Ethanol Production from cheese whey powder solution by fermentation

Ethanol production from cheese whey powder (CWP) solution was investigated using batch, fed-batch and continuous fermentation systems. In batch experiments ethanol production from cheese whey, CWP and lactose solutions with the same initial sugar contents were compared by using two different Kluyveromyces marxianus strains (NRRL?1109, NRRL?1195) in order to determine the most suitable substrate and the yeast strain.Then, the effects of initial pH, CWP concentration and external nutrient supplementation on ethanol production were investigated using K. marxianus NRRL-1195. The rate and extent of ethanol formation did not increase with external nutrient addition indicating no requirement for external nutrients. Final ethanol and the rate of ethanol formation increased with increasing CWP indicating no substrate or product inhibitions, but substrate limitations.Performances of two different K. marxianus strains (NRRL-1195 and DSMZ-7239) were compared for ethanol fermentation. DSMZ-7239 was found to be the most suitable strain and was used in further experiments.Effects of initial CWP and yeast concentrations were investigated and a kinetic model describing the rate of sugar utilization as function of the initial substrate and the biomass concentrations was developed in batch fermentation.Then, a five- cycle repeated fed- batch operation with different feed CWP concentrations was used for the same purpose. The growth yield coefficient (Yx/s) decreased and product yield coefficient (Yp/s) increased with increasing feed sugar content.A continuous culture at different feed sugar contents and hydraulic residence times (HRT) was tested for ethanol production. Material balances for yeast growth, sugar utilization and ethanol formation with suitable kinetic models were used to predict the system performance and to determine the kinetic constants.Finally, a continuously operated packed column bio-reactor (PCBR) using olive pits as support particles was used at different HRTs and feed sugar cotent. Sugar concentration decreased and ethanol increased with the height of the column operated in up-flow mode. Effluent ethanol increased with increasing HRT and feed sugar content up to certain levels. Ethanol yields closer to the theoretical predictions were obtained