A membrane separator/bioreactor coupled with absorbance measurement for detection of Escherichia coli O157 : H7

A membrane separator/bioreactor system was developed for rapid detection of Escherichia coli O157:H7. The system consisted of a membrane separator/bio reactor (0.45 gm of the pore size) to separate the complexes of E. coli O15 7:H7 and alkaline phosphatase-conjugated anti-E. coli O157:H7 antibodies fr om the sample and to produce p-nitrophenol through the enzymatic reaction ( p-nitrophenyl phosphate hydrolysis), and an optical detector for measuring the p-nitrophenol absorbance at 400 nm. The membrane material and the flow rate of the substrate for the enzymatic hydrolysis had great effects on the absorbance of p-nitrophenol. The optimum conditions for the enzymatic reac tion were determined as 1.0 M Tris buffer, pH 8.0, and 0.1 M MgCl2 for this system. The detection range was 10(4) similar to 10(7) CFU/mL with a relat ive standard deviation of 4.3 similar to 14.2%, and whole procedure could b e completed in 50 min without any enrichment and culture. Other bacteria su ch as Salmonella typhimurium, Campylobacter jejuni and Listeria monocytogen es had no significant interference with the detection of E. coli O157:H7.