Selection of mutants tolerant of oxidative stress from respiratory cultures of Lactobacillus plantarum C17

Aims: Lactobacillus plantarum is a lactic acid bacterium involved in the production of many fermented foods. Recently, several studies have demonstrated that aerobic or respiratory metabolism in this species leads to improved technological and stress response properties. Methods and Results: We investigated respiratory growth, metabolite production and stress resistance of Lact. plantarum C17 during batch, fed- batch and chemostat cultivations under respiratory conditions. Sixty mutants were selected for their ability to tolerate oxidative stress using H2O2 and menadione as selective agents and further screened for their capability to growth under anaerobic, respiratory and oxidative stress conditions. Dilution rate clearly affected the physiological state of cells and, generally, slow-growing cultures had improved survival to stresses, catalase production and oxygen uptake. Most mutants were more competitive in terms of biomass production and ROS degradation compared with wild-type strain (wt) C17 and two of these (C17-m19 and C17-m58) were selected for further experiments. Conclusions: This work confirms that, in Lact. plantarum, respiration and low growth rates confer physiological and metabolic advantages compared with anaerobic cultivation. Significance and Impact of the Study: Our strategy of natural selection successfully provides a rapid and inexpensive screening for a large number of strains and represents a food-grade approach of practical relevance in the production of starter and probiotic cultures