Mathematical modeling characterization of mannitol production by three heterofermentative lactic acid bacteria

Abstract

This study developed a non-structured mathematical model for describing the effect of carbon sources and culture pH on the mannitol production by three heterofermentative lactic acid bacteria (LAB), including Leuconostoc mesenteroides NRRL B-512F and NRRL B-523 as well as Lactobacillus fermentum NRRL B-1840. Mannitol production was studied in batch culture using four culture media containing the same carbon sources (glucose and fructose, but different glucose concentration) and different nitrogen sources (yeast extract, peptone, and meat extract) with diverse concentrations. The results obtained in the early stages of the estimation algorithm suggested that cell growth on fructose could be neglected. Therefore, the initially proposed mathematical model was redefined and subsequently confirmed. The strains NRRL B-512 F, NRRL B-523, and NRRL B-1840 reached the highest volumetric productivities (2.26 ± 0.05, 2.30 ± 0.05, and 1.95 ± 0.05 g L−1h−1; respectively) and mannitol yields (0.95 ± 0.01, 0.98 ± 0.04, and 1.00 ± 0.01 mol mannitol mol initial fructose−1; respectively) in medium A. The mannitol and biomass yields suggested a higher carbon concentration favored mannitol production and growth, but a lower nitrogen concentration directly impacted both yields. Mannitol production was associated with cell growth according to the estimated parameters.