Production of a novel dimeric 4-deoxy-L-erythro-5-hexoseulose uronic acid by a PL-17 exolytic alginate lyase from Hydrogenophaga sp. UMI-18.

Hydrogenopahaga sp. strain UMI-18 is an alginolytic bacterium that can produce poly(3-hydroxybutylate) (PHB) using alginate as its sole carbon source. Genome analysis indicated that this strain harbors both PHB-synthesizing and alginate-assimilating gene clusters. In the present study, we cloned HyAly-I gene that encodes a PL-17 exolytic alginate lyase and investigated its enzymatic properties using recombinant HyAly-I (recHyAly-I) that was produced by Escherichia coli. The recHyAly-I preferably depolymerized poly(ß-D-mannuronate) block of alginate in an exolytic manner at an optimal temperature and a pH at 40 °C and pH 6.0, respectively. It released 4-deoxy-L-erythro-5-hexoseulose uronic acid (DEH) from the non-reducing terminus of polymer and oligomer substrates. Interestingly, recHyAly-I was found to produce a novel unsaturated disaccharide, i.e., dimeric DEH (diDEH), along with monomeric DEH. Production of diDEH was prominent in the degradation of trisaccharides.

Production of poly(3-hydroyxybutylate) by a novel alginolytic bacterium Hydrogenophaga sp. strain UMI-18 using alginate as a sole carbon source.

A novel alginolytic bacterium Hydrogenophaga sp. strain UMI-18 that produces poly(3-hydroyxybutylate) (PHB) in the alginate-mineral salt (AMS) medium containing 1% (w/v) sodium alginate as a sole carbon source was isolated from a decayed brown seaweed litter. The yield of PHB produced by strain UMI-18 was 1.1 ± 0.15 g/L of AMS and the PHB content in dried cell pellet was 58 ± 4% (w/w). Glucose, fructose, galactose, mannose, mannitol, sucrose and lactose were also available for the production of PHB by strain UMI-18. The yield of PHB in 1% (w/v) carbohydrate media reached 2.03-2.24 g/L for glucose and fructose, 0.75-1.64 g/L for alginate, galactose, mannitol and sucrose, and ∼0.15 g/L for lactose. The PHB produced by strain UMI-18 showed a glass-transition temperature (Tg) at 4°C, a melting temperature at 175°C, and an average molecular mass of 860 kDa. Draft genome analysis of the strain UMI-18 revealed that an alginate-assimilating gene cluster is located in contig 8 comprising 453,520 bp and the PHB-synthesis gene cluster is in contig 15 comprising 653,793 bp.

Polysaccharide-Degrading Enzymes From Marine Gastropods.

Seaweed polysaccharides have been widely used as viscosifier, gelling agents, and stabilizer in the various application fields, e.g., food, pharmaceutical, nutraceutical, and chemical industries. Applications of seaweed polysaccharides are further expanding to versatile directions, e.g., biofuels, bioactive compounds, and functional materials for medical and basic researches. Production of functional oligo- and monosaccharides by the use of specific enzymes is also expected to improve the value of seaweed polysaccharides. The enzymes that depolymerize seaweed polysaccharides are distributed largely among seaweed-associating organisms like marine invertebrates and bacteria. Among them, herbivorous marine gastropods such as abalone and sea hare are the most prominent producers of polysaccharide-degrading enzymes. To date, various kinds of polysaccharide-degrading enzymes have been isolated from the digestive fluid and hepatopancreas of these animals. Among them, alginate lyase, ß-1,3-glucanase, mannanase, and cellulase are the major constituents of their digestive fluid. In this chapter, the authors describe the general methods for the preparation and activity assay of the gastropod polysaccharide-degrading enzymes and provide basic knowledge for their primary structures.