Abstract
Alginate-degrading bacteria were isolated from seawater and a-systematic classification was
performed using 16S rDNA sequence. The isolated strain was identified as Microbulbifer sp. strain
KIT-19. The properties of alginate lyase (ALG19) derived from the strain KIT-19 were investigated.
ALG19 was purified by various column chromatography techniques, with specific activity of 10.1
units/mg and 7.08-fold purity. When the substrate was sodium alginate, the optimum pH of the
purified ALG19 was 8.5 and optimum temperature was 40°C. The activity of the purified ALG19
increased by 2.34-fold in the presence of 100 mM Na+
. Alginate is composed of β-D-mannuronic acid
(M) and 1,4-linked α-L-guluronic acid (G) residues. The activity toward poly- M blocks and poly-G
blocks of purified ALG19 on the basis of relative activity scale were 123% and 91% respectively,
when the decomposed activity to sodium alginate was 100%. Since ALG19 was poly-M blocks specific
alginate lyase, it was thought that ALG19 belongs to the polysaccharide lyase (PL)-7 family. ALG19
could be considered to be an endo-type enzyme because it lowers the kinematic viscosity of sodium
alginate from 23.5 to 1.65 cSt (mm2
/s).
