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Titolo:
Computer-aided control of water activity for lipase-catalyzed esterification in solvent-free systems
Autore:
Won, K; Lee, SB;
Indirizzi:
Pohang Univ Sci & Technol, Dept Chem Engn, Div Mol & Life Sci, Pohang 790784, South Korea Pohang Univ Sci & Technol Pohang South Korea 790784 790784, South Korea Pohang Univ Sci & Technol, Inst Environm & Energy Technol, Pohang 790784, South Korea Pohang Univ Sci & Technol Pohang South Korea 790784 790784, South Korea
Titolo Testata:
BIOTECHNOLOGY PROGRESS
fascicolo: 2, volume: 17, anno: 2001,
pagine: 258 - 264
SICI:
8756-7938(200103/04)17:2<258:CCOWAF>2.0.ZU;2-6
Fonte:
ISI
Lingua:
ENG
Soggetto:
PHASE ENZYMATIC ESTERIFICATION; ORGANIC MEDIA; NONAQUEOUS SOLVENTS; REACTION-RATES; FATTY-ACID; BIOCATALYSIS; AGGLOMERATION; EFFICIENCY; DEPENDENCE; ENZYMES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Agriculture,Biology & Environmental Sciences
Life Sciences
Citazioni:
29
Recensione:
Indirizzi per estratti:
Indirizzo: Lee, SB Pohang Univ Sci & Technol, Dept Chem Engn, Div Mol & Life Sci, San31,Hyoja Dong, Pohang 790784, South Korea Pohang Univ Sci & Technol San 31,Hyoja Dong Pohang South Korea 790784
Citazione:
K. Won e S.B. Lee, "Computer-aided control of water activity for lipase-catalyzed esterification in solvent-free systems", BIOTECH PR, 17(2), 2001, pp. 258-264

Abstract

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 wateractivity 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, 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, 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 activitycontrol. 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, 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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Documento generato il 11/07/20 alle ore 19:26:05