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.

We examined the feasibility of using the green seaweed Enteromorpha prolifera as an alternative carbon source for chemical production. For this purpose, the chemical composition (proximate analysis, ultimate analysis, and mineral analysis) and acid hydrolysis of E. prolifera were investigated. In addition, lactic acid fermentation of E. prolifera hydrolysate was carried out using five Lactobacillus strains. The lactic acid yield, which is defined as the ratio of the lactic acid production to total sugar consumption, varied depending on the strains. Lactobacillus salivarius showed the highest lactic acid yield (68.5%), followed by Lactobacillus plantarum (66.0%), Lactobacillus rhamnosus (55.8%), Lactobacillus brevis (54.5%), and Lactobacillus casei (51.4%). The results shown in this study imply that E. prolifera would be competitive with lignocellulosic biomass such as corn stover in terms of lactic acid production yield and that green seaweed can be used as a feedstock for industrial production of chemicals.