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Carbonic anhydrase assisted calcium carbonate crystalline composites as a biocatalyst
Hwang, Ee Taek,Gang, Haemin,Chung, Jinyang,Gu, Man Bock The Royal Society of Chemistry 2012 GREEN CHEMISTRY Vol.14 No.8
<P>In the present study, we report on the carbonic anhydrase (CA)-assisted formation of biomineralized calcium carbonate crystalline composites (CCCCs). Ellipsoidal CCCCs, such as calcite polymorphism, in a micro-size range catalyzed by CA were successfully synthesized with polyethylene glycol and magnetic nanoparticles in the constant CO<SUB>2</SUB> pressure controlled chamber, for the first time. CA-assisted CCCCs characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and dynamic light scattering, showed their crystalline phase with mesoporous property according to Fourier transform infrared and Brunauer–Emmett–Teller area. These CCCCs retained about 43% of free CA esterase activity. Furthermore, the magnet-based separation was also successful for the reuse of the CCCCs. As a result, the CCCCs produced preserved their catalytic activity even after its ten repeated usages, and were stable for more than 50 days under room temperature. The reported method paves the way for novel biomineralization <I>via</I> CA for the formation of functional CA containing nanocomposites and biocatalyst technology applications.</P> <P>Graphic Abstract</P><P>Carbonic anhydrase-assisted calcium carbonate crystalline composites as a reusable biocatalyst. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2gc35444f'> </P>
Shape reformable polymeric nanofibers entrapped with QDs as a scaffold for enzyme stabilization
Hwang, Ee Taek,Tatavarty, Rameshwar,Lee, Hyun,Kim, Jungbae,Gu, Man Bock Royal Society of Chemistry 2011 Journal of materials chemistry Vol.21 No.14
<P>In this study, we report the structure and shape of new polymeric nanofibers entrapped with QDs, which were prepared by electrospinning a homogenous mixture of polymers and QDs. Uniformly distributed QDs within the polymer matrix seem to induce the high degree of compactness and shape rigidity in the nanofibers, and resulted in the efficient enzyme immobilization. After immobilization, the esterase enzymes coated on the QDs–nanofibers showed good stability with no loss of enzyme activity even after being recycled for more than ten times. The present study demonstrates the successful application of shape reformable polymeric nanofibers entrapped with QDs for enzyme immobilization for the first time, and so it is anticipated that this technology can be employed in various enzyme applications due to its facile shape control feature in the fabrication of the nanofibers.</P> <P>Graphic Abstract</P><P>QDs entrapped shape reformable polymeric nanofibres as a novel carrier for enzyme stabilization. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0jm02969f'> </P>
Hwang, Ee Taek,Lee, Byoungsoo,Zhang, Meiling,Jun, Seung-Hyun,Shim, Jongmin,Lee, Jinwoo,Kim, Jungbae,Gu, Man Bock The Royal Society of Chemistry 2012 GREEN CHEMISTRY Vol.14 No.7
<P>Subtilisin Carlsberg (SC) was immobilized and stabilized on magnetically-separable mesoporous silica (Mag-MSU-F) in the form of nanoscale enzyme reactors (NERs) based on the ship-in-a-bottle mechanism. Stabilized NERs of SC (NER-SC) were freeze-dried and successfully used for the transesterification of <I>N</I>-acetyl-<SMALL>L</SMALL>-phenylalanine ethyl ester with <I>n</I>-propanol in isooctane. Magnetic separation of Mag-MSU-F facilitated the repeated usages of stable NER-SC. This is the first demonstration for the use of stable and magnetically-separable NERs in an organic solvent, which has the potential for environmentally-friendly synthesis using enzymes in organic solvents.</P> <P>Graphic Abstract</P><P>Highly-stable and magnetically-separable nanoscale enzyme reactors for enzyme-catalyzed synthetic reactions. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2gc35559k'> </P>
New Functional Amorphous Calcium Phosphate Nanocomposites by Enzyme-Assisted Biomineralization
Hwang, Ee Taek,Tatavarty, Rameshwar,Chung, Jinyang,Gu, Man Bock American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.3
<P>In the present study, we report on enzyme-assisted formation of biomineralized amorphous calcium phosphate nanocomposites (ACP-NCs). About 100–200 nm sizes of the spherical porous enzyme-assisted ACP-NCs were successfully synthesized via double reverse microemulsion, but no ACP-NCs formed without the enzyme. It is believed that the enzyme was used as an organic template or additive that could regulate the biomineralization process. The enzyme-assisted ACP-NCs were well characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, dynamic light scattering, and Brunauer–Emmett–Teller (BET) criteria. The BET surface area, total pore volume, pore size from adsorption, and pore size from desorption of the ACP-NCs were 163 m<SUP>2</SUP> g<SUP>–1</SUP> or 0.37 cm<SUP>3</SUP> g<SUP>–1</SUP>, 8.87 nm, and 7.48 nm, respectively. The enzyme-assisted ACP-NCs retained about 43% of the catalytic activity of free carboxyl esterase. Furthermore, they preserved their bioactivity even after the 10th reuse and were stable over 10 days even under a stringent shaking conditions. The reported method paves the way for novel biomineralization via enzyme molecules to form functional enzymes containing nanocomposites.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-3/am302580p/production/images/medium/am-2012-02580p_0010.gif'></P>
Highly-stable magnetically-separable organic-inorganic hybrid microspheres for enzyme entrapment
Hwang, Ee Taek,Lee, Hyun,Kim, Ji Hoon,Tatavarty, Rameshwar,Gu, Man Bock Royal Society of Chemistry 2011 Journal of materials chemistry Vol.21 No.18
<P>Organic-inorganic hybrid microspheres for a magnetically separable and highly stable enzyme system were successfully fabricated. After enzymes were entrapped, these hybrid microspheres were found to be highly stable for more than 120 days with about 75% of the initial activity preserved, and were successfully reused more than 10 times repeatedly. Furthermore, magnet-based separation was also found to be successful for the repeated usage.</P> <P>Graphic Abstract</P><P>Highly stable and magnetically separable enzyme entrapped organic-inorganic hybrid microspheres. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1jm10690b'> </P>