Use of water to evaluate hydrophobicity of organically-modified xerogel enzyme supports

Abstract

Silica xerogels are a new class of materials suitable for the immobilization of enzymes for various applications including biotransformations and biosensors. The physicochemical properties of xerogels, such as hydrophobicity, can be manipulated by the introduction of organically-modified silicates. This allows the immobilization matrix to be engineered to suit the enzyme and its application. Interfacial activation of lipase is a phenomenon in which the enzyme displays increased activity when it is bound to a hydrophobic interface. Lipase was entrapped in organically-modified xerogels in which the hydrophobicity of the enzyme support was modulated by the selection of different alkyltrimethoxysilane co-precursors and the ratio in which they were combined with tetramethyl orthosilicate. Interaction between the enzyme support and water was investigated with two methods to quantitatively assess the hydrophobicity of the entrapment matrix. The contact angle formed between the xerogel and water was used to determine hydrophobicity on a macroscopic level. Temperature-controlled water desorption was used to determine hydrophobicity on a microscopic level. Both methods were suitable for quantitatively discriminating between hydrophobic and hydrophilic materials. Further, the hydrophobicity of the enzyme support influenced the hydrolytic activity of the entrapped lipase under non-aqueous conditions. The specific activity of lipase increased only when entrapped in xerogels which could be classified as hydrophobic materials, that is with contact angles greater than 90 degrees or hydrophobicity values as determined by water desorption greater than 0.65.

Antibiofilm Properties of Interfacially Active Lipase Immobilized Porous Polycaprolactam Prepared by LB Technique

“…Motile populations, such as swarming bacteria, can rapidly reach niches, which they can colonize [51]. In the present study, the motility of E.coli on UP was 4.11 µm/s/V/cm; which decreased to 2.11 on the LIP surface (Table 3).…”

Improvement of Catalytic Efficiency, Thermo-stability and Dye Decolorization Capability of Pleurotus ostreatusIBL-02 laccase by Hydrophobic Sol Gel Entrapment

“…chrysosporium in Sol-gels caused hyper-activation but an increase in hydrophobic character above certain optimum limits caused a decrease in LiP activity. As the concentration of silane increases, the degree of immobilization also increases but the activity of enzyme decreases [25]. However, the covalent binding strategy is much more expensive because it requires glutareldehyde as coupling agent.…”

Favourable influence of hydrophobic surfaces on protein structure in porous organically-modified silica glasses

“…The hydrophobic character of such glasses has been verified by several means including contact angle measurements [43], solid-state 29 Si MAS NMR, and Fourier transform infrared spectroscopy [17,44]. Although most enzymes prefer an aqueous environment, it is rational to place lipases in a hydrophobic environment because these enzymes mediate reactions at lipid-water interfaces and because the substrates of these enzymes are highly nonpolar molecules.…”