Aminoacids requirement and metabolism by lactic acid bacteria

Abstract

Lactic acid bacteria (LAB) have numerous nutritional requirements for growth, especially nitrogen sources. The amino acid requirements appear to be strain dependent in Oenococcus oeni strains isolated from wines. By contrast in the most of Lactobacillus plantarum strains from oranges needed six common amino acids for growth in synthetic medium.Similar results were obtained for Lactococcus lactis since the majority of strains needed the five same essential amino acids for growth. The amino acid auxotrophies are due to minor genetic lesions that, in most cases, are reparable by single-step mutations. Several distinct amino acid transport systems allow lactic acid bacteria to utilize free amino acids as nitrogen sources. The general assumption is that biomass synthesis in LAB is predominantly from building blocks present in the culture medium. The dissociation between catabolism of the energetic substrates (glucose, organic acids) and carbon assimilation from organic nitrogen sources (amino acids) may be less complete in deficient nutritional conditions, with some exchange of carbon flux between the different types of carbon substrates. The results of organic acids addition individually or in combination to the media deficient in one amino acid on the growth of the lactic acid bacteria, suggest that the essential amino acids can be synthesized from intermediaries metabolic derived from components of the medium such as L-malic and citric acids. Amino acids catabolism could have an important role in the ability to obtain energy in nutrient-limited environments; however, the catabolic pathway for many amino acids remains partially characterized in LAB. Arginine utilization in some LAB when is degraded to citrulline, ornithine and ammonium, via ADI pathway, produces additional energy.ed six common amino acids for growth in synthetic medium.Similar results were obtained for Lactococcus lactis since the majority of strains needed the five same essential amino acids for growth. The amino acid auxotrophies are due to minor genetic lesions that, in most cases, are reparable by single-step mutations. Several distinct amino acid transport systems allow lactic acid bacteria to utilize free amino acids as nitrogen sources. The general assumption is that biomass synthesis in LAB is predominantly from building blocks present in the culture medium. The dissociation between catabolism of the energetic substrates (glucose, organic acids) and carbon assimilation from organic nitrogen sources (amino acids) may be less complete in deficient nutritional conditions, with some exchange of carbon flux between the different types of carbon substrates. The results of organic acids addition individually or in combination to the media deficient in one amino acid on the growth of the lactic acid bacteria, suggest that the essential amino acids can be synthesized from intermediaries metabolic derived from components of the medium such as L-malic and citric acids. Amino acids catabolism could have an important role in the ability to obtain energy in nutrient-limited environments; however, the catabolic pathway for many amino acids remains partially characterized in LAB. Arginine utilization in some LAB when is degraded to citrulline, ornithine and ammonium, via ADI pathway, produces additional energy.