Microbial Synthesis of Chalcogenide Nanoparticles Combining Bioremediation and Biorecovery of Chalcogen in the Form of Chalcogenide Nanoparticles

Recent years have seen a growing interest in the application of chalcogenide nanoparticles (NPs), e.g. Se, Te, CdSe and CdTe NPs, in various industrial sectors including energy, petroleum refining and in the field of biology and medicine. Moreover, due to the high toxicity of chalcogen oxyanions, their release into the environment is of great concern. Thus, emphasis was given in this study on the development of a novel microbial synthesis process of chalcogenide NPs by combining biological treatment of Se/Te containing wastewaters with biorecovery in the form of Se NPs, Te NPs and CdSe NPs. Enrichment of Se-oxyanion reducing microorganisms was carried out to simultaneously remove selenite (Se(IV)) and cadmium (Cd(II)) from wastewaters by combining bioremediation of toxic Se-rich wastewater with the biorecovery of Se as CdSe NPs. The results showed compositional changes in the extracellular polymeric substances (EPS) matrix of the anaerobic granular sludge upon exposure to Cd(II) and Se(IV) and identified the roles of EPS fractions in the biogenesis of CdSe NPs. Besides, it was found that the EPS on the surface of the biogenic Se NPs play a major role in lowering the bioavailability and toxicity of biogenic Se(0) compared to chemogenic Se(0) NPs. An upflow anaerobic sludge blanket (UASB) reactor was used for the first time to continuously remove tellurite from wastewater and recover biogenic Te(0).

1 General introduction 1.1. Background 1.2. Problem description 1.3. Research objectives 1.4. Structