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Our purpose in the work here described2 has been to develop a method whereby the responses in the weight curves of properly standardized experimental animals may become means of measuring the relative vitamin G (B2) values of foods or of concentrates obtained in research work.The factor here designated as vitamin G or B2 may or may not be identical with that to which the term pellagra-preventive has been applied; 1 Published as Contribution No. 667 from the Department of Chemistry of Columbia University.* This paper is a brief summary of the work described in the privately printed dissertation submitted by Anne Bourquin in partial fulfilment of the requirements for the degree of Ph.D., Columbia University, 1929, together with the results of subsequent experience in the use of the method in the Columbia laboratories.

The aim of this study is to investigate the separation of astaxanthin from the cells of Phaffia rhodozyma using colloidal gas aphrons (CGA), which are surfactant stabilized microbubbles, in a flotation column. It was reported in previous studies that optimum recoveries are achieved at conditions that favor electrostatic interactions. Therefore, in this study, CGA generated from the cationic surfactant hexadecyl trimethyl ammonium bromide (CTAB) were applied to suspensions of cells pretreated with NaOH. The different operation modes (batch or continuous) and the effect of volumetric ratio of CGA to feed, initial concentration of feed, operating height, and flow rate of CGA on the separation of astaxanthin were investigated. The volumetric ratio was found to have a significant effect on the separation of astaxanthin for both batch and continuous experiments. Additionally, the effect of homogenization of the cells on the purity of the recovered fractions was investigated, showing that the homogenization resulted in increased purity. Moreover, different concentrations of surfactant were used for the generation of CGA for the recovery of astaxanthin on batch mode; it was found that recoveries up to 98% could be achieved using CGA generated from a CTAB solution 0.8 mM, which is below the CTAB critical micellar concentration (CMC). These results offer important information for the scale-up of the separation of astaxanthin from the cells of P. rhodozyma using CGA.

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