Microbial Production And Downstream Processing Of 2,3-Butanediol

For the bioconversion of sugar to 2,3-butanediol,some technical problems in fermentation and separation process were explored from the following aspects.Firstly,the productivity of 2,3-butanediol with different substrates was investigated in this paper.Glucose was proved to be the best substrate and the effect of fermentation conditions on product concentration was then studied.The optimum initial substrate concentration for cultivation of inoculum was 8%.The optimum conditions for batch fermentation were 0.04vvm of air flow,5.8 of pH value.The fed-batch fermentation showed that the productivity of Klebsiella pneumoniae CICC 10011 was better than K.pneumoniae CGMCC 1206.The maximum concentration of 2,3-butanediol and acetoin was 103.38 g/L (90.98 g/L of 2,3-butanediol),and the yield reached 82.2%of its theoretical value.The fermentation conditions for K.pneumoniae.CICC 10011 needed to be further optimized.Secondly,the floeculation pretreatment of 2,3-butanediol fermentation broth with chitosan and the reuse of K.pneumoniae cells in floes were investigated.The flocculation effect was evaluated by cell and protein removal rates,and the optimum flocculation conditions for Klebsiella pneumoniae ceils in 2,3-butanediol broth were as follows:0.375 g/L of chitoson with 40 kDa molecular weight,0.250 g/L of sodium alginate,5.0 of pH,30 min of stirring time and 1 h of settling time.The OD of broth was 0.075,the flocculation ratio of cells reached 98%,the retained ratio of 2,3-butanediol reached 99%,and the supernatant in the broth was clear.After flocculation the cells of Klebsiella pneumoniae in the floes grew well(OD 13.5)and were used repeatedly.Furthermore,the effect of concentration multiple and salt concentration on the salting out of 2,3-butanediol in flocculated broth was studied.The experimental results showed that the partition coefficients and yields of 2,3-butanediol and acetoin reached 11.9,9.10,83.48%, 79.37%,respectively,when the concentration multiple was 70%(v/v),the concentration of K₂HPO₄ added was 45%(w/w),and the concentration of 2,3-butanediol in top phase reached 420 g/L.Finally,the effect of different aqueous two-phase extraction systems on the extraction of 2,3-butanediol was investigated and the ethanol/ammonium sulphate aqueous two-phase system was chosen.The optimum phase composition for the extraction of 2,3-butanediol by ethanol/ammonium sulphate system were 20%(w/w)of ammonium sulphate,27%(w/w)of ethanol for flocculated broths.The partition coefficient and yield of 2,3-butanediol were 7.4 and 90.2%,respectively.The process is simple,easy to be enlarged,and of good potential for application.