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Lactobacillus plantarum is a facultatively anaerobic bacterium that can perform respiration under aerobic conditions in the presence of haem, with vitamin K 2 acting as a source of menaquinone. We investigated growth performance and oxidative stress resistance of Lb. plantarum WCFS1 cultures grown in de Man, Rogosa and Sharpe (MRS) medium without and with added manganese under fermentative, aerobic, aerobic with haem, and respiratory conditions. Previous studies showed that Lb. plantarum WCFS1 lacks a superoxide dismutase and requires high levels of manganese for optimum fermentative and aerobic growth. In this study, respiratory growth with added manganese resulted in significantly higher cell densities compared to the other growth conditions, while without manganese added, similar but lower cell densities were reached. Notably, cells derived from the respiratory cultures showed the highest hydrogen peroxide resistance in all conditions tested, although similar activity levels of haem-dependent catalase were detected in cells grown under aerobic conditions with haem. These results indicate that oxidative stress resistance of Lb. plantarum is affected by respiratory growth, growth phase, haem and manganese. As levels of haem and manganese can differ considerably in the raw materials used in fermentation processes, including those of milk, meat and vegetables, the insight gained here may provide tools to increase the performance and robustness of starter bacteria.

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Aims:  To assess the inhibitory activity and the influence of culture condition on the growth and bacteriocin, Thermophilin 1277, production by Streptococcus thermophilus SBT1277. Methods and Results:  Thermophilin 1277, which was produced by S. thermophilus SBT1277, showed an antimicrobial activity against several lactic acid bacteria and food spoilage bacteria including Clostridium butylicum, C. sprogenes and Bacillus cereus. Thermophilin 1277 was inactivated by proteinase K. Heating treatment did not affect the antimicrobial activity. The partially purified Thermophilin 1277 had an apparent molecular mass of 3·7 kDa. N‐terminal sequence analysis revealed 15 amino acid residues that correspond with amino acid sequence of the lantibiotics bovicin HJ50 produced by Streptococcus bovis HJ50. The effects of culture condition for the bacteriocin production by S. thermophilus SBT1277 were studied. During the batch fermentation, Thermophilin 1277 was produced in M17 broth, but no bacteriocin production occurred in the sucrose‐tryptone (ST) broth. Bacteriocin production was detected in pH controlled ST broth at pH values of 5·5–6·5. Conclusions:  Thermophilin 1277 production from S. thermophilus strain depended on the culture conditions. Some characters and N‐terminal amino acid sequence of Thermophilin 1277 differed from bacteriocins produced by S. thermophilus reported previously. Significance and Impact of the Study:  Streptococcus thermophilus SBT1277 or its bacteriocin which has a wide inhibitory spectrum has a potential use as a biopreservative in dairy products.

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