title: PH-sensing 96-well microtitre plates for the characterization of acid production by dairy starter cultures.
abstract: A new method for characterization of acid production by dairy starter cultures is presented. Microplates with integrated optical pH sensors are developed. Two fluorophores, a pH-sensitive and a pH-insensitive one are immobilised at the bottom of a polystyrene 96-well microtitre plate. The pH-insensitive fluorophore serves as an internal reference and makes calibration unnecessary. The sensor measures pH accurately in optically well-defined media. Particles and fluorophores contained in the bulk medium disturbed the measurements. Despite these disturbances it was possible to clearly sense differences in inoculum type and in inoculum sizes of cultures of Lactococcus lactis and of Streptococcus thermophilus at 30 and 37 degrees C. Besides a pH-related signal there is information about other changes during milk fermentation. The cultivation results were compared with those from the established CINAC-method. From this comparison it can be concluded that the new method can be used reliably to characterize particularly a large number of strains for screening purposes but also for quality control.
authors.affiliation: Technische Biochemie, Saarland University, 66123 Saarbrücken, Germany.
authors.forename: Gernot T
authors.initials: GT
authors.lastname: John
authors.forename: Detlef
authors.initials: D
authors.lastname: Goelling
authors.forename: Ingo
authors.initials: I
authors.lastname: Klimant
authors.forename: Holger
authors.initials: H
authors.lastname: Schneider
authors.forename: Elmar
authors.initials: E
authors.lastname: Heinzle
mesh_terms: D000818:Animals; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D002138:Calibration; D002417:Cattle; D018929:Cell Culture Techniques / Q000379:methods; D002851:Chromatography, High Pressure Liquid; D005260:Female; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000032:analysis; D013294:Lactococcus lactis / Q000378:metabolism*; D008892:Milk / Q000382:microbiology* / Q000592:standards; D008954:Models, Biological; D011786:Quality Control; D013050:Spectrometry, Fluorescence; D013291:Streptococcus / Q000378:metabolism*
chemical_list: D019344:Lactic Acid