利用纤维原料在串联式生物反应器中协同酶解发酵乳酸

采用廉价的纤维素原料代替粮食发酵生产乳酸,具有重要的社会意义和经济价值。在串联式生物反应器中,将纤维原料酶水解与固定化乳酸杆菌发酵相耦联,纤维素的酶解产物葡萄糖被有效转化成乳酸,纤维素对乳酸的转化率和乳酸产率分别为70.3%和0.713g?(L?h)?1。在酶解体系中添加纤维二糖酶可以提高酶解得率。将酶解罐、固定化纤二糖酶柱和固定化细胞柱相串联,可有效消除纤维二糖积累所造成的反馈抑制作用,纤维素对乳酸的转化率和乳酸产率分别提高到90.6%和0.986g?(L?h)?1。串联式生物反应器性能稳定,在重复分批发酵工艺中,连续10批纤维素对乳酸的转化率平均为89.6%。采用分批添料工艺,纤维底物的终浓度可增加到200g?L?1,发酵终点的乳酸浓度达105.2g?L?1,乳酸产率为1.315g?(L?h)?1。对等量底物而言,反应时间明显缩短,同时纤维素酶的利用率也得到了有效提高。

Simultaneously Saccharification and Lactic Acid Fermentation for Using Cellulosic Material as Raw Material in a Coupling Bioreactor

The enzymatic saccharification of cellulose and the fermentation of lactic acid were carried out simultaneously in a coupling bioreactor. The glucose from cellulose hydrolysis could be converted to lactic acid effectively by the immobilized Lactobacillus delbrueckii cells, and the yield and productivity of lactic acid were 70.3% and 0.713 g?(L?h)?1, respectively. The hydrolysis process of cellulose could be enhanced by adding cellobiase to the cellulase system of Trichoderma reesei. When an immobilized cellobiase column was joined into the coupling bioreactor, the accumulation of cellobiose disappeares and its feed back inhibition to the cellulase reaction is completely eliminated. The yield and productivity of lactic acid may be improved to 90.6% and 0.986 g?(L?h)?1, respectively. The bioreactor is quite stable, and the average lactic acid yield of repeated 10 batches is 89.6%. Under fed-batch process the final concentration of cellulosic substrate increases to 200 g?L?1, and the lactic acid concentration and productivity reach 105.2 g?L?1 and 1.315 g?(L?h)?1, respectively. The research results are helpful to advance the bioconversion of renewable resource.