ARS | Publication request: Acceptor products of alternansucrase with gentiobiose

Submitted to: Carbohydrate Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 20, 2008
Publication Date: N/A

Interpretive Summary: New carbohydrate-derived functional foods are desirable from both an economic and health standpoint. The carbohydrate known as gentiobiose can be made from corn syrup, and has some potential applications in nutrition. However, gentiobiose is bitter, limiting its usefulness in foods. We have found that the bacterial enzyme known as alternansucrase can make a variety of complex carbohydrates that are proving to be useful for low-glycemic sweeteners and other nutritional supplements and ingredients by combining sugar with other carbohydrates. The reactions and products we describe show that alternansucrase can modify gentiobiose in a manner that could be useful for making food and feed ingredients. The improved prebiotic profile, lack of bitterness, and the relatively high yields (approaching 90% in unoptimized reactions) suggest promise for the use of these oligosaccharides as food or feed ingredients. This represents a potentially new product for food ingredient manufacturers, new markets for corn and sugar growers, and healthier diets for everyone.

Technical Abstract: In the presence of suitable acceptor molecules, dextransucrase makes a homologous series of oligosaccharides in which the isomers differ by a single glucosyl unit, whereas alternansucrase synthesizes one trisaccharide, two tetrasaccharides, etc. Previously, we showed that alternansucrase only forms certain isomers of DP>4 from maltose in measurable amounts, and that these oligosaccharides belong to the oligoalternan series rather than the oligodextran series. We now demonstrate that the acceptor products from gentiobiose, also formed in good yields, follow a pattern similar to those formed from maltose. The initial product is a single trisaccharide, alpha-D-Glcp-(1'6)-beta-D-Glcp-(1'6)-D-Glc. Two tetrasaccharides were formed in approximately equal quantities: alpha-D-Glcp-(1'3)-alpha-D-Glcp-(1'6)-beta-D-Glcp-(1'6)-D-Glc and alpha-D-Glcp-(1'6)-alpha-D-Glcp-(1'6)-beta-D-Glcp-(1'6)-D-Glc. Just one pentasaccharide was isolated from the reaction mixture, alpha-D-Glcp-(1'6)-alpha-D-Glcp-(1'3)-alpha-D-Glcp-(1'6)-beta-D-Glcp-(1'6)-D-Glc. Our hypothesis that the enzyme is incapable of forming two consecutive alpha-(1'3) linkages, and does not form products with more than two consecutive alpha-(1'6) linkages, apparently applies to other acceptors as well as to maltose. The distribution of products may be kinetically determined.