Production of Ethyl-agarobioside, a Novel Skin Moisturizer, by Mimicking the Alcoholysis from the Japanese Sake-Brewing Process.

Agarobiose (AB; d-galactose-ß-1,4-AHG), produced by one-step acid hydrolysis of agarose of red seaweed, is considered a promising cosmetic ingredient due to its skin-moisturizing activity. In this study, the use of AB as a cosmetic ingredient was found to be hampered due to its instability at high temperature and alkaline pH. Therefore, to increase the chemical stability of AB, we devised a novel process to synthesize ethyl-agarobioside (ethyl-AB) from the acid-catalyzed alcoholysis of agarose. This process mimics the generation of ethyl α-glucoside and glyceryl α-glucoside by alcoholysis in the presence of ethanol and glycerol during the traditional Japanese sake-brewing process. Ethyl-AB also showed in vitro skin-moisturizing activity similar to that of AB, but showed higher thermal and pH stability than AB. This is the first report of ethyl-AB, a novel compound produced from red seaweed, as a functional cosmetic ingredient with high chemical stability.

Evolution-aided improvement of the acid tolerance of Levilactobacillus brevis and its application in sourdough fermentation.

Levilactobacillus brevis is crucial in food fermentation, particularly in sourdough production. However, the cultivation of L. brevis faces a challenge with accumulation of lactic acid, a major inhibitor. We aimed to increase the acid tolerance of L. brevis, an industrial strain for sourdough fermentation. We used the adaptive laboratory evolution (ALE) to obtain lactic acid tolerant strains. The evolved strain's fermentation and metabolite profiles, alongside sensory evaluation, were compared with the parental strain by using various analytical techniques. The ALE approach increased lactic acid tolerance in the evolved strain showing an increased growth rate by 1.1 and 1.9 times higher than the parental strain at pH 4.1 and 6.5, respectively. Comprehensive analyses demonstrated its potential application in sourdough fermentation, promising reduced downstream costs. The evolved strain, free from genetically modified organisms concerns, has great potential for industrial use by exhibiting enhanced growth in acidic conditions without affecting consumers' bread preferences.

Metabolic and enzymatic elucidation of cooperative degradation of red seaweed agarose by two human gut bacteria.

Various health beneficial outcomes associated with red seaweeds, especially their polysaccharides, have been claimed, but the molecular pathway of how red seaweed polysaccharides are degraded and utilized by cooperative actions of human gut bacteria has not been elucidated. Here, we investigated the enzymatic and metabolic cooperation between two human gut symbionts, Bacteroides plebeius and Bifidobacterium longum ssp. infantis, with regard to the degradation of agarose, the main carbohydrate of red seaweed. More specifically, B. plebeius initially decomposed agarose into agarotriose by the actions of the enzymes belonging to glycoside hydrolase (GH) families 16 and 117 (i.e., BpGH16A and BpGH117) located in the polysaccharide utilization locus, a specific gene cluster for red seaweed carbohydrates. Then, B. infantis extracted energy from agarotriose by the actions of two agarolytic ß-galactosidases (i.e., Bga42A and Bga2A) and produced neoagarobiose. B. plebeius ultimately acted on neoagarobiose by BpGH117, resulting in the production of 3,6-anhydro-L-galactose, a monomeric sugar possessing anti-inflammatory activity. Our discovery of the cooperative actions of the two human gut symbionts on agarose degradation and the identification of the related enzyme genes and metabolic intermediates generated during the metabolic processes provide a molecular basis for agarose degradation by gut bacteria.

Increased Production of Colanic Acid by an Engineered Escherichia coli Strain, Mediated by Genetic and Environmental Perturbations.

Colanic acid (CA) is a major exopolysaccharide synthesized by Escherichia coli that serves as a constituent of biofilm matrices. CA demonstrates potential applications in the food, cosmetics, and pharmaceutical industry. Moreover, L-fucose, a monomeric constituent of CA, exhibits various physiological activities, such as antitumor, anti-inflammatory, and skin-whitening. Here, the effects of genetic and environmental perturbations were investigated for improving CA production by E. coli. When rcsF, a positive regulator gene of CA synthesis, was expressed in E. coli ΔwaaF, a CA-producing strain constructed previously, the CA titer increased to 3051.2 mg/L as compared to 2052.8 mg/L observed with E. coli ΔwaaF. Among the environmental factors tested, namely, osmotic and oxidative stresses and pH, pH was a primary factor that significantly improved CA production. When the pH of the culture medium of E. coli ΔwaaF + rcsF was maintained at 7, the CA titer significantly increased to 4351.6 mg/L. The CA yield obtained with E. coli ΔwaaF + rcsF grown at pH 7 was 5180.4 mg CA/g dry cell weight, which is the highest yield of CA reported so far. This engineered E. coli system with optimization of environmental conditions can be employed for fast and economically-feasible production of CA.