Influence of substrate on beta-galactosidase production by Kluyveromyces strains

The aim of the present research was to investigate the influence of culture conditions on the levels of β-galactosidase (EC 3.2.1.23) activity produced by Kluyveromyces strains. Interest was focused on evaluating enzyme activity levels when lactose or cheese whey was employed as substrate in culture medium formulation. From an overall look at the obtained results, the tested strains were found to be able to produce β-galactosidase at promising levels. The use of cheese whey, either for strain maintenance and production trials, allowed to obtain a high cell yield associated with β-galactosidase production. The maximum β-galactosidase volumetric activity, EA max 66.5 IU/ml, corresponding to 3184 EAspec IU/g cell dw, was obtained with K. marxianus MIM 782 at 37 °C and 72 h incubation

Purified sakacin A shows a dual mechanism of action against Listeria spp: proton motive force dissipation and cell wall breakdown

Sakacin A was purified to homogeneity through simple chromatographic procedures from cultures of Lactobacillus sakei DSMZ 6333 grown on a low-cost medium. The highly purified protein dissipated both transmembrane potential (\u394\u3a8) and transmembrane pH gradient (\u394pH) in Listeria cells in a very intense, rapid, and energy-dependent fashion. On a slower timescale, purified sakacin A also showed a lytic activity toward isolated cell walls of Listeria. Mass spectrometry was used to analyze the products of sakacin A action on cell walls, evidencing that sakacin A acts on various types of bonds within peptoglycans

DEVELOPMENT OF A LOW COST CULTURE MEDIUM FOR SAKACIN A PRODUCTION BY L. SAKEI

MRS is currently the medium of choice for promoting sakacin A production by L. sakei (180 AU/ml): however, this medium is expensive and not applicable for large scale production. In the present study, an OVAT (One Factor at a Time) approach was used to formulate an alternative culture medium. The subsequent full factorial design (25) investigated the influence of ingredients on bacteriocin production and interactions among the ingredients. A series of adaptation steps were used to develop an equation model that allowed for estimation of all first order variables and sakacin production. The formula of the alternative culture medium consisted as follows (g/l): bacto peptone (X1) 10, meat peptone (X2) 8, yeast autolysate (X4) 4, glucose 10, CaCO3 30, inoculum 5 % (v/v) and use of deionised water. The cost of the alternative medium was approximately half that of MRS and sakacin A production was increased from 180 to 480 AU/ml

Influence of temperature and sakacin A concentration on survival of Listeria innocua cultures

The antimicrobial activity of sakacin A, a bacteriocin produced by L. sakei, was investigated at 30, 10 and 4 \ub0C against L. innocua in stationary and lag phases of growth. When sakacin was added to L. innocua cells in stationary phase, two death kinetics were observed. Populations of L. innocua were reduced up to three log cycles when sakacin A was increased from 0 (control) to 1600 AU ml-1. When sakacin A was added to L. innocua cells in lag phase, lag time, inhibition time and rate were proportionally extended, and maximum population decreased when employing higher bacteriocin levels. Sakacin A was found to influence L. innocua growth, a microorganism able to grow at 4 \ub0C. At refrigerated temperatures, the addition of sakacin A was found to inhibit L. innocua cell growth. Sakacin A may be considered a promising molecule to be used as antimicrobial agent to preserve the shelf life of refrigerated foods