Integrated reactive absorption process for synthesis of fatty esters

Reactive separations using green catalysts offer great opportunities for manufacturing fatty esters, involved in specialty chemicals and biodiesel production. Integrating reaction and separation into one unit provides key benefits such as: simplified operation, no waste, reduced capital investment and low operating costs.This work presents a novel heat-integrated reactive absorption process that eliminates all conventional catalyst related operations, efficiently uses the raw materials and equipment, and considerably reduces the energy requirements for biodiesel production - 85% lower as compared to the base case. Rigorous simulations based on experimental results were carried out using Aspen Plus and Dynamics. Despite the high degree of integration, the process is well controllable using an efficient control structure proposed in this work. The main results are provided for a plant producing 10 ktpy fatty acid methyl esters from methanol and waste vegetable oil with high free fatty acids content, using sulfated zirconia as solid acid catalyst.     

A two-stage enzymatic process for synthesis of extremely pure high oleic glycerol monooleate

This paper presents a research interest concentrating on aims to establish a feasible industrial process for enzymatic production of highly pure glycerol monooleate (GMO). The synthesis of high oleic glycerol monooleate by enzymatic glycerolysis of high oleic sunflower oil, using Novozyme 435 as the biocatalyst, in a binary solvent mixture of tert-butanol and tert-pentanol (80/20, v/v), at a lab scale has been studied. A yield of 75.31% monoacylglycerol has been achieved at the first stage. A yield of 93.3% GMO was finally reached after further purification at the second stage. To evaluate the possibility of the process for industrialization, production of GMO was performed at a pilot-plant scale under the correspondingly adjusted conditions. A yield of 68.17% and 93.4% of GMO was obtained, respectively, at the end of the three stages.     

Large scale enzymatic synthesis of oligosaccharides and a novel purification process

Herein we report the practical chemo enzymatic synthesis of trisaccharide and derivatives of iGb3 and Gb3, and a novel purification process using immobilized yeast to remove the monosaccharide from the reaction mixture. High purity oligosaccharide compounds were achieved in large scale. This study represents a facile enzymatic synthesis of and novel purification process of oligosaccharide.     

Development of a recovery and recycle process for a pseudomonas lipase used for large-scale enzymatic synthesis

Enzymes are potential catalysts for a wide range of large-scale chemical synthesis steps, particularly when the creation of a specific chiral center is desired. The efficient recycling of the enzyme catalyst and the removal of carryover impurities were crucial factors in the improvement of a stereoselective ester hydrolysis step used in the synthesis of a selective leukotriene antagonist. In this enzymatic reaction step, the substrate and product were both largely insoluble, while the enzyme was soluble in the aqueous reaction mixture. Microfiltration and ultrafiltration of the slurry reaction mother liquor indicated near 100% enzyme protein recovery, while activity recovery was about 70% to 80%. These activity losses might be accounted for by enzyme degradation (1 to 2 mg/L . h) during the 40-hour reaction period. Dissolved impurities, principally a diacid byproduct, in the enzyme recycling stream were reduced 60% to 70% by either lowering the solution pH to 4.0 or raising the solution ionic strength to 1 M. (c) 1993 John Wiley & Sons, Inc.     

Novel method for enzymatic synthesis of CMP-NeuAc

A novel method for synthesizing CMP-NeuAc was established. We first confirmed that the putative neuA gene of Haemophilus influenzae, identified by its whole genome sequence project, indeed encodes CMP-NeuAc synthetase (EC 2.7.7.43). The enzyme requires CTP as a cytidylyl donor for cytidylylation of NeuAc. The enzyme was coupled with an enzymatic CTP-generating system from CMP and inorganic polyphosphate as a sole phospho-donor driven by the combination of polyphosphate kinase and CMP kinase, where phosphorylation of CMP is done by the combined activity expressed by both enzymes, and subsequent phosphorylation of CDP by polyphosphate kinase itself occurred efficiently. When CMP-NeuAc synthetase of H. influenzae, polyphosphate kinase, and CMP kinase were added to the reaction mixture containing equimolar concentrations (15 mM) of CMP and NeuAc, and polyphosphate (150 mM in terms of phosphate), CMP-NeuAc was synthesized up to 10 mM in 67% yield.     

