Production of Lactulose from Lactose in Subcritical Aqueous Ethanol

Abstract

AbstractProduction of lactulose from lactose was performed in subcritical aqueous ethanol. The effects of ethanol concentration (0–60% (w/w)) and temperature (160–220C) on the isomerization of lactose were studied. The maximum yield of lactulose (34%) was obtained from the treatment of lactose in 60% (w/w) aqueous ethanol at 200C. The isomerization and hydrolytic reactions of lactose were promoted and suppressed, respectively, by increasing ethanol concentration. The use of higher concentrations of ethanol was restricted due to the low solubility of lactose. Additionally, different feed concentrations (0.5–2.5% w/w) were studied. The maximum lactulose productivity of 63 kg/(h m3‐reactor) was obtained from the treatment employing a 2.5% (w/w) feed concentration, indicating that subcritical aqueous ethanol is promising for the production of lactulose.Practical ApplicationsLactulose is a synthetic disaccharide comprising galactose and fructose. It has been broadly used as prebiotic food additives and drugs against constipation, hepatic encephalopathy and anti‐endotoxin effects. Industrial production of lactulose is currently performed by alkaline isomerization of lactose which has several drawbacks such as high level of by‐products and high cost of downstream processing. Subcritical aqueous ethanol is a novel technique for lactulose production. It can be used to overcome the disadvantages of chemical methods. The simplicity, high productivity, cost‐effectiveness and environmental benignity make this technique applicable to large‐scale lactulose production.