Abstract:
To determine proper conditions for extraction of alkaline protease from fermentation broth of Bacillus Subtilis TISTR25 using aqueous two phase systems of PEG 1000 and potassium phosphate. The research was divided into three sections. The first section was to study effects of system pH (7.5, 8.5, 9.5, and 10.5), volume ratio of upper and lower phases (22:1, 3:1, 1:1 ,1:3 and 1:25), and fermentation broth concentrations (10, 20, 30, 40, 50% w/w) on partition coefficients and specific activity of alkaline protease. The optimal conditions for alkaline protease extraction were pH value of 7.5, volume ratio of 1:25, 50% w/w fermentation broth which gave the partition coefficient, specific activity, and yield percent of 48.3 , 17.7 U/mg protein, and 62.2, respectively. The second section was to select type and design suitable extraction column. The criteria used were: total throughput, numbers of equilibrium stages, physical properties of the aqueous two phase system, volumetric flow rate ratio, ability to handle solid, ease of cleaning, and low maintenance characteristic. Judging from all these criteria, Oldshue Rushton column was selected and designed for further study. The column was 500 mm. high with the column diameter of 45 mm., impeller diameter of 18 mm., ring internal diameter of 23 mm., and compartment height of 23 mm. The third and final section of this research was the study of impeller revolution speed (0, 50, 100, 150, and 200 rpm), dispersed (1.0, 2.1, 3.4, and 5.3 ml/min) and continuous phase flow rates (17.9 and 11.8 ml/min), and fermentation broth concentration (20, 40, 60, 72% w/w in continuous phase) effects on purity factor, yield percent, and column extraction efficiency. Extraction was done in continuous mode with dispersed phase composed of 42.5% w/w PEG1000, 2.5% w/w potassium phosphate, and 55.0% w/w water flowing upwards, and continuous phase of 28.0% potassium phosphate, and 72.0% w/w water flowing downwards. It was found that the optimal conditions for alkaline protease extraction in the Oldshue Rushton column were impeller speed of 100 rpm, dispersed and continuous phase flow rates of 3.4, and 11.8 ml/min, and 20% w/w of fermentation broth which gave purity factor, yield percent, and extraction efficiency of 6.0, 73.7, and 0.79, respectively. It was also found the activity of the extracted alkaline protease dissolve in PEG1000 rich phase system reduced from its initial activity 12.9, 9.2, and 6.2 percent when left at 32+-, 4 and -20ํC respectively, for one month. The proper conditions found for alkaline protease extraction in Oldshue Rushton column in this work can be used for further investigation to determine characteristic velocity, and mass transfer coefficient for the design of larger extractor