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Title: Potential of Extracellular Polymeric Substances and Biofilm Produced by Bacterial Isolates in Calcium Carbonate Mineralization
Authors: Bains, Amrita
Supervisor: Reddy, M. S.
Keywords: Biomineralization, MICCP, Bacillus megaterium, Specific media, Urease, EPS, Biofilm, Calcium carbonate precipitation
Issue Date: 29-Aug-2014
Abstract: Microbially induced calcium carbonate precipitation (MICCP) is a biomineralization process. It has emerged as a novel and eco-friendly technology for protecting consolidating decayed constaruction materials. Various factors including presence of nucleation site on bacterial surface affects the microbially induced calcite precipitation. Bacterial surface formed of extracellular polymeric substances (EPS) plays a very important role in capturing calcium carbonate and resulting in precipitation. In the present study, best ureolytic alkalophilic bacterial isolate (Bacillus megaterium) was screened and grown in best nutritive media (Specific media) for the maximum production of extracellular polymeric substances. B. megaterium showed highest production of EPS in presence of urea and calcium chloride. EPS production came out to be 4881 µg/100ml. Specific media was optimized by one factor at a time approach (OFAT) by taking variable carbon, nitrogen, calcium source and pH profile for maximum EPS production and enhancing calcium carbonate precipitation. EPS production by Bacillus megaterium was maximum in media with glucose as carbon source (3651 µg/100ml); peptone as organic (6661 µg/100ml) and ammonium sulphate (4365 µg/100ml) as inorganic nitrogen source, calcium chloride as calcium source (4192 µg/100ml) at pH 7.0 with value of 3762 µg/100ml. EPS and calcium carbonate crystals produced by B. megaterium were characterized by staining, scanning electron microscopy (SEM), X-ray diffraction (XRD) and fourier transform infra red (FTIR) spectrum analysis. SEM analysis of EPS revealed smooth and rough surface in nutrient broth and specific media whereas SEM analysis of crystals depicted the shape and size of calcite crystals in smooth, circular, triangular forms in nutrient broth and rhombohedral in specific media. XRD and FTIR analysis of EPS and calcium carbonate crystals depicted the presence of functional groups on their surface. In case of, XRD of EPS of B. megaterium in nutrient broth and specific media the highest peak of carbon and calcium ions were depicted at 45 and 56° 2theta positions whereas in case of XRD of calcite crystals of B. megaterium in nutrient broth and specific media the highest peak was observed at 30° 2theta positions. FTIR analysis of EPS of B. megaterium in nutrient broth and specific media was showing highest absorption peaks at λ=1400 cm-1 and λ=1000 cm-1, whereas in case of FTIR analysis of calcite crystals of B. megaterium in nutrient broth and specific media the highest absorption peak was observed at λ=800 cm-1 and λ=1000 cm-1. It was concluded that extracellular polymeric substances (EPS) produced by alkalophilic ureolytic Bacillus megaterium has the potential for efficient calcium carbonate precipitation and hence can be serve as new remediation tool in MICCP.
Description: MS, DBTS
Appears in Collections:Masters Theses@DBT

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