Lactobacillus brevis CD2: Fermentation Strategies and Extracellular Metabolites Characterization
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Lactobacillus brevis CD2: Fermentation Strategies and Extracellular Metabolites Characterization Alberto Alfano 1 & Filomena Perillo 1 & Alessandra Fusco 2 & Vittoria Savio 2 & Maria Michela Corsaro 3 & Giovanna Donnarumma 2 & Chiara Schiraldi 1 & Donatella Cimini 1
# Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Functional foods and nutraceuticals frequently contain viable probiotic strains that, at certain titers, are considered to be responsible of beneficial effects on health. Recently, it was observed that secreted metabolites might play a key role in this respect, especially in immunomodulation. Exopolysaccharides produced by probiotics, for example, are used in the food, pharmaceutical, and biomedical fields, due to their unique properties. Lactobacillus brevis CD2 demonstrated the ability to inhibit oral pathogens causing mucositis and periodontal inflammation and to reduce Helycobacter pylori infections. Due to the lack of literature, for this strain, on the development of fermentation processes that can increase the titer of viable cells and associated metabolites to industrially attractive levels, different batch and fed-batch strategies were investigated in the present study. In particular, aeration was shown to improve the growth rate and the yields of lactic acid and biomass in batch cultures. The use of an exponential feeding profile in fed-batch experiments allowed to produce 9.3 ± 0.45 × 109 CFU/mL in 42 h of growth, corresponding to a 20fold increase of viable cells compared with that obtained in aerated batch processes; moreover, also increased titers of exopolysaccharides and lactic acid (260 and 150%, respectively) were observed. A purification process based on ultrafiltration, charcoal treatment, and solvent precipitation was applied to partially purify secreted metabolites and separate them into two molecular weight fractions (above and below 10 kDa). Both fractions inhibited growth of the known gut pathogen, Salmonella typhimurium, demonstrating that lactic acid plays a major role in pathogen growth inhibition, which is however further enhanced by the presence of Lact. brevis CD2 exopolysaccharides. Finally, the EPS produced from Lact. brevis CD2 was characterized by NMR for the first time up to date. Keywords Lactobacillusbrevis . Probiotic . Exopolysaccharides . Fed-batch processes . Ultrafiltration membrane . Antimicrobial activity
Introduction Chiara Schiraldi and Donatella Cimini contributed equally to this work. * Chiara Schiraldi [email protected] * Donatella Cimini [email protected] 1
Department of Experimental Medicine, Section of Biotechnology Medical Histology and Molecular Biology, University of Campania “Luigi Vanvitelli”, via L. De Crecchio n 7, 80138 Naples, Italy
2
Department of Experimental Medicine, Section of Microbiology and Clinical Microbiology, Università della Campania “Luigi Vanvitelli”, via L. De Crecchio n 7, 80138 Naples, Italy
3
Department of Chemic1al Science, University Federico II, Complesso Uni
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