共固定化细胞协同糖化发酵纤维素原料产乳酸

为提高纤维素原料对乳酸的转化率，将富含纤维二糖酶的黑曲霉（Aspergillus niger ZU-07）孢子和德氏乳酸杆菌（Lactobacillus delbrium）细胞共固定在海藻酸钙凝胶珠中，将共固定化细胞体系与纤维素原料的酶水解相耦联，组建成新型串联式生物反应器。研究表明，共固定化细胞中的纤维二糖酶可将纤维素水解液中的纤维二糖迅速转化成葡萄糖，而葡萄糖又能被乳酸杆菌迅速转化成乳酸，从而解除了纤维二糖及葡萄糖对纤维素酶的反馈抑制作用。当酶解罐和共固定化细胞反应柱的温度分别控制在50 ℃和48 ℃，共固定化细胞反应柱的装填量为40％时，串联式生物反应器中生成的乳酸浓度和纤维素对乳酸的转化率分别达到55.7 g·L^-1和91.5%。采用分批添料工艺，乳酸终浓度和反应器生产效率分别提高到106.7 g·L^-1和1.270 g·L^-1·h^-1，而单位底物的纤维素酶用量降低了25%。

Synergetic saccharification and lactic acid fermentation by coimmobilized cells using cellulosic materials

In order to improve the conversion efficiency of lactic acid from cellulose, the spores containing cellobiase with high activity from Aspergillus niger ZU-07 and the cells of Lactobacillus delbrium were embedded together into calcium alginate gel beads, and the formed coimmobilized cell system was coupled with the enzymatic hydrolysis of cellulosic material to set up a novel coupling bioreactor.The research results showed that the cellobiose in the hydrolysate was converted to glucose rapidly by the cellobiase in the coimmobilized cells, and the glucose was utilized rapidly by L.delbrium to produce lactic acid.Therefore, the feedback inhibition on cellulase caused by cellobiose and glucose was eliminated effectively.When the hydrolysis temperature and fermentation temperature were controlled at 50℃ and 48℃, respectively, and the volume ratio of the coimmobilized cells to the column reactor was 40%, the produced lactic acid concentration and the yield of lactic acid from cellulose were 55.7 g·L^-1 and 91.5%, respectively.Under the fed-batch process, the final concentration of lactic acid and productivity increased to 106.7 g·L^-1 and 1.270 g·L^-1·h^-1, respectively, while the dosage of cellulase per gram substrate reduced by 25%.