Direct fermentation

Fermentation. Much time and effort has been spent in undertaking to find fermentation processes for vitamin C (47). One such approach is now practiced on an industrial scale, primarily in China. It is not certain, however, whether these processes will ultimately supplant the optimized Reichstein synthesis. One important problem is the instabiUty of ascorbic acid in water in the presence of oxygen it is thus highly unlikely that direct fermentation to ascorbic acid will be economically viable. The successful approaches to date involve fermentative preparation of an intermediate, which is then converted chemically to ascorbic acid. 

In this chapter we consider amino acid production by fermentation and by chemo-enzymatic methods. We first consider the stereochemistry of amino adds and the importance of chirality in chemical synthesis. General approaches to amino add fermentation and recovery of amino adds from fermentation broths are then dealt with, followed by a detailed consideration of the production of L-phenylalanine by direct fermentation. Later in this chapter, chemo-enzymatic methods of amino acid... 

Wild strains of E. coli are not used for L-phenylalanine production by direct fermentation. 

Auxotrophic mutants of E. cdi are particularly useful for the production of L-phenylalanine by direct fermentation. 

The optimum cell concentration was between 10 and 20 g l 1, which is not different from the concentrations employed in direct fermentation. 

Extra cost compared to direct fermentation are mainly concerned with addition of PPA (precursor addition) or ACA (bioconversion). Table 8.9 compares estimated costs for foe PPA and ACA process based on foe data considered previously (section 8.6.1 and 8.6.2). Costs are estimated for production of 100 tonnes per year. 

Assume that the cost price of L-phenylalanine produced by direct fermentation is 285 kg 1 (100 tonnes per annum capacity). What percentage reduction in substrate costs are required for 1) precursor feeding and 2) biotransformation to be competitive on a cost price basis with direct fermentation ... 

Like benzylpenieillin, penicillin V is still widely used in its own right but can also be used as a starting material for the manufacture of the semisynthetic penicillins, none of which can be made by direct fermentation. 

In this chapter, we will introduce an exciting class of natural product biosynthetic enzymes, the modular synthases, as well as their associated enzyme partners. We will discuss the use of metabolic engineering as a tool for small-molecule discovery and development, both through directed fermentation and combinatorial biosynthesis. In addition, we will review six classes of partner enzymes involved in the modification of polyketide (PK) and nonribosomal peptide (NRP) natural products. We believe that these enzymatic transformations hold great opportunities for synthetic chemists and will serve as the foundation for a new trend in both discovery and process chemistry. 

Yeast Fermenting in Dough. When yeast is in a bread dough the traces of sugars present can be fermented directly. As yeast contains the enzyme invertase, any sucrose present can be inverted into dextrose and fructose which can then be fermented. If any dextrose from a high DE glucose syrup is present then it can be directly fermented. If there is any lactose present it can not be fermented at all. Similarly, any polyols such as sorbitol can not be fermented. 

Once any directly fermentable sugars have been used up the yeast can only be fed by sugars produced from the starch. The only starch that can be broken down is the damaged starch. This explains why a certain amount of starch damage and some amylase activity is desirable in a bread flour. 

Konetschny-Rapp S, Jung G, Raymond KN, Meiwes J, Zahner H (1992) Solution Thermodynamics of the Ferric Complexes of New Desferrioxamine Siderophores by Directed Fermentation. J Am Chem Soc 114 2224... 

Meiwes J, Fiedler HP, Zahner H, Konetschny-Rapp S, Jung G (1990) Production of Desferrioxamine E and New Analogues by Directed Fermentation and Feeding Fermentation. Appl Microbiol Biotechnol 32 505... 

Obtained by directed fermentation. Cyclic hydroxamines are obtained when = —CH2CH2CO- - and the carbonyl group form an amide bond with... 

Huang L.P., Jin, B., Lant, (2005a). Direct fermentation of potato starch wastewater to lactic acid by Rhizopus oryzae and Rhizopus arrhizus. Biopro. Biosyst. Eng. 27. 229-238. 

Vishnu, C., Seenayya, G., Reddy, G. (2002). Direct fermentation of various pure and crude starchy substrates to L(+) lactic acid using Lactobacillus amylophilus GV6. World J. Microbiol. BiotechnoL, 18,429-433. 

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. 

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