Cloning and characterization of a new cold-adapted and thermo-tolerant ι-carrageenase from marine bacterium Flavobacterium sp YS-80-122

iota-Carrageenases play a role in marine iota-carrageenan degradation, and their enzymatic hydrolysates are thought to be excellent antioxidants. In this study, we identified a new iota-carrageenase, encoded by cgiF, in psychrophilic bacterium Flavobacterium sp. YS-80-122. The deduced iota-carrageenase, CgiF, belongs to glycoside hydrolase family 82 and shows less than 40% amino acid identity with characterized iota-carrageenases. The activity of recombinant CgiF peaked at 30 C (1,207.8 U/mg). Notably, CgiF is a cold-adapted iota-carrageenase, which showed 36.5% and 57% of the maximum activity at 10 degrees C and 15 degrees C, respectively. In addition, it is a thermo-tolerant enzyme that recovered 58.2% of its initial activity after heat shock. Furthermore, although the activity of CgiF was enhanced by NaCI, the enzyme is active in absence of NaCl. This study also shows that CgiF is an endo-type iota-carrageenase that hydrolyzes beta-1,4-linkages of iota-carrageenan, yielding neo-iota-carratetraose as the main product. Its cold-adaptation, thermo-tolerance, NaCl independence and high neo-iota-carratetraose yield make CgiF an excellent candidate for industrial applications in production of iota-carrageen oligosaccharides from seaweed polysaccharides. (C) 2017 Published by Elsevier B.V.