**Abstract**

Lactobacilli are widespread microorganisms and are broadly employed in a variety of applications. It is one of the LAB genera that has been designated as Generally Regarded as Safe (GRAS) and many of its member species are included in the Qualified Presumption of Safety (QPS) list. *Lactobacillus* is commonly utilized as a starter culture in many fermented food products, probiotics, and has long been used as natural bio-preservatives to increase shelf life and improve food quality and safety. Aside from the many benefits, it delivers in the food sector, the use of *lactobacillus* strains in the clinical setting as a prophylactic and/or treatment for a variety of diseases has gained increasing attention. These uses of *lactobacillus* are all made possible through the diverse bioactive molecules it generates. *Lactobacillus* exerts its positive health and nutritional effects through a variety of mechanisms, including inhibition of pathogen adhesion or colonization, metabolic activity through the synthesis of metabolites and enzymes, and immune system modulation among others. The ability of many *lactobacillus* strains to mediate the bio-conversion of certain metabolites has also been shown in numerous studies. This chapter describes the recent findings on the impact of the diverse bioactive molecules produced by different *lactobacillus* strains, their mode of action, and their application in different industries.

**Keywords:** lactic acid bacteria, GRAS, *lactobacillus*, bioactive compounds, probiotics
