Pretreatment of lignocellulosic materials may result in the release of inhibitors and deactivators of cellulose enzyme hydrolysis. We report the identification of phenols with major inhibition and/or deactivation effect on enzymes used for conversion of cellulose to ethanol. The inhibition effects were measured by combining the inhibitors (phenols) with enzyme and substrate immediately at the b...

Studies on the interaction of calcineurin with its activator, calmodulin, showed that the 1:l complex is the activated species. Concomitant with activation, a time-dependent deactivation of the phosphatase was observed. The process followed first order kinetics and was dependent on the presence of both Ca2+ and calmodulin. The deactivation rate constant at pH 7.6 and 30 "C was 0.06 min", which ...

In this study, the hydrolysis of pretreated sorghum stem and rice husk was investigated at various initial enzyme concentrations and substrate loadings. The slowdown in enzymatic hydrolysis of lignocellulosic materials with conversion has often been attributed to decreasing the activity of enzyme. A kinetic model was developed and expressed mathematically based on enzyme deactivation for enzyma...

The enzymatic synthesis of organic compounds in continuous bioreactors is an efficient way to obtain industrially important chemicals. However, few works have focused on the study of the operational conditions and the bioprocess performance. In this work, the aliphatic ester pentyl octanoate was obtained by direct esterification using a continuous packed bed bioreactor containing the immobilize...

The thermal deactivation of TEM-1 β-lactamase was examined using two experimental techniques: a series of isothermal batch assays and a single, continuous, non-isothermal assay in an enzyme membrane reactor (EMR). The isothermal batch-mode technique was coupled with the three-state "Equilibrium Model" of enzyme deactivation, while the results of the EMR experiment were fitted to a four-state "m...

Escherichia coli AdhE has been reported to harbor three distinct enzymatic activities: alcohol dehydrogenase, acetaldehyde-CoA dehydrogenase, and pyruvate formate-lyase (PFL) deactivase. Herein we report on the cloning, expression, and purification of E. coli AdhE, and the re-investigation of its purported enzymatic activities. While both the alcohol dehydrogenase and acetaldehyde-CoA dehydroge...

The unique feature of mitochondrial complex I is the so-called A/D transition (active-deactive transition). The A-form catalyses rapid oxidation of NADH by ubiquinone (k ~104 min-1) and spontaneously converts into the D-form if the enzyme is idle at physiological temperatures. Such deactivation occurs in vitro in the absence of substrates or in vivo during ischaemia, when the ubiquinone pool is...

Catalyst activity and performance are the most important factors for selecting a catalyst in different processes. The Fischer-Tropsch synthesis is a very important synthesis that extensive action has been taken place to increase the activity of its catalysts in the recent century. Deactivation of the catalysts of the process is influenced by many factors, among which coking and sintering have c...