Effects of Soil Surface Chemistry on Adsorption and Activity of Urease from a Crude Protein Extract: Implications for Biocementation Applications

Rayla Pinto Vilar,Kaoru Ikuma

doi:10.3390/catal12020230

Abstract

In the bacterial enzyme-induced calcite precipitation (BEICP) technique for biocementation, the spatial distribution of adsorbed and catalytically active urease dictates the location where calcium carbonate precipitation and resulting cementation will occur. This study investigated the relationships between the amount of urease and total bacterial proteins adsorbed, the retained enzymatic activity of adsorbed urease, and the overall loss of activity upon adsorption, and how these relationships are influenced by changes in soil surface chemistry. In soils with hydrophobic contents higher than 20% (w/w) ratio, urease was preferentially adsorbed compared to the total amount of proteins present in the crude bacterial protein extract. Conversely, adsorption of urease onto silica sand and soil mixtures, including iron-coated sand, was much lower compared to the total proteins. Higher levels of urease activity were retained in hydrophobic-containing samples, with urease activity decreasing with lower hydrophobic content. These observations suggest that the surface manipulation of soils, such as treatments to add hydrophobicity to soil surfaces, can potentially be used to increase the activity of adsorbed urease to improve biocementation outcomes.

Highlights

Biocementation is a sustainable engineering technique that has received significant attention as an environmentally friendly alternative to chemical stabilization methods for soils [1,2,3,4,5]
Sorbent surfaces with greater numbers of available adsorption sites have higher adsorption capacities, but the likelihood of protein adsorption and surface coverage is dictated by the affinity of the proteins to the solid surface
The findings from this study showed that similar amounts of adsorbed proteins from the original crude protein extract adsorbed onto all soil surfaces regardless of surface chemistry

Summary

Introduction

Biocementation is a sustainable engineering technique that has received significant attention as an environmentally friendly alternative to chemical stabilization methods for soils [1,2,3,4,5]. Biocementation is based on the generation of calcium carbonate precipitates from urea hydrolysis, a chemical reaction that is only feasible when catalyzed by the urease enzyme [9]. Biocementation methods consist of an injection of a mixture containing urea, calcium, and the catalyst urease into the soil. The generated calcium carbonate deposits between the soil grains bridge them like a cement, which leads to a stronger soil matrix [10]

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