Process for producing alternan-oligosaccharide

A process for producing alternan-oligosaccharide, comprising contacting in a stirred tank reactor sucrose with a catalytically effective amount of alternansucrase enzyme and acceptor molecules with stirring,

• wherein the alternansucrase enzyme and acceptor molecules are present in the reactor in an aqueous liquid, wherein the alternansucrase enzyme is dissolved, emulsified, or suspended in the aqueous liquid, and the sucrose is continuously or half-continuously fed to the reactor, and
• wherein the sucrose and the acceptor molecules are converted to alternan-oligosaccharide, and fructose is formed as a by-product,
• continuously or half-continuously removing at least a part of the fructose and at least a part of leucrose, formed as a by product, from the reactor by membrane filtration,
• wherein removing of at least a part of the fructose and at least a part of leucrose comprises continuously or half-continuously circulating the content of the reactor through a device comprising a membrane and contacting the content of the reactor with the membrane,
• wherein at least a portion of the fructose at least a part of the leucrose and a portion of the aqueous liquid pass the membrane, and
• wherein a remainder, comprising the alternan-oligosaccharide, is returned to the reactor,
• wherein the average degree of polymerization DPw of the alternan-oligosaccharide is greater than 14.