IMPROVEMENT OF USING CRUDE EXTRACT UREASE FROM WATERMELON SEEDS FOR BIOCEMENTATION TECHNOLOGY

Abstract

In recent years,the formation of artificial beachrock and bio-cementation method has gained considerable attention as a sustainable alternative tool in the area of geotechnical and geo-environmental engineering field for soil improvement and construction materials. In general, earlier methods of soil improvement were mostly concentrated on microbes (Bacteria, Fungi, etc.) as a source of urease enzyme widely known as MICP method (Microbial Induced Carbonate Precipitation). To address some of the keylimitations of MICP method this study focused on using crude enzyme (low cost, eco-friendly). Crude enzyme was extracted from watermelon seeds (Citrullus lanatus)considered as “food waste material” and the carbonate formation process known as EICP “Enzyme Induced Carbonate Precipitation.” Crushed and blended watermelon seeds (both dry and germinated) used as a source of urease enzyme. Subsequently, their urease activity was also investigated with various environmental parameters (Temperature, pH, etc.) and investigated the carbonate precipitation trend using calcium chloride (CaCl2) and urea [(CO(NH2)2]. The form of carbonate (calcite, aragonite, vaterite, etc.) was also confirmed by XRD and SEM-EDX analysis. Finally, syringe (d = 2.3 cm, h = 7.1 cm) sand solidification test was conducted using commercially available “Mikawa sand” (mean diameter, D50 = 870 mm) and successfully achieved unconfined compressive strength (UCS) of about 1.2 MPa at neutral pH (~7) and temperature condition (30 °C) considering various curing days and conditions. This study could be useful as an eco-friendly and sustainable method for numerous bio-geotechnical applications (for instance, ground improvement, liquefaction mitigation, artificial beach rock formations, coastal erosion protection, etc.) and the extracted crude urease from watermelon seeds could play as an alternative to replace commercially available urease for carbonate precipitation.