Production, Recovery and Characterization of an Enterocin with Anti-Listerial Activity Produced by Enterococcus hirae OS1

Lactic acid bacteria, used in food processing for a long time, can produce various metabolites during their growth, including bacteriocins. These antimicrobials, used as natural bio-preservatives, enhance the food safety. The objective of this study was to assess lactic acid bacteria bacteriocins with anti-listerial activity and optimize their production and recovery process.

Isolate was identified using conventional assays (morphological and biochemical characteristics) and 16S rRNA gene sequencing. Lactic acid bacteria bacteriocins were characterized based on their physicochemical properties (nature, pH stability and thermo-resistance). The production process was based on optimization of media components (growth media and addition of glucose, nitrogen source and tween 20) and culture conditions (temperature, pH, agitation and inoculum size). Furthermore, optimization of the recovery process was studied using ion exchange chromatography on amberlite IRC-50 (effects of resin size and NaCl eluent concentration).Results and

Enterococcus hirae OS1 was isolated from Moroccan raw cow milk as bacteriocinogenic strain. After optimization of the bacteriocin production process, results showed that the key parameters for increasing of production included temperature of 30°C, pH of 6.5 and inoculum size of 5%. Production with whey-based and economic food-grade substrate allowed high production of enterocin OS1 (1,600 AU ml-1) (P<0.001). Simultaneous addition of glucose (1%) and Tween 20 (1%) increased enterocin titer significantly (5,866 AU ml-1) (P<0.01). Recovery efficiency increased with use of 70% amberlite IRC-50 resin and elution with 2M NaCl. Indeed, recovery of 75.4% of bacteriocin was achieved in comparison to 15.7% of bacteriocin without optimization. This promises achieving high quantities of enterocin at low costs.Conflict of interest: The authors declare no conflict of interest.