Review of lactose and galactose metabolism in Lactic Acid Bacteria dedicated to expert genomic annotation

Abstract

The term LAB (Lactic Acid Bacteria) relates to the metabolic capabilities of microorganisms to ferment various carbohydrates predominantly into lactic acid. LAB are involved in a large number of industrial food fermentations. Their primary contribution is in rapid acid production and acidification of foods. The ability of starter cultures to metabolize lactose and the resulting galactose is therefore a major aspect of starter selection. Genome sequencing and the use of microbial genomics are powerful tools to rapidly screen for functions of interest in the starter culture industry.The annotation of the metabolic pathway encoding genes requires thorough knowledge of the literature and a vast comprehension of the metabolic pathways and of the level of genetic variability that LAB can exhibit. In this review an overview of lactose and galactose metabolism as a basis for expert genomic annotation is presented. It includes a detailed literature overview of the mechanism of internalization, subsequent metabolization of these carbohydrates and the underlying genetics. In addition, a comparative genomic analysis of genes related to the Leloir and Tagatose-6-P pathways is described in 237 LAB and other related Gram-positive genomes with low GC content available in the MicroScope platform.This analysis delineates the extent of genetic variability that can be expected for future genomic investigation of LAB regarding lactose and galatose metabolism.