Abstract:
The aim of this research was to determine optimal conditions for extraction of alkaline protease from Bacillus subtils TISTR 25 fermentation broth using aqueous two-phase system in Oldshue-Rushton column 5.7 liter. Extraction was done in continuous mode with dispersed phase composed of (by weight) PEG 1000 42.5%, dipotassium hydrogenphophate 1.75%, potassium dihydrogen phosphate 0.75%, water 55% flowing upwards and continuous phase of dipotassium hydrogenphosphate 19.65%, potassium dihydrogenphosphate 6.35%, water 55% flowing downwards. The research was to study effects of fermentation broth concentration (20, 40 and 55% w/w), continuous/dispersed flow rates(42/12, 69/20 and 97/28 ml/min), and impeller revolution speed(100 and 140 rpm) on purification factor, yield percent, over all mass transfer coefficient, and enzyme activity in continuous phase profile in extraction column. The stability of the extracted alkaline protease in PEG rich-phase was also studied. It was found that the optimal conditions for alkaline protease extraction in Oldshue-Rushton column 5.7 liter were 55% w/w fermentation broth, continuous/dispersed phase flow rate of 97/28/ ml/min, and impeller speed of 100-140 rpm. These conditions gave purification factor, yield percent, and overall mass transfer coefficient of 1.39-1.48, 52.14-51.78% and 4.49-4.52 x 10⁻⁴ min⁻¹, respectively, with this volumetric flow rate fermentation broth of 76.82 1 could be extracted within one day of operation. It was also found that the activity of the extracted alkaline protease dissolve in PEG 100 rich phase system reduced its initial activity form 14.3 percent after keeping at 30±2 ℃ for 3 weeks.