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

Abstract

Pickering emulsion systems have created new opportunities for two-phase biocatalysis, however their catalytic performance is often hindered by biphasic mass transfer process relying on the interfacial area. In this study, lipase-immobilized mesoporous silica particles (LMSPs) are employed as both Pickering stabilizers and biocatalysts. A series of alkyl silanes with the different carbon length are used to modify LMSPs to obtain suitable wettability and enlarge the interfacial area of Pickering emulsion. The results show the water/paraffin oil Pickering emulsions stabilized by 8 carbon atoms silane grafted LMSPs (LMSPs_C8) with a three-phase contact angles of 95° get the relatively large interfacial area. Moreover, the conversion of enzymatic reaction catalyzed by LMSPs_C8 Pickering emulsion system is 3.4 times higher than that unmodified LMSPs with the reaction time of 10 min. Additionally, the effective recycling of LMSPs is achieved by simple low-speed centrifugation. As evidenced by a 6-cycles reaction of remaining 75% of relative enzymatic activity, the protection of 350–450 nm mesoporous silica particles can alleviate the inactivation of enzyme from the shear stress and make a benefit to form stabile Pickering emulsion. Therefore, the biphasic reactions in the Pickering emulsion system can be effectively enhanced through changing interfacial area only by the means of adjusting the wettability of biocatalysts.

Catalysis in Pickering emulsions

“…Meng et al prepared mesoporous silica particles of different wettabilities by using silylating agents with different carbon chain lengths. 49 However, only w/o emulsions could be prepared with substantial fractions of water and oil released in some cases. 49 Therefore, the catalytic evaluation was only carried out in emulsions of one type, with the conversion higher for the emulsion with the highest stability against sedimentation and coalescence and smaller droplets.…”

“…49 Therefore, the catalytic evaluation was only carried out in emulsions of one type, with the conversion higher for the emulsion with the highest stability against sedimentation and coalescence and smaller droplets. 49 In ref. 50, Pd supported on amphiphilic carbonaceous microspheres (Pd/CM) was used in the catalytic hydrodeoxygenation of vanillin as a model bio-oil upgrading reaction.…”

“…58 Other examples are based on the use of mesoporous silica particles or zeolites (aluminosilicates). 22,48,49,[59][60][61][62][63] They are widely employed as enzyme carriers due to their porous nature, which brings a large internal surface area where enzymes can be adsorbed and protected from the organic solvent. Moreover, due to their composition, they have outstanding biocompatibility and thermal and mechanical stability.…”

“…Moreover, due to their composition, they have outstanding biocompatibility and thermal and mechanical stability. 49,59 Despite silica nanospheres being broadly employed as a stabilizer in Pickering emulsions, the influence of the particle meso-structure on the catalytic performance of Pickering emulsions has rarely been investigated. Zhao et al compared the catalytic activity in the hydroformylation of 1-octene with water-soluble Rh-tris(m-sulfonatophenyl) phosphine complexes as catalysts of two o/w Pickering emulsion systems stabilized either by mesoporous or non-porous silica nanospheres with a similar particle diameter (100 nm).…”

“…3(b)). 49 The transformation of tributyrin to butyric acid was evaluated in water-in-paraffin oil Pickering emulsions and was catalyzed by Lipase B from Pseudomonas cepacia (PCL). While the starting material was dispersed in the oil phase, the final product was recovered in the water phase.…”