การประยุกต์ใช้ไมโครฟิลเตรชันในกระบวนการกำจัดความขมออกจากสเปนท์บริวเวอร์ยีสต์ / ปราณี กิตติอนงค์ = Application of microfiltration in debittering process of spent brewer's yeast / Pranee Kittianong
The study of separating cell debris from intracellular product for debittering spent brewer's yeast by rotating microfiltration, the research work consists of two parts. Firstly, cells were disrupted by a homogenizer. It was found that the amount of protein release varied directly with pressure and number of passes of operating homogenizer. The optimum condition was 12% (w/V) spent brewer's yeast, 500 bar and 2 passes. The protein and bitterness content were found to be 0.223 g/gcdw. and 0.433 mg.IAA./gcdw. Secondly, the separated cell debris by microfiltration was further treated in the debittering process in pH ranges of 5, 6 and 7.5. It was indicated that the bitterness substances were adsorbed on cell debris at pH 5-6 and was removed by the membrane. The pore sizes of ceramic membrane were 0.2 mu m and 0.9 mu m providing 100% rejection. From this investigation, when the membrane pore size was larger, the cell debris plugged on it. An experimental study of the permeation of yeast homogenate and yeast autolysate (autolysis after homogenized) was carried out at transmembrane pressure of 0.3 bar, feed rate of 35 l/h, rotating speed of 600 rpm and ceramic pore size of 0.2 mu m. The production rate of protein from yeast autolysate (yeast extract) was 8-times higher than that obtained from yeast homogenate (yeast protein concentrate) with 80% debittering. The study of production rate of yeast extract by separating cell debris from yeast autolysate was conducted at 20 g/l yeast autolysate, 0.3 bar transmembrane pressure various feed rates (11, 15 and 35 l/h) and rotating speeds (600 and 1000 rpm). It was found that the protein productivity increased with increasing rotating speed and lowering feed rate. Maximum productivity of protein was 379 g/m2-h, bitterness 644 mg.lAA./m2-h, solid yield 37.79%, protein content 0.354 g/gdw, bitterness content 0.6 mg.lAA./gdw and 68.14% debittering efficiency and 11 l/h feed rate and 1000 rpm rotating speed.
