Butanol Extractive Fermentation To Simultaneously Produce "properties Improved" Biodiesel And Butanol In Water And Energy-saving Operation Mode

Biodiesel is a kind of clean and renewable liquid fuel. The existing biodiesels have a couple of disadvantages such as poor ignition performance and lower combustion power. Using biodiesels as extractant for acetone-butanol (AB) extractive fermentation, the biodiesels extracting more than 10g/L butanol could be used as "properties improved" biodiesel directly. This method would greatly reduce the energy consumed in distilling and recovering the fermentative solvents. However, AB extractive fermentation with biodiesels as the extractant also produces a large amount of waste supernatant which still contains about 8 g/L butanol. Direct disposal of the waste supernatant not only causes severe environmental pollution but also wastes valuable fermentation products and water resource.This study aimed at increasing waste supernatant utilization ratio in butanol extractive fermentation to simultaneously and stably produce "properties improved" biodiesel and pure butanol in an energy-saving operation mode, as well as realizing the target of products diversity. The main conclusion could be summarized as follows:(1) A small amount of n-octanol could be used to recover butanol remaining in the residual supernatant (octanol/supernatant:0.2:1). Under this condition, more than 56%of the remaining butanol could be recovered and butanol in n-octanol could be concentrated to a level of 25.7 g/L for easy and energy-saving purification, and the total butanol yield increased 44%.(2) The waste supernatant was pre-treated by 3%(w/v) activated carbon to adhere the fermentative inhibitor-melanoidin accumulated in the waste supernatant. After the pre-treatment, the maximal recycle ratio of waste supernatant could be increased from 50% to 100% and the fermentation performance did not deteriorate as compared with that of using fresh water for medium preparation.(3) With biodiesel as the extractant for butanol extractive fermentation, fully recycling fermentation waste supernatant could at least continued for 14 runs without any fermentation performance deterioration. In each fermentation run, butanol concentration in bio-diesel stabilized over 10g/L, which would potentially ensure the quality of "properties improved" bio-diesel.(4) The proposed water & energy-saving butanol extractive fermentation system to simultaneously produce "properties improved" biodiesel and pure butanol was testified in a 7L static and anaerobic bioreactor. In this case, the "aimed" butanol yield increased to a level of 20%,0.97L "properties improved" biodiesel and about 5g pure butanol could simultaneously produced per one liter fermentation broth.