Effect of sausage ingredients and additives on the production of enterocinA and B by Enterococcus faecium CTC492. Optimization of in vitro production and anti-listerial effect in dry fermented sausages

Enterocin A and B in Enterococcus faecium CTC492 were co-induced by the dif ferent factors assayed in this study (r = 0.93) and followed primary metabo lic kinetics. Enterocin production was significantly inhibited by sausage i ngredients and additives, with the exception of nitrate. The addition of so dium chloride and pepper decreased production 16-fold. The temperature and pH influenced enterocin production, with optima between 25 and 35 degrees C , and from 6.0 to 7.5 of initial pH. The maximum activity was achieved, und er favourable growth conditions, with MRS supplemented with sucrose (2%) pl us glucose (0.25%) and Tween-80 (1%). MRS concentration, NaCl plus pepper a ddition, absence of Tween-80 in the growth medium, incubation at 45 degrees C and an initial pH under 5.5 were detrimental to bacteriocin production. Stress conditions did not favour enterocin production. Desadsorption was Tw een-dependent. Enterocin A activity in the crude extracts stored at -80 deg rees C was better preserved than enterocin B (when tested against their spe cific indicator strain), but anti-listerial activity remained intact. Appli ed as anti-listerial additives in dry fermented sausages, enterocins signif icantly diminished Listeria counts by 1.13 log (P < 0.001), while Enterococ cus faecium CTC492 added as starter culture did not significantly reduce Li steria counts (P > 0.1) compared with the standard starter culture (Bac(-)) . Enterocins A and B could be considered as extra biopreservative hurdles f or listeria prevention in dry fermented sausages.