GOS is conventionally manufactured from lactose, a waste product of the dairy industry, by enzymatic synthesis reactions catalysed by β-galactosidase enzymes [33]. Potentially prebiotic GOS has been synthesised using lactulose as a substrate [37]. The resulting oligosaccharides displayed similar fermentation profiles to conventional GOS using in vitro testing with faecal batch cultures. These preparations did not contain residual lactose but residual lactulose, itself a prebiotic. These preparations may prove to be more potent per gram than conventional GOS products.