[Isolation, identification of a κ-carrageenase-producing bacterium and κ-Carrageenase characterization]

The aim of this study was to screen and identify carrageenase-producing strain from mangrove soil leaf and to characterize produced carrageenase.

The culture medium with κ-carrageenan as sole carbon source was used to isolate the strain exhibiting carrageenase activity. The isolated strain was identified by morphology observation and 16S rDNA sequencing. κ-carrageenase produced by Pseudoalteromonas sp. ASY5 was purified and characterized by DNS method.

A bacterial strain ASY5 with high carrageenase activity was isolated from mangrove soil humus, and was identified as Pseudoalteromonas sp. The molecular mass of the purifiedenzyme was estimated to be 30 kDa. The optimal temperature and pH of the enzyme were 60°C and 7.5, respectively. The enzyme was stabileat 50°C, and more stable between pH 7.0 and 9.0. The enzyme could convert κ-carrageenan. The Km and Vmax values of the enzyme for κ-carrageenan was 2.28 mg /mL and 147.06 μmol/(min · mg), respectively. The enzyme was significantly stimulated by Na+, K+, Ca2+, Mg2+ and Al3+. The enzyme was inhibited strongly by Ag+, Zn2+, Cd2+ and SDS.

κ-carrageenase produced by Pseudoalteromonas sp. ASY5 was stable at high temperature and alkaline pH, with potential application in carrageenan oligosaccharides production.