Resumo

Bacteriocins produced by lactic acid bacteria compose a large and diverse group of ribossomally synthesized peptides. Bovicin HC5, a bacteriocin produced by Streptococcus bovis HC5, shows wide spectrum of activity and has several biochemical features that are useful for commercial applications. The aim of this study was to investigate the effect of media composition, pH, temperature and growth atmosphere on bovicin HC5 production by Streptococcus bovis HC5. S. bovis HC5 was grown in BHI, MRS, M17 or basal media (pH 6,5) at 39 °C, and incubations were carried out under aerobic and anaerobic conditions. To assess the effect of temperature and pH, S. bovis HC5 was cultivated anaerobically in basal media at temperatures of 25, 30, 36, 39 and 45 ºC, and the media pH was adjusted to initial values ranging from 4.5 to 7.0. Alternatively, cultures were grown under controlled conditions, with the media pH maintained at constant values (pH 5.5 to 7.0). Cultures grown aerobically in MRS, M17 and BHI broth showed lower specific growth rates and greater bovicin HC5 activity in the cell-free supernatant. However, cultures grown in basal media under anaerobic conditions yielded greater cell densities and specific growth rates, which was related with higher cell-associated bovicin HC5 activity. Batch culture experiments indicated that S. bovis HC5 could grow if the initial pH was as low as 5.5, but both growth rate and maximum optical density increased at higher pH values. Cell-associated bovicin HC5 activity was highest when cultures were grown in basal media with the initial pH adjusted to 6.5. When the media pH was controlled throughout the incubation, bacteriocin production was always higher at lower pH values and highest at pH 5.5. S. bovis HC5 was able to grow and produce bovicin HC5 in temperatures ranging from 30 °C to 45 ºC. These results suggest that acidic pH and anoxic conditions favor cell-associated bovicin HC5 production by S. bovis HC5.