Dextransucrase production by Leuconostoc mesenteroides

Microbes produce an array of exopolysaccharides which form a biofilm around the cells facilitating attachment of the cells to surface, colonization and providing protection against unfavourable conditions. Xanthan, alginate, pullulan, dextran, alternan, levan and inulan are some of the examples. Dextran, alternan, levan and inulan are produced by a group of bacteria belonging to Lactobacillus family. These compounds are derived from sucrose derivatives like glucose and fructose, where glucose gets polymerized to dextran while fructose is used as energy source by the exocellular or cell membrane bound enzymes. The gram-positive Leuconostocmesenteroides NRRL B-512F, which synthesizes the extracellular homopolysaccharide dextran, is an extensively used organism for the industrial production of dextransucrase. Dextran gained importance owing to its applications in the pharmaceutical, food, photo film manufacturing and fine chemical industries. The maintenance and production media composition and culture conditions have been optimized for the large scale production of dextransucrase. Low cost carbon and nitrogen sources like sugar-beet molasses, corn steep liquor and wheat bran extract have been successfully employed for large-scale preparation of dextransucrase by fermentation process. Mutants were developed and fermentation techniques like batch, semi-continuous fermentation by free and immobilized cells were tried to economize commercial production of dextransucrase. Present communication reviews the available information on cultural conditions and nutritional requirements for the production of dextansucrase by Leuconostoc sp.