18- The reducing power of LAB in fermentation and biomass production

International audienceLactic acid bacteria (LAB) are found in highly variable environments. Among the various parameters that characterize these environments, the redox state has already been indirectly addressed in studies on the impact of oxidative stress. Nevertheless, it is possible to offer a broader vision about the capacity of LAB to extracellular electron transfer. The metabolism of LAB, which are chemotrophic organisms, involves a series of reactions of dehydrogenation (oxidation) and hydrogenation (reduction). This metabolism obeys the principle of conservation of energy and matter, and therefore it requires the availability of a final electron acceptor; in LAB a carbon intermediate will be reduced. The vision of perfect coupling, which is theoretically consistent, must however be qualified depending on environmental conditions, and in particular the redox state of the extracellular medium. This process is not without influence on metabolism fluxes, growth, and physicochemical environment in which the microorganism bathes. This multifactorial interaction system is a difficulty in studying extracellular electron transfer by lactic acid x, but also a subject of interest to understand better the redox activity of these microorganisms. The purpose of this chapter is to present how LAB manage their reducing power according to the redox environment