The screening, identification of alginate degrading bacteria and optimization of fermentation conditions

A screening work was carried out to obtain a bacterium with high alginate lyase activity by using alginate as sole source of carbon. The strain was identified as Alteromonas based on physiology and biochemistry analysis, 16 S rDNA sequence analysis, and was named Alteromonas sp. H4. It was shown that the optimal culture medium composition of producing alginate lyase was as follows(w/v): alginate 0.6%, yeast extracts 0.5%, peptone 0.25% and NaCl 3%. The optimized culture condition was as follows: culture temperature 28℃, initial pH value 7.5, inoculum size 1.5%(v/v) and optimal harvest time 48 h. The activity of alginate lyase was activated by Fe3+, which hasn't been reported in other alginate lyase production strains, and the inhibitory effect by Cu2+ was up to 45.78%. Under optimized conditions, the alginate lyase activity of the Alteromonas sp. H4 was146.45 U/ml, which was increased by 39.4% than that before optimization.