Ultrafiltration reactor

Deeslie, W. D. and Cheryan, M. (1981). Continuous enzymatic modification of proteins in an ultrafiltration reactor. ]. Food Sci. 46,1035-1042. 

Bordenave, S., Sannier, F., Ricart, G., and Piot, J.M. 1999. Continuous hydrolysis of goat whey in an ultrafiltration reactor generation of alpha-lactorphin. Prep. Biochem. Biotechnol. 29, 189—202. 

E. Drioli, et al., High-Temperature Immobilized Ceil Ultrafiltration Reactors , J. Membr. Sci. 11, 365, 1982. 

A membrane cell recycle reactor with continuous ethanol extraction by dibutyl phthalate increased the productivity fourfold with increased conversion of glucose from 45 to 91%.249 The ethanol was then removed from the dibutyl phthalate with water. It would be better to do this second step with a membrane. In another process, microencapsulated yeast converted glucose to ethanol, which was removed by an oleic acid phase containing a lipase that formed ethyl oleate.250 This could be used as biodiesel fuel. Continuous ultrafiltration has been used to separate the propionic acid produced from glycerol by a Propionibacterium.251 Whey proteins have been hydrolyzed enzymatically and continuously in an ultrafiltration reactor, with improved yields, productivity, and elimination of peptide coproducts.252 Continuous hydrolysis of a starch slurry has been carried out with a-amylase immobilized in a hollow fiber reactor.253 Oils have been hydrolyzed by a lipase immobilized on an aromatic polyamide ultrafiltration membrane with continuous separation of one product through the membrane to shift the equilibrium toward the desired products.254 Such a process could supplant the current energy-intensive industrial one that takes 3-24 h at 150-260X. Lipases have also been used to prepare esters. A lipase-surfactant complex in hexane was used to prepare a wax ester found in whale oil, by the esterification of 1 hexadecanol with palmitic acid in a membrane reactor.255 After 1 h, the yield was 96%. The current industrial process runs at 250°C for up to 20 h. 

Macromolecular substrates such as proteins offer unique opportunities in processing modes with enzymes. Ultrafiltration membrane reactors (10) can be used to retain the protein substrate and the proteolytic enzyme in the reactor, while the hydrolytic products escape through the membrane to be collected. Using an ultrafiltration reactor, Cheftel (11) was able to solubilize 95% of FPC in 24 hr using pronase digestion. 

This system of preparing protein hydrolysates may be of general utility however, Roozen and Pilnik (12) treated a soybean isolate in an ultrafiltration reactor and experienced problems of a thickened retentate... 

Figure 6.30 A process for the synthesis of an L-amino acid (leucine) from a racemic hydroxy acid (2-hydroxyisocaproate, i.e. 2-hydroxy-4-methylpentanoate). The reaction is carried out in an ultrafiltration reactor with the cofactor NAD immobilized to a soluble polymer, polyethylene glycol 20 000, so that it remains behind the ultrafiltration membrane with the enzymes...

In open fibers the fiber wall may be a permselective membrane, and uses include dialysis, ultrafiltration, reverse osmosis, Dorman exchange (dialysis), osmotic pumping, pervaporation, gaseous separation, and stream filtration. Alternatively, the fiber wall may act as a catalytic reactor and immobilization of catalyst and enzyme in the wall entity may occur. Loaded fibers are used as sorbents, and in ion exchange and controlled release. Special uses of hoUow fibers include tissue-culture growth, heat exchangers, and others. 

Many procedures have been suggested to achieve efficient cofactor recycling, including enzymatic and non-enzymatic methods. However, the practical problems associated with the commercial application of coenzyme dependent biocatalysts have not yet been generally solved. Figure A8.18 illustrates the continuous production of L-amino adds in a multi-enzyme-membrane-reactor, where the enzymes together with NAD covalently bound to water soluble polyethylene glycol 20,000 (PEG-20,000-NAD) are retained by means of an ultrafiltration membrane. 

Surface-modified electrodes were used for prevention of high overpotentials with direct oxidation or reduction of the cofactor, electrode fouling, and dimerization of the cofactor [7cj. Membrane electrochemical reactors were designed. The regeneration of the cofactor NADH was ensured electrochemically, using a rhodium complex as electrochemical mediator. A semipermeable membrane (dialysis or ultrafiltration) was integrated in the filter-press electrochemical reactor to confine... 

Aim of this work was to optimise enzymatic depolymerization of pectins to valuable oligomers using commercial mixtures of pectolytic enzymes. Results of experiments in continuous and batch reactor configurations are presented which give some preliminary indications helpful to process optimisation. The use of continuous reactors equipped with ultrafiltration membranes, which assure removal of the reaction products, allows to identify possible operation policy for the improvement of the reaction yield. 

Figure 3. Oligouronides evolution in a reactor without cross-flow ultrafiltration membrane, (a) Native Rh. nigricans endoPG. (b) Pasteurised Rh. nigricans endoPG.

Figure 4.2 Enzyme-hi-membrane-reactor synthesis of 1-pheny 1-2-propanol from l-phenyl-2-propanone applying a stirred-tank reactor, ultrafiltration module, extraction module and distillation...

Figure 4.7 Classical kinetic resolution synthesis of L-methionine from IV-acetyl-methionine applying an ultrafiltration-membrane reactor and crystallization step as well as racemization step...

Figure 4.18 Enzyme membrane reactor synthesis of L-tert-leucine from trimethylpyruvic acid in an continuously operated enzyme membrane reactor with ultrafiltration followed by a crystallization step...

