Laminarin and its derived oligosaccharides have diverse bioactivities. The b-1,3-glucanase in marine bacteria can be employed as a tool to digest laminarin in the cell wall of brown algae. Here, we cloned, expressed and characterised a b-1,3-glucanase (laminarinase), MaLamNA, from the previously characterised marine bacterium Microbulbifer sp. ALW1, phylogenetically distinct from the glycoside hydrolase families of characterised laminarinases. The recombinant laminarinase was heterologously expressed and purified from Pichia pastoris GS115 cells with a molecular mass of 57.3 kDa. MaLamNA exerted its hydrolytic activity specifically against laminarin, with the highest activity at 45°C and pH 4.5-5.5, respectively, and demonstrated high stability against extreme acidic and alkaline pH exposure. The addition of reducing agent dithiothreitol could significantly enhance the activity of MaLamNA. The hydrolytic products of laminarin by MaLamNA exhibited more effective antioxidant activities than the undigested laminarin. These characteristics of MaLamNA provide clues to its industrial application for laminarin bioresource development.

Data are presented for the amino acid and sugar compositions of gum talha (tahl), i.e. the exudate from Acacia seyal Del., and for four sequential Smith-degradation (SD) products (0.10, 0.19, 0.38, 1.60 and 2.22% N respectively). Gum talha, which is not permitted as a food additive, is liable to occur as a contaminant of shipments of legitimate gum arabic (Acacia senegal (L.) Willd.). The molar polysaccharide/protein ratio in the whole gum (113:1) decreased to 58:1, 27:1, 5.5:1 and 4:1 in the first, second, third and fourth SD products respectively. From previous studies, SD-IV is known to be a branched galactan; hydroxyproline, aspartic acid, serine, valine, proline, and leucine account jointly for 70% of its amino acids. The first SD eliminated large amounts of sugars (ca 50%, including all of the rhamnose and glucuronic acid present) but only very small amounts of amino acids (molar ratio 807/1). The second and third degradations eliminated all of the arabinose and 99% of the galactose originally present. The very small yield of the final SD product is an established characteristic of dextrorotatory Acacia exudates of the A. seyal type (Bentham's Gummiferae). Overall (four SD stages), 99.7% of the original sugars but only 91.3% of the amino acids were eliminated. Hydroxyproline accounts for ca 25% of the low amino acid content of A. seyal gum and each of its SD products; the proteinaceous enrichment of the branched galactan core also involves aspartic acid, glutamic acid and iso-leucine.(ABSTRACT TRUNCATED AT 250 WORDS)

No abstract

No abstract