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At least 19 recordsLinked to original sources
PubMed1985

Chemical reaction, diffusion, and ionization model for dissolution of oxygen acids and carbon acids.

A chemical reaction, diffusion, and ionization model, which assumes the establishment of ionization equilibrium at an equilibrium plane located within the diffusion layer, is tested by use of experimental dissolution rates for some oxygen acids and carbon acids. For oxygen acids both two- and three-zone models predict observed dissolution rates; however, for barbituric acid dihydrate and phenylbutazone neither model successfully depicts the dissolution behavior. Although the three-zone model approximately predicts dissolution rates of oxygen acids, its complexity does not add to the accuracy of the calculated rate. The three-zone model does support the frequent assumption that ionization is instantaneous and can be ignored in modeling.

Barbiturates↗
PubMed1970

Carbonic acid from decarboxylation by "malic" enzyme in lactic acid bacteria.

Carbonic anhydrase studies were used to determine the primary form of carbonic acid produced from decarboxylation of l-malic acid by "malic" enzyme in malolactic strains of five different species of lactic acid bacteria. Addition of carbonic anhydrase to the reaction mixture containing crude bacterial extract and l-malic acid, at pH 7, in all five cases resulted in an increase (13 to 23%) in the rate of carbon dioxide evolution over the control. The results indicated that the primary form of carbonic acid released from "malic" enzyme was not anhydrous carbon dioxide as previously supposed and as has been shown for other decarboxylating enzymes. The standard free-energy changes of the malo-lactic reaction with the various forms of carbonic acid as the primary decarboxylation product were calculated. The reaction is less exergonic when carbonic acid, bicarbonate ion, or carbonate ion is the primary decarboxylation product compared to anhydrous carbon dioxide. The free-energy of the reaction is not biologically available to the bacteria; with carbon dioxide not the primary decarboxylation product, the potential energy lost in a malo-lactic fermentation is not as great as previously considered. Endogenous carbonic anhydrase activity was not found.

Carbon Dioxide↗