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|Title||Isolation, Characterization and Application of Calcite Producing Bacteria from Urea Rich Soils|
Background The hydrolysis of urea by the enzyme urease is unique in that it is one of the few biologically occurring reactions that can generate carbonates. Calcium carbonate is one of the most common minerals widespread on earth (4% by weight of the earth's crust). Bacteria are incredibly diverse and abundant and many bacterial species contribute to the precipitation of mineral carbonates in various natural environments. Alkaline pH is the primary means by which microbes promote calcite precipitation which results from the hydrolysis of urea. Materials and methods The study used selective enrichment culture technique to isolate urease-producing bacteria from local urea rich soil and others materials. Isolates were subjected to increasing urea concentrations. All isolates were identified using conventional biochemical tests. In addition, all isolates were tested for their ability to enhance the consolidation of sand and compressive strength of mortar as well as absorption reduction properties. One strain with promising results was selected and the environmental and nutritional conditions were characterized. The growth curve of the selected strain with optimized condition was investigated. Results Thirty three isolates were obtained from the enrichment culture technique. Among them 13 isolates showed increased consolidation of sand. An isolate designated TN 1B showed the highest performance which was identified as Bacillus mycoides. The optimum pH of the isolate was shown to be 7.0 and an optimum temperature of 35 oC was found. There were no significant differences in the growth promoting properties among the tested media, therefore, the cheapest formulation (rabbit feed) was selected for subsequent experiments. The growth curve was constructed with a stationary phase starting after 10 hours. The test results indicated that inclusion of Bacillus mycoides isolate in cement mortar enhanced the compressive strength, with a maximum increase of 17% in compressive strength and 32% reduction in water absorption was observed with a 28-day mortar sample. This improvement in compressive strength may be due to deposition of calcite on the bacteria cell surfaces within the pores. Conclusion Locally isolated strain identified as Bacillus mycoides was obtained from urea rich soil and the growth conditions were partially optimized. The use of the selected isolate showed enhanced properties of the cement mortar. It is recommended that further investigation to utilize this isolate in several applications be performed.
|Publisher||الجامعة الإسلامية - غزة|
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