Showing 6 results for Urease
F. Noorbakhsh, S. Hajrasuliha, G. Emtiazy,
Volume 5, Issue 3 (10-2001)
Abstract
The urease enzyme plays an important role in the efficient use of urea fertilizer and some environmental risk assessment. Urease activities in 20 different soil samples of arid to semi-arid regions of Isfahan Province were determined and their correlations with some soil physical, chemical and biological characteristics were studied. Urease activities range from 5.3 to 79.2 µg NH4
+ g
-1 soil 2hr
-1.
Results indicated that soil organic carbon was significantly correlated with urease activity (r=0.899***). None of sand, silt and clay percentages were significantly correlated with urease activity. Total nitrogen was significantly correlated with urease activity (r=0.797***). Electrical conductivity of saturated paste extracts were also negatively correlated (r=-0.499*) but sodium adsorption ratio (SAR), pH, equivalent calcium carbonate and cation exchange capacity failed to be correlated significantly with urease activity. No significant correlations were found between urease activity and total bacteria (on nutrient agar) or total fungi (on potato dextrose agar), but the bacteria that could colonize urea-agar media were significantly correlated with urease activity (r=0.47*). Multiple stepwise regression analysis showed that organic carbon accounted for most of the variation in urease activity.
A.a. Besalatpour , M.a. Hajabbasi, V. Dorostkar , Gh. Torabi,
Volume 14, Issue 53 (10-2010)
Abstract
Presence of petroleum contaminants in soil may be toxic to human and organisms and act as a source of ground water contamination hence, remediation of these compounds from environment is vital. In this study, first the feasibility of remediation of two petroleum-contaminated soil samples around Tehran Oil Refinery (oil refinery landfill and agricultural soils) was assessed using landfarming technique during a four month experimental period. The elimination of total petroleum hydrocarbons (TPHs) from soils treated through landfarming technique was then investigated in the rhizosphere of agropyron and fescue. The results showed that microbial respiration increased due to landfarming processes in both soils. Urease activity in the landfarming treatment for agricultural soil was 21, 45, 26, and 23% higher than the control at the end of first to the 4th months of experiment, respectively. However, no significant differences were observed between the landfarming and control treatments for landfill soil at the end of experiment. Furthermore, about 50 and 57% reduction in TPH-concentration was observed in the landfarming treatment for landfill and agricultural soils at the end of experiment, respectively. In the phytoremediation study, presence of TPHs in both landfarming and control treatments reduced dry matter yield of the studied plants. Urease activity in the rhizosphere of fescue and agropyron was higher than in the unplanted soil. Degradation of petroleum-compounds in the landfill soil under landfarming treatment was more than 20 and 40% in the presence of fescue and agropyron, respectively. The influence of agropyron on TPH-removal from agricultural soil under the landfarming treatment was also higher than fescue.
H. Dehghan-Menshadi, M. A. Bahmanyar, S. Salek Gilani, A. Lakzian,
Volume 16, Issue 60 (7-2012)
Abstract
Biological indicators are considered soil quality elements, due to their dependence on soil organisms. In order to investigate The effect of compost and vermicompost enriched by chemical fertilizers and manure on soil organic carbon, microbial respiration, and enzymes activity in basil plant's rhizosphere, a field experiment was conducted as a split-plot design with randomized complete blocks and three replications in 2006. The main plot involved six levels of fertilizer including: 20 and 40 tons of compost enriched, 20 and 40 tons of vermicompost enriched per hectare, chemical fertilizer and control without fertilizer and sub-plot, and period of application (two, three and four years). The results showed that application of compost and vermicompost at all levels increased soil organic carbon (OC) and soil microbial respiration, microbial biomass and urease activity compared to the controls (p<0.05), but increasing trend among the treatments was not similar. The maximum amounts of OC, soil microbial respiration and enzyme activity were observed in 40 tons of vermicompost enriched with chemical fertilizer ha-1 with four years of application. In high levels of compost application, the urease activity was decreased.
H. Rahmani, A. Lakzian, A. R. Karimi Karouyeh, A. Halajnia,
Volume 17, Issue 65 (12-2013)
Abstract
Urease is one of the most important enzymes in nitrogen cycle. The clay particles (with high surface area) play an important role in the stability of these protein compounds (enzymes) against various environmental factors. In order to examine the interactions between urease with sepiolite and vermiculite, three in vitro experiments were conducted separately in a completely randomized design. Two experiments were carried out with two replications. Treatments included six incubation times (0, 1, 2, 5, 10 and 20 days) and five levels of temperature (10, 20, 30, 40 and 50 ˚C). The third experiment was carried out in a factorial arrangement with two replications. Factors included three levels of pH (5, 7 and 9), and six-levels of enzyme concentrations (0.05, 0.25, 1, 5, 15 and 30 units). The results showed that the activity of adsorbed enzyme was more than free enzyme during the incubation time. The optimum temperatures for activity of free and adsorbed enzymes were 30 and 50 ˚C, respectively. It was concluded that enzyme adsorption on clay surfaces increases enzyme stability against environmental changes. Also, the results showed that the highest levels of urease adsorption on sepiolite and vermiculite occurred at pH 9 and 7, respectively. Adsorption isotherms of Enzyme showed that Vermiculite adsorbed urease with higher affinity compared to Sepiolite.
H. Rahmani, A. Lakzian, A. R. Karimi, A. Halajnia,
Volume 20, Issue 78 (1-2017)
Abstract
Urea is one of the most commonly used nitrogen fertilizers in agricultural lands. The fate of this fertilizer in soils is greatly related to the soil urease enzyme activity, while this enzyme commonly exists in the adsorbed state on the surface of soil colloids, and especially clay minerals. In order to examine the kinetic properties of free and adsorbed Urease on the surface of sepiolite and vermiculite, an experiment was carried out with eight levels of urea concentration (5, 10, 20, 40, 60, 80, 100 and 120 mM). This experiment was done with enzyme concentration of 1 unit in temperature of 25˚C and pH=7. Adsorption of urease on the clay surfaces affected its kinetic properties compared to the free state. The results showed that urease enzyme obeyed Michaelis-Menten kinetic in both free and adsorbed states on the clay surfaces. Except free urease, the highest and lowest values of Vmax and Km were observed in urease-sepiolite and urease-vermiculite complexes, respectively. Also, the results showed that except free urease, the highest levels of Catalytic Efficiency were related to urease in the presence of vermiculite and sepiolite, respectively. The Effectiveness Factor was more for adsorbed urease on the sepiolite surface than adsorbed urease on the vermiculite surface, and the fact somehow suggests more complete diffusion in the presence of sepiolite.
M. Maleki-Kakelar, M. Yavari,
Volume 24, Issue 1 (5-2020)
Abstract
Biocementation through microbial induced carbonate precipitation (MICP) is a recently developed new branch in geotechnical engineering that improves the mechanical properties of bio-treated soils. The potential application of MICP to handle problems such as liquefaction and erosion has been established; this technique offers an environmentally friendly, cost-effective and convenient alternative to traditional soil improvement approaches. Nevertheless, in spite of the widespread demonstration of the process at laboratory scale, few field and practical applications have been implemented to assess the efficiency of the biochemical process. Therefore, this paper presents a review of the utilization of MICP for soil improvement and discusses the treatment process including the key constituents involved and the main affecting factors, especially in field scale applications. The major contribution of this research is to identify the main parameters restricting the application of this method on site. Finally, technical and commercial progress in the industrial adoption of the technology and the main challenges that are ahead for the future research prior to real practical application are briefly discussed.
