General rules for the optimization of different biocatalytic systems in various types of media containing organic solvents are derived by combining data from the literature, and the logarithm of the partition coefficient, log P, as a quantitative measure of solvent polarity. (1) Biocatalysis in organic solvents is low in polar solvents having a log P 4. It was found that this correlation between polarity and activity parallels the ability of organic solvents to distort the essential water layer that stabilizes the biocatalysts. (2) Further optimization of biocatalysis in organic solvents is achieved when the polarity of the microenvironment of the biocatalyst (log P(i)) and the continuous organic phase (log P(cph)) is tuned to the polarities of both the substrate (log P(s)) and the product (log P(p)) according to the following rules: |log P(i) - log P(s)| and |log P(cph) - log P(p)| should be minimal and |log P(cph) - log P(s)| and |log P(i) - log P(p)| should be maximal, with the exception that in the case of substrate inhibition log P(i), should be optimized with respect to log P(s) In addition to these simple optimization rules, the future developments of biocatalysis in organic solvents are discussed.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/bit.22209

Rules for optimization of biocatalysis in organic solvents

A study is conducted to demonstrate catalytic dehydrogenation of light alkanes on metals and metal oxides. The study provides a complete overview of the materials used to catalyze this reaction, as dehydrogenation for the production of light olefins has become extremely relevant. Relevant factors, such as the specific nature of the active sites, as well as the effect of support, promoters, and reaction feed on catalyst performance and lifetime, are discussed for each catalytic Material. The study compares different catalysts in terms of the reaction mechanism and deactivation pathways and catalytic performance. The duration of the dehydrogenation step depends on the heat content of the catalyst bed, which decreases rapidly due to the endothermic nature of the reaction. Part of the heat required for the reaction is introduced to the reactors by preheating the reaction feed, additional heat being provided by adjacent reactors that are regenerating the coked catalysts.

Catalytic dehydrogenation of light alkanes on metals and metal oxides.

Although many methods for enzyme immobilization have been described in patents and publications, relatively few processes employing immobilized enzymes have been successfully commercialized. The cost of most industrial enzymes is often only a minor component in overall process economics, and in these instances, the additional costs associated with enzyme immobilization are often not justified. More commonly the benefit realized from enzyme immobilization relates to the process advantages that an immobilized catalyst offers, for example, enabling continuous production, improved stability and the absence of the biocatalyst in the product stream. The development and attributes of several established and emerging industrial applications for immobilized enzymes, including high-fructose corn syrup production, pectin hydrolysis, debittering of fruit juices, interesterification of food fats and oils, biodiesel production, and carbon dioxide capture are reviewed herein, highlighting factors that define the advantages of enzyme immobilization.

Industrial use of immobilized enzymes

Thermodynamic predictions for biocatalysis in nonconventional media: theory, tests, and recommendations for experimental design and analysis.

Tetrahedron report number 203

The mean specific resistance of the cakes of various microorganisms was evaluated by measurement of either a change in the amount of permeate with time or of steady-state flux under constant pressure. The mean specific resistance was different with different shapes and sizes of microorganisms. The large differences arose from different packing structures of the cake. The effect of a filter aid on the filtration rate and cake structure was studied experimentally and theoretically. The effects of a filter aid were best explained by a series model, in which a cake layer composed of microbial cells and a layer of randomly distributed microbial cells and filter aid are packed on the membrane surface in series with respect to the directions of permeation.

On the specific resistance of cakes of microorganisms

A mathematical model is proposed for the elution of proteins on ion exchange columns by a linear gradient increase and stepwise increase of ionic strength in order to predict relationships between the elution characteristics (the peak position, the peak width, etc.) and the operating conditions (the flow rate, the slope of gradient, etc). This model is in principle based on the continuous-flow plate theory, in which the protein concentration and ionic strength dependent distibution coefficient between proteins and ion exchangers and zone sperading effects are taken into consideration. The advantage of this model is its simplicity since it requires only two parameters: The distribution coefficient and the number of plates. Since the distribution coefficient of proteins depends on both the protein concentration and ionic strength of the elution buffer, the number of plates should vary with time. However, it is extremely difficult to take into consideration the time-dependent number of plates. Therefore, we assume that the number of plates is constant and related to that number derived from a mass balance model which includes longitudinal dispersion and gel phase diffusion. On the basis of these assumptions, a method for determining the number of plates by the moment method is presented. Although the dependencies of the peak position and peak width on the slope of linear gradient are predictable by numerical calculations of the present model, simpler methods for prediction of these dependencies are desirable. A graphical method is proposed for prediction of the peak position. For prediction of the peak width, an asymptotic solution is derived from a quasi-steady-state model.

Ion exchange chromatography of proteins-prediction of elution curves and operating conditions. I. Theoretical considerations.

βS-Galactosidases (EC 3.2.1.23) from Bacillus circulans were purified and separated into two different enzyme forms, using Sephadex G-150, ion-exchange, polybuffer chromatography, and preparative polyacrylamide gel electrophoresis. The molecular weights estimated for these two enzymes were 2.4 × l05 (β-galactosidase-1) and 1.6 × 105 (β-galactosidase-2). They showed similar isoelectric points of about 4.5 and the same optimum pH of 6.0, whereas they were considerably different in Km values, substrate specificity, and particularly oligosaccharide-producing activity. /?-Galactosidase-2 produced many galacto-oligosaccharides, including di-,tri-, tetra-, and pentasaccharides, during hydrolysis of 4.56% lactose. When 60% of the lactose was converted, the total amount of oligosaccharide production reached a maximum at which about 41% of the products formed were oligosaccharides. β-Galactosidase-1 produced only 6% at its maximum.

Purification and Properties of β-Galactosidases from Bacillus circulans

N - (benzyloxycarbonyl) - L - aspartyl - L - phenylalanine methyl ester, the precursor of the synthetic sweetener aspartame, was continuously synthesized in an organic solvent with immobilized thermolysin. Ethyl acetate was found to be the most effective organic solvent for the synthesis of this precursor. The plug flow type reactor was found unsuitable, because the immobilized enzyme in it was gradually inactivated even if calcium, the essential stabilizing factor for thermolysin, was added to the substrate. In addition, a severe channeling of the flow occurred in a column. A stirred tank reactor was successfully operated for over 300 hours with a yield of approximately 90 percent and a large space velocity.

Kazuhiro Nakanishi

Papers

On the specific resistance of cakes of microorganisms

Ion exchange chromatography of proteins-prediction of elution curves and operating conditions. I. Theoretical considerations.

Purification and Properties of β-Galactosidases from Bacillus circulans

Continuous Synthesis of N-(Benzyloxycarbonyl)-L-Aspartyl-L-Phenylalanine Methyl Ester with Immobilized Thermolysin in an Organic Solvent

Properties of immobilized β-d-galactosidase from Bacillus circulans