Fermentative Production Of2,3-butanediol From Sugarcane Molasses

2,3-Butanediol (2,3-BD) is a promising platform chemical, which has a wide application in solvent, liquid fuel, and synthetic chemistry. Sugarcane molasses is the by-product of sugar industry, which contains approximately50%total sugar, organic acid and inorganic salts. In addition, the coloring matters in sugarcane molasses is a valuable product in pharmaceuticals.. In this study, sugarcane molasses was used as carbon source to produce2,3-BD. Due to its multi-composition, the fermentation medium and procedure were simplified to reduce the fermentation cost, and the recovery of coloring matters were explored.Firstly, Response Surface Methodology(RSM) was used to optimize the medium for2,3-BD production. Plackett-Burman(PB) design was used to pick up factors that significantly influenced diol (2,3-BD and acetoin) production. The significant factors were acidified molasses (a-molasses), urea and K2HPO4. Steepest ascent experiments were employed to approach the optimal region of these three factors and the experiment of Box-Behnken design was applied to determine their optimal levels. The results of second-order polynomial model indicated it was reasonable to use the regression model to analyze the trends in the responses. Using the optimum medium the concentration of diol was40.19g/1by shaking flask culture, which increased40%.Secondly, the effects of non-sterilization of medium, non-pretreatment of molasses and the shortage of organic nitrogen source on the formation of diol were investigated. The results indicated that those three factors didn’t effect the production of diol obviously. So the batch and fed-batch fermentation experiments were performed via a non-sterile process, molasses was utilized without pretreatment and no organic nitrogen source was added into fermentation medium. In batch fermentation,45.6g/L diol was obtained after12h culture. In fed-batch fermentation, the yield of diol was99.50g/L after60h culture, in which2,3-BD was90.82g/L and acetoin was8.67g/L, and the productivity diol was1.66g/(L-h).Thirdly, the two-step salting-out extraction system (ethanol/K2HPO4and ethyl acetate/K2HPO4) was tried to separate2,3-BD and coloring matters from fermentation broth. The pink liquid product was obtained after reduced pressure distillation of up-phase solution from SOE system. GC analysis showed the crude product contained80.2%2,3-BD and9.8%acetoin. D-101macroporous resin was used to adsorb coloring matters from the bottom phase solution in the first step. The adsorption capacity was25g/100mL bottom phase solution, and the adsorption rate of coloring matters was72.02%.10mL20%ethanol was applied as eluent of1g macroporous resin to harvest the coloring matters, and the desorption rate of coloring matters was61.33%.