Enhancement Of Residual Supernatant Utilization Recycle Ratio In Butanol Extractive Fermentation

Biodiesel was a cleanly and reproducible resource. However, ignition performance of biodiesel was very poor and large amount of black smoke was produced during ignition process. Using biodiesel as extractant for AB extractive fermentation could improve biodiesel's quality and biodiesel could be used as"properties improved"biodiesel for direct utilization. At the same time , end-products inhibition could be moderated and the energy consuming solvents distillation recovery process could be eliminated. However, this process also produced a large amount fermentative waste supernatant. Fermentation could not carry through when recycle ratio of waste supernatant was over 50% when using waste supernatant directly.Aiming at saving the valuable water resource, this study focused on recycling fermentative waste supernatant for medium preparation for the next fermentation run. Therefore, the optimal technology of supernatant waste pretreatment for once and many times reuse, factors/mechanisms for the recycling limit were carefully investigated. The main conclusion was as follows:First ,the reason and possible mechanism of fermentation failure when recycling high ratio of waste supernatant was studied. The results suggested that higher concentration of soluble protein formed during in fermentation process and residue solvent and starch did not affect the waste supernatant recycling. Apart from soluble and large inhibitory molecule ,unknown and small molecule would also lead to fermentation failure when recycling high ratio of waste supernatant.Second, getting rid of small and large inhibitory molecule when recycling high ratio of waste supernatant, fermentation performance could be inproved, but lower compared with using fresh water. The maximal recycle ratio of waste supernatant could be increased from 50% to 75% when treating the supernatant with a combinational manner of simultaneously using 3% silicalite absorption and membrane filtration and fermentation performance was close to using fresh water, so large amount of precious water could be saved. In addition, when using the same pretreatment of waste supernatant and maintaining a steady fermentation performance , the continuous repeated cycle number times could reach 3-4.Third, before reusing waste supernatant to prepare culture medium, getting rid of more residue butanol in waste supernatant could avoid the reaction between residue butanol and various residue substance of waste supernatant and avoid forming new fermentiton inhibitory substance in medium preparation and sterilization process, and stability of fermentation performance could be enhanced when recycling high ratio of waste supernatant.Fourth, in-situ addition of tiny amount of silicalite in both traditional and extractive AB fermentation with olyel alcohol as the extractant was carried out. 5% and 8% enhancement in butanol productivity was observed in each case respectively.