Modelling gene-dependent PEF resistance of E. coli K-12

The current study investigated the antimicrobial mechanisms of Pulsed Electric Fields (PEF) by evaluating the resistance of 22 Escherichia coli K12 mutants. Initial screening at PEF treatment (23 kV/cm, 53.3 μs, 95.4 kJ/kg), pH 7.0, revealed increased sensitivity (p < 0.05) of ΔclpB, ΔrpoS, and ΔdnaK expressed in Log₁₀ reductions. Further inactivation kinetic analysis of 8 selected strains at pH 7.0 and 4.0 revealed a non-linear, polyphasic behaviour. This was described by a global modelling approach combining a log-linear primary model with a second-order polynomial model incorporating treatment time, total specific energy, and survival data as variables. The calculated model parameters (C₁, C₂, and C₃) significantly differed (p < 0.05) among strains at pH 7.0, but not at pH 4.0. Furthermore, the calculated inactivation rates, k_max, varied in relation to the total specific energy. At pH 7.0, k_max was higher at low (0-40 kJ/kg) and high (140-180 kJ/kg) total specific energies, while at pH 4.0, it raised at high total specific energies (120-160 kJ/kg). In conclusion, E. coli response to PEF was dependant on the stress regulator rpoS. This response also involved genes which encode molecular chaperones such as dnaK, clpB and recA, related proteins for DNA repair. In conclusion, resistance to PEF was found to be influenced by pH and total specific energy, indicating that E. coli mounts a multifaceted response to PEF treatments, informing advanced microbial inactivation strategies for food safety.