Using the general concept of a dry multilayer analytical element, we can change chemical procedures and configurations to assay several blood components. In the assay of serum urea nitrogen, urease in the reagent layer catalyzes the hydrolysis of urea. A semipermeable membrane excludes aqueous base, but allows ammonia to diffuse to an underlying indicator layer. For the amylase determination, the enzyme hydrolyzes a dyed-starch substrate coated on top of the spreading layer; this produces small fragments, which diffuse to a registration layer. The increase of absorbance at 540 nm is correlated with amylase activity. Bilirubin complexes with a cationic polymer at the interface between the spreading and reagent layers. The direct reading at 460 nm allows determination of total bilirubin in the range 1 to 500 mg/liter. Tirglycerides are hydrolyzed in the spreading layer, and the resulting soluble glycerol readily diffuses into the reagent layer, where it is phosphorylated and subsequently oxidized by glycerophosphate oxidase to yield dihydroxyacetone phosphate and hydrogen peroxide. Peroxidase catalyzes production of a color commensurate with the hydrogen peroxide produced.

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summaryA process for the bacterial oxidation of isobutyric acid to L ( + ) 8-hydroxyisobutyric acid has been developed. The strain of Pseudomoms putisla (ATCC 21244) used in this fermentation was isolated from local soil. The process was carried out in a 15-liter fermentor over a period of 70 hr and produced L( +) 8-hydroxyisobutyric acid in conversions as high as 48%. Hydroxylation of the methyl group of isobutyric acid has special interest because it is difficult to perform chemically. The useful chemical syntheses of phydroxyisobutyric acid available at present do not start with isobutyric acid and are not stereospecific.

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