequencing of the isolate and homology searches identified four putative agarase-encoding genes. The genes encoding for the agarolytic enzymes were cloned in Escherichia coli for characterization. Additionally, the strain possesses genes involved in the utilization of L-AHG. The respective enzymes were cloned and characterized as well. Elucidation of the entire agarose metabolic pathway in the Cellulophaga isolate may be applied to marine biomass utilization for the synthesis of biofuels and fine chemicals. This work was supported by Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education (No. 2009-0093816), and Korea Research Fellowship Program through the NRF funded by the Ministry of Science, ICT and Future Planning (No. 2015H1D3A1062172).