Processing of ethanol fermentation broths by Candida krusei to separate bioethanol by pervaporation using silicone rubber-coated silicalite membranes

摘要

BACKGROUND: Pervaporation employing ethanol-permselective silicalite membranes as an alternative to distillation is apromising approach for refining low-concentration bioethanol solutions. However, to make the separation process practicable,it is extremely important to avoid the problems caused by the adsorption of succinate on the membrane during the separationprocess. In this work, the pervaporation of an ethanol fermentation broth without succinate was investigated, as well as theinfluence of several fermentation broth nutrient components. RESULTS: Candida krusei IA-1 produces an extremely low level of succinate. The decrease in permeate ethanol concentrationthrough a silicone rubber-coated silicalite membrane during the separation of low-succinate C. krusei IA-1 fermentationbroth was significantly improved when compared with that obtained using Saccharomyces cerevisiae broth. By treating thefermentation broth with activated carbon, bioethanol was concentrated as efficiently as with binary mixtures of ethanol/water.The total flux was improved upto 56% of that obtained from the separation of binary mixtures, compared with 43% beforethe addition of activated carbon. Nutrients such as peptone, yeast extract and corn steep liquor had a negative effect onpervaporation, but this response was distinct from that caused by succinate. CONCLUSION: For consistent separation of bioethanol from C. krusei IA-1 fermentation broth by pervaporation, it is usefulto treat the low nutrient broth with activated carbon. To further improve pervaporation performance, it will be necessary tosuppress the accumulation of glycerol.