PERFORMANCE-CHARACTERISTICS OF YEAST GROWTH IN A MODIFIED AIRLIFT FERMENTER

Two types of airlift fermenters, conventional (UT-ALF) and modified (C DT-ALF) were investigated to evaluate their performance with respect t o baker's yeast growth. The riser tube of conventional external loop a irlift fermenter is replaced by a converging diverging tube, which is named as modified airlift fermenter having downcomer to riser cross-se ctional area ratio A(d)/A(r) = 1.8. The results were compared for the two types of airlift fermenter. A modified growth kinetics model for b aker's yeast with oxygen as limiting substrate, has been proposed. The values of K(s) and K(d) of the growth model were determined from expe rimental data. The proposed model represented better for CDT-ALF syste m compared to UT-ALF. Compared to UT-ALF, CDT-ALF always showed higher cell mass concentration and low residual sugar concentration irrespec tive of the operating conditions. At optimum operating condition (init ial glucose concentration 30 g/l, air flow rate 0.5 vvm and fermentati on time 8 hrs.) 16.7% higher cell mass was observed in CDT-ALF compare d to that in UT-ALF and yield (Y(x/s)) was found to be 0.51 which was theoretically very near to maximum achievable value.