Another reaction performed in the dead-end reactor discussed before, is the allylic amination of 3-phenyl-2-propenyl-carbonic acid methyl ester with morpholine. [30] First and second generation commercially available DAB-dendrimers were functionalized with diphenylphosphine groups (Figure 4.13). Two different membranes were used, the Nadir UF-PA-5 (ultrafiltration) and the Koch MPF-50 (former SELRO) (nanofiltration), which gave retentions of 99.2% and 99.9% respectively for the second generation functionalized dendrimers. 

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. 

Fig. 3.95. Chromatogram of H-acid in the ultrafiltration permeate from the anaerobic reactor injection volume 20 /A, retention time 9.39 min, concentration 0.02 g/1 original, 0.25 g/1 after 11 h biomass treatment. Reprinted with permission from A. Rehorek et al. [155].

An excellent production figure for (R)-mandelonitrile (2400 g/1 per day) was achieved by Kragl et al. [105] using a continuously stirred tank reactor in which an ultrafiltration membrane enables continuous homogenous catalysis to occur from an enzyme (PaHnl) which is retained within the reaction vessel. In order to quench the reaction the outlet of this vessel was fed into a vessel containing a mixture of chloroform and hydrochloric acid, which allowed for accurate product analysis. 

Ultrafiltration has been used for the separation of dendritic polymeric supports in multi-step syntheses as well as for the separation of dendritic polymer-sup-ported reagents [4, 21]. However, this technique has most frequently been employed for the separation of polymer-supported catalysts (see Section 7.5) [18]. In the latter case, continuous flow UF-systems, so-called membrane reactors, were used for homogeneous catalysis, with catalysts complexed to dendritic ligands [23-27]. A critical issue for dendritic catalysts is the retention of the catalyst by the membrane (Fig. 7.2b, see also Section 7.5). 

Unmodified poly(ethyleneimine) and poly(vinylpyrrolidinone) have also been used as polymeric ligands for complex formation with Rh(in), Pd(II), Ni(II), Pt(II) etc. aqueous solutions of these complexes catalyzed the hydrogenation of olefins, carbonyls, nitriles, aromatics etc. [94]. The products were separated by ultrafiltration while the water-soluble macromolecular catalysts were retained in the hydrogenation reactor. However, it is very likely, that during the preactivation with H2, nanosize metal particles were formed and the polymer-stabilized metal colloids [64,96] acted as catalysts in the hydrogenation of unsaturated substrates. 

A biological step is always necessary to remove the carbonaceous fraction from the influent wastewater suspended biomass treatments are the most common. These entail long SRTs (>25-30 d), and compartmentalization of the biological reactor is necessary for the removal of recalcitrant compounds. Furthermore, as many micro-pollutants tend to adsorb/absorb to the biomass flocks, efficient solid/ liquid separation can greatly improve their removal from wastewater and, at the same time, guarantee consistently good effluent quality. MBRs have been suggested for this purpose by many authors [9, 58, 80, 93], some of whom found that ultrafiltration (UF) membranes are more efficient than MF membranes [9, 93]. 

Large hospital in a small catchment area a dedicated treatment should be adopted, featuring advanced biological and oxidation processes (AOPs), such as ultrafiltration membrane biological reactors (MBRs), and then ozone/UV, which also guarantees efficient disinfection. 

Membrane reactors have been investigated since the 1970s 11). Although membranes can have several functions in a reactor, the most obvious is the separation of reaction components. Initially, the focus has been mainly on polymeric membranes applied in enzymatic reactions, and ultrafiltration of enzymes is commercially applied on a large scale for the synthesis of fine chemicals (e.g., L-methionine) 12). Membrane materials have been improved significantly over those applied initially, and nanofiltration membranes suitable to retain relatively small compounds are now available commercially (e.g., mass cut-off of 400—750 Da). 

Cabral and coworkers [253] have investigated the batch mode synthesis of a dipeptide acetyl phenylalanine leucinamide (AcPhe-Leu-NH2) catalyzed by a-chymotrypsin in a ceramic ultrafiltration membrane reactor using a TTAB/oc-tanol/heptane reverse micellar system. Separation of the dipeptide was achieved by selective precipitation. Later on the same group successfully synthesized the same dipeptide in the same reactor system in a continuous mode [254] with high yields (70-80%) and recovery (75-90%). The volumetric production was as high as 4.3 mmol peptide/l/day with a purity of 92%. The reactor was operated for seven days continuously without any loss of enzyme activity. Hakoda et al. [255] proposed an electro-ultrafiltration bioreactor for separation of RMs containing enzyme from the product stream. A ceramic membrane module was used to separate AOT-RMs containing lipase from isooctane. Application of an electric field enhanced the ultrafiltration efficiency (flux) and it further improved when the anode and cathode were placed in the permeate and the reten-tate side respectively. 

A solution to this problem is the enzyme membrane reactor (Figure 10.8). This is a kind of CSTR (continuous stirred tank reactor), with retains the enzyme and the cofactor using an ultrafiltration membrane. This membrane has a cut-off of about 10000. Enzymes usually have a molecular mass of 25000-250000, but the molecular mass of NAD(H) is much too low for retention. Therefore it is first derivatized with polyethylene glycol (PEG 20000). The reactivity of NAD(H) is hardly affected by the derivatization with this soluble polymer. Alanine can now be produced continuously by high concentrations of both enzymes and of NAD (H) in this reactor. 

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