Xylanase recovery by ethanol and Na2SO4 precipitation

Xylans are the major components of the hemicellulosic fraction of lignocellulosic biomass and their hydrolysis can be obtained using xylanases from Penicillium janthinellum. In this work, sugarcane bagasse hemicellulosic hydrolysate was used as the substrate for producing xylanase. The precipitation of these enzymes was studied using ethanol and Na2SO4 as precipitating agents. Ethanol precipitation experiments were performed batchwise in concentrations ranging from 10 to 80%, pH 4.0 to 7.0, at 4 degrees C. The concentrations used in the precipitations with Na2SO4 were from 5 to 60% at pH 5.5 and 25 degrees C. Solubility curves as a function of xylanase activity and total protein for both precipitating agents were made. According to the results, Na2SO4 is not appropriate for precipitating xylanases in this medium since at salt concentrations higher than 25%, the enzyme was denaturated and at this concentration less than 80% of the enzyme and total protein were precipitated. Because of differences in xylanase and total protein solubility, a fractionated precipitation using ethanol can be performed, since with 40% ethanol, 49% of the total protein was precipitated and more than 95% of the enzyme was kept in solution. On the other hand approx 100% of the xylanases were recovered by precipitation after adding 80% ethanol.