Clxv. Studies in the Biochemistry of Micro-organisms. Xx. on the Production of Mannitol from Hexoses and Pentoses by a White Species of Aspergill Us. by Frederick

THE production of mannitol by bacterial fermentation has been extensively studied, since the organisms concerned are a source of trouble in the wine industry. Gayon and Dubourg [1901] showed that although glucose, sorbose, galactose, mannose, sucrose, maltose, lactose, raffinose and xylose are all fermented, laevulose alone yields mannitol. They found that arabinose and trehalose are not attacked. Peterson and Fred [1920, 1] reported that certain pentose-fermenting bacteria isolated from silage and manure also possess the power of producing mannitol. These organisms ferment glucose, galactose, mannose [Peterson and Fred, 1920, 2], xylose and arabinose [Fred, Peterson and Anderson, 1921], but again mannitol is obtained from laevulose alone, and not from any of the other sugars. With sucrose and raffinose some strains give traces of mannitol [Stiles, Peterson and Fred, 1925]. This fact was also observed by Gayon and Dubourg [1901], and it appears probable that fermentation of these sugars is not preceded by hydrolysis to monosaccharides, since invert sugar yields relatively large amounts of mannitol. It is most probable that mannitol arises by direct hydrogenation of one molecule of laevulose, coincidently with the oxidation of another molecule to lactic acid, acetic acid and carbon dioxide [Peterson and Fred, 1920, 1]. The presence of mannitol in the tissues of higher fungi was first discovered by Braconnot [1811], whose observation has been confirmed repeatedly and extended to the lower fungi. Obaton [1929], in a review on the evolution of mannitol in plants, studied in detail the production of mannitol and of trehalose in the mycelium of Aspergillus niger, but found no correlation between these two products, since factors affecting the one were without any effect on the other. Recently Birkinshaw, Charles, Hetherington and Raistrick [1931] have shown that mannitol may be regarded as a product of mould fermentation. In the case of one white species of Aspergillus (Ac. 55), the yield of mannitol