Enzymatic ester synthesis with continuous measurement of water activity

Goldberg, M; Parvaresh, Firooze; Thomas, Daniel; Legoy, Marie‐Dominique

doi:10.1016/0167-4838(88)90226-9

Cited by 42 publications

(11 citation statements)

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“…) has numerous applications:¯avors, emulsi®ers, stabilizing and conditioning molecules, fatty esters of polyols as drug carriers, surfactants in the detergent and cosmetic industries, and ecient processes for enantiomerically pure products in the pharmaceutical industry (Ballesteros et al, 1995;Brink et al, 1988;Dordick, 1990;Klibanov, 1985, 1988). This reversal of their original hydrolytic activity is usually obtained by using them in organic solvents at low water activity (Chulalaksananukul et al, 1990;Khmelnitsky et al, 1988) or in solventfree media composed only of the mixture of substrates (Bourg-Garros et al, 1998;Ergan et al, 1990;Fonteyn et al, 1994;Goldberg et al, 1988;Kim and Rhee, 1991). Biphasic media have also proven to be eective but are not very convenient (Brink et al, 1988;Luisi and Laane, 1986;Tweddell et al, 1998).…”

Section: Introductionmentioning

confidence: 98%

Esterification by immobilized lipase in solvent‐free media: Kinetic and thermodynamic arguments

Sandoval

Condoret

Monsan

et al. 2002

Biotech & Bioengineering

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The aim of this study is to characterize, in solvent-free systems (SFS), the kinetic and thermodynamic performance of batch lipase-catalyzed esterification. SFS are compared to a conventional organic solvent, n-hexane. The esterification of oleic acid with ethanol was chosen as a model reaction. The TABEK (thermodynamic activity-based enzyme kinetics) approach was used to rationally analyze kinetics. Influence of the reaction medium on final conversions was also studied. Several factors, such as initial molar ratio of substrates, reactant availability, initial water content, and quantity of immobilized enzyme, were examined. Special attention was also turned to enzyme stability and reuse after reaction, this last item being a prerequisite in the development of industrial processes. SFS proved to be almost as efficient as n-hexane from a kinetic and thermodynamic point of view and offered a better volumetric production.

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Section: Introductionmentioning

confidence: 98%

Esterification by immobilized lipase in solvent‐free media: Kinetic and thermodynamic arguments

Sandoval

Condoret

Monsan

et al. 2002

Biotech & Bioengineering

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“…Several dehydration methods have been suggested in the literature. These include free evaporation (Selmi et al, 1997), vacuum evacuation (Napier et al, 1996), pervaporation (Kwon et al, 1995), dry gas bubbling (Kosugi and Azuma, 1994), and the use of selective adsorbents such as silica gel (Goldberg et al, 1988;Lee, 1996a, 1996b) and molecular sieves (Ergan et al, 1990).…”

Section: Introductionmentioning

confidence: 99%

Computer‐Aided Control of Water Activity for Lipase‐Catalyzed Esterification in Solvent‐Free Systems

Won

Lee

2001

Biotechnology Progress

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A computer system for on-line monitoring and control of the water activity (a(w)) in solvent-free media has been developed. The performance of this system was investigated by carrying out the lipase-catalyzed esterification of n-capric acid with n-decyl alcohol. A humidity sensor measured the relative humidity in the reactor headspace, which was then transmitted electrically to a digital computer that was used as a feedback controller. The water activity control was achieved by sparging either humidified air or dried air through the reaction medium at a flow rate determined by the digital feedback controller. The use of humid air and dry air for a(w) control made it possible to induce a larger a(w) gradient and thereby higher water transfer rate. As a result, the water activity quickly reached the desired a(w) values. We tested whether water activity in the reaction medium can be monitored by measuring relative humidity in the headspace. When the water activity in the liquid phase was determined from measurements of water content in the medium and compared to that measured directly with the humidity sensor, the a(w) in the reaction medium did not differ significantly from that in the headspace. This indicates that there is a near-equilibrium between the liquid medium and the exit air stream. Water activity was also successfully maintained close to the set point despite the massive production of water during the esterification process. Thus, the control system developed in this study is particularly useful for systems where large amounts of water are produced and where conventional methods make it difficult to control water activity as a result of a low water transfer rate. The effects that computer control of the water activity had on the reaction rate and yield were also examined. The reaction yield was significantly improved with water activity control. The conversions obtained at 28 h without and those with water activity control were 70% and 96%, respectively. In addition, from the fact that the final yields increased with decreasing a(w), computer-aided water activity control was performed with a set-point change. By controlling a(w) at 0.55 during initial reaction phase, followed by a step change of a(w) from 0.55 to 0 after 11 h of reaction, it was possible to enhance the final conversion to 100%.

