Growth and end‐product formation in fermenter cultures of Brochothrix thermosphacta ATCC 11509T and two psychrotrophic Lactobacillus spp. in different gaseous atmospheres

Abstract

The effects of different gaseous atmospheres were determined on the maximum specific growth rate (.mu.max) and end-product formation by B. thermosphacta ATCC 11509T, L. viridescens SMRICC 174 and Lactobacillus sp. SMRICC 173 (homofermentative). The highest .mu.max-value for L. viridescens (0.47/h) and B. thermosphacta (0.49/h) were obtained in air. Under anaerobic conditions .mu.max was reduced, an atmosphere containing CO2 alone giving the greatest reduction. Lactobacillus sp. 173 did not grow in air of N2. Aerobic growth was obtained by adding peroxidase, while anaerobic growth occurred in the presence of 5-20% CO2. CO2 alone reduced the growth rate. All test organisms produced mainly lactic acid anaerobically. L. viridescens also produced ethanol while B. thermosphacta produced small amounts of ethanol and formic acid. With O2 present, the number of end-products increased for all organisms. Lactobacillus sp. 173 produced small amounts of acetic acid and acetoin together with lactic acid. O2 induced acetic acid production in L. viridescens and B. thermosphacta. Aerobically, B. thermosphacta also produced a large amount of acetoin and smaller amounts of 2,3-butanediol, iso-valeric acid and iso-butyric acid. The production of lactic acid by B thermosphacta was completely prevented under strictly aerobic conditions. All test organisms consumed O2 during aerobic growth. H2O2 was produced by L. viridescens and Lactobacillus sp. 173. [This study relates to food spoilage.].