GB763055A - Improvements in and relating to the production of ascorbic acid - Google Patents

Abstract

A process for the production of L-ascorbic acid from one or more of the g -lactone, and methyl, ethyl and propyl esters and amides of L-gulonic or of L-galactonic acid comprises oxidizing in the presence of oxygen one or a mixture of such substances by means of a group of enzymes obtained in an extraction medium at a pH between 6.0 and 8.5 from animal or vegetable tissues, such group being one which transfers electrons from sugar lactones to molecular oxygen and includes a dehydrogenase enzyme and cytochrome oxidase or similar enzymes, but not including substantial proportions of enzymes which oxidize ascorbic acid. The gamma lactones or esters of L-gulonic or L-galactonic acid may be prepared in situ by the reduction of the corresponding derivatives of D-glucuronic and D-galacturonic acids catalysed by the action of an enzyme system in the whole cell extract. The enzymes are found in mitochondria occurring in seeds and animal tissues, algae and yeasts, pea-seeds being one suitable source. The extraction medium is suitably a cooled solution of an organic nonelectrolyte having an osmotic pressure sufficient to prevent disintegration of the mitochrondria, e.g. sucrose, mannitol, glycerol and urea, and also containing sufficient phosphate or arsenate to give it a pH between 6.0 and 8.5 together with a trace of a magnesium salt. The concentration (with sucrose) is preferably 0.4 M with plants tissues and 0.25 M with animal tissues, that of the phosphate or arsenate being 0.1 M and of the magnesium salt 4 X 10-3 M. In examples: (1) pea-seeds after 12 to 48 hours germination in water are extracted at 0 DEG C. and pH 7.5 with 0.4 M sucrose containing 0.1 M phosphate and 0.1 per cent magensium sulphate. After removing starch and cell debris the solution (Extract A) may be centrifuged giving a precipitate (Extract B) containing the active elements. The g -lactone of either L-galactonic or L-gulonic acid is then incubated with Extract A or Extract B at 37 DEG C. to give L-ascorbic acid. After 4 or 5 hours additional g -lactone may be added for the production of further L-ascorbic acid. The product may be isolated by ion-exchange; (2) rat-liver is homogenized in 0.25 M sucrose solution. After removing cell debris the solution is centrifuged at 20,000 g., the precipitate is suspended in 0.25 M sucrose/phosphate buffer, and employed in a similar incubation process to (1). Methyl, ethyl or propyl esters or amides may also be used as in Example (1).