Integrated enzymatic reactions and analysis

Summary Enzymatic reactions were performed in a modified auto-injector unit of a Shimadzu HPLC system. The reactions were analyzed by automated injections directly into the HPLC separation system. Two reactions were studied, and the enzymes mandelonitrile lyase and α-chymotrypsin were immobilized by adsorption onto a solid support, e.g., Celite and Chromosorb. The reactions were performed in various organic solvents e.g., diisopropyl ether, heptane/ethyl acetate mixtures and acetonitrile.     

Kinetics of the enzymatic synthesis of benzylpenicillin

The kinetics of the enzymatic synthesis of benzylpenicillin catalysed by penicillin amidase (EC 3.5.1.11) from Escherichia coli have been studied. Both free phenylacetic acid (PAA) and its activated derivative, phenylacetylglycine (PAG), were used in the synthesis as acylating agents for 6-aminopenicillanic acid (6-APA). The catalytic rate constants for synthesis carried out at pH 6.0 were 11.2 and 25.2 s⁻¹, respectively, i.e. they are close and have high absolute values. The main feature of the enzymatic synthesis of benzylpenicillin from phenylacetylglycine, compared with the synthesis from phenylacetic acid, is the shape of the progress curve of antibiotic accumulation. In the former case, benzylpenicillin gradually accumulates until equilibrium is reached. Thus, if the reaction is carried out at the thermodynamically optimum pH of synthesis (low pH), penicillin can be obtained in high yield. In the case of phenylacetylglycine, the kinetic curves are more complex and are characterized by a clear-cut maximum. The presence of the maximum, its value and position on the time axis depend on reagent concentration and on the pH used. A kinetic scheme is proposed which describes well the experimental dependencies. The possibility of using activated acid derivatives in synthesis and the advantages of using computer calculations for process optimization are discussed.     

An integrated process: ester synthesis in an enzymatic membrane reactor and water sorption

In the case of such reactions as ester synthesis, water is produced during the reaction. Because these reactions are carried out in hydrophobic solvents an additional (water) phase in the system must not be allowed, i.e. the concentration of water saturation in the organic solvent should not be exceeded. In such a case, the reaction kinetics and product equilibrium concentration undergo undesirable changes because of the partition coefficient of the components and hampered process of product separation. Hence, removal of the water produced in the reaction determines whether the process is successful or not. For this purpose, the integrated process with water sorption in the column with molecular sieves was applied. Integration of the process of synthesis and dehydration of a reaction phase, in which a biocatalyst is suspended and not dissolved as in water solutions, requires holding up of the catalyst in the reactor before directing the stream of reaction mixture to dehydration process. This hold-up and a possibility of multiple use of the catalyst may be accomplished by using a separating barrier, e.g. an ultrafiltration membrane or by permanent fixing of the catalyst to the matrix, e.g. a polymeric membrane. The efficiency and activity of a biocatalyst (lipase CAL-B) immobilized on a polymer membrane by sorption and chemical binding, were determined. A subject of study was the synthesis of geranyl acetate, one of the most known aromatic compound. A hydrophobic (polypropylene) matrix was shown to be a much better carrier in the reactions performed in an organic solvent than a hydrophilic (polyamide) membrane being tested. The reaction kinetics of geranyl acetate synthesis with the use of geraniol and acetic acid as substrates, was described by the equation defining the "Ping-Pong Bi Bi" mechanism that was related additionally to the inhibition of a substrate (acetic acid). The following constants of kinetic equation were obtained k(3)(')=0.344 mol g(-1)h(-1), K(mA)=0.257 mol l(-1), K(mG)=1.629 and K(iA)=0.288 for the native enzyme and v(max,Gel)=111.579 mol l(-1)h(-1), K(mA)=0.255 mol l(-1), K(mG)=1.91 mol l(-1), K(iA)=0.238 mol l(-1) for the one immobilized by sorption on a polypropylene membrane. Half-life time of the native enzyme activity was 204 h and stability of the immobilized preparation was 70 h. With respect to the reaction kinetics and stability of the native enzyme and immobilized preparation, from both types of membrane bioreactor more attractive appears to be the one in which the membrane is used not as a catalyst layer but only as a barrier that immobilizes the native enzyme within the bioreactor volume. When an integrated process proceeds, the method to collect water in the sorption column during the process, appeared to work very well. The reaction proceeded with a very high efficiency (after 120 h alpha=98.2% for native enzyme and 83.2% for immobilized enzyme) and due to low water concentration in the system ( approximately 0.000% v/v) the second phase was not created.