与膜耦合的细胞固定化串联发酵制乙醇的研究

Ethanol Fermentation Process in Series with Gel Immobilized Cells and Integrated with Membrane

利用植物纤维作为廉价的糖源生产燃料乙醇是解决世界能源危机的最有效途径。今研究采用海藻酸钙固定普通酿酒酵母细胞和嗜鞣管囊酵母细胞于两个串联的发酵罐内,连续发酵葡萄糖和木糖组成的糖液并与膜耦合来制取酒精。通过硅橡胶膜(PDMS)的渗透蒸发过程,将产品乙醇从发酵液中移出,减少了产物乙醇对发酵的抑制作用。实验结果表明,这套采用海藻酸钙固定酵母细胞进行连续发酵并与膜耦合的生物反应器系统,在稀释率为0.321h-1下稳定运行,剩余葡萄糖和木糖浓度分别为0.134、4.921g·L-1,乙醇得率为0.457g(乙醇)·g-1(糖),是理论得率的92.64%,生产能力达到10.996g·L-1·h-1。与其它发酵方式相比较,用海藻酸钙来固定细胞并与膜耦合的发酵过程可增大酵母细胞浓度,明显降低乙醇对酵母的抑制作用,并提高糖的转化率。

The production of fuel alcohol by using the inexpensive and renewable sugar of biomass as raw material is one of the most effective methods to solve energy crisis in the world. The continuous ethanol fermentation with mixed substrates consisting of glucose and xylose was conducted in two fixed columns connected in series and packed with calcium alginate beads encapsulating immobilized yeast cells of Saccharomvces cerevisiae and Pachysolen tannophilus, respectively. The porous PDMS membranes were used to separate the volatile compounds from the fermentation liquid by pervaporation. Since these volatile compounds inhibit the viability of the yeast cells, the elimination of these compounds increases the productivity and yield of ethanol from sugar fermentation. When the fermentation system was operated at the dilution rate of 0.321 h^-1, the effluent containing glucose of 0.134 g·L^-1 and xylose of 4.92 g·L^-1 is steadily produced; the yield of ethanol is 0.457 g（ethanol）·g^-1（sugar）, it is equivalent to 92.64% of its theoretical value （0.4933 g（ethanol）·g^1（sugar））, and the ethanol productivity reaches 10.996 g·L^-1·h^-1. From above results, it can be concluded that the novel fermentation process of using immobilized yeast cells matching with PDMS membrane could increase the concentration of yeast cells and the conversion rate of sugar by decreasing the fermentation inhibition caused by the ethanol product.