Enzymes continuous processes

Manufacture of Fatty Acids and Derivatives. Splitting of fats to produce fatty acids and glycerol (a valuable coproduct) has been practiced since before the 1890s. In early processes, concentrated alkaU reacted with fats to produce soaps followed by acidulation to produce the fatty acids. Acid-catalyzed hydrolysis, mostly with sulfuric and sulfonic acids, was also practiced. Pressurized equipment was introduced to accelerate the rate of the process, and finally continuous processes were developed to maximize completeness of the reaction (105). Lipolytic enzymes maybe utilized to spHt... 

Ornithine decarboxylase is a pyridoxal dependent enzyme. In its catalytic cycle, it normally converts ornithine (7) to putrisine by decarboxylation. If it starts the process with eflornithine instead, the key imine anion (11) produced by decarboxylation can either alkylate the enzyme directly by displacement of either fluorine atom or it can eject a fluorine atom to produce viny-logue 12 which can alkylate the enzyme by conjugate addidon. In either case, 13 results in which the active site of the enzyme is alkylated and unable to continue processing substrate. The net result is a downturn in the synthesis of cellular polyamine production and a decrease in growth rate. Eflornithine is described as being useful in the treatment of benign prostatic hyperplasia, as an antiprotozoal or an antineoplastic substance [3,4]. 

When you eat starchy foods, they are broken down into glucose by enzymes. The process starts in your mouth with the enzyme amylase found in saliva. This explains why, if you chew a piece of bread long enough, it starts to taste sweet The breakdown of starch molecules continues in other parts of the digestive system. Within 1 to 4 hours after eating, all the starch in food is converted into glucose. 

Several L-amino acids are produced on a large scale by enzymatic resolution of N-acetyl-D,L-amino adds (Figure A8.4). Acylase immobilised on DEAE-Sephadex is for example employed in a continuous process while Degussa uses the free acylase retained in a membrane reactor. In the latter process the advantage of reuse of the enzyme and homogeneous catalysis are combined. 

Like enzymes, whole cells are sometime immobilized by attachment to a surface or by entrapment within a carrier material. One motivation for this is similar to the motivation for using biomass recycle in a continuous process. The cells are grown under optimal conditions for cell growth but are used at conditions optimized for transformation of substrate. A great variety of reactor types have been proposed including packed beds, fluidized and spouted beds, and air-lift reactors. A semicommercial process for beer used an air-lift reactor to achieve reaction times of 1 day compared with 5-7 days for the normal batch process. Unfortunately, the beer suffered from a mismatched flavour profile that was attributed to mass transfer limitations. 

Since many years, pectolytic enzymes have been widely used in industrial beverage processing to improve either the quality and the yields in fruit juice extraction or the characteristics of the final product [1,2]. To this purpose, complex enzymatic mixtures, containing several pectolytic enzymes and often also cellulose, hemicellulose and ligninolytic activities, are usually employed in the free form. The interactions among enzymes, substrates and other components of fruit juice make the system very difficult to be investigated and only few publications are devoted to the study of enzymatic pools [3-5], An effective alternative way to carry out the depectinisation process is represented by the use of immobilized enzymes. This approach allows for a facile and efficient enzymatic reaction control to be achieved. In fact, it is possible to avoid or at least to reduce the level of extraneous substances originating from the raw pectinases in the final product. In addition, continuous processes can be set up. 

US5344778 19 A process for reducing sulfur content Extract and/or enzymes Continuation in part of [52] [55]... 

A first application using ferroceneboronic acid as mediator [45] was described for the transformation of p-hydroxy toluene to p-hydroxy benzaldehyde which is catalyzed by the enzyme p-cresolmethyl hydroxylase (PCMH) from Pseudomonas putida. This enzyme is a flavocytochrome containing two FAD and two cytochrome c prosthetic groups. To develop a continuous process using ultrafiltration membranes to retain the enzyme and the mediator, water soluble polymer-bound ferrocenes [50] such as compounds 3-7 have been applied as redox catalysts for the application in batch electrolyses (Fig. 12) or in combination with an electrochemical enzyme membrane reactor (Fig. 13) [46, 50] with excellent results. 

Thus, it was shown that flavo enzymes and comparable systems can be used for synthetic applications in a continuous process under anaerobic reactivation of the prosthetic group in the electrochemical enzyme membrane reactor [46, 50],... 

The immobilization of microbial cells under conditions where an activity or set of enzymic activities remains intact, but the normal metabolic processes cease, represents a novel technique for enzyme immobilization. Moreover, immobilized cells might enable the standard fermentation methods to be replaced by immobilized -cell -based continuous processes. 

As an alternative to chemical epimerization, NAG epimerase may be used to maintain a constant NAM NAG ratio in a one-pot reaction with pyruvate and NANA aldolase. The epimerase is itself inhibited by pymvate, which must, therefore, be added continuously or via aliquots to the reaction. In a refined version of this reaction at laboratory scale, Kragl et al produced NANA by a continuous process, using a membrane reactor to contain both enzymes in solution. 

In the development of cell or enzyme-based processes, many process configurations exist, including batch, fed batch and continuous operation. In general, the conversion and the separation processes (downstream processing) are regarded as separate units, and most industrial processes are based on this approach. In the last decades, however, more attention is paid to the integration of conversion and separation, leading to the development of membrane bioreactors [49, 50], and some of these concepts have reached an industrial scale. The membranes used for this type of reactors are almost exclusively polymeric, as temperatures seldomly exceed 100 °C for obvious reasons. 

B. Nidetzky, K. Schmidt, W. Neuhau-SER, et al, Application of charged ultrafil-tration membranes in continuous, enzyme-catalysed processes with coenzyme regeneration, in Separations for Biotechnology 3 (ed. D. L. Pyle) Royal Society of Chemistry, 1994, 351. 

The lead time, for incorporation of enzymes as an adjunct in whatever form into commercial food processes, appears to be far longer than equivalent innovation lead times m non-food, or even pharmaceutical processes. The exception to this finding is that there are enzymes which play an important role in many analytical and quality control procedures in the food industry, without the use of which, for batch or continuous process monitoring, many product lines would not be possible. 

Semibatch reactors are especially important for bioreactions, where one wants to add an enzyme continuously, and for multiple-reaction systems, where one wants to maximize the selectivity to a specific product. For these processes we may want to place one reactant (say, A) in the reactor initially and add another reactant (say, B) continuously. This makes Ca large at all times but keeps Cg small. We will see the value of these concentrations on selectivity and yield in multiple-reaction systems in the next chapter. 

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