L-Glutamic acid production by lactic acid bacteria from Brazilian fermented foods: screening, optimization, and probiotic-related properties of Limosilactobacillus fermentum CCMA 0205.

L-Glutamic acid (L-Glu) is an amino acid of considerable industrial importance owing to its widespread application as a flavor enhancer and its increasing use in food biotechnology. The identification of novel microbial producers and the optimization of fermentation processes remain essential to improve sustainable L-Glu production. In this study, 142 lactic acid bacteria (LAB) isolated from fermented foods were screened for their ability to produce L-Glu. Seventeen high-producing strains were selected for further characterization, and intracellular and extracellular L-Glu production was quantified by HPLC. Among the evaluated isolates, Limosilactobacillus fermentum CCMA 0205, isolated from the traditional Brazilian indigenous fermented beverage Yakupa, exhibited the highest extracellular L-Glu production and favorable in vitro probiotic-related properties, including high cell surface hydrophobicity (> 98%) and strong coaggregation with enteropathogenic bacteria (up to 65.71% with E. coli and 65.39% with S. Enteritidis). Fermentation conditions were optimized using a Central Composite Rotational Design (CCRD). For extracellular L-Glu production, temperature and incubation time were the main factors, whereas pH showed no significant effect. For intracellular L-Glu accumulation, only the quadratic terms were significant, indicating a nonlinear response with a well-defined optimum within the evaluated design space. Numerical optimization within the evaluated design space identified distinct model-predicted optima for extracellular and intracellular L-Glu production: 3.86 mM at pH 5.5, 30 °C, and 48 h for extracellular production, and 4.13 mM at pH 4.69, 35.3 °C, and 72.7 h for intracellular accumulation. These predictions require experimental validation. Overall, this study identifies L. fermentum CCMA 0205 as a promising L-Glu-producing LAB strain and highlights traditional indigenous fermented beverages as valuable sources of microorganisms with potential applications in food biotechnology.