Novel metabolites from cereal-associated lactobacilli - novel functionalities for cereal products?

Predictions from genome sequence data of sourdough lactobacilli, novel applications of known metabolic traits such as glycansucrases, as well as the exploitation of biodiversity of lactobacilli from traditional fermentations remain an important resource for identification of novel metabolic traits of lactobacilli for use in bread production and the production of value-added food ingredients. Cornerstones of heterofermentative lactic metabolism in cereal fermentations are the rapid utilization of maltose as preferred carbon source, and the production of lactate, CO(2), and the alternative products ethanol and acetate. This review will highlight selected novel aspects of carbohydrate metabolism that are related to the production of maltose and the utilisation of lactate by lactobacilli in cereal fermentations. Several species of lactobacilli convert glycerol and lactate to 1,3 and 1,2 propanediol, respectively. Both metabolic pathways are relevant for food preservation as reuterin is an intermediate of 1,3 propanediol formation, and 1,2 propanediol is further converted to propionate. Glycansucrases, disaccharide hydrolases and disaccharide phosphorylases catalyse oligosaccharide formation from sucrose, maltose, or lactose. Lactobacilli in sourdough generally harbour several enzymes capable of oligosaccharide formation from disaccharides. Oligosaccharide formation by sourdough lactobacilli can be exploited for fermentative production of novel oligosaccharides in bread and a wide spectrum of other food applications.