“…The decrease of enzyme activity in a batch reactor could be due to the leakage of the enzyme during the washing process 46 . To some extent, using the non-covalent technique to immobilizing enzyme easily led to the inactivation of the enzyme 47 . On the other hand, the life of the enzyme was decreased gradually with the reutilization for several recycles.Figure 8Reusability ( A ) and relative enzyme activity ( B ) of immobilized enzyme in a batch reactor and a microchannel reactor.…”
Enzymatic catalysis in microreactors has attracted growing scientific interest because of high specific surface enabling heat and mass transfer and easier control of reaction parameters in microreactors. However, two major challenges that limit their application are fast inactivation and the inability to the biocatalysts in microchannel reactors. A fluid and unsinkable immobilized enzyme were firstly applied in a microchannel reactor for biocatalysis in this study. Functionalized forms of graphene-immobilized naringinase flowing in microchannels have yielded excellent results for isoquercitrin production. A maximum yield of 92.24 ± 3.26% was obtained after 20 min in a microchannel reactor. Ten cycles of enzymatic hydrolysis reaction were successively completed and an enzyme activity above 85.51 ± 2.76% was maintained. The kinetic parameter V
m/K
m increased to 1.9-fold and reaction time was decreased to 1/3 compared with that in a batch reactor. These results indicated that the moving and unsinkable graphene sheets immobilized enzyme with a high persistent specificity and a mild catalytic characteristic enabled the repetitive use of enzyme and significant cost saving for the application of enzyme catalysis. Thus, the developed method has provided an efficient and simple approach for the productive and repeatable microfluidic biocatalysis.
“…The decrease of enzyme activity in a batch reactor could be due to the leakage of the enzyme during the washing process 46 . To some extent, using the non-covalent technique to immobilizing enzyme easily led to the inactivation of the enzyme 47 . On the other hand, the life of the enzyme was decreased gradually with the reutilization for several recycles.Figure 8Reusability ( A ) and relative enzyme activity ( B ) of immobilized enzyme in a batch reactor and a microchannel reactor.…”
Enzymatic catalysis in microreactors has attracted growing scientific interest because of high specific surface enabling heat and mass transfer and easier control of reaction parameters in microreactors. However, two major challenges that limit their application are fast inactivation and the inability to the biocatalysts in microchannel reactors. A fluid and unsinkable immobilized enzyme were firstly applied in a microchannel reactor for biocatalysis in this study. Functionalized forms of graphene-immobilized naringinase flowing in microchannels have yielded excellent results for isoquercitrin production. A maximum yield of 92.24 ± 3.26% was obtained after 20 min in a microchannel reactor. Ten cycles of enzymatic hydrolysis reaction were successively completed and an enzyme activity above 85.51 ± 2.76% was maintained. The kinetic parameter V
m/K
m increased to 1.9-fold and reaction time was decreased to 1/3 compared with that in a batch reactor. These results indicated that the moving and unsinkable graphene sheets immobilized enzyme with a high persistent specificity and a mild catalytic characteristic enabled the repetitive use of enzyme and significant cost saving for the application of enzyme catalysis. Thus, the developed method has provided an efficient and simple approach for the productive and repeatable microfluidic biocatalysis.
“…The optimum temperature of precipitated urease was detected, results in Figure 3 appeared the optimum temperature of enzyme activity was 50°C and the enzyme activity was 99.3U/ml. Other researchers [14]mentioned the optimum temperature of free urease activity was40°C while the optimum temperature of immobilized urease activity ranged between 40-50°C. The optimum temperature of urease stability was 40°C.the precipitated urease maintain 100% of activity as in Figure 4.…”
Section: Effect Of Temperaturementioning
confidence: 98%
“…In order to investigate the pH effect on urease activity, the precipitated enzyme was incubated with urea solution in a different pH values ranged between (5.0-9.0) and the enzyme activity was determined. The optimum pH of precipitated urease stability was determined by incubating the extracted enzyme in different buffers pH 5.0-9.0 for 30 min at 4°C,then the stability pH was determined in the presence of urea solution [14] In order to estimate the optimal temperature of precipitated urease activity, the precipitated enzyme was incubated with urea solution and the enzyme activity was estimated in a different temperature values ranged between (30-90) °C . On the other hand the optimal temperature of precipitated enzyme stability was estimated by incubation the extracted enzyme in different temperature value ranged between (30-70)°C and determining the enzyme activity in the presence of urea solution [15].…”
Section: Preparation Of Aqueous Extractmentioning
confidence: 99%
“…The activity of precipitated urease was estimated after enzyme storage at 4°C in refrigerator for a regular time ranged between (1-10 days). Urease activity was determined daily till tenth day [14] In order to estimate number of times using the precipitated urease, the enzyme activity was checked at different time of use, after each step of using the enzyme it washed with100 mM of Tris acetate buffer and stored until the next use [16]. Different salts were experimented to estimate their effect on the activity of precipitated urease, these are consisted of CuSO 4 , MgSO 4 , MgCl 2 , KCl, CaCl 2 and FeSO 4 ; they were added to reaction solution in a different concentration 10 -3 and 10 -5 M as described in [17] with a slight modification.…”
This study aimed to extract urease enzyme from available plant source which was broad beans (Vicia faba L.) using aqueous solution in a ratio1:3(w:v) .The crude extract appeared enzyme activity 33.3 U/ml. Results of this study revealed the possibility to precipitate urease enzyme after extraction using different precipitation methods consisted of Acetone precipitation; Alcohol precipitation and Ammonium sulfate precipitation, these ways of urease precipitation gave enzyme activities 74.8; 43.6 and 82.2 U/ml respectively .The enzyme precipitation using 60% saturation ratio of Ammonium sulfate gave the maximum activity of urease precipitation among other precipitation methods. Enzyme characterization appeared the optimum pH of urease activity was 8.0 and gave enzyme activity 93.8U/ml, while the optimum pH of urease stability was 6.0; the enzyme maintains its activity. On the other side the optimum temperature of precipitated urease activity was 50°C and the enzyme activity reached 99.3U/ml while the optimal temperature of urease stability was 40°C ,the precipitated urease maintain 100% of activity. The effect of other factors on urease action were studied also, these are consisted of the storage time of enzyme ,urease maintain its activity for 8days and the activity begun to decline after that time; the effect of time reusability was also revealed that the enzyme could be used for six times and maintain its activity. The influence of different mineral salts on precipitated urease were also recorded ;these salts were CuSO4 , MgSO4, MgCl2,KCl,CaCl2and FeSo4, results appeared that magnesium and calcium salts were activator for the precipitated urease while copper ,potassium and ferrous salts were inhibitor of the precipitated urease. Urea concentration as an enzyme substrate were also examined and results appeared the optimal substrate concentration was 30mM; enzyme activity reached to125.2U/ml.
“…In this way, the production of FUM and PRO would be explained by the action of phycobionts immobilisates. Enzymes entrapped in calcium alginate are more stable than those free enzymes during the storage in solution (Busto et al, 1987;Danial et al, 2015). The fungal enzyme that produced FUM from PRO depends on the algal photoassimilates and on the supply of succinyl-Coa from the fungal respiration (Fontaniella et al, 2000b).…”
Section: Production Of Lichen Compounds During Bionts-immobilizationmentioning
Bionts isolated from thalli of Cladonia verticillaris, immobilized in calcium alginate, produce two depsidones, fumarprotocetraric and protocetraric acids, and the depside atranorin, that exhibit antimicrobial activity against Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae. Organic lichen extract (acetone/ether/chloroform) shows the highest antimicrobial activity due to a possible synergism between these substances. Antioxidant capacity of soluble metabolites secreted from the immobilisates to the bath medium of incubation during the first 12 days of immobilization has been found (˃80% oxidation inhibition). The concentration of soluble phenolic substances depends on the immobilization time (during 32 days), exogenous supply of acetate (1.0m mM sodium or calcium acetate) and on the type of isolated biont (phycobionts, mycobionts, whole thallus or immobilized phycobionts co-incubated with the mycobionts ones).
The role of phycobionts in phenol production has been interpreted as a possible modification of the polymalonyl pathway; for example, atranorin is actively produced and secreted during immobilization while it is not detected in thallus in natura. Co-incubated bionts secrete higher amounts of atranorin to the media during the first 12 days of immobilization. Immobilization of isolated bionts could be used as a biotechnological technique to obtain a potential source of biological active compounds.
On the other hand, the physiological state detected of C. verticillaris in the Cerrado is much better for experimentation than that of the specimens collected in Caatinga since, in this case, the thalli showed the fragility that the extreme environmental conditions of the semi-arid region of NE Brazil impose on this lichen species. To date, no priority has been defined for lichen conservation in Brazilian ecosystems. It is therefore suggested that it imust important to include lichen ecophysiology studies in public conservation policies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
