A calorimetric and equilibrium investigation of the hydrolysis of lactose.

Published

Journal Article

The thermodynamics of the hydrolysis of lactose to glucose and galactose have been investigated using both high pressure liquid chromatography and heat-conduction microcalorimetry. The reaction was carried out over the temperature range 282-316 K and in 0.1 M sodium acetate buffer at a pH of 5.65 using the enzyme beta-galactosidase to catalyze the reaction. For the process lactose(aq) + H2O(liq) = glucose(aq) + galactose(aq), delta G0 = -8.72 +/- 0.20 kJ.mol-1, K0 = 34 +/- 3, delta H0 = 0.44 +/- 0.11 kJ.mol-1, delta S0 = 30.7 +/- 0.8 J.mol-1.K-1, and delta Cop = 9 +/- 20 J.mol-1.K-1 at 298.15 K. The standard state is the hypothetical ideal solution of unit molality. Thermochemical cycle calculations using enthalpies of combustion and solution, entropies, solubilities, activity coefficients, and apparent molar heat capacities have also been performed. These calculations indicate large discrepancies which are attributable primarily to errors in literature data on the enthalpies of combustion and/or third law entropies of the crystalline forms of the substrates.

Full Text

Duke Authors

Cited Authors

  • Goldberg, RN; Tewari, YB

Published Date

  • June 15, 1989

Published In

Volume / Issue

  • 264 / 17

Start / End Page

  • 9897 - 9900

PubMed ID

  • 2498341

Pubmed Central ID

  • 2498341

International Standard Serial Number (ISSN)

  • 0021-9258

Language

  • eng

Conference Location

  • United States