# Plant Organic Acids as Natural Inhibitors of Foodborne Pathogens
## 4 Discussion
aureus, E. faecium, B. cereus, E. coli, P. aeruginosa_ & 0.8–4.0 mg/mL & 0.63–5.0 & [35] \\ \cline{2-3}  & Tanic acid & _Penicillium digitatum_ & 1 mg/mL & [38] \\ \hline \multirow{2}{*}{Tartaric acid} & _S. Typhimuriumurium_ & 0.312\% (3.1 mg/mL) & 1.25–5.0 & [33] \\ \cline{2-3}  & _S. subtilis_ & 1\% (10 mg/mL) & [37] \\ \cline{2-3}  & _S. subtilis_ & 1\% (10 mg/mL) & [38] \\ \cline{2-3}  & _S. subtilis_ & 1\% (10 mg/mL) & [38] \\ \cline{2-3}  & _S. subtilis_ & 1\% (10 mg/mL) & [39] \\ \hline \multirow{2}{*}{Citric acid} & _S. subtilis_ & 1\% (10 mg/mL) & [41] \\ \cline{2-3}  & _S. subtilis_ & 1\% (10 mg/mL) & [42] \\ \cline{2-3}  & _S. subtilis_ & 1\% (10 mg/mL) & [42] \\ \hline \multirow{2}{*}{Citric acid} & _E. coli_ & 1 mg/mL & [31] \\ \cline{2-3}  & _S. subtilis_ & 0.5–4.1 mg/mL & [32] \\ \cline{2-3}  & _S. subtilis_ & 1\% (10 mg/mL) & [37] \\ \hline \multirow{2}{*}{Formic acid} & _E. coli_ & 1.25–2.5 & [32] \\ \cline{2-3}  & _S. subtilis_ & 0.5–4.1 mg/mL & [32] \\ \cline{2-3}  & _V. harveyi_ & 0.025–0.05\% (0.25–0.5 mg/mL) & [34] \\ \hline \multirow{2}{*}{Malic acid} & _L. monocytogenes_ & 0.5–32 mM (67–4288 mg/mL) & [36] \\ \cline{2-3}  & _B. subtilis_ & 2\% (20 mg/mL) & [37] \\ \hline \multirow{2}{*}{Succinic acid} & _S. aureus, E. faecium, B. cereus, E. coli, P. aeruginosa_ & 0.8–4.0 mg/mL & 0.63–5.0 & [35] \\ \cline{2-3}  & _Penicillium digitatum_ & 1 mg/mL & [38] \\ \hline \multirow{2}{*}{Tartaric acid} & _S. Typhimuriumurium_ & 0.312\% (3.1 mg/mL) & 1.25–5.0 & [33] \\ \cline{2-3}  & _S. subtilis_ & 1\% (10 mg/mL) & [37] \\ \cline{2-3}  & _S. subtilis_ & 1\% (10 mg/mL) & [38] \\ \hline \multirow{2}{*}{Citric acid} & _S. subtilis_ & 1\% (10 mg/mL) & [37] \\ \cline{2-3}  & _S. subtilis_ & 1\% (10 mg/mL) & [38] \\ \cline{2-3}  & _S. subtilis_ & 1\% (10 mg/mL) & [39] \\ \cline{2-3}  & _S. subtilis_ & 1\% (Some organic acids, including acetic, citric, lactic, and malic acids, have been generally recognized as safe (GRAS) [45]. However, in the presented studies, we demonstrated that organic acids vary in terms of toxicity. Unfortunately, for many of them, the required antibacterial concentration is higher than the predicted lethal dose, LD50. The acids that appear to be safe (MIC! LD50) based on our results include ascorbic acid, chlorogenic acid, malic acid, nicotinic acid, rosmarinic acid, salicylic acid, succinic acid, tannic acid, and tartaric acid. The mechanism of action of organic acids is based on the fact that undissociated molecules are lipophilic and can cross the lipid membrane of microorganisms. After penetrating the bacterial cytoplasmic membrane, they dissociate into anions and protons in the cytoplasm. The protons lower the intracellular pH, leading to the inhibition of bacterial glycolysis, a decrease in ATP, and a reduction in active transport [9; 10]. A similar mechanism might occur in mammalian cells. Unfortunately, the literature on the toxicity of organic acids is sparse. In in vivo studies, the LC50 for acetic acid and benzoic acid were reported to be 273 and 277 mg/L for tilapia (_Oreochromis mosambicus_) [46]. These values are similar to the results obtained in this work, namely 333 and 290 mg/kg, respectively. However, the LC50 decreases for other organisms. For cladoceran crustacea (_Moina micrura_), the LC50 values of acetic acid and benzoic acid were 164 and 72 mg/L and for the oligochaete worm (_Branchiura sowerybi_), they were 15 and 39 mg/L, respectively. Although the genotoxicity of organic acids was not demonstrated in this study, it has been described for citric acid at a concentration of 20 ppm or 0.02 mg/mL [47]. The high values of the predicted LD50 ranging from several 10s to 5000 mg/kg obtained in this study might explain why the maximum daily intake for many acids has not been determined. The Food and Agriculture Organization (FAO) of the United Nations has not specified a daily intake limit for acetic, citric, lactic, malic, and propionic acids.