Study on spoilage potential and its molecular basis of Shewanella putrefaciens in response to cold conditions by Label-free quantitative proteomic analysis.

Abstract

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 20h and 120h longer than at 30°C, respectively. The TVB-N increased to 89.23mgN/100g within 28h at 30°C, and it needed at least 72h and 224h 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.