The influence of calcium ions (Ca2+) on the enzymatic hydrolysis of lipopolysaccharide aggregates to liberate free fatty acids (FFA) in aqueous solution

Abstract

The chemical environment in aqueous solutions greatly influences the ability of amphiphilic molecules such as lipopolysaccharides (LPS) to aggregate into different structural phases in aqueous solutions. Understanding the substrate's morphology and conditions of aqueous solution that favor both enzymatic activity and the disruption of LPS aggregates are crucial in developing agents that can counteract the new trend of multidrug resistance by gram-negative bacteria. In this study, we developed two LPS morphologies using LPS from Escherichia coli as a model to study the in vitro hydrolytic response when using a lipase treatment. The hydrolysis was performed using lipase b from Candida antarctica to understand the catalytic effect in removing fatty acids from its lipid A moiety on different LPS aggregates. Physical and chemical characterizations of the products included dynamic light scattering, small angle X-ray scattering, Fourier transform infrared spectroscopy, thin-layer chromatography, and gas chromatography. Our results suggest a trend of prominent hydrolytic response (72% enhancement) upon the addition of calcium ions to induce LPS aggregates into bilayer formations. Moreover, our results revealed the detection of myristic acid (C14:0) as the product of the hydrolysis when using RaLPS in its aggregate forms.