Effect of inulin on growth and bacteriocin production by Lactobacillus plantarum in stationary and shaken cultures

Summary The prebiotic effect of inulin added to MRS medium on growth and bacteriocin production by L. plantarum ST16 Pa was investigated in stationary cultures in anaerobic jars with medium containing 0.025% sodium thioglycolate or in flasks shaken at 100 rpm. In the presence of 1% inulin in anaerobic stationary cultures, this strain produced lactic acid at a level that was 36.5% higher than in the absence of the polysaccharide. In shaken cultures without inulin, cell count was 54% higher than in the stationary ones. Under stationary conditions in anaerobic jars, the addition of inulin increased the maximum specific growth rate from 0.37 to 0.49 h−1 and reduced the generation time from 1.85 h to 1.40 h. Consequently, the exponential phase was shortened from 12 to 9 h when the cells were grown in stationary cultures with the oxygen scavenger. Despite this effect of inulin on growth rate, stationary cultures without inulin displayed higher antimicrobial activity against Listeria monocytogenes L104 (3200 AU/mL) than cultures with inulin (1600 AU/mL); therefore, inulin behaved as a compound able to accelerate growth rather than to stimulate bacteriocin production. The results presented in this study are very promising, as L. monocytogenes is a well-known foodborne pathogenic microorganism. Moreover, L. plantarum ST16 Pa has proven to be a potential producer of a natural food preservative at an industrial level.