Hidetaka Noritomi

Representation of activity coefficients of fundamental biochemicals in water by the UNIFAC model

Abstract The assignment of UNIFAC parameters has been newly examined to represent the activity coefficients of fundamental biochemicals in aqueous solutions containing sugars, imino acids, urea, amino acid salts, inorganic salts, and sugar salts. In this work, several new groups have been introduced to represent the activity coefficients for many biochemicals with better accuracy. For sugars, a portion containing asymmetric carbon atoms in an aldohexose molecule was defined as a new group for many stereoisomers. In the case of electrolytes like amino acid salts, the Pitzer-Debye-Huckel term was added to the UNIFAC equation to take the long-range electrostatic interaction into account. All new interaction parameters for the fundamental biochemicals have been determined from osmotic coefficient as well as activity coefficient data reported in the literature. The new parameters provided good calculated results for these biochemicals. In addition, the activity coefficient data for the ternary systems water/amino acid/urea and water/amino acid/sucrose were used to determine the interaction parameters between the constituent groups of an amino acid and those of the second solute, urea or sucrose. The correlated results for the system containing urea were in satisfactory agreement with the literature data.

Measurements of Solubilities of Two Amino Acids in Water and Prediction by the UNIFAC Model

The solubility of an amino acid in an aqueous solution containing another amino acid was measured at 298 K. The measured amino acid pairs were dl‐alanine/dl‐serine and dl‐alanine/dl‐valine. The invariant eutectic compositions of these pairs of amino acids were also determined. In addition, a prediction model of solubility for such a system was developed on the basis of solid−liquid equilibria. To represent more accurately the activity coefficient of amino acids and homopeptides by Larsens UNIFAC model, new assignments of UNIFAC groups were proposed and their interaction parameters were determined from experimental osmotic coefficient data. Finally, the prediction of solubilities of mixed solid amino acids was made and the results were compared with experimental data.

Extraction of polyunsaturated fatty acid ethyl esters from sardine oil using Ag+-containing o/w/o emulsion liquid membranes

Using silver ion as a carrier in o/w/o type emulsion liquid membranes, batch-wise extraction experiments were performed to separate polyunsaturated fatty acid ethyl esters originating in sardine oil. It was possible to separate polyunsaturated fatty acid (PUFA) esters from the mixture of PUFA and saturated fatty acid esters. The operating conditions for stable liquid membranes were experimentally determined. A new membrane breakage model that successfully describes the membrane stability behavior is proposed.

Recovery of protein from reverse micelles through gas hydrate formation

The recovery of cytochrome c and ribonuclease A from di-2-ethylhexyl sodium sulfosuccinate (AOT) reverse micelles have been examined by the gas hydrate formation. The recovery of cytochrome c depended upon the kind of gas and the water content (w0=[H2O]/[AOT]) of reverse micellar solution containing cytochrome c prepared. Recoveries of cytochrome c and ribonuclease A were more than 80%, when 1,1,1,2-tetrafluoroethane (TFE) was used as a hydrating gas. The activity of cytochrome c recovered from reverse micelles was maintained perfectly.

Enzymatic synthesis of peptide in acetonitrile/supercritical carbon dioxide

SummaryThe peptide synthesis from N-acetyl-L-tyrosine ethyl ester (Ac-Tyr-OEt) and amino acid amides was realized using α-chymotrypsin (CT) in acetonitrile (MeCN) or acetonitrile/supercritical carbon dioxide (SCCO2) containing small amounts of water. In both solvent systems there was an optimum water content for peptide synthesis, above which peptide hydrolysis became more important. After an incubation for 5 hours, the yields of the peptide was 64% in MeCN and 91% in MeCN/SCCO2, respectively.

Increased Thermostability of Cross-Linked Enzyme Crystals of Subtilisin in Organic Solvents

Cross-linked enzyme crystals(CLECs) of subtilisin display the improved thermostability in organic solvents, compared to free subtilisin. CLECs are more stable than the free enzyme in octane with a half life of 200 days at 45°C, while that of free enzyme is 5.4 days. CLECs in octane is more stable than in acetonitrile.

Protease-catalyzed esterification of amino acid in water-miscible ionic liquid

The activity of two proteases in the esterification of N-acetyl-l-phenylalanine with ethanol was examined in the water-miscible ionic liquid, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim][Tf]). The activity of subtilisin was not only improved 9-fold by changing from a water-miscible organic solvent, acetonitrile, to [emim][Tf], but also was about three times greater than that in a water-immiscible organic solvent, octane. Likewise, the activity of α-chymotrypsin in [emim][Tf] was more effectively enhanced compared with that in a water-miscible or a water-immiscible organic solvent. The water content in [emim][Tf] affected the activity of subtilisin.

Enzyme recovery from reversed micellar solution through formation of gas hydrates

Abstract The phase behavior of gas hydrate in reversed micellar solution without as well as with an enzyme were measured using propane and HCFC22 as gas species ,and cytochrome c and α-chymotrypsin as enzymes. Equilibrium pressure without an enzyme decreased as the water to surfactant(AOT) ratio, W 0 , decreased like the hydrate-formation from salt containing aqueous solution. After the hydrate was formed, the final value of W 0 were constant(W 0 =3 ∼ 4) independent of the initial W 0 . By adding HCFC22 and also cooling the reversed micellar solution containing an enzyme and AOT, most of the free water in the pool of the micelle was converted to gas hydrate and caused the desolubilized enzyme to precipitate as a solid phase. Propane could form gas hydrate for the enzyme-containing micellar solution but not result in so much precipitation as HCFC22 because of the small solubility of propane in water. Finally we have proposed a new method for the recovery of enzyme from reversed micellar solution involving precipitation of the enzyme through formation of gas hydrate.

Application of UNIFAC models to partition coefficients of biochemicals between water and n-octanol or n-butanol

Abstract The objective of this work is to examine whether the various UNIFAC models can represent phase behavior of biochemicals in the dilution solution such as partition coefficients (log P i ). Especially, the log P i of a solute in the n -octanol/water system was used as main target for the examination in this work. First, the log P i of common chemical solutes was tested by use of various UNIFAC models. It was concluded that the original model and Larsen et al.s model [B.L. Larsen, P. Rasmussen, Aa. Fredenslund, Ind. Eng. Chem. Res., 26 (1987) 2274–2286] were suitable for the prediction of the log P i . In the next, both models were applied to calculation of log P i of biochemicals such as amino acids, their derivatives, and sugars. In addition, hydrophobicity constants ( π ) of an amino acid side chains were calculated from the log P i of amino acids. From the above results, the performance of the UNIFAC models for log P i and π was discussed.

Extraction of eicosapentaenoic acid ethyl ester from a model media using Ag(I)-containing o/w/o-type emulsion liquid membranes

Abstract Using silver ion as a carrier in oil/water/oil-type emulsion liquid membranes, batchwise extraction experiments were done to separate eicosapentaenoic acid ethyl ester (EPA-Et) from a model mixture consisting of EPA-Et and ethyl laurate. Moderate operating conditions were chosen for the concentration of Ag(I), the type of surfactant, and agitation strength. The emulsion liquid membranes thus formed were stable, and the concentration of Ag(I) and the surfactant types had strong effects on the permeation behavior of EPA-Et. The overall volumetric coefficients of EPA-Et obtained in the present study were equal to or smaller than those of organic solutes obtained with the data available in literature. It was found that the overall volumetric coefficients of these organic solutes increase linearly on a log-log scale, with increasing distribution ratios.