Alginase was produced as an extracellular alginate-degrading enzyme by a newly isolated Flavobacterium sp. LXA. The maximal alginase activity was obtained when strain LXA was cultured in the medium with alginate as carbon source, whereas some other carbohydrates including mannose, maltose, glucose, and fructose supported only a little alginase production. The addition of nitrogen sources was not necessary for alginase production by strain LXA grown in the mineral solution with alginate as carbon source. The endolytic mode on the molecule alginate was supported by the better correlation between the viscosity loss and the reducing group released in the process of alginate degradation. The relationship between the formation of reducing terminus and the increase in OD235 suggested that alginase was an eliminase cleaving alginate to form an unsaturated uronate residue absorbable at 235 nm and a reducing group at 1:1 ratio. (C) 2008 Elsevier Ltd. All rights reserved.