Pickering interfacial catalysts at oil-water interfaces have gone through rapid development in the past few years. However, numerous challenges have been faced in the process. For example, the restriction of the biocatalytic reactions by their biphasic environments requires an effective solution that does not have a negative impact on other activities. In a recently published literature, researchers have identified Pickering emulsions as a promising candidate for biphasic enzyme-catalyzed bioreactors. As such, the development of efficient Pickering biocatalysts systems with relatively high oil/water ratio, recyclability, and super-stability is highly desirable. This requires a good balance between the high-volume ratio, stability, and recyclability which is difficult to achieve.
To this note, Meng Wang, Mengjie Wang, Jianding Chen and led by Professor Shengmiao Zhang from the East China University of Science and Technology developed a Pickering gel emulsion stabilized by enzyme-decorated copolymeric nanoparticle for biphasic biocatalysis. The main objective was to address the gap between the Pickering high internal phase emulsion (HIPEs) and their application as biphasic catalysis. Their work is currently published in the journal, Reaction Chemistry & Engineering.
In brief, the authors commenced their research work by preparing an enzyme-decorated polymeric nanoparticle to stabilize oil-in-water HIPEs by surfactant-free emulsion copolymerization of styrene and glycidyl methacrylate. Next, they were covalently decorated with a model lipase Candida Antarctica lipase B (CALB). Finally, taking the enzyme decorated polymeric nanoparticles as a stabilizer, stable Pickering HIPE was obtained by homogenizing heptane into nanoparticle aqueous dispersion.
The Pickering gel system was placed at room temperature to analyze the catalyzing efficiency through the enzymatic esterification of hexanoic acid with hexanol in the oil phase. The immobilized CALB on the nanoparticle in the Pickering gel emulsion exhibited significantly enhanced enzymatic activities more than free CALB. Interestingly, a conversion rate of up to 96.5% was obtained. CALB exhibited unique advantages that enabled successful esterification of the hexanoic acid with hexanol. This strongly demonstrated the potential of the CALB decorated nanoparticle-stabilized Pickering gel emulsion as a promising candidate for Pickering interfacial biocatalysis.
After the enzymatic reaction, the enzyme-decorated polymeric nanoparticles were recollected from the emulsion by the centrifugal method. Therefore, they could be reused as Pickering interfacial biocatalysts which is a cost-saving element, especially in large scale operation. The centrifugal process was instrumental in separating the oil and aqueous phases in each cycle while at the same time maintaining the residual activity of the Pickering gel emulsion at 92.5% after 10 reaction cycles. Unlike the non-emulsified two-phase system, the newly developed biphasic system resulted in a 6.7-fold improvement in the overall catalytic performance.
Because the Pickering interfacial catalysts could be centrifuged, washed and homogenized several times without losing its biocatalytic properties, it could be recycled to recover the enzymatic reaction product located in the oil phase. Therefore, the study by Professor Shengmiao Zhang and his research team will advance sustainable applications of biphasic catalysis by developing a highly efficient Pickering interfacial biocatalytic system in terms of volume ratio, stability, recyclability, and overall operating costs.
Wang, M., Wang, M., Zhang, S., & Chen, J. (2019). Pickering gel emulsion stabilized by enzyme immobilized polymeric nanoparticles: a robust and recyclable biocatalyst system for biphasic catalysis. Reaction Chemistry & Engineering, 4(8), 1459-1465.Go To Reaction Chemistry & Engineering