1Department of Chemical Engineering, Faculty of Engineering, Tarbiat Modares University, P.O. Box 14115-143 Tehran, I.R. IRAN
2Department of Biotechnology, Science Faculty, Tehran University, Tehran, I.R. IRAN
Recovery of metabolites from fermentation broth by solvent extraction can be used to optimize fermentation processes. End-product reutilization, low product concentration and large volumes of fermentation broth and the requirements for large bioreactors, in addition to the high cost largely contributed to the decline in fermentative 2,3-butanediol production. Extraction can successfully be used for in-situ alcohol recovery in 2,3-butanediol fermentations to increase the substrate conversion. In the present work organic extraction of 2,3-butanediol produced by Klebsiella pneumoniae fermentation was studied to determine solvent effect on 2,3-butanediol production. The aim of this project was liquid-liquid extractive fermentation systems evaluation as an alternative to overcome the end product effect and to increase of 2,3-butanediol production by K.pneumoniae because Conventional fermentative production of 2,3-butanediol by K. pneumoniae has the disadvantage of product reutilization by the organism. Alternatives to overcome this problem have met with limited success. Extractive fermentation has been shown to solve this problem. An effort has been made in this study to use for the extractive fermentation of 2,3-butanediol using oleyl alcohol as extract-ant. Eighteen organic solvents were examined to determine their biocompatibility for in situ extraction of fermentation products from cultures of the K. pneumoniae. From 18 tested solvents, 13 of which were non-toxic to K.pneumoniae. The highest 2,3-butanediol production (23.01 g l-1) was achieved when oleyl alcohol was used. In situ removal of end products from K.pneumoniae resulted in increased productivity. In conclusion 2,3-butanediol productivity increased from 0.5 g l-1h-1 to 0.66 g l-1h-1 in extractive fermentation using oleyl alcohol as the extraction solvent.
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