Influence of nitrogen sources on Lactobacillus curvatus ACU-1 growth and production of its bacteriocin sakacin Q

ALVAREZ O.; CAYRÉ, M.E.; CASTRO M.

CAMPINAS

Simposio; 11th SLACA. Latin American Symposium of Food Science; 2015

Biopreservation can be applied to food by the incorporation of bacteriocinogenic strains as protective cultures or by the addition of the bacteriocin produced by conventional fermentation. In both cases, it is necessary to determine the influence of factors involved in fermentative processes to optimize biomass or bacteriocin production. Lactobacillus curvatus ACU-1 is a bacteriocin-producing strain from Chaco (Argentina) ?isolated from artisanal dry sausages. It has bactericidal activity against pathogens and evidenced excellent technological features for the biopreservation of cooked meat products. The aim of this work was to evaluate the influence of nitrogen sources on the growth of L. curvatus ACU-1 and the production of its bacteriocin sakacin Q to optimize culture fermentation. MRS broth was taken as basal medium (BM) and fermentation proceeded at 30°C. Different sources of nitrogen: yeast extract (YE), meat extract (ME), triptone (T), cysteine (Cys), and histidine (His), were added -alone or in combination- to BM. Cell density was monitored spectrofotometrically (optical density at 600 nm, OP600nm). These data, expressed as Log OP600nm, were used to fit modified Gompertz equation from which kinetic growth parameters were estimated. Antimicrobial activity was checked by agar well diffusion method. All the assessed sources of nitrogen extended lag phase and reduced bacterial growth rate. However, maximum OP600nm values were reached when the combination YE-ME-Cys-His was tested; these values were 15% higher than those obtained with BM. Bacteriocin production halved in the presence of YE, ME, or T, as unique sources of nitrogen, or the combinations YE-T and ME-T. Yet, sakacin Q production was stimulated by the joint use of YE-ME as solely source of nitrogen; an enhancement of 98% in antimicrobial activity was evidenced compared to the activity observed with the BM. These promising results led us to adopt this source of nitrogen for future optimization.