To elucidate how Shewanella putrefaciens survives and produces spoilage products in response to cold conditions, the metabolic and protease activity of S. putrefaciens DSM6067 cultured at three different temperatures (30 °C, 10 °C, and 4 °C) was studied by determining the bacterial growth, total volatile basic nitrogen (TVB-N), biogenic amines, extracellular protease activity, as well as the differential expressed proteins via Label-free quantitative proteomics analysis. The lag phase of the strain cultured at 10 °C and 4 °C was about 20 h and 120 h longer than at 30 °C, respectively. The TVB-N increased to 89.23 mg N/100 g within 28 h at 30 °C, and it needed at least 72 h and 224 h at 10 °C and 4 °C, respectively. Cold temperatures (10 °C and 4 °C) also inhibited the yield factors and the extracellular protease activity per cell at the lag phase. However, the protease activity per cell and the yield factors of the sample cultivated at 10 °C and 4 °C well recovered, especially at the mid and latter stages of the log phase. The further quantitative proteomic analysis displayed a complex biological network to tackle cold stress: cold stress responses, nutrient uptake, and energy conservation strategy. It was observed that the protease and peptidase were upregulated, so as to the degradation pathways of serine, arginine, and aspartate, which might lead to the accumulation of spoilage products. This study highlighted the spoilage potential of S. putrefaciens still should be concerned even at low temperatures.
Keywords: Cold temperature; Extracellular protease; Metabolic activity; Proteomics; Spoilage products.
© 2022. The Author(s), under exclusive licence to Springer Nature B.V.