Substrate and water adsorption phenomena in a gas/solid enzymatic reactor.
The adsorption of water and substrates to dry deposited alcohol dehydrogenase from Lactobacillus brevis (LBADH) is studied in a continuous enzymatic gas/solid reactor. This work is aiming at obtaining a deeper and more thorough understanding of the enzyme microenvironment in the gas/solid system of acetophenone reduction with concomitant oxidation of 2-propanol. Extensive water adsorption studies showed that the effect of sucrose in the enzyme preparation on the water adsorption isotherm is significant for water activities exceeding 0.5 and reaches a factor 2 with respect to bead mass at water activity of 0.9. Significant hysteresis during water desorption is identified, resulting in up to 0.6 mg(water)/mg(protein), for lyophilized enzyme preparation and up to 10 mg(water)/mg(protein) for deposited enzyme preparation. The adsorption of the substrates is quantified here for the first time. Whereas the adsorption of the main substrate, acetophenone, may reach a significant level of up to 6 mg/mg(protein), at an acetophenone activity of 0.32, the secondary substrate, 2-propanol is not adsorbed at a detectable degree. The presence of water leads to a decrease of the adsorbed amount of acetophenone, by approximately 25%, at a water activity of 0.54.
Dimoula
Kerasina
K
RWTH Aachen University, Aachener Verfahrenstechnik - Biochemical Engineering, Aachen, Germany.
Pohl
Martina
M
Büchs
Jochen
J
Spiess
Antje C
AC
D019840:2-Propanol / Q000737:chemistry / Q000378:metabolism; D000098:Acetophenones / Q000737:chemistry / Q000378:metabolism; D000327:Adsorption; D000426:Alcohol Dehydrogenase / Q000737:chemistry* / Q000378:metabolism; D055162:Biocatalysis; D019149:Bioreactors; D004867:Equipment Design; D005612:Freeze Drying; D005740:Gases; D052196:Levilactobacillus brevis / Q000201:enzymology; D008855:Microscopy, Electron, Scanning; D013379:Substrate Specificity; D013395:Sucrose / Q000737:chemistry; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
D000098:Acetophenones; D005740:Gases; D014867:Water; D013395:Sucrose; D000426:Alcohol Dehydrogenase; D019840:2-Propanol; C038699:acetophenone