Screening for Urease-Producing Bacteria from Limestone Caves of Sarawak

Abstract

Urease is a key enzyme in the chemical reaction of microorganism and has been found to be associated withcalcification, which is essential in microbially induced calcite precipitation (MICP) process. Three bacterialisolates (designated as LPB19, TSB31 and TSB12) were among twenty-eight bacteria that were isolated fromsamples collected from Sarawak limestone caves using the enrichment culture technique. Isolates LPB19, TSB31and TSB12 were selected based on their quick urease production when compared to other isolates. Phenotypiccharacteristics indicate all three bacterial strains are gram-positive, rod-shaped, motile, catalase and oxidasepositive. Urease activity of the bacterial isolates were measured through changes in conductivity in the absence ofcalcium ions. The bacterial isolates (LPB19, TSB12 and TSB31) showed urease activity of 16.14, 12.45 and 11.41mM urea hydrolysed/min respectively. The current work suggested that these isolates serves as constitutiveproducers of urease, potentially useful in inducing calcite precipitates.

Isolation and Characterization of Urease-Producing Soil Bacteria

“…To enrich urease-producing bacteria from soil samples, 1 g of each soil sample was inoculated into 100 mL of urea broth medium (Sigma-Aldrich) consisting of 1.00 mg/L peptone, 1.000 mg/L dextrose, 5.00 mg/L sodium chloride, 1.2 mg/L disodium phosphate, 0.8 mg/L monopotassium phosphate, 0.012 mg/L of phenol red, and 6% (w/w) urea (HiMedia, sterile filtered 0.45 μm, added after autoclaving) (in 250 mL shake flasks) and incubated under aerobic batch conditions at 30°C for 120 h under shaking condition at 130 rpm [21]. For subsequent enrichment, 20% (v/v) of the culture samples were intermittently transferred (up to four times) into a fresh medium [28].…”

“…Reference [20] estimated that the microorganisms capable of hydrolyzing urea comprised between 17 and 30% of the aerophilic, microaerophilic, and anaerobic microorganisms isolated from their soil samples. eir ability to produce urease can be exploited to enrich and isolate such bacteria from the environment for future applications [21]. While the occurrence of these bacteria and their characteristics have been explored in some regions and soil types [1,12,21,22] and other novel bacterial strains isolated from Ethiopian sediments and soils [23,24], this study is the first report on the characterization of ureolytic bacteria from Ethiopian soil.…”

“…eir ability to produce urease can be exploited to enrich and isolate such bacteria from the environment for future applications [21]. While the occurrence of these bacteria and their characteristics have been explored in some regions and soil types [1,12,21,22] and other novel bacterial strains isolated from Ethiopian sediments and soils [23,24], this study is the first report on the characterization of ureolytic bacteria from Ethiopian soil. is study aimed to isolate and characterize rapid ureaseproducing bacteria from Ethiopian soils.…”

Isolation and Screening for Ureolytic Bacteria from Bukilat Cave, Camotes Islands, Cebu

“…To con rm their ability to produce urease, urea agar base or Christensen's medium (HiMedia, India) was used (Omoregie et al, 2016). The agar was distributed into sterile test tubes, and each bacteria colony was introduced into individual test tubes and then incubated at 37°C for 72 h. A color change was observed from pale yellow to pink-red for colonies that successfully initiated the ureolytic pathway.…”

“…When urea is hydrolyzed by urease released by bacteria, ammonia is released and increases the pH changing the color of the medium to pink-red (Omoregie et al, 2016). Following Omoregie and his colleagues (2016), only isolates that were able to change approximately 10 mL of the medium were chosen to be studied quantitatively based on their ability to produce urease quickly.…”