Effects of additives on the lyophilized and thermal stability of d-galactose-6-sulfurylase activity from Eucheuma striatum (Rhodophyta)
We extracted and purified d-galactose-6-sulfurylase from Betaphycus gelatinus by ammonium sulfate precipitation, ion exchange chromatography and hydrophobic interaction chromatography and investigated the desulfation of carrageenan by the purified enzyme. The purity of the enzyme increased 4.9 fold with approximately 3.7% yield of the crude extract. It was able to catalyze the conversion of μ- to κ-carrageenan. The purified enzyme was a monomeric protein with a molecular weight at about 65 kDa. The maximum activity of the enzyme was observed at pH 7.0 and temperature 40 °C. 26% of the total sulfate was removed from the carrageenan when treated with 18 U purified enzyme. The conversion from μ- to κ-carrageenan was confirmed through the IR spectral analysis of both the control and enzyme treated carrageenan. This study proved that there is a congeneric enzyme that has the same mechanism with alkali treatment on carrageenan from a new kind of red algae Betaphycus gelatinus, which is an alternative way of alkali treatment to the production of carrageenan. The existence of precursor μ-carrageenan in Betaphycus gelatinus was evidently found in this study.