Lactic Acid Bacteria | Lactobacillus spp.: General Characteristics

Abstract

Lactobacillus is the largest genus within the group of lactic acid bacteria. Based on the 16S rRNA sequences, lactobacilli are phylogenetically distributed in seven groups: Lb. buchneri (bu), Lb. casei (ca), Lb. delbrueckii (de), Lb. plantarum (pl), Lb. reuteri (re), Lb. sakei (sa), and Lb. salivarius (sl). Traditionally, the genus is split into three groups based on the carbohydrate fermentation pathways: (1) obligate homofermentative, (2) facultative heterofermentative, and (3) obligate heterofermentative lactobacilli. The two most obvious beneficial roles of lactobacilli are as starter cultures (to produce acid rapidly) and as probiotic cultures. Lactobacilli are one of the few contaminant bacteria that are able to grow in cheese after manufacture (as nonstarter lactic acid bacteria (NSLAB)). Lactobacilli as starters and as NSLAB may play different roles in the metabolism of lactose, lactate, and citrate, and in proteolysis and lipolysis, which are considered the primary events during cheese ripening. This article focuses on (1) the taxonomy of the genus Lactobacillus; (2) isolation, enumeration, and identification of Lactobacillus spp.; and (3) the principal role of Lactobacillus as starter, NSLAB, and probiotics in fermented milks and cheeses.