Hydrolytic characteristics of chitosan-immobilized As 1.398 neutral proteinase (from B. subtilis) to soybean protein

As 1.398 neutral proteinase (from B. subtilis As 1.398) was immobilized on the loose chitosan-precipitate by simultaneous adsorption and covalent bonding. The optimum activity of the chitosan-immobilized proteinase to soybean protein is at pH 8.O. The profiles of proteolytic activity with regard to temperature, as with soybean protein as substrate, show two peaks at 40 and 60 °C, respectively. The proteolytic activity toward soybean protein at 60 °C is significantly higher than that at 40 °C. The maximum extent of hydrolysis of soybean protein by the immobilized proteinase is about 23% which is substantially lower than that of casein. Heating increases the susceptibility of soybean protein to the immobilized proteinase, but not the maximum extent of hydrolysis. In addition, the composition of free amino acids in hydrolyzed soybean protein was analyzed.