Thèse soutenue

Auteur / Autrice : Zhiqiang Zhang
Direction : Didier LéonardSiqing Xia
Type : Thèse de doctorat
Discipline(s) : Chimie analytique
Date : Soutenance en 2008
Etablissement(s) : Lyon 1 en cotutelle avec Université de Tongji (Chine)


FR  |  

Environmental biotechnologies can bring both environmental and economical benefits, playing an especially important role in eliminating pollution and improving the environmental quality. The present thesis deals with the development and application of two environmental biotechnologies: microbial flocculant (MBF) and conductometric biosensor. A MBF named TJ-F1 of strong flocculating activity, produced by strain TJ-1 identified as Proteus mirabilis, was investigated with regards to its production, characterization and applications. The flocculating activity of TJ-F1 obtained under the optimized culture conditions was up to 93. 13%. About 1. 33 g of the purified solid MBF with a molecular weight of 1. 2×105 Da could be recovered from 1. 0 L of fermentation broth. Chemical analysis of TJ-F1 indicated that it contains proteins (30. 9%, w/w) and acid polysaccharide (63. 1%, w/w). Scanning electron microscopy image of the purified solid-state TJ-F1 showed that it has a crystal-linear structure. Spectroscopic analysis of TJ-F1 by Fourier-transform infrared spectrometry indicated the presence of hydrogen bonds, hydroxyl, amino and carboxyl groups which are the preferred ones for the flocculation process. The flocculation mechanism of TJ-F1 was discussed according to its physical & chemical characteristics and to the Zeta potential variation in the flocculation system. The successful application to the dewatering of activated sludges and the dye removal from water validated its excellent flocculating performance. A cost-effective culture medium using wastewaters as nutriments was also developed, which can not only cut down the production cost of TJ-F1, but also save the treatment cost of the wastewaters. Two conductometric biosensors respectively for phosphate and nitrite analysis were developed. The process parameters for the fabrication of the biosensors and various experimental variables were investigated with regards to their influence on the sensitivity, the detection limit, the dynamic range, the operation and storage stability. The biosensor for phosphate analysis showed a fast response (about 10 s) to phosphate with a detection limit of 1. 0 μM, and two linear ranges of 1. 0-20 μM and 20-400 μM. The biosensor for nitrite analysis showed a similar fast response to nitrite with a detection limit of 0. 05 μM and a linear range of 0. 2-120 μM. Both of them showed satisfactory reproducibility and good stability. For both biosensors, no obvious interference from other ionic species familiar in natural waters was detected. The application experiments showed that the biosensors are suitable for use in real water samples