Yeast extract

Escherichia coli ATCC25922 is conserved by the Key Laboratory of Dairy Biotechnology and Safety Control, Yangzhou University (Yangzhou, China). Before use, E. coli cultures were stored in a 1:1 ratio with 70% (v/v) glycerol solution in a −40 °C refrigerator. E. coli was cultured in Luria–Bertani (LB) broth containing 0.5% yeast extract (Macklin Biochemical Co., Ltd., Shanghai, China), 1.0% tryptone (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China), and 1.0% NaCl (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China). The organic acids (AA, LA, BA, CA, and MA) were purchased from Macklin.
Configuration of organic acid solutions: Organic acid solutions of different concentrations for treating E. coli are shown in Table 1. Based on our previous research [28 (link)], the minimum inhibitory concentration (MIC) was obtained by the microdilution method, and the optimal inhibitory concentration was obtained by the checkerboard method.

All chemicals used in this work were of analytical grade. Sodium sulfide nonahydrate (Na₂S•9H₂O) was purchased from Wenjiang Chemical Technology. Iron sulfate heptahydrate (FeSO₄·7H₂O), 1, 5-diphenyl carbazide, FeS, carboxymethyl cellulose (abbreviated as CMC), Phosphoric acid, potassium permanganate(KMnO_4), urea (NH₂)₂CO, sodium nitrite(NaNO₂₎, NaCl, K₂Cr₂O₇, C₆H₁₂O₆, C₁₂H₂₂O₁₁, (C₆H₁₀O₅)n, C₂H₃O₂Na·3H₂O, CH₄N₂O, NaH₂PO_4, and Na₃PO₄ were provided from Sinopharm Chemical Reagent Co., Ltd (Shanghai, China). Sulfuric acid were supplied by Xilong Science Chemical Technology. The Beef Extract, Peptone, Tryptone and yeast extract were purchased from shanghai Macklin Biochemical Co., Ltd (Shanghai, China). (NH₄)₂SO₄ and NH₄H₂PO₄ were supplied by Damao Chemical Reagent Co., Ltd (Tianjin, China). KH₂PO₄ was purchased from Hengxing Chemical Reagent Co., Ltd (Tianjin, China). Dissolve 2.0 g K₂Cr₂O₇ in 1 L of deionized water to obtain a Cr(VI) mother solution with a final concentration of 2000 mg L⁻¹.