title: Flow injection analysis of lactose using covalently immobilized beta-galactosidase, mutarotase, and glucose oxidase/peroxidase on a 2-fluoro-1-methylpyridinium salt-activated Fractogel support.
abstract: Milk samples were analyzed for their lactose content using flow injection analysis and incorporating immobilized beta-galactosidase or beta-galactosidase/mutarotase and glucose oxidase/peroxidase bioreactors. These enzymes were immobilized, under mild conditions, on to a 2-fluoro-1-methylpyridinium salt-activated Fractogel support. The use of a phosphate buffer (0.15 M) was found to facilitate the rapid mutarotation of alpha-D-glucose and hence could obviate the need for the more expensive mutarotase. The chromogenic agents of choice for monitoring the reaction were 3-methyl-2-benzothiazolinone hydrazone and 3-dimethylaminobenzoic acid. Linearity was observed over the concentration range 16-160 micrograms/ml using lactose standards (r = 0.996). Between 30 and 40 milk samples/h can be analyzed. Comparisons are made with existing HPLC and alkaline methylamine methods for a range of milk matrices. The FIA method consistently gives the lowest standard deviations and coefficient of variation for the various milk matrices analyzed.
authors.affiliation: Department of Chemistry, University of the West Indies, St. Augustine, Trinidad.
authors.forename: D
authors.initials: D
authors.lastname: Narinesingh
authors.forename: V A
authors.initials: VA
authors.lastname: Stoute
authors.forename: G
authors.initials: G
authors.lastname: Davis
authors.forename: T T
authors.initials: TT
authors.lastname: Ngo
mesh_terms: D000818:Animals; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000378:metabolism*; D005949:Glucose Oxidase / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007785:Lactose / Q000032:analysis*; D008892:Milk / Q000737:chemistry; D010544:Peroxidases / Q000378:metabolism*; D011108:Polymers; D011726:Pyridinium Compounds; D013696:Temperature; D001616:beta-Galactosidase / Q000378:metabolism*
chemical_list: D004800:Enzymes, Immobilized; D011108:Polymers; D011726:Pyridinium Compounds; C070192:2-fluoro-1-methylpyridinium fractogel; C066037:2-fluoro-1-methylpyridinium; D005949:Glucose Oxidase; D010544:Peroxidases; D001616:beta-Galactosidase; D007785:Lactose