Optimization and some characteristics of bacteriocin produced by Enterococcus sp. CM9 collected from Mauritanian Camel milk

Abstract

The use of bacteriocin as a bioconservation is very promising in the agri-food industry to substitute the chemical preservatives. The production of bacteriocin by lactic acid bacteria (LAB) depending on various conditions, the purpose of the present work was to assess the effect of some ingredients of medium on the bacteriocin production. Twenty-four strains of LAB of the genera Leuconostoc, Lactobacillus, and Enterococcus, isolated from camel milk, were tested for antibacterial activity and bacteriocin production. Among these strains, three isolates showed bacteriocinogenic activity, two Enterococcus strains (bacteriocin CM9, bacteriocin CM18), and one Leuconostoc strain (bacteriocin CHBK310). The bacteriocin produced by Enterococcus sp CM9 was subject of optimisation study. The modified MRS with nitrogen sources in media containing tryptone, meat extract and yeast extract and with potassium sources in media containing 2% of K2HPO4 allowed higher activity with inhibition zone of 10 mm and this production remained stable at incubation temperatures from 25 to 40°C with an inhibition zone which reached 12 mm at 25°C. The diffusion of this bacteriocin in the neutrality condition, allowed a better evaluation of its inhibitory effect. The activity of the bacteriocin was not affected, neither by acidic or basic pH nor by heat treatments, its activity remaining stable even after 2 weeks at -20 and 4°C. The bacteriocin CM9  belonged to class II, had a molecular weight of 7.6 kDa. These results indicated that the growth and diffusion conditions have a role in the bacteriocin production and its activity.