Fumaric acid molar yield

Fumaric acid (molar yield of approximately 100% moles of acid produced per moles of glucose utilized x 100), L-malic acid (15 mol%), and succinic acid (5 mol%) were the major acids formed during the fermentation. C4 acid (fumaric, L-malic, and succinic acid) molar yields of 120-145%, with a maximal fumaric acid concentration of 107 g/L, were obtained after 4-5 days (Goldberg and Stieglitz, 1985,1986 Kenealy et al., 1986 Ng et al., 1986). These high yields confirmed earlier data obtained by Rhodes et al. (1959, 1962). 

Direct proof that this reductive TCA pathway participates in fumaric acid production came from C NMR experiments using [1- C] and [U- C] glucose as a carbon source for R. oryzae (Kenealy et al., 1986). The unexpectedly high fumaric acid molar yields can thus be explained in terms of pyruvate carboxylation as the initial reaction of a reductive TCA pathway (Figure 15.1). 

Battat et al. [87] used A. flavus ATCC 13697 as the biocatalyst for the production of malic acid from glucose in a 16-1 stirred-tank fermentor. The optimal fermentation conditions are as follows agitation rate, 350 rpm Fe +, 12 mg/1 nitrogen (as ammonium sulfate), 271 mg/1 phosphate, 1.5 mM. Total amount of CaCOj added was 90 g/1. Fermentation was carried out at 32 °C for up to 200 h. Under the aforementioned conditions, 113 g/1 of L-malic acid were produced from 120 g/1 glucose utilized with an overall productivity of 0.59 g/l/h. Based on the molar yield, it was 128% for mahc acid and 155% for total acid (malic, fumaric and succinic acid). The increase in acid accumulation during the course of incubation coincides with the increase in the activities of NAD -malate dehydrogenase, fumarase and citrate synthase. 

How Can the High Molar Yield of Fumaric Acid be Explained ... 

How can we explain the unusually high molar yield of fumaric acid obtained by a Rhizopus strain ... 

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