Enhancement of Crsup6+/sup removal by iAspergillus niger/i RH19 using a biofermenter.

摘要

Microbial bioremediation is an emerging technology for environmental cleanup. Microorganisms are advantageous for metal detoxification as they are easy to grow, resulting in a rapid production of biomass, and are part of natural environment. Cr6+ biosorption potentials of four bacterial isolates (Bacillus sp. RH69, Bacillus sp. RH70, Bacillus pumilis RH84 and Bacillus fumus RH109), and two fungal isolates, Aspergillus niger strains, RH17 and RH19, were determined. Bacillus fumus RH109 showed maximum tolerance against Cr6+ of 1000 mg/litre and Aspergillus niger RH19 exhibited resistance up to 275 mg/litre. Bacillus sp. RH69, in VB mineral salt media, containing 25 mg/litre Cr6+, showed 42.60 removal at 30 degrees C (pH 5.0) within 24 h, but soon after that desorption took place. On the other hand, Aspergillus niger RH19 removed 46.00 Cr6+ from the same initial concentration of Cr6+ at identical pH, temperature and agitation. Growth conditions for this strain were optimized. In batch biosorption studies, Aspergillus niger RH19 removed 74.00 Cr6+ at 30 degrees C with pH 8.0 from aqueous solution containing 25 mg/litre of Cr6+ at 100 rpm agitation. A pilot study was then conducted to scale up biosorption of Cr6+ using stirred tank biofermenter. Cr6+ removal by Aspergillus niger RH19 was recorded as 60.00 at pH 6.0, 35 degrees C, 100 rpm agitation and 5 DOT (dissolved oxygen tension). These results are promising in terms of development and design of bioreactors for removal of hazardous heavy metal ions from industrial waste water, according to indigenous industrial requirements.