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Influence of controlled-pH and uncontrolled-pH operations on recombinant benzaldehyde lyase production by Escherichia coli

Paper ID Volume ID Publish Year Pages File Format Full-Text
18616 42728 2006 11 PDF Available
Title
Influence of controlled-pH and uncontrolled-pH operations on recombinant benzaldehyde lyase production by Escherichia coli
Abstract

To select the host microorganism having the highest benzaldehyde lyase (BAL) production capacity, pUC18∷bal gene was transferred into four Escherichia coli strains. As the highest enzyme activity was obtained with E. coli K12 (ATCC 10798) carrying pUC18∷bal gene, BAL production medium was designed for K12. Using the designed medium containing 8.0 kg m−3 glucose, 5.0 kg m−3 (NH4)2HPO4 and the salt solution, the effects of uncontrolled-pH and controlled-pH operations were investigated at uncontrolled-pH pHUC 7.2 and controlled-pH values pHC 5.0, 6.4, 6.7, 7.0, 7.2 and 7.8 in 3.0 dm3 bioreactor systems with a VR = 1.65 dm3 working volume at the air inlet rate of Qo/VR = 0.5 vvm and agitation rate of N = 500 min−1. The uncontrolled-pH (pHUC 7.2) operation produced the highest cell concentration and BAL activity as CX = 2.3 kg m−3 and A = 860 U cm−3, respectively. Among the controlled-pH operations, the highest cell concentration and enzyme activity were obtained at pHC 7.0 operation, respectively, as CX = 2.1 kg m−3 and A = 775 U cm−3. The accumulation of the metabolic by-product acetic acid and the total organic acid concentrations were the highest at pHC 7.2 and 7.8 operations. On the other hand, there was no significant difference in the acetic acid concentration profiles of pHC 5.0, 6.4, 6.7 and 7.0 operations; however, the highest total organic acid concentration was attained at pHC 5.0 because of the lactic acid excretion, and the lowest total organic acid was obtained at pHC 6.7. KLa values varied between 0.01 and 0.03 s−1. To compare the mass transfer and biochemical reaction rates, the maximum possible oxygen utilization rate, possible mass transfer rate, Damköhler number, and effectiveness factor, were also calculated. Damköhler number increased with the cultivation time indicating that mass transfer resistances were becoming more effective than biochemical reaction resistances. The yield and maintenance coefficients as well as the kinetic constants for BAL production process were also reported.

Keywords
ATCC, American Type Culture Collection; BAL, benzaldehyde lyase; BP, by-product; DNS, dinitrosalicilyc acid; DO, dissolved oxygen; EC, enzyme commission; OD, oxygen demand; OUR, oxygen uptake rate; OTR, oxygen transfer rate; OTRmax, maximum possible mass
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Influence of controlled-pH and uncontrolled-pH operations on recombinant benzaldehyde lyase production by Escherichia coli
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Publisher
Database: Elsevier - ScienceDirect
Journal: Enzyme and Microbial Technology - Volume 38, Issue 5, 2 March 2006, Pages 617–627
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us