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“…However in some cases, the solvent can be responsible for enzyme denaturation or inhibition [6]. Moreover, the solvent can be unnecessary in the case of co-soluble substrates (liquids or solids and liquids) for ester synthesis or transesterification C. cjlindracea lipase is known to remain active in organic phases composed only of the substrates [12]. However, we have shown in a previous paper [I31 that the enzyme activity of a preparation equilibrated with previously dehydrated substrates can be drastically decreased because of enzyme dehydration.…”

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confidence: 99%

The control of lipase‐catalysed transesterification and esterification reaction rates

Goldberg¹,

Thomas²,

Legoy³

1990

European Journal of Biochemistry

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The reaction rate of two lipase-catalysed reactions, esterification and transesterification, were studied in a liquid/solid two-phase system in order to investigate the effect of water partition between the enzyme preparation and the liquid phase composed of only the reactants, i.e. without the conventional solvents.Lipase from Candidu cylirzdrucea was used for these studies. The enzyme was inactive in dehydrated systems. In the case of monoester synthesis, the reaction rate increased with increasing water activity. The reaction rates of the non-specific C. cylindraceu lipase-catalysed reactions were very sensitive to the nature of the substrates in this unusual system. For instance, the transesterification reaction rate of ethyl propionate was 48 times higher with nonanol than heptanol in the case of dehydrated substrates, but only 2.2 times higher in the case of watersaturated substrates. The results presented here demonstrate the absolute necessity to consider the polarity of every substrate, because of its ability to modify the water partition between the solid phase (enzyme preparation) and the liquid phase (substrate and product), which results in drastic changes in enzyme activity.Contrary to esterification, which is known to be activated by the water produced, the rate of transesterification remained constant at the beginning of the reaction. However, when transesterification and esterification were carried out in the same liquid phase, the transesterification reaction rate was controlled by the water produced by the concomitant esterification. Activation effects of the water molecules produced during the enzymatic reaction were of exactly the same order of magnitude for both reactions.The effect of solvents on enzyme activity, specificity and stability have been extensively studied, and many solvent parameters have been compared in order to develop a simple strategy for choosing the appropriate solvent for each enzyme and reaction [l, 21. A solvent is necessary for solubilizing the substrates, and for partitioning the substrates and products in different phases [3]. It can be also used for increasing enzyme thermal stability [4] or for avoiding hydrolysis [ 5 ] . However in some cases, the solvent can be responsible for enzyme denaturation or inhibition [6]. Moreover, the solvent can be unnecessary in the case of co-soluble substrates (liquids or solids and liquids) for ester synthesis or transesterification C. cjlindracea lipase is known to remain active in organic phases composed only of the substrates [12]. However, we have shown in a previous paper [I31 that the enzyme activity of a preparation equilibrated with previously dehydrated substrates can be drastically decreased because of enzyme dehydration. A decrease of enzyme activity was also shown to occur in the case of highly hydrated enzyme preparations. The wide variation in the enzyme activities occurring due to the interaction of water, substrates and enzyme preparations in substrate-concentrated liquid phases needs to be understood.[7-131. A...

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Enzymatic ester synthesis with continuous measurement of water activity

Cited by 42 publications

References 4 publications

Esterification by immobilized lipase in solvent‐free media: Kinetic and thermodynamic arguments

Esterification by immobilized lipase in solvent‐free media: Kinetic and thermodynamic arguments

Computer‐Aided Control of Water Activity for Lipase‐Catalyzed Esterification in Solvent‐Free Systems

The control of lipase‐catalysed transesterification and esterification reaction rates

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