LPS was extracted using a LPS extraction kit (iNtRON Biotechnology, Seongnam City, Republic of Korea) according to the manufacturer’s protocol. DPBs samples (DPB#1, DPB#2, or DPB#3) were harvested when the culture was at an optical density at 600 nm (OD600) of 0.8 to 1.2. Lysis and purification buffers were sequentially applied, and the LPS pellet was dissolved by boiling for 3 min. LPS was quantified using the Limulus Amebocyte Lysate Chromogenic Endotoxin Quantitation Kit (Pierce Biotechnology, Rockford, IL) according to the manufacturer’s protocol. Escherichia coli O111:B4 was used as the standard of known concentration. Ten endotoxin units (EU)/mL equaled approximately 1 ng/ml.