2 research outputs found
Hollow Microgel Based Ultrathin Thermoresponsive Membranes for Separation, Synthesis, and Catalytic Applications
Thermoresponsive
core–shell microgels with degradable core
are synthesized via surfactant based free radical polymerization using
N,N′-(1,2-dihydroxy-ethylene)ÂbisÂ(acrylamide) (DHEA) as a cross-linker
for core preparation. The 1,2-glycol bond present in DHEA is susceptible
to NaIO<sub>4</sub> solution, and thus, the structure can be cleaved
off resulting in hollow microgel. Ultrathin membranes are prepared
by suction filtration of a dilute suspension of core–shell
microgels over a sacrificial layer of CdÂ(OH)<sub>2</sub> nanostrand
coated on track etched membrane. After removal of the degraded cores
from microgels, the membranes are cross-linked with glutaraldehyde
and the nanostrands are removed by passing a 10 mM HCl solution. The
prepared membranes are thoroughly characterized using scanning electron
microscopy (SEM), atomic force microscopy (AFM), dynamic light scattering
(DLS), and dynamic contact angle for morphology, thermoresponsive,
and hydrophilic properties, respectively. The prepared membranes showed
thermoresponsive permeation behavior and remarkable separation performance
for low molecular weight dyes and lysozyme protein. These membranes
are also used to synthesize gold nanoparticles and immobilize lactate
dehydrogenase enzyme for catalytic and biocatalytic application. The
results for water permeation, solute rejection, and ability to immobilize
gold nanoparticles and enzymes showed its wide range of applicability.
Furthermore, the synthesis of hollow microgel is simple and environmentally
friendly, and the membrane preparation is easy, scalable, and other
microgel systems can also be used. These responsive membranes constitute
a significant contribution to advanced separation technology
Enhanced Activity of Acetyl CoA Synthetase Adsorbed on Smart Microgel: an Implication for Precursor Biosynthesis
Acetyl coenzyme A (acetyl CoA) is an essential precursor molecule
for synthesis of metabolites such as the polyketide-based drugs (tetracycline,
mitharamycin, Zocor, etc.) fats, lipids, and cholesterol. Acetyl CoA
synthetase (Acs) is one of the enzymes that catalyzes acetyl CoA synthesis,
and this enzyme is essentially employed for continuous supply of the
acetyl CoA for the production of these metabolites. To achieve reusable
and a more robust entity of the enzyme, we carried out the immobilization
of Acs on polyÂ(<i>N</i>-isopropylacrylamide)-polyÂ(ethylenimine)
(PNIPAm-PEI) microgels via adsorption. Cationic PNIPAm-PEI microgel
was synthesized by one-step graft copolymerization of NIPAm and <i>N</i>,<i>N</i>-methylene bis-acrylamide (MBA) from
PEI. Adsorption studies of Acs on microgel indicated high binding
of enzymes, with a maximum binding capacity of 286 μg/mg of
microgel for Acs was achieved. The immobilized enzymes showed improved
biocatalytic efficiency over free enzymes, beside this, the reaction
parameters and circular dichroism (CD) spectroscopy studies indicated
no significant changes in the enzyme structure after immobilization.
This thoroughly characterized enzyme bioconjugate was further immobilized
on an ultrathin membrane to assess the same reaction in flow through
condition. Bioconjugate was covalently immobilized on a thin layer
of preformed microgel support upon polyethylene terephthalate (PET)
track etched membrane. The prepared membrane was used in a dead end
filtration device to monitor the bioconversion efficiency and operational
stability of cross-linked bioconjugate. The membrane reactor showed
consistent operational stability and maintained >70% of initial
activity
after 7 consecutive operation cycles