Studies on the Microbiological Determination of Niacin in Some Marine Algae.

Abstract

The test organisms used were Streptococcus faecalis ATCC 8043, Lactobacillus arabinosus ATCC 8014, and L. casei ATCC 7469. A single basal medium, with minor changes, was used for all 3. A cup plate assay method for niacin with S. faecalis as the test organism is described in detail. In the concentration range of 0.05- 100 ug of niacin/ml, well defined zones of dense growth were obtained. Comparative assays for niacin on 8 selected algal samples were carried out in 2 laboratories using the cup plate method with S. faecalis and also the turbidimetric tube assay method with S. faecalis and L. arabinosus. The most favorable conditions for the extraction of niacin were determined. Recovery tests with added niacin were also performed. The highest niacin assay values were obtained by hydrolyzing the samples with N sulfuric acid for 1 hour at 120[degree]C and assaying by the L. arabinosus tube method. For the purpose of screening a large number of algal samples, hydrolyzing with 3 N sulfuric acid for 1 hour at 120[degree]C and assaying by the S. faecalis cup plate method is recommended. This assay method generally gives 0-20% lower niacin assay values than the L. arabinosus tube method. Bioautography of extracts of the 8 selected algal samples was made with L. arabinosus plates. In extracts prepared by hydrolyzing with N or 3 N sulfuric acid, only niacin was found. However, in extracts prepared by hydrolyzing with 0.1 N sulfuric acid, niacinamide was predominant while niacin was either absent or found only in trace amounts. A simple method for the bioautographic detection of "bound" niacin (an alkali-labile complex containing niacin) was developed. Bioautographic tests for the presence of "bound" niacin in the algal samples were negative. Comparative assays for niacin on another set of selected algal samples were carried out by the turbidimetric tube assay method with L. arabinosus, L. casei and S. faecalis. The results with L. arabinosus L. casei and S. faecalis. The results with L. arabinosus and L. casei agreed very well, although the former test organism in some cases gave slightly higher assay values than the latter. The S. faecalis tube method gave considerably lower niacin assay values.