Nongrowing cells of Halobacterium saccharovorum oxidized lactose to a product identified as lactobionic acid by thin-layer, paper, and column chromatography, and by identification of the galactose and gluconic acid produced from it after acid hydrolysis. Growing cells oxidized lactose to a product that was identical with lactobionate except that it did not serve as a substrate for galactose oxidase. While the identity of this compound has not been established, it is suggested that the product is lactobionic acid in which the galactose moeity is in the furanose form. Neither lactobionate nor the product produced by growing cells was further metabolized, suggesting that lactose oxidation is not coupled to growth.
