Relationship between sol–gel conditions and enzyme stability: a case study with β-galactosidase/silica biocatalyst for whey hydrolysis

Abstract

The sol-gel process has been very useful for preparing active and stable biocatalysts, with the possibility of being reused. Especially those based on silica are well known. However, the study of the enzyme behavior during this process is not well understood until now and more, if the surfactant is involved in the synthesis mixture. This work is devoted to the encapsulation of β-galactosidase from Bacillus circulans in silica by sol-gel process, assisted by non-ionic Triton X-100 surfactant. The correlation between enzyme activity results for the β-galactosidase in three different environments (soluble in buffered aqueous reference solution, in the silica sol, and entrapment on the silica matrix) explains the enzyme behavior under stress conditions offered by the silica sol composition and gelation conditions. A stable β-galactosidase/silica biocatalyst is obtained using sodium silicate, which is a cheap source of silica, in the presence of non-ionic Triton X-100, which avoids the enzyme deactivation, even at 40 °C. The obtained biocatalyst is used in the whey hydrolysis for obtaining high value products from this waste. The preservation of the enzyme stability, which is one of the most important challenges on the enzyme immobilization through the silica sol-gel, is achieved in this study.

Self-protected nitrate reducing culture for intrinsic repair of concrete cracks

“…Visual crack closure should always be coupled with other quantification methods to further assess the self-healing performance of mortar specimens (Palin et al, 2015 ). For example, functionality regain is one of the major interests in self-healing studies (Reinhardt and Jooss, 2003 ; Van Tittelboom et al, 2011 ; Li and Herbert, 2012 ; Wang et al, 2012a , b ). So far, strength and water tightness are the common properties being investigated to quantify self-healing efficiency in many studies (Bang et al, 2001 ; Ramachandran et al, 2001 ; Van Tittelboom et al, 2011 ; Li and Herbert, 2012 ).…”

Self-healing of early age cracks in cement-based materials by mineralization of carbonic anhydrase microorganism

“…Three methods were used to characterize the cracks healing efficiency. The crack healing efficiency of specimens was evaluated by water permeation coefficient according to the method reported with a modification (Wang et al, 2012 ). The cylinder specimen was casted into PVC mold when molding.…”

“…In this study, one type of bacteria which can produce carbonic anhydrase was incorporated in cement-based materials to repair cracks. Compared to other self-healing in concrete with bacteria (Bang and Ramakrishnan, 2001 ; Jonkers, 2007 ; Wang et al, 2012 ), the new bacteria can promote the inter-conversion between CO 2 which from atmosphere and CaCO 3 . That means CO 2 can be transferred to minerals precipitated in cracks when reacting with soluble Ca 2+ rapidly.…”

Thermal Hyperactivation and Stabilization of β-Galactosidase from Bacillus circulans through a Silica Sol–Gel Process Mediated by Chitosan–Metal Chelates

“…The commercial β-galactosidase from Bacillus circulans (Bgal) is an example of monomeric, nonmetal dependent enzymes , stabilized by SSGE, without further complicated, laborious, time-consuming, and expensive purification processes. This encapsulated Bgal is used for whey hydrolysis and GOS synthesis, − preserving its specific affinity for β 1 → 4 sugar links and the preference for producing β 1 → 6 trisaccharides. − The enzymes also behave as silica templates in the SSGE route, modifying the silica polycondensation, which in turn affect the characteristics of the silica-based biocatalysts . In general, the factors that affect the sol–gel process (pH, ionic strength, etc.)…”