Alginic acid is a natural acidic linear polysaccharide and the main component of brown algae which plays an important role in keeping seaweed flexible and its intercellular tissues strong. 1) It is composed of β D mannuronate (M) and α L guluronate (G), which are linked by (1 4) glycosidic bonds. Alginate may be organized in three ways: as homopolymeric M blocks, homopolymeric G blocks, or heteropolymeric M G blocks in random arrangements. The proportion of these blocks depends upon the source of the alginate, and varies in different parts of the algal tissue. 2) Alginates are widely used in foods, pharmaceuticals, and cosmetics as gelling agents, stabilizers, or agents providing high viscosity. 3) To date, many studies have been reported on alginate degrading enzymes that have been isolated from many sources, including brown algae, 4) mollusks 5 7) and marine bacteria. 8 14) It is well known that most enzymes are of the lyase type that degrade alginate polysaccharide by a β elimination mechanism, a double bond being formed between the C4 and C5 carbons at the non reducing terminal (4 deoxy α L erythro hex 4 enopyranosyluronic acid, ∆). 15) Alginate lyase is classified into two groups in the substrate specificity. One is poly(β D 1,4 mannuronate)lyase (EC 4.2.2.3) and the other is poly(α L 1,4 guluronate)lyase (EC 4.2.2.11).Previously, we found that a crude enzyme from a marine bacterium which catalyzed the degradation of alginate, resulted in alginate oligosaccharides. 16) However, only limited information has been reported about the bacterium and the enzyme. In the present study, we attempted to characterize the bacterium in detail. Moreover, the enzyme was purified by DEAE HPLC and some properties of the enzyme were studied.
MATERIALS AND METHODS
Materials.Sodium alginate (320 380 cps, 1% solution at 20 C, Kimica Corp., Kimitsu, Japan) was used as a carbon source. Poly β D mannuronate (PM) rich and poly α L guluronate (PG) rich solutions were prepared from the sodium alginate according to the method of Haug et al . 17) Other materials and reagents were commercially available.Bacterial strains and growth media. The bacterium (strain No. 1786) was isolated from the intestinal contents of an arthropod. The bacterium was maintained in medium composed of 1.00% sodium alginate, 1.00% Na2SO4, 0.08% KCl, 1.24% MgSO4, 0.01% K2HPO4, 0.10% NH4Cl, 0.01% ammonium ferric citrate, and 0.15% CaCl2. The bacterium was inoculated into 500 mL flasks containing 200 mL of the above medium, and grown at 25 C for 48 h.Classification of the marine bacterium. Classification of the strain No. 1786 bacterium was performed based on morphological, biochemical and physiological characteristics and 16S rDNA sequence. Phenotypic tests were performed as described by Barrow and Feltham. 18) We also performed biochemical characterization and utilization test using the API 20NE system (bioMerieux, Lyon, France). Abstract: High activity of alginate lyase was produced by a marine bacterium (strain No. 1786), which was isolated from the intesti...
