Improvement of NaNO ₂ -Oxidizing Activity in Nitrobacter vulgaris by Coentrapment in Polyacrylamide Containing Polydimethylsiloxane Copolymer and DEAE-Sephadex

Abstract

Removal of nitrite and nitrate from drinking water has attracted great attention in recent years because of the human health risk induced by the exposure to contaminated groundwater and surface water. We have therefore tested a model nitrite oxidation system by coentrapping the NaNO 2 oxidizer Nitrobacter vulgaris with polydimethylsiloxane (PDMS) copolymer and DEAE-Sephadex in a polyacrylamide gel. The copolymer and the anion exchanger facilitate the diffusion of oxygen and NaNO 2 , respectively, into the gel matrix. To test the nitrite-oxidizing activity, the entrapped cells were coupled to a thermal sensor. Coentrapment of 5% (wt/vol) DEAE-Sephadex with Nitrobacter vulgaris increased the nitrite-oxidizing activity by a factor of 3.7 compared to entrapped cells alone, and by the addition of 0.86% (wt/vol) artificial oxygen carrier PDMS copolymer increased the activity further to 4.3 times higher. Operational and storage stability of the coentrapped N. vulgaris also improved. This suggests that this enhanced immobilized cell system can also be used for nitrite oxidation to nitrate in drinking water as an on-line thermally monitored bioreactor.

Characterization of luminescent Vibrio campbelliiLZ5 and its potential application in the detection of environmental heavy metals

“…From this point of view, development of immobilized whole‐cell preparations with a better storage and operational stability would be attractive. Some of the entrapment techniques for biosensors immobilize microbial cells on synthetic polymeric gels, including polyacrylamide , polyurethane‐based hydrogels , and polyvinyl alcohol . However, the complicated preparation process is costly and time consuming.…”