19-08-2014, 11:37 AM
The present work was undertaken with the following objectives - I) Screening studies for the best urease producing microorganism II) Fermentation studies for maximum enzyme production III) Downstream processing of the enzyme and IV) Application in microbiologically induced calcite deposition in civil structures.
Urease (urea amidohydrolase E. C. 3.5.1.5) is an enzyme, which catalyzes the decomposition reaction of urea into ammonia and carbon dioxide. It is found in various sources like plants, animals, and microorganisms. Urease has many applications e.g. in diagnostic kits for measuring urea, in alcoholic beverages as a urea reducing agent etc. One of the novel applications of the urease is in the calcite deposition in civil structures such as concrete where urease plays major role in remediation of the micro-cracks in the form of insoluble calcium carbonate.
The present work was undertaken with the following objectives - I) Screening studies for the best urease producing microorganism II) Fermentation studies for maximum enzyme production III) Downstream processing of the enzyme and IV) Application in microbiologically induced calcite deposition in civil structures.
In screening studies, various soil samples and microbial cultures were tested for urease producing isolates. Among the few that were selected from the initial screening, Bacillus pasteurii showed maximum activity and hence it was used for further studies. Using one factor at a time methodology, effect of physical parameters such as pH, inoculum sizes etc. as well as media parameters like carbon and nitrogen sources were studied. Enzyme production was found maximum at pH 7 with an optimum inoculation size of 2 %. Among the different carbon sources 2 % dextrose (glucose) showed maximum activity. From various nitrogen sources 1 % yeast extract showed maximum activity. Effect of urea concentration was analyzed and 2 % urea concentration was found optimum. With this optimum media Plackett-Burman design was used to find significant parameters. In downstream processing, precipitation studies have been carried out. Further purification by gel chromatography is in progress. In application part calcite deposition studies in bricks and concrete cubes were carried out and analyzed for different parameters such as moisture absorption and compressive strength.