Immobilization of protease in polyvinyl alcohol

In this study, protease from Bacillus sp. was immobilized in polyvinyl alcohol and the free and mmobilized proteases were characterized. The optimum pH was determined to be 8.0 and the optimum temperature was found to be 55 °C for the both free and immobilized proteases. The free protease was protected 19% of its initial activity after 24 h incubation time at 55 °C, whereas the immobilized protease remained 72% of its initial activity under the same conditions. The half-lives values of free and immobilized proteases were calculated as 10.6 and 53.3 hour at 55 °C, respectively. The Km and Vmax values of free protease were determined to be 0.5 mg/mL and 23.3 U/mg protein, respectively towards casein. These values were found to be 0.2 mg/mL ve 23.8 U/mg protein, respectively for the immobilized protease. The immobilized protease retained 58% of its initial activity after 5 reuses in a batch reactor. As a result, the immobilization of Bacillus sp. protease in polyvinyl alcohol is an effective immobilization method due to its ease, low cost and 5-fold increase in thermal stability.