Comparative determination of two probiotics by QCM and OWLS-based immunosensors.
The regular consumption of foods containing probiotic bacteria has beneficial physiological effects on the health and the digestion system. There is a need for novel analytical approaches for the determination of these bacteria that are faster than the classical plate counting method. For this purpose, two label-free biosensors were investigated and presented in this paper: Quartz Crystal Microbalance (QCM) and Optical Waveguide Lightmode Spectroscopy (OWLS) based direct immunosensors were developed for real-time direct detection of probiotic bacteria in fermented dairy products. Bifidobacterium bifidum O1356 and Lactobacillus acidophilus O1132 were detected by polyclonal anti-B. bifidum IgG and anti-L. acidophilus IgG immobilized on the sensors' surface. Sulfo-LC-SPDP cross linking agent was used to bind antibodies to the gold surface of the QCM's AT-cut quartz wafer. Concerning OWLS, antibodies were covalently bound to the amino groups of the silanized surface of the waveguide by glutaraldehyde. The dynamic measuring range was found between 1.0E+3 and 5.0E+5CFUmL(-1) in 100 fold diluted fermented milk products by QCM and with OWLS. Considering the current legislation of the probiotic content in probiotic products, the two developed immunosensors can be applied for rapid quantification of L. acidophilus and B. bifidum in fermented milk. These examinations offer effective alternatives to the microbiological plate counting method.
Eszterházy Károly College, Institute of Food Science, Leányka u. 6., Eger H-3300, Hungary. Electronic address: h.szalontai@ektf.hu.
Helga
H
Szalontai
Central Environmental and Food Science Research Institute, Herman Ottó u. 15., Budapest H-1022, Hungary.
Nóra
N
Adányi
Eszterházy Károly College, Institute of Food Science, Leányka u. 6., Eger H-3300, Hungary.
Attila
A
Kiss
D000907:Antibodies, Bacterial / Q000737:chemistry; D001688:Biological Products; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D003611:Dairy Products / Q000382:microbiology*; D005504:Food Analysis / Q000295:instrumentation / Q000379:methods*; D005516:Food Microbiology / Q000295:instrumentation / Q000379:methods*; D007074:Immunoglobulin G / Q000737:chemistry; D007779:Lactobacillus acidophilus; D019936:Probiotics / Q000032:analysis*; D013057:Spectrum Analysis / Q000295:instrumentation / Q000379:methods
D000907:Antibodies, Bacterial; D001688:Biological Products; D007074:Immunoglobulin G; C010546:bifidobacterin