Substrate utilization by Clostridium estertheticum cultivated in meat juice medium

Blown pack spoilage of vacuum packaged beef, which results in packs being grossly distended with gas, is caused by the psychrophile Clostridium estertheticum. To determine what substrates are utilized by C. estertheticum during growth on beef, C. estertheticum subsp. estertheticum ATCC 51377, the type strain for that organism, and two isolates from blown pack spoiled beef that were identified as C. estertheticum by 16 S rRNA gene sequencing were grown in meat juice medium at 10 °C for up to 14 days. Analysis of the growth media showed that all three organisms grew exponentially on glucose with simultaneous hydrolysis of glycogen. Growth ceased when glucose in the media was depleted; but hydrolysis of glycogen continued at a reduced rate, and lactate was consumed rapidly. The pH values of media fell during growth of the organisms, but rose as the concentrations of lactate subsequently decreased. The major products of fermentation during utilization of glucose were butyrate and acetate, with butyrate greatly predominating. During fermentation of lactate the major products were butyrate and butanol, which were produced in similar amounts. The findings suggest that growth of C. estertheticum on vacuum packaged beef may be limited by the availability of glucose, as is the growth of other organisms that usually predominate in the flora of vacuum packaged meat. However, production of gas by fermentation of lactate will likely continue after growth ceases.