Mannitol Production From Inulin By Whole Cell Catalyst With Inulinase

Mannitol is a natural sugar alcohol, which has been widely used in clinical practice, food and chemical industries. The traditional methods have the problems of high energy consumption and high cost of production. Among them, mannitol production by whole cell catalyst was considered to be apromising method. However, the high cost of fructose substrate is the bottleneck that restricts the realization of industrialization. As an inulin-rich energy plant, Jerusalem artichoke can growth in the infertile soil. After hydrolysis by inulinase, we can get chip inulin from Jerusalem artichoke. Therefore, it has important significance to transform Jerusalem artichoke-derived inulin to mannitol through biotransformation method.In the present study, a whole-well biotransformation system for mannitol production was established by using molecular biology method. The mannitol dehydrogenase(mdh) derived from Leuconostoc mesenteroides, the formate dehydrogenase gene(fdh) derived from Mycobacterium vaccae and the glucese facilitator protein(glf)derived from Zymomonas mobilis were co-expressed in BL21(DE3) as Strain I. The optimum p H and temperature for mannitol production was 6.5 and 30℃, respectively. The yield of mannitol could reach 0.91 g/g. In order to construct whole-cell catalyst Strain II, the expression vector of inulinase was constructed and then transferred into the whole-cell catalyst Strain I to express. By enzyme activity assay and SDS-PAGE analysis, we found that the overexpression of inulinase greatly reduced the expression and activity of mannitol dehydrogenase and formate dehydrogenase. Therefore, the synthesis of mannitol cannot complete in Strain II. In order to achieve the biotransformation from inulin to mannitol, the inulin from Jerusalem artichoke was firstly utilized as substrate for mannitol production by whole catalyst strain I with inulinase in this study. A yield of 0.93 g/g inulin was reached. This study represented that the inulin from Jerusalem artichoke could be a cheap material for mannitol production by the whole catalyst.