Abstract
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 Vm/Km 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.
Highlights
In the past decades, microreactors have been used for many biocatalytic reactions[1]
Carbon nanotubes had been used as carriers of immobilized lipase for conversion of Jatropha oil to fatty acid methyl esters, and the maximum adsorbing capacity was obtained with 0.41 g/g24
The specific surface area, temperature and other factors could result in the difference of the adsorbing capacity
Summary
Choice of nanoparticle carrier for enzyme immobilization. Table 1 shows the adsorbing capacities of different nanoparticles. A higher narrow peak intensity and a maximum of protein loading (1.30 g/g of support) were observed after the naringinase immobilized on graphene. The relative stability of graphene-immobilized naringinase at the 50 °C was 25% higher than that of the free enzyme[41] It showed the thermal inactivation at increasing temperatures was lower, compared with the free enzyme. The results indicated the consequence of efficient reaction-diffusion dynamics in the microchannel system[44], where graphene immobilized enzymes were provided more opportunities for contacting with substrate molecules in a microreactor.
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