Carbohydrate - continued requirements

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. 

Production of fine chemicals and active pharmaceutical ingredients (APIs) will also continue to benefit from the judicious application of biocatalysis, in many cases as part of multistep synthetic schemes. Of particular relevance is the increasing demand for chirally pure pharmaceuticals, driven by concerns about the unwanted side-effects often associated with racemic drugs. Another growth area is likely to be the production of biologically active carbohydrates, traditionally requiring complex and expensive chemistries for production, to be used as pharmaceuticals, in infant formula, and as nutritional supplements. 

Effective utilization of biomass for value-added chemical product synthesis will require development of new applications of important unit operations. Carbohydrate recovery from the biomass is the key near-term application for production of commodity chemicals. Protein recovery will continue to have an important niche market in tlie purified form as food and a larger low-value market in the crude form as animal feed. Important processing information for carbohydrate depolymerization can be found in the literature from biochemical conversion of biomass. New process applications of separation technologies are just now being developed and refined for use with biomass-derived carbohydrate and protein streams. The use of an aqueous processing environment for carbohydrates will require careful consideration of the differences that type of environment entails, such as the effect on catalyst formulations. 

Studies show that the production of 1kg dry biomass requires 2.0 kg sugar, 0.7 kg oxygen, 0.1 kg ammonia, with the liberation of 12,300 k Joules heat. A typical continuous fermentation operates at a dilution rate (D) = 0.2 h 1, with sugar concentration of 3% (w/v) in the incoming medium. With a fermentor of 50 m3 capacity and 90% utilisation of carbohydrate [ie 0.3% (w/v) sugar in the outgoing medium] what would be ... 

The fact that enzymes also work in organic solvents [42], ranging from apolar alkanes up to the very polar N,N-dimethylformamide [65], has (Fig. 13.10) and will continue to open up new cascade opportunities for the integration of enzymatic conversions with chemocatalytic methods that require organic solvents. Notably, however, some enzyme classes, for instance the carbohydrate-converting enzymes, do not show activity in non-aqueous media [40, 41]. 

First, the above-mentioned sensors have major drawbacks, as the detection and recognition event is a function of the nature and characteristics of the side chains, and the side chain functionalization of the CP requires advanced synthesis and extensive purification of numerous monomeric and polymeric derivatives. Second, this generation of sensors primarily employed optical absorption as the source for detection, resulting in lower sensitivity when compared with other sensing systems for biological processes. However, the use of fluorescence detection within these sensing systems could justify continued development. More recent examples include a fluorescent polythiophene derivative with carbohydrate functionalized side chains for the detection of different bacteria [15] and novel synthesis schemes for ligand-functionalization of polythiophenes [16]. 

It is used in IC systems when the amperometric process confers selectivity to the determination of the analytes. The operative modes employed in the amperometric techniques for detection in flow systems include those at (1) constant potential, where the current is measured in continuous mode, (2) at pulsed potential with sampling of the current at dehned periods of time (pulsed amperometry, PAD), or (3) at pulsed potential with integration of the current at defined periods of time (integrated pulsed amperometry, IPAD). Amperometric techniques are successfully employed for the determination of carbohydrates, catecholamines, phenols, cyanide, iodide, amines, etc., even if, for optimal detection, it is often required to change the mobile-phase conditions. This is the case of the detection of biogenic amines separated by cation-exchange in acidic eluent and detected by IPAD at the Au electrode after the post-column addition of a pH modiher (NaOH) [262]. 

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