DOI: 10.5176/978-981-08-8119-1_BioTech2011_12
Authors: S.K. Verma
Abstract:
Industrialization and urbanization has led to an increase in metal contamination of aquatic environment. Current practices for the removal of soluble metal ions like chemical precipitation, ion exchange resins, solvent extraction and electro-winning, suffers limitation in low bulk metal concentration, ion specificity, narrow pH and poor settling colloidal properties. The search for new technologies to detect and remove toxic metal/radionuclides from water has directed attention towards exploiting genetically engineered microorganisms (GEM). We report an EGFP based whole cell bacterial biosensor for arsenic detection by creating a transcriptional fusion between the ars regulatory sequences and EGFP gene in plasmid pEGFP. The resultant recombinant plasmid pJSKV51 was used to transform E. coli DH5α Under optimal conditions, the arsenic biosensor strain responds to arsenic from 5ppb to 500ppb. The genetically engineered Nostoc calcicola expressing mouse metallothionein in stable expression plasmid based on
pDU1 replicon has been developed. The recombinant strain showed resistance to Co, Ni, Cu, Sr, Zn, Cd and the MIC were raised to 52.5, 12.5, 15, 100, 1000 and 67.5 as compared to 35, 10, 10, 70, 750 and 250μM for wild type cells. Silica coated calcium alginate (Si-CAG) and silica gel (SiO2) were developed for whole-cell immobilization. These matrices were characterized for their pore size, chemical and physical stability. Scanning electron microscopy (SEM) revealed superior metal accumulation, mechanical strength and membrane thickness of 10μm of silica layer over CAG prevents cell leakage. Immobilized recombinant cells packed in an up-flow columnar bioreactor remove heavy metals in the order Cu2+>Cd2+>Ni2+>Zn2+. Genetically engineered N.Calcicola has potential for removal and recovery of
different heavy metals from industrial effluents.
Keywords: Biosensor, Arsenic, Bioremediation, Nostoc calcicola, immobilization, EGFP
Updating...