Carbohydrate Metabolism in Cheese. II. Coenzymes, 2-Deoxy-D-Ribose, and 2-Deoxy-D-Ribose-5-Phosphate

Higher concentrations of free deoxyribose were frequently observed in cheese made from raw milk as compared with that made from pasteurized milk. The bacteria from aged cheese made from raw milk and pasteurized milk were isolated and in both cases glucose-6-phosphate dehydrogenase could be demonstrated. However, the possibility that the free sugar may arise from metabolism of the starter cultures was considered. Production of free deoxyribose by starter cultures was markedly increased if the pasteurized milk curd was supplemented with nicotinamide adenine dinueleotide phosphate. Even after three months of ripening, the amounts of free deoxyribose were equal in the two types of cheese when equal concentrations of the coenzyme were maintained. During ripening of cheese, the concentration of free deoxyribose increased the first two months. A deoxyribokinase was then induced and large amounts of deoxyribose-5-phosphate were present from the second to the fourth month. When labeled deoxyribose was added to raw milk curd and to curd made from pasteurized milk, the rate of disappearance of the sugar was approximately the same in spite of the large difference in total bacterial population. Several varieties of cheese have been examined and in all cases both the free sugar and the phosphorylated derivative were found but the ratios showed extreme variations.