Submicron Inverse Pickering Emulsions for Highly Efficient and Recyclable Enzymatic Catalysis

Abstract

Herein, we report the utilization of a submicron Pickering emulsion (SPE) for the encapsulation of enzymes (e.g., lipase from Candida sp.) in water droplets that were solely stabilized by hydrophobic solid or mesoporous silica nanoparticles in toluene for use in biphasic reactions. The catalytic performance of encapsulated lipase was evaluated in the esterification of 1-hexanol and hexanoic acid under stirring-free conditions, which was favorable for maintaining enzymatic activity. Remarkably, the SPE significantly increased the specific activity of encapsulated lipase, owing to the exceptionally high water/oil interfacial area and short diffusion distance of the reagents in the SPE. With mesoporous silica nanoparticles, the activity of lipase was approximately 25.5- and 2.8-times higher than that of free lipase and encapsulated lipase in the micron Pickering emulsion, respectively. The higher water/toluene interfacial area was attributed to the smaller submicron-scale water droplets and the increase in the mass transfer of enzymes or substrates was further improved by using mesoporous Pickering stabilizers. In addition, the encapsulated lipase in SPE also demonstrated excellent stability and could be recycled up to 15 times without significant loss of activity.

Enzyme-Loaded Mesoporous Silica Particles with Tuning Wettability as a Pickering Catalyst for Enhancing Biocatalysis

“…Up to now, there are two kinds of strategies for biphasic enzymatic catalysis in Pickering emulsions. One includes free enzymes located in the inner aqueous phase [12][13][14][15][16][17]. The other includes enzyme-immobilized particles anchored around droplet interfaces [18][19][20][21][22][23][24][25][26], by contrast, it enables enzymes to be recycled, maximizes the contact area between enzymes and substrates, reduces diffusion distance of substrate molecules and improves the stability of enzymes.…”

Catalysis in Pickering emulsions

“…Jiang et al prepared w/o Pickering emulsions stabilized by silica particles of various sizes in the nanometer range to follow the esterification reaction between 1-hexanol and hexanoic acid catalyzed by lipase from Candida sp. 22 As shown in Fig. 2(c) the conversion increased by decreasing the particle size due to a decrease in the average droplet diameter.…”

“…In general, examples of PAC are widely found in the field of biocatalysis, where the enzyme (catalyst) is dissolved in the aqueous phase and the solid particles are located at the liquidliquid interface. 15,22,24,47,[54][55][56][57] In most of these examples, silica particles were selected as the emulsifier for the preparation of w/o emulsions to study hydrolysis and esterification reactions using lipase enzymes as the biocatalyst dissolves in water. However, in ref.…”

“…The specific activity of the enzyme in the Pickering emulsion stabilized with 50 nm silica particles was 21 times higher than that of the free enzyme in a biphasic system without stirring. 22 Li et al studied the effect of the particle size (90-460 nm) and surface roughness of catalytic nanoparticles on the reactivity of a non-aqueous immiscible mixture (ethyleneglycol/dodecanal) in Pickering emulsions. The catalytic productivity was enhanced for smaller sized and rough nanoparticles (o210 nm) as a result of the formation of more compact interfacial particle assemblies and a higher specific surface area of the particles, reducing diffusion resistances near the acid sites.…”

Biocatalytic Pickering Emulsions Stabilized by Lipase-Immobilized Carbon Nanotubes for Biodiesel Production

“…Since MWCNTs are small, the recovery of MWCNT-immobilized enzymes after the reaction is a difficult task. Until now, a series of particles including mesoporous silica [15], polymersomes [16], microgels [17], and carbonaceous microspheres [18] have been used to construct enzyme-containing Pickering emulsions. These reports have confirmed that the immobilization of enzymes using Pickering emulsion systems is a facile and effective means for facilitating the nanoparticle/nanobiocatalyst recovery and reaction product separation.…”