Abstract
Sericin has been utilized in various products and commercialized with high value added. Silk degumming waste water of intense yellow color from silk factory in Bangkok, Thailand, which contains sericin, gives two choices to corporate managers; isolation for production of commercial goods or disposal after digestion by protease. In this study, sericin isolation by pH adjustment and salting out with (NH4)2SO4 and organic solvents, and sericin digestion with proteases were investigated. Isolation of sericin by adjustment of pH of waste water to 1-9 and by salting out yielded 93% w/v sericin. In contrast, ethanol and methanol treatments could not precipitate sericin from the waste water. Sericin isolated at pH 7 had the highest antioxidant activity compared to those obtained from other methods. Its activity was much lower than that of vitamin C. Digestion by a commercial protease or by crude papain for 24 h resulted in reduction of sericin concentration in the waste water as much as 66.04±3.06% and 55.66±2.31%, respectively. When low antioxidant activity of isolated sericin and the cost for sericin isolation were considered, digestion of sericin with papain is the most appropriate way to deal with sericin in silk degumming waste water.
