Sorbose fermentative

Srivastava AK, Lasrado PR (1998) Fed-batch sorbitol to sorbose fermentation by A suboxydans. BioprocEng 18(6) 457- 1... 

L-Sorhose to 2-KGA Fermentation. In China, a variant of the Reichstein-Grbssner synthesis has been developed on an industrial scale (see Fig. 5). L-Sorbose is oxidized direcdy to 2-ketogulonic acid (2-KGA) (24) in a mixed culture fermentation step (48). Acid-catalyzed lactonization and enolization of 2-KGA produces L-ascorbic acid (1). 

A Chinese pubHcation (47) with 17 references reviews the use of genetically engineered microorganisms for the production of L-ascorbic acid and its precursor, 2-KGA (49). For example, a 2-keto-L-gulonic acid fermentation process from sorbose has been pubUshed with reported yields over 80% (50). 

Sterile aqueous D-sorbitol solutions are fermented with y cetobacter subo >gichns in the presence of large amounts of air to complete the microbiological oxidation. The L-sorbose is isolated by crystallisation, filtration, and drying. Various methods for the fermentation of D-sorbitol have been reviewed (60). A.cetobacter suboyydans is the organism of choice as it gives L-sorbose in >90% yield (61). Large-scale fermentations can be carried out in either batch or continuous modes. In either case, stefihty is important to prevent contamination, with subsequent loss of product. 

Important results have recently been obtained by Simon. Among other things he ascertained that glycerol yields butyric acid. The formation of four-carbon compounds from six-carbon substrates is independent of the grouping (aldehyde, hydroxyl, carboxyl, phosphory-lated hydroxyl) at the first carbon atom of the molecule. L-Rhamnose and D-arabitol are fermented, but not n-arabinose and D-sorbitol. In contrast to the studies of Underkofler and Hunter, " L-sorbose has been found fermentable. Results obtained with fresh and acetone-dried Cl. hutylicum are identical in principle. 

L-Iditol (sorbi6rite), the last of the four naturally occurring hexitols, occurs in service berries along with sorbitol. After removing sorbitol from the juice by fermentation to L-sorbose with the sorbose bacterium, Acetobacter xylinum, the n-iditol is crystallized as a benzylidene derivative. It has been prepared by the action of sodium amalgam on... 

Commercially available ascorbic acid still includes isolation from natural sources, such as rose hips, but large-scale production will involve the microbiological approach, i.e., Acetobacter suboxidans oxidative fermentation of calcium d-gluconate or the chemical approach, i.e.. the oxidation of /-sorbose. 

Clearly, an improved synthesis of L-ascorbic acid would result from the direct oxidation of L-sorbose (25) to L-xy/o-2-hexulosonie acid (28), thus eliminating the protecting-deprotecting steps currently required in the Reichstein-Griissner synthesis (see Scheme 4). Efforts to perform this oxidation may be divided into two categories, namely, chemical and fermentative. The results of each method will be summarized. 

Two different mechanisms for the formation of L-xyZo-2-hexulosonic acid (28) from L-sorbose (25) have been proposed, depending on the organism used for the fermentative oxidation. It was concluded280-283 that the metabolism of 25 by Pseudomonas aeruginosa IFO 3898 most probably follows the sequence 25 — L-idose (41) — L-idonic acid (42) — 28. Both 41 and 42 were isolated from the fermentation broth. With Gluconobacter melanogenus, it was concluded284-287 that 25 is... 

L-Sorbose (25) has also been converted into 28 by using bacteria of the genera Achromobacter, Alcaligenus, and Serratia.29° From S. mar-cescens,290 2.8 g of 28 in 3.8 L of broth was produced in 10 days, starting with a 2% concentration of L-sorbose. It has been reported that Pseudomonas fluorescens No. 806 converts 25 into 28 in 25-35% yield.291 At the present time, the direct fermentation of 25 to 28 clearly is not efficient enough to compete with the Reichstein-Griissner, chemical procedure. 

This result supports earlier findings" - " which suggested that L-sorbose is oxidized directly at C-l. See the direct oxidation of 25 to 28 by fermentation (Section III,4b). 

Dihydroxyacetone (HOCH2COCH2OH, melting point 89°C) is made by the action of sorbose bacterium fermentation of glycerin (HOCH2CHOHCH2OH). 

D-fructose were removed by alcoholic fermentation and the remaining sugars, L-gulose and L-sorbose, were converted into the phenylosazone that is common to these two hexoses. Although the presence of both L-sorbose and L-gulose is altogether probable, the isolation of the so-called sorbose phenylosazone is evidence only that at least one of these unfer-mentable hexoses, or indeed sorbose (gulose) osone, was present. 

Methyl-L-sorbose (LXXI)150 was prepared from the corresponding 4-methyl-L-gulitol (3-methyl-D-glucitol) (LXX) by oxidative fermentation with Acetobacter xylinum. The starting material was obtained by hydrogenation of 3-methyl-D-glucose (LXIX). 

The semi-synthetic production of vitamin C is rapidly moving to a full biotech process. Vitamin C (ascorbic acid) is an important segment in the worldwide vitamin market with a market share of approximately 20 percent. Its worldwide sales amounted to around USD 0.5 bilHon in 1999. The traditional route to vitamin C is a multistep process involving chemical and fermentative steps. It starts with the catalytic hydrogenation of D-glucose to D-sorbitol, followed by the fermentative oxidation of D-sorbitol to L-sorbose, which is then converted... 

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