Effect and mechanism of carvacrol on putrescine production by Obesumbacterium proteus in Xinjiang sausage

Here, we explored the effect of carvacrol on growth, gene expression, and putrescine accumulation in O. proteus isolated from Xinjiang sausages. Scanning electron microscopy was used to analyze the cell morphology of the test bacteria. Reverse transcription real-time fluorescence quantitative polymerase chain reaction was used to analyze the gene expression of arginine decarboxylase and ornithine decarboxylase in the test bacteria at different carvacrol concentrations, and single-molecule real-time sequencing was used to identify the species composition in sausage. Moreover, relevant parameters like putrescine accumulation and microbial growth were evaluated. Results showed that the production of putrescine was not only dependent on putrescine-producing strains, but also on the expression of key genes in the putrescine production pathway. Carvacrol was found to inhibit the growth of putrescine-producing strains and decrease putrescine accumulation by releasing O. proteus content, while also reducing putrescine levels through the downregulation of arginine decarboxylase (adiA) and ornithine decarboxylase (speF) genes involved in the putrescine biosynthesis pathway. Moreover, carvacrol significantly reduced the abundance of harmful bacteria (Enterobacteria and Pseudomonas) and the putrescine content in the sausage. Consequently, adding carvacrol extracted from spices to sausages is an effective means to inhibit putrescine content.