Stimulation of lactic acid bacteria by a micrococcus isolate: evidence for multiple effects

Area of Science:

• Microbiology
• Biochemistry

Background:

• Lactic acid bacteria (LAB) are crucial in food fermentation.
• LAB growth can be inhibited by hydrogen peroxide (H₂O₂).
• Micrococcus species can influence LAB metabolism.

Purpose of the Study:

• To investigate the stimulatory effect of Micrococcus isolate F4 on LAB growth and acid production.
• To determine the role of Micrococcus isolate F4's capsular material in this interaction.
• To elucidate the mechanisms behind micrococcal stimulation of LAB.

Main Methods:

• Culturing six LAB strains with Micrococcus isolate F4 or its capsular preparation.
• Measuring LAB growth and acid production rates.
• Quantifying hydrogen peroxide (H₂O₂) concentrations in pure and mixed cultures.
• Assessing the effect of catalase on LAB.

Main Results:

• Micrococcus isolate F4 significantly increased LAB growth and acid production.
• H₂O₂ levels were reduced in mixed cultures with Micrococcus isolate F4.
• The capsular material was less effective than whole cells in reducing H₂O₂.
• Catalase partially stimulated LAB, but less than Micrococcus isolate F4 in some cases.

Conclusions:

• Micrococcus isolate F4 stimulates LAB growth and acid production.
• A primary mechanism involves the removal of inhibitory hydrogen peroxide (H₂O₂).
• A second, uncharacterized mechanism also contributes to LAB stimulation.