共固定化细胞发酵纤维素水解液产乳酸的研究

Lactic acid production by coimmobilized cells using cellulosic hydrolysate

针对在纤维素酶法水解过程中,由于纤维素酶系中纤维二糖酶的不足造成纤维二糖的累积,而酶解产物纤维二糖和葡萄糖的累积又会对纤维素酶的催化反应产生明显的反馈抑制作用等问题,将富含纤维二糖酶的黑曲霉(Aspergillus nigerZU-07)孢子和德氏乳酸杆菌(Lactobacillus delbrium)一起包埋固定在海藻酸钙凝胶珠中,利用共固定化细胞转化纤维素水解液生产乳酸.研究结果表明,共固定化细胞中的纤维二糖酶可以将纤维素水解液中存在的纤维二糖迅速水解成葡萄糖,而固定化乳酸杆菌又能将葡萄糖迅速转化成乳酸.共固定化细胞的最适作用温度为48℃,在纤维素水解液(总还原糖质量浓度为49.40 g/L)中协同反应48 h,生成的乳酸质量浓度为41.71g/L.在反复分批协同反应工艺中,共固定化细胞性能稳定,可重复利用12批以上.

During the process of enzymatic hydrolysis of cellulose, the conversion of cellobiose to glucose is restricted due to the deficiency of cellobiase in the cellulase system. The accumulation of the hydrolysis product, cellobiose and glucose, caused severe feedback inhibition on the cellulase catalytic reaction. An effective solution was presented to resolve the problems. The spores containing cellobiase from Asperillus niger ZU-07 and the cells of Lactobacillus delbrium were entrapped together into calcium alginate gels to form a coimmobilized cell system, which was used to convert cellulosic hydrolysate to lactic acid. Analysis indicated that the cellobiose in the cellulosic hydrolysate could be hydrolyzed to glucose quickly by the cellobiase in the coimmobilized cells, and that the glucose could be converted to lactic acid effectively by the immobilized L. delbrueckii cells. The optimum reaction temperature of the coimmobilized cells was 48 ℃, and the produced lactic acid concentration by the coimmobilized cells reached 41.71 g/L after 48 h synergetic reaction in the cellulosic hydrolysate containing 49.40 g/L reducing sugar. The coimmobilized cells were quite stable and efficient, and could be repeatedly used for at least 12 batches.