Molecular identification and development of a novel recombinant alginate lyase as the biocatalyst for alginate saccharification are prerequisite for bioethanol fermentation from brown seaweed biomass. We identified and characterized a novel oligoalginate lyase for complete degradation of alginate from Stenotrophomonas maltophilia KJ-2 that grow on alginate as the sole carbon source. KJ-2 oligoalginate lyase consisted of AlgL- and heparinase II/III-like domains. The recombinant KJ-2 oligoalginate lyase exhibited substrate preference toward polymannuronate and alginate as well as oligoalginate. The recombinant KJ-2 oligoalginate lyase completely degraded alginate into unsaturated uronate monomer most efficiently at pH 7.5 and 37 °C. Interestingly, AlgL-like recombinant proteins showed more like endolytic activity. The recombinant KJ-2 oligoalginate lyase was a novel oligoalginate lyase consisting of AlgL- and heparinase-like domains and could be used as a candidate for biocatalyst selection to saccharify alginate for bioethanol production from brown seaweed.

A bacterium possessing alginate-degrading activity was isolated from marine brown seaweed soup liquefied by salted and fermented anchovy. The isolated strain was designated as Sphingomonas sp. MJ-3 based on the analyses of 16S ribosomal DNA sequences, 16S-23S internal transcribed spacer region sequences, biochemical characteristics, and cellular fatty acid composition. A novel alginate lyase gene was cloned from genomic DNA library and then expressed in Escherichia coli. When the deduced amino acid sequence was compared with the sequences on the databases, interestingly, the cloned gene product was predicted to consist of AlgL (alginate lyase L)-like and heparinase-like protein domain. The MJ-3 alginate lyase gene shared below 27.0% sequence identity with exolytic alginate lyase of Sphingomonas sp. A1. The optimal pH and temperature for the recombinant MJ-3 alginate lyase were 6.5 and 50°C, respectively. The final degradation products of alginate oligosaccharides were analyzed by electrospray ionization mass spectrometry and proved to be alginate monosaccharides. Based on the results, the recombinant alginate lyase from Sphingomonas sp. MJ-3 is regarded as an oligoalginate lyase that can degrade oligoalginate and alginate into alginate monosaccharides.