Pseudomonas fragi and Pseudomonas lundensis drove the co-spoilage in chilled pork: Insights from the metabolome.

Pseudomonas fragi and Pseudomonas lundensis are key spoilage microorganisms in aerobically stored chilled meat, which had co-spoilage effect on chilled pork. However, the mechanism of co-spoilage interaction of P. fragi and P. lundensis has not been elucidated. The metabolism of nutrients in pork by mixed bacteria may differ from that by single strains. This study applied metabolomics and in vitro metabolite utilization experiment to assess the mechanism of that co-metabolize raw pork during storage. Results showed that co-spoilage group had 104 differential metabolites (histamine, N-methylhydantoin and D-gluconic acid, etc.) and 78 differential metabolites (putrescine, uracil acid and uracil, etc.) compared to P. fragi and P. lundensis group, respectively. These differential metabolites were mainly related to histidine metabolism, arginine biosynthesis, and purine. The co-spoilage effect of P. fragi and P. lundensis was related to the promotion of deamination and decarboxylation of histidine to produce histamine, the promotion of α-ketoglutarate and glutamate-mediated transamination, and the full utilization of the arginine deiminase pathway by the co-culture bacteria in the degradation of arginine to produce putrescine. In vitro experiment, co-cultures of these strains resulted in greater consumption of glucose, higher utilization activity, and promoted deamination and decarboxylation of amino acids. These findings reveal the complex and competitive interactions of co-culture of P. fragi and P. lundensis, providing insight into microbial spoilage mechanisms in chilled pork.