Reichstein-Griissner process

The Genencor-Eastman process to ascorbic acid (vitamin C) ferments glucose in one step to 2-ketogulonic acid, with subsequent chemical conversion to ascorbic acid. It replaces the old Reichstein-Griissner process with its 55% overall yield, 3 d cycle time, five chemical steps, 17-20 different downstream processing steps, and at least seven different solvent systems. 

The Reichstein-Griissner process, developed in 1934, takes in all five chemical steps (hydrogenation, fermentative oxidation, acetonization, oxidation, and hydroly-sis/rearrangement) (Table 20.3). Over the course of the whole synthesis there are 17-20 different downstream processing steps, six solid-handling steps, and at least seven different solvent systems to handle. The overall yield is about 55%, and overall cycle time is around three days. Such values clearly suggest possible improvement in the process towards ascorbic acid. 

Reichardt s dye, 26 854 Reichert cone, 16 632 Reich process, 4 810 Reichstein-Griissner synthesis, 26 401 of ascorbic acid, 25 752-753, 754, 755-758, 782 Reich test, 23 665 Reid vapor pressure (RVP), 22 396 ... 

There are a total of three ascorbic acid processes either in place or in late stages of development with firm expectations of commercialization (i) the traditional chemical Reichstein-Griissner synthesis (ii) the two-step fermentation process to 2-ketogulonic acid with subsequent chemical esterification/lactonization to ascorbic acid and (iii) the one-step fermentation to 2-ketogulonic acid with the same last chemical step. Figure 20.8 and Table 20.3 provide an overview of the three processes. 

AH of the vitamins, except Vitamin B12, are produced nowadays by chemical syntheses. Many of them are also obtained via biotechnological processes (Vitamins Bj, Bg, B12) or isolated from natrual products (Vitamins A, D, E, K). For Vitamin C, the exclusively chemical process (the Reichstein-Griissner synthesis) has been replaced by a mixed chemical/fermentation procedure. 

Synthesis of vitamin C (ascorbic acid) is conventionally performed via the Reichstein-Griissner procedure, which involves the fermentation of glucose followed by five chemical steps. Cerestar/ BASF recently developed a new process that consists of one fermentation step and two simple chemical steps (via 2-keto-L-gluconic acid). It is predicted that soon a fermentation process will be developed to convert glucose into vitamin C in a single step, eliminating several recovery steps and reducing extraction solvents. 

In 1898, Gabriel Bertrand reported the formation of L-sorbose from D-sorbitol for the first time. In 1934, this reaction was adopted to produce vitamin C in the so-called Reichstein process (Reichstein and Griissner 1934) ... 

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