Escherichia fermentation

A culture of Bacillus polymyxa in a tube with Trypticase soybean broth was incubated overnight at 25°C. 5 ml of this culture was transferred to 100 ml of the tank medium in a 500 ml Erlenmeyer flask which was incubated for 48 hours at room temperature. This 100 ml culture served as inoculum for one tank. During the course of fermentation the medium was aerated at the rate of 0.3 volume of air per volume of mash per minute. The temperature was maintained at about 27 C. Samples of mash were taken every 8 hours in order to determine pH and the presence of contaminants and spores. After 88 hours of fermentation the pH was about 6.3 and an assay using Escherichia coll showed the presence of 1,200 units of polymyxin per cubic centimeter. The polymyxin was extracted and purified by removing the mycelia, adsorbing the active principle on charcoal and eluting with acidic methanol. 

Another way to enhance the production of an amino acid is to make use of DNA-recombinant technology, often in combination with foe mutations already described. In this way foe negative features of foe micro-organisms are avoided. To help explain this, we will consider a well known fermentation of L-phenylalanine using Escherichia coli. We have already seen foe metabolic pathway leading to foe production of L-phenylalanine in Figure 8.4. 

Escherichia coli and Klebsiella pneumoniae subsp, aerogenes produce acid from lactose on this medium, altering the colour of the indicator, and also adsorb some of the indicator which may be precipitated around the growing cells. The organisms causing typhoid and paratyphoid fever and bacillary dysentery do not ferment lactose, and colonies of these organisms appear transparent. 

Fermentation of D-xylose by Escherichia coli at pH 5.5 (in bicarbonate buffer) gives more than one mole of lactic acid per mole because of fixation of carbon dioxide by the two-carbon fragment,198(a> an observation that may have an important bearing on theories of photosynthetic fixation of carbon dioxide.198[Pg.223]

Walker and Dhurjati1421 have used culture fluorescence for on-line discrimination of host and plasmid-carrying strains of Escherichia coll In addition, culture fluorescence has also been used in the control of fed-batch fermentation on yeast cell production/29, 431... 

Figure 13.11. Dissolved oxygen profile during a typical Escherichia coli fermentation. Using a cubic spline interpolation of the data shown in Figure 13.3, the responses of the two sensors have been converted into percent oxygen and plotted as shown. The optical sensor closely tracks the response of the Clark-type electrode throughout the fermentation.

One interesting paper addresses amino acid production.37 The authors describe a fed-batch process for production of amino acids, such as L-lysine (from Corynebacterium glutamicium) and L-threonine (from Escherichia coli). For the fermentation broth of the L-lysine, the optical density, ammonium, and L-lys were measured. For L-threonine, OD, ammonium, and L-thr were measured. For all materials, the values were deemed acceptable and comparable with the reference methods. 

Hydrogenase isoenzymes are also common among the metabolically more versatile bacteria (see Chapter 2). For instance, H2 metabolism and isoenzyme composition in enteric bacteria, including Escherichia coli and Salmonella typhimurium, appear to be differentially regulated under the two modes of anaerobic life, fermentation and anaerobic respiration (Table 3.1). Furthermore, biosynthesis of the individual isoenzymes appears to be controlled at a global level by the quality of the carbon source. 

Clostridium acetobutylicum Escherichia [Fe] hydrogenase [NiFe] Putative cytoplasmic, ferredoxin linked H2 production during fermentation Fermentation pathway, phosphate limitation 4... 

Escherichia coli [NiFe] hydrogenase 3 Membrane-associated component of the formate hydrogen lyase complex H2 production during fermentation H2 uptake under anaerobic conditions Anaerobiosis, carbon source limitation, phosphate limitation, molybdenum, nitrate, formate 7.8... 

Formate dehydrogenase (several types) Sugar fermentation Escherichia coli 93-95... 

It did not deviate from the values found with pure cultures (Freudenreich and Orla-Jensen 1906 van Niel 1928). The analytical methods allowed the determination of the products of glucose fermentation by Escherichia coli, and the general equation calculated (Harden 1901) does not differ from that accepted today. Harden even correctly deduced that hydrogen arises from formic acid the Aerobacter modihcation was recognized by Harden in 1906. Thus the methods for the analysis of fermentation products were completed within the nineteenth century. 

Bock A, Sawers G. 1996. Fermentation. In Neidhardt FC, Cnrtiss R III, Ingraham JL, et al., editors. Escherichia coli and Salmonella cellular and molecnlar biology. 2nd ed. Washington, DC ASM Press, p 262-82. 

It has been shown that radio frequency impedance (RFI) is an effective tool for moifitoring cell density and cell growth of bioprocesses. The fermentation process, quite complex, is oftentimes difficult to sample and monitor. The RFI measurement could detect cell viability of Escherichia coli during the fermentation, serving as a qualitative measure of the metabolic load of the cell, and thus provide an in situ indicator of the optimal harvesting times. 

Condensation products of DHB (which usually is found also in the fermentation broth) with amino acids were reported, viz. with glycine ixom Bacillus subtilis (164) named subsequently itoic acid (282) with serine from Escherichia coli (261) and Klebsiella oxytoca (196) with threonine from Klebsiella oxytoca (196) and Rhizobium spp. (275, 327) with arginine from Pseudomonas stutzeri (62) with glycine and threonine from Rhizobium sp. (240) with threonine and lysine as well as with leucine and lysine from Azospirillum lipoferum (312, 320). In most cases the isolate (sometimes designated as being a siderophore) was hydrolyzed and the constituents were determined by paper chromatography. The relative amounts of the constituents, the chiralities of the amino acids and the molecular mass of the isolate have not been determined. Hence it is not known whether condensation products of the enterobactin type exist. 

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