Organic acids production

If continuous addition of solids is not possible, additions should be made at as short intervals as possible. Alkahnity levels are normally maintained at about 3000 to 5000 mg/L to keep the pH in the range 6.5-7.5 as a buffer against variable organic-acid production with vaiy-ing organic loads. Proteins will produce an adequate buffer, but carbohydrates wall require the addition of alkalinity to provide a sufficient buffer. Sodium bicarbonate should be used to supply the buffer. 

A feed concentration of 15 g glucose and 15 g xylose per litre was used over a feed rate of 20-200 ml/hr. Samples were taken at successive points along the reactor length, and the usual analysis for glucose and xylose consumption, organic acid production and cell density were done. A kinetic model for the growth and fermentation of P. acidipropionici was obtained from these data. 

The ICR flow rate was five to eight times faster than the CSTR. The overall conversion of sugars in the ICR at a 12 hour retention time was 60%, At this retention time, the ICR was eight times faster than CSTR, but in the CSTR an overall conversion rate of 89% was obtained. At the washout rate for the chemostat, the ICR resulted in a 38% conversion of total sugars. Also, the organic acid production rate in the ICR was about four times that of the CSTR. At a higher retention time of 28 hours, the conversion of glucose in the ICR and CSTR are about the same, but the conversion of xylose reached 75% in the ICR and 86% in the CSTR. 

Based on the practical history of scale-up, most fermentation processes for alcohol and organic acid production have followed the concepts of geometric similarity and constant power per unit volume. From the above concept, and as a strong basis for translation of process criteria, only physical properties of the process were considered in the scale-up calculation. For power consumption in an agitated vessel, there is a fixed relation between impeller speed, N, and impeller diameter, l)t. The constant power per unit volume, for a mechanical agitated vessel is given by ... 

Too low pH either overall or in acid spots in the event of poor microhomogenization of the acid alkaline phase should be avoided to prevent hydrolysis of the organic acid product to alcohol (alcohol ether) and sulfuric acid, which will catalyze further hydrolysis ... 

Plant roots are known to exude a fluid containing a number of amino and carboxylic acids, the amount of the exudate increasing under conditions of metal deficiency. Chlorotic plants, i.e. those suffering from iron defidency, have been found to contain more of the citric and malic acids than their normal green counterparts.21 Differences in the susceptibilities of plant species to trace metal deficiencies have indeed frequently been attributed to variations in organic acid production. 

Besides the engineering of S. cerevisiae for organic acid production, through metabolic engineering it is possible to reconstruct entire pathways. In 1994, Yamano et al. [163] reported the reconstruction of a complete secondary metabolic pathway in S. cerevisiae, resulting in the ability of the yeast to produce p-carotene and lycopene. Carotenoids are a class of pigments used in the food industry and, due to their antioxidant properties, they have wide commercial interest. The biosynthesis of these compounds does naturally not occur in S. cerevisiae and to allow... 

Comprehensive studies of metal adsorption by lichens and fungi as a function of pH, ionic strength and solute biomass concentration, using lichens of different growth form, taxonomic affinity and character of organic acid production. 

Anaerobic treatment, a multistep complex process, can be described from a kinetic viewpoint as a three-step process involving (1) hydrolysis of complex organic material (2) organic acid production (3) methane fermentation (2). In the first step complex organics are converted to less complex soluble organic compounds by enzymatic hydrolysis. In the... 

Chemical processing Organic acid production recovery... 

Organic acid production (specialty chemical Methane sulfonic acid production... 

Organic compound production (fine chemical Organic acid production (China) (agro Organic acid recovery (Germany)... 

FIGURE 21.37 (See color insert following page 588.) Organic acid production in France. (From Eurodia Co.)... 

Figure 1 H2 and organic acids production from PYG media containing 1% glucose by C. butyricum NCIB 9576. pH O Cell concentration (Abs. 660nm) ...

Production of organic acids is found among various bacterial and fungal species. This is particularly common among all lactic acid bacteria (LAB) (Vesterlund et al., 2004). Heterofermentative LAB are able to ferment various organic acids, predominantly citrate, malate, and pyruvate (Zaunmuller et al., 2006). In various species and strains of LAB, organic acid production may, however, vary. For example, in Lactococcus ladus pyruvate is partially converted to a-acetolactate when electron acceptors (such as citrate) are present, whereas Lactobacillus sanfranciscensis... 

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