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It is known that seaweeds differ greatly from land plants in their sugar composition. The current research on the L-lactic acid fermentation process focuses on land plant sugars as a carbon source, with the potential of seaweed sugars being largely ignored. This study examined the feasibility of seaweed biomass as a possible carbon source for the production of L-lactic acid, by comparing the fermentation of seaweed sugars (D-galactose, D-mannitol, L-rhamnose, D-glucuronic acid, and L-fucose) and land plant sugars (D-glucose, D-xylose, D-mannose, and L-arabinose). The experiments were repeated with 2 sugar acids (D-gluconic acid, D-glucaric acid) in order to investigate the effect of the degree of reduction of carbon source on the fermentation yield. This research also examined the effect of bacterial strain on the characteristics of fermentation reactions, by conducting L-lactic acid fermentation with 7 different Lactobacillus species. Taking into account the sugar composition of seaweed and the levels of lactic acid production from each pure sugar, it was possible to predict the lactic acid production yield of various seaweeds and land plants. From comparative analysis of the predicted lactic acid production yield, it was found that seaweeds are already comparable to lignocellulosics at the current stage of technology. If new technologies for the utilization of non-fermentable seaweed sugars are developed, seaweeds show promise as an even more useful biomass feedstock than lignocellulosics.

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Recently, seaweeds have gained attention as possible renewable sources for biofuel and bioproduct production. To investigate the possibility of using green seaweeds as biomass feedstocks, the chemical composition and saccharification yield of the green seaweed Ulva pertusa were investigated. In this study, we evaluated U. pertusa that was harvested from the seashore in Jeju Island, Korea. By proximate composition analysis, dried U. pertusa was found to contain 52.3% carbohydrate, 25.1% protein, 0.1% lipid, and 22.5% ash. The elemental analysis of U. pertusa indicated the content of carbon to be 34.9%, hydrogen 5.3%, oxygen 46.5%, nitrogen 3.8%, sulfur 3.1%, and phosphorous 0.12%. The optimal conditions for the acid hydrolysis and saccharification of U. pertusa were investigated by varying the types of catalysts, catalyst concentration, reaction time, reaction temperature, and seaweed concentration. Under optimized acid hydrolysis condition, 32.9% of seaweed was recovered as monosaccharides and the monosaccharide composition was 11.5% D-glucuronic acid and D-glucuronic acid lactone, 11.1% L-rhamnose, 6.7% D-glucose, and 3.7% D-xylose. The concept of degree of reductance was introduced to assess the potential of U. pertusa as an industrial feedstock. It was found that the degree of reductance of U. pertusa was lowest among the biomass considered in this study. Based on the comparison of chemical composition and reductance degree of various biomass resources, the competitiveness of U. pertusa as a biomass feedstock for biofuel and bioproduct production was discussed.

Glucuronic acid dehydrogenase (GluUADH), the product of the Csal-2474 gene from the halophilic bacterium Chromohalobacter salexigens DSM 3043, is an enzyme with potential use in the conversion of glucuronic acid in seaweed biomass to fuels and chemicals. GluUADH is an enzyme that catalyzes the oxidation of glucuronic acid (GluUA) and galacturonic acid (GalUA) and has a preference for NAD + rather than NADP + as a cofactor. Recombinant GluUADH was crystallized in the presence of 0.2 M calcium acetate, 0.1 M TrisHCl pH 7.0 and 20% PEG 3000 at 295 K. X-ray diffraction data were collected to a maximum resolution of 2.1 Å . The GluUADH crystal belonged to space group P6 3 , with unit-cell parameters a = b = 122.58, c = 150.49 Å , = 120. With one molecule per asymmetric unit, the crystal volume per unit protein weight (V M ) is 2.78 Å 3 Da À1 . The structure was solved by the single anomalous dispersion method and structure refinement is in progress.