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Dr. Hamed Khodadadi Tirkolaei
Center for Bio-mediated and Bio-inspired Geotechnics, Arizona State University, Tempe, AZ 85281, USA

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0 Geotechnical Engineering
0 Biogeotechnical Engineering
0 Sustainable Geotechnics
0 Resource Recovery for Geotechnical Applications
0 Bio-based Ground Improvement

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Journal article
Published: 06 May 2021 in Sustainable Chemistry
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The stability (longevity of activity) of three crude urease extracts was evaluated in a laboratory study as part of an effort to reduce the cost of urease for applications that do not require high purity enzyme. A low-cost, stable source of urease will greatly facilitate engineering applications of urease such as biocementation of soil. Inexpensive crude extracts of urease have been shown to be effective at hydrolyzing urea for carbonate precipitation. However, some studies have suggested that the activity of a crude extract may decrease with time, limiting the potential for its mass production for commercial applications. The stability of crude urease extracts shown to be effective for biocementation was studied. The crude extracts were obtained from jack beans via a simple extraction process, stored at room temperature and at 4 ℃, and periodically tested to evaluate their stability. To facilitate storage and transportation of the extracted enzyme, the longevity of the enzyme following freeze drying (lyophilization) to reduce the crude extract to a powder and subsequent re-hydration into an aqueous solution was evaluated. In an attempt to improve the shelf life of the lyophilized extract, dextran and sucrose were added during lyophilization. The stability of purified commercial urease following rehydration was also investigated. Results of the laboratory tests showed that the lyophilized crude extract maintained its activity during storage more effectively than either the crude extract solution or the rehydrated commercial urease. While incorporating 2% dextran (w/v) prior to lyophilization of the crude extract increased the overall enzymatic activity, it did not enhance the stability of the urease during storage.

ACS Style

Neda Javadi; Hamed Khodadadi Tirkolaei; Nasser Hamdan; Edward Kavazanjian. Longevity of Raw and Lyophilized Crude Urease Extracts. Sustainable Chemistry 2021, 2, 325 -334.

AMA Style

Neda Javadi, Hamed Khodadadi Tirkolaei, Nasser Hamdan, Edward Kavazanjian. Longevity of Raw and Lyophilized Crude Urease Extracts. Sustainable Chemistry. 2021; 2 (2):325-334.

Chicago/Turabian Style

Neda Javadi; Hamed Khodadadi Tirkolaei; Nasser Hamdan; Edward Kavazanjian. 2021. "Longevity of Raw and Lyophilized Crude Urease Extracts." Sustainable Chemistry 2, no. 2: 325-334.

Journal article
Published: 01 October 2020 in Crystals
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Beach sands are composed of a variety of minerals including quartz and different carbonate minerals. Seawater in beach sand contains several ions such as sodium, magnesium, calcium, chloride, sulfate, and potassium. These variations in mineralogy and the presence of salts in beach sand may affect the treatment via enzyme-induced carbonate precipitation (EICP). In this study, set test tube experiments were conducted to evaluate the precipitation kinetics and mineral phase of the precipitates in the presence of zero, five, and ten percent seawater (v/v). The kinetics were studied by measuring electrical conductivity (EC), pH, ammonium concentration, and carbonate precipitation mass in EICP solution at different time intervals. A beach sand was also treated using EICP solution containing zero and ten percent seawater at one, two, and three cycles of treatment. Unconfined compressive strength (UCS), carbonate content, and mineralogy of the precipitates in the treated specimens were evaluated. The kinetics study showed that the rate of urea hydrolysis and the rate of precipitation for zero, five, and ten percent seawater were similar within the first 16 h of the reaction. After 16 h, it was observed that the rates dropped in the solution containing seawater, which might be attributed to the faster decay rate of urease enzyme when seawater is present. All the precipitates from the test tube experiments contained calcite and vaterite, with an increase in vaterite content by increasing the amount of seawater. The presence of ten percent seawater was found to not significantly affect the UCS, carbonate content, and mineralogy of the precipitates of the treated beach sand.

ACS Style

Ahmed Miftah; Hamed Khodadadi Tirkolaei; Huriye Bilsel. Biocementation of Calcareous Beach Sand Using Enzymatic Calcium Carbonate Precipitation. Crystals 2020, 10, 888 .

AMA Style

Ahmed Miftah, Hamed Khodadadi Tirkolaei, Huriye Bilsel. Biocementation of Calcareous Beach Sand Using Enzymatic Calcium Carbonate Precipitation. Crystals. 2020; 10 (10):888.

Chicago/Turabian Style

Ahmed Miftah; Hamed Khodadadi Tirkolaei; Huriye Bilsel. 2020. "Biocementation of Calcareous Beach Sand Using Enzymatic Calcium Carbonate Precipitation." Crystals 10, no. 10: 888.