Partial characterization of sulfohydrolase from Gracilaria dura and evaluation of its potential application in improvement of the agar quality

Sulfohydrolase extracted from Gracilaria dura was purified to homogeneity and investigated for improving the quality of commercial agar. The purified enzyme (50 kDa) showed optimum activity at pH 8.0 and temperature 35 degrees C. The agar treated with similar to 50 U of purified enzyme exhibited 1.66-fold increase in 3,6-AG content with 60% sulfate removal and also resulted an increase of >= 2-fold in viscosity and gel strength with a recovery of 90% agar. Further, the gelling and melting temperatures were markedly decreased to 31 degrees C and 82 degrees C respectively over the control values of 39 degrees C and 90 degrees C. The scanning electron microscopy revealed higher cross-linking and rigidity in the treated agar while FT-IR spectral analysis confirmed the increased 3,6-AG content with decreased sulfate. Therefore, the possibility for cloning of sulfohydrolase encoding gene(s) for its commercial production and exploitation in desulfation of agar could be an eco-friendly and alternative method to alkali treatment. (C) 2011 Elsevier Ltd. All rights reserved.