Salting-out Extraction Of 2,3-Butanediol From Jerusalem Artichoke-based Fermentation Broths

Jerusalem artichoke is a non-grain plant grown widely in marginal lands, and its tuber and stalk is a kind of cheap raw materials for fermentation of 2,3-butanediol(2,3-BD). Through the fermentation process part of cellulose and hemicellulose is hydrolyzed to reducing sugar and is utilized by bacteria, while lignin is left which increases the viscosity of the fermentation broth and makes the separation of target products very difficult. This main purpose of this thesis is to solve this problem in downstream separation.Firstly, salting-out extraction (SOE) of 2,3-BD from viscous fermentation broth was explored with different systems and the K2HPO4/ethanol system is selected for the following study. After the process of SOE, the recovery of 2,3-BD reached 99%, about 85% proteins and 98% solid impurity were removed, and the selectivity coefficient of 2,3-BD to reducing sugars was 34.0 when 17%K2HPO4 and 21%ethanol (w/w) were existed. When the scale was enlarged 40 folds, the recovery of 2,3-BD remained constant, the viscosity in top phase was 4.4mPa-s and in the bottom was 8mPa·s which were greatly reduced compared to that of original fermentation broth (72.5mPa·s), thus the subsequent operation become more easily.Secondly, the recovery and recycled use of salt and ethanol were studied. The yield of ethanol was 88.9% from the top phase, the yield of salt was above 75% from the bottom phase. For the recycling of salt and ethanol, the best pH value of 9.5 was determined for the bottom phase. The removal of lactic acid and acetic acid increased from the fermentation broth, the removal of protein and residual sugar decreased slightly and other parameters remained unchanged after SOE.Thirdly, the distillation of top phase after SOE was taken. The fraction of acetoin and 2,3-BD were eluted sequencially during the process of distillation, and the purity of 99.7% for 2,3-BD was obtained. On the basis of above results, the economic analysis was done. Under a production scale at hundred tons of 2,3-BD per year, the sepration cost of 2,3-BD from Jerusalem artichoke-based fermentation broth by SOE is 13,500 yuan/ton.Finally, the SOE system formed by hydrophobic organic solvent and inorganic salt was studied. When the ratio of fermentation broth/K2HPO4/tertiary butanol was 61/20/40 (w/w), the recovery of 2,3-BD was 92% and about 70% of coluring matter were removed. For the extraction of flavonoids from the fermentation broth, the secondary extraction method for the separation of flavonoids and 2,3-BD was adopted. The highest recovery of flavonoids was 95% which provided the feasibility for the comprehensive utilization of tuber and stalk of Jerusalem artichoke.In a word, by SOE the taget products from high viscous fermentation broth were separated, which solved the downstream separation problem in the utilization of lignocellulosic materials as substrates for fermentation of bio-based chemicals, the cost was reduced, and the scale was easily to be enlarged.