In conclusion, this overall process, fulfilling the principles of green chemistry and being applicable to produce organic prebiotic, is an elegant solution, from an economical, environmental, nutri-functional and techno-functional point of view. Indeed, it can lead to original prebiotic preparations, with yields close to 100%, by avoiding product loss, as the digestible saccharides portion is converted to gluconic acid. Furthermore, gluconic acid can also provide many functional properties to the prebiotic preparations for their incorporation in food products. Dorothée Goffin 1,2, Christophe Blecker 2, Yves Malmendier 3, Michel Paquot 1 1 Department of Industrial Biological Chemistry, University of Liège, Gembloux Agro-Bio Tech, Passage des Déportés, 2, B-5030, Gembloux, Belgium 2 Department of Food Technology, University of Liège, Gembloux Agro-Bio Tech, Passage des Déportés, 2, B-5030, Gembloux, Belgium 3 Meurens Natural S.A., Rue des martyrs, 21, B-4650, Herve, Belgium A method for the production of prebiotic preparations containing isomaltooligosaccharides and gluconic acid. Isomaltooligosaccharides (IMOs) are non-digestible oligosaccharides, considered as prebiotics and therefore aim to selectively feed probiotics indigenous to the human colon. They consist of glucose monomers linked by at least one α-1-6, or in a lower proportion α -1-3 (nigerose family) or α -1-2 (kojibiose family) glucosidic linkages. In our case they are produced enzymatically using an Aspergillus niger transglucosidase (EC ) starting from either corn, tapioca, or rice hydrolyzed starch and result in very complex mixture. However, the reaction only permits to reach yields between % in IMOs. Impurities are composed of residual maltooligosaccharides (glucose with exclusively α -1-4 linkages) from the starting vegetal material and glucose released during the transglucosylation step. These digestible saccharides are deleterious for the prebiotic preparation and must therefore be eliminated from the medium. In our original method, residual maltooligosaccharides are thus specifically hydrolyzed by a thermostable α-glucosidase (EC ) in order to produce glucose as the only unwanted specie. This glucose can then be converted to gluconic acid and/or its salts using a glucose-oxidase (EC ) in combination with a catalase. Gluconic acid (C 6 H 12 O 7 ) is a saccharide derivative with various health benefits and has been recognized as a prebiotic compound. Gluconic acid can then be left in the medium in order to obtain an original product enjoying new prebiotic potential properties or separated using an anion-exchange resins (Dowex AcO-) as gluconic acid is charged compared to glucose. Transgluco sylation α-(1-2) α -(1-6) α-(1-4) α-(1-3) Target oligosaccharide Substrates = glucooligosaccharides with preferably α-(1-4) at the reducing end * Released maltooligosaccharides or glc * Tranglucosylation with Aspergillus niger transglucosidase starting from either corn, tapioca or rice hydrolyzed starch Substrate : Maltose, glucose, α-(1-4) and rarely α- (1-6) glucooligosaccharides Transglucosylation Gluconic acid method Residual maltose and maltooligosaccharides Selective enzymatic hydrolysis (α-glucosidase) Released glucose and maltooligosaccharides Glucose 1 Selective enzymatic glucose-oxydation (glucose-oxydase + catalase) Glucose 2 Gluconic acid New original product containing two prebiotic compounds : IMO and gluconic acid without loss of the digestible fraction with new nutri-functional and techno-functional properties Glucose- oxydation Process for the production of a composition, the composition and the use there-of as food additive’. Goffin D., Paquot M., Blecker C., Robert C. European patent, n°PCT/EP2010/ published on 22 july 2010 under number 2010/ IMO (50-85%) α-(1-6) α-(1-2) α-(1-3) Residual maltose and maltooligosaccharides Released glucose and maltooligosaccharides digestible saccharides = deleterious for the prebiotic preparation  must be eliminated from the medium. mixte  Low column capacity  Need for recycling  Cheap and popular  Doesn’t get rid of all digestibles  Loss of part of IMO  Use of living organisms  Expensive equipment  Low DP IMO loss  Low efficiency Classical purification methods Adsorption Process Selective fermentation Membrane separation Productivity Problem : loss of the digestible fraction