Sporicidal activity of sodium linear alkylbenzene sulfonate against Bacillus spores under acidic and high-temperature conditions

Abstract

The sporicidal activity of sodium linear alkylbenzene sulfonate (LAS), a major anionic surfactant used in detergents, against Bacillus subtilis, B. cereus, and Geobacillus stearothermophilus was evaluated. Bacterial suspensions including spores were treated with 0.01–10 mM LAS under various pH (2.7–7.8) and temperature conditions (25°C–70°C). Zeta potential analysis and spore quantification were performed to explore the mechanism of action of LAS. LAS displayed pronounced sporicidal activity only under both acidic conditions (pH ≤5) and elevated temperature (≥50°C). In the presence of 1 mM LAS in 10 mM citric acid (pH 2.7) at 70°C, B. subtilis spore counts were reduced by >5.7 log₁₀ colony forming units/mL within 5 min. Zeta potential measurements and HPLC quantification indicated enhanced penetration of LAS into spores at both low pH and high temperature. Considering that the typical LAS concentration in commercial cleaning formulations is approximately 1 mM, the present findings suggest that common detergent systems can achieve significant sporicidal activities when combined with high-temperature washing protocols.