Metabolic profiling and stress response of anaerobic and respiratory cultures of Lactobacillus plantarum C17 grown in a chemically defined medium

We investigated the effect of anaerobic (AN) and respiratory conditions (RS; oxygen, hemin and menaquinone) on the growth, enzymatic activities (POX, NOX, NPR), metabolic profile (1H-NMR spectroscopy), and response to oxidative (catalase, tolerance of H2O2) and heat stresses of Lactobacillus plantarum C17 (wild-type) and its natural oxidative stress-tolerant mutant C17-m58, using chemostat cultivation in a modified chemically defined medium (mCDM). Respiratory growth impaired biomass production and tolerance of heat stress in mCDM compared with cultivation in the complex Weissella medium broth (WMB). POX activity, oxygen consumption, and H2O2 tolerance were higher in respiratory cells and in C17-m58. Significant amounts of formate and acetate were found in AN cultures of wild-type and mutant strains, confirming the activation of an anaerobic pyruvate formate lyase–acetate kinase (PFL-ACK) pathway in L. plantarum. The presence of succinate supports the presence of an incomplete TCA cycle in this species. High concentrations of pyruvate were measured in RS supernatants, indicating reduced functionality of POX in vivo (35 °C) and the need to clarify the regulation and control of oxygen metabolism. Adipate was found in respiratory samples, likely because of lipid peroxidation, and its production by respiring lactic acid bacteria may be investigated and exploited for biotechnological uses.