Abstract
In 1953,the authors reported the formation of Ca-L-idonate (intermediate to L-ascorbic acid) by the catalytic reduction of Ca-5-keto-D-gluconate. Afterwards, Hamilton et al. reported the reduction of 5-keto-D-gluconate with NaBH_4. The results of these two types of reaction indicated that the equal amounts of L-idonate and D-gluconate were formed. Recently, the authors have attempted to research the production of Ca-L-idonate from crude crytals of freshly prepared Ca-5-keto-D-gluconate by oxidative fermentation of D-glucose. Thirty g of Ca-5-keto-D-gluconate and 5g of Raney-Ni catalyst were suspended in 100ml of water and adjusted to pH7.5 with NaOH. The mixture was reduced at 80℃ for 3-4 hours under 84kg/cm^2 of H_2 pressure. The yield of Ca-L-idonate, thus obtained, was 94% (basis on the crude material).
