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 °C. The agar treated with ∼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 °C and 82 °C respectively over the control values of 39 °C and 90 °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.