Volume No. 4 Issue No.: 2 Page No.: 372-379 Oct.-Dec 2009

 

GROWTH, EXOPOLYMER PRODUCTION AND METAL BIOREMOVAL BY Nostoc punctiforme IN Na+ AND Cr (VI) SPIKED MEDIUM

 

Mona Sharma, Nisha Rani, Anjana Kamra, Anubha Kaushik*1 and Kiran Bala2

1. Department of Environmental Science and Engineering, Guru Jambheshwar University of Science and Technology, Hisar (INDIA)
2. Centre for Environmental Studies, The Energy and Resources Institute, New Delhi (INDIA)

 

Received on : July 15, 2009

 

ABSTRACT

 

Wastewaters of industries like textile and tannery contain large quantities of salts besides chromium (VI) ions which pose serious environmental problems and need to be removed to meet the environmental standards. With increasing emphasis on bioremediative techniques new microbial systems are being explored. In this context the present study reports on sodium and chromium (VI) tolerance of Nostoc punctiforme, a filamentous, heterocystous cyanobacterium isolated indigenously from soil for its potential use in bioremediation of such wastewaters. Various parameters like biomass, chlorophyll content, exopolysaccharide (EPS) production and percent removal of Na+ and Cr (VI) were studied in response to varying Na+ concentrations
(55mM and 110mM corresponding to electrical conductivity 5 and 10 dSm-1 using NaCl) and Cr (VI) concentrations (0.05, 0.1, 0.15 and 0.2 mM corresponding to 5, 10, 15 and 20 mg/L using K2Cr2O7). These treatments were given keeping in view the range of concentration of total dissolved solids (TDS) and Cr (VI) in the wastewaters of textile industries. The Nostoc punctiforme strain was found to be both halophilic and Cr tolerant as it showed significant increase in dry weight in response to salt and Cr (VI) stress. Chlorophyll concentration of the cyanobacterium under salt stress was significantly more (P<0.05) as compared to that of control, showing 4 to 5.5 times increase. The cyanobacterium also showed 2 times increase in biomass in response to Cr (VI). Exopolysaccharide (EPS) production by the cyanobacterium increased when exposed to higher concentration of salt or Cr (VI) which seems to play a role in metal biosorption. Scanning electron micrographs (SEM) of the exopolysaccharides also revealed complete coverage of the rough EPS surface by the metal indicating its biosorption on the exopolymer surface. Bioremoval of salt and metal ions by the EPS of the cyanobacterium suggest that it can be used in bioremediation programs of wastewaters containing these metals.

 

Keywords : Tolerance, Chromium, Sodium, Nostoc punctiforme, Exopolysaccharides, Biosorption

 

 

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