All protocols for LPS extraction implies damaging of the bacterial cell wall which in turn results in killing the bacterial cells. in general, a simple protocol (hot phenol-water method) for extraction and purification of LPS Is provided:

In brief, bacterial suspensions (108 colony-forming units/mL) were centrifuged at 10,000×g for 5 min. The pellets were washed twice in PBS (pH = 7.2) (0.15 M) containing 0.15 mM CaCl2 and 0.5 mM MgCl2. Pellets were then resuspended in 10 ml PBS and sonicated for 10 min on ice.

In order to eliminate contaminating protein and nucleic acids, treatment with proteinase K, DNase and RNase was performed prior to extraction step. For this purpose, proteinase K (100 µg/mL) (Roche, Mannheim, Germany) was added to the cell mixture and the tubes were kept at 65°C for an additional hour. Mixture was subsequently treated with RNase (40 µg/mL) (Roche, Mannheim, Germany) and DNase (20 µg/mL) (Roche, Mannheim, Germany) in the presence of 1 µL/mL 20% MgSO4 and 4 µL/mL chloroform and incubation was continued at 37°C overnight.At the next step, an equal volume of hot (65–70°C) 90% phenol was added to the mixtures followed by vigorous shaking at 65–70°C for 15 min. Suspensions were then cooled on ice, transferred to 1.5 mL polypropylene tubes and centrifuged at 8500×g for 15 min. Supernatants were transferred to 15 mL conical centrifuge tubes and phenol phases were re-extracted by 300 µL distilled water. Sodium acetate at 0.5 M final concentration and 10 volumes of 95% ethanol were added to the extracts and samples were stored at -20°C overnight in order to precipitate LPS.

Tubes were then centrifuged at 2000×g 4°C for 10 min and the pellets were resuspended in 1 ml distilled water. Extensive dialysis against double distilled water at 4°C was carried out at the next step until the residual phenol in the aqueous phases was totally eliminated. Final purified LPS product was lyophilized and stored at 4°C.

I hope you find a proper method.

Reference:

Westphal O, Jann K. Bacterial lipopolysaccharides. Extraction with phenol-water and further applications of the procedure. In: Whistler RL, Wolfan ML, editors. Methods in Carbohydrate Chemistry. New York: Academic press; 1965. pp. 83–91.

Dear Stefan,

thank you for your answer, but I looking for a protocol to induce the release of LPS in the growth medium without adding of drugs or chemicals. In my experiment the medium with LPS will directly carry on through microfluidic system to the brain compartment and since I want to measure the effect of LPS I can't have other substances in the media. Maybe temperature or pH changing could induce E. coli to release LPS...I was hoping someone had tried physical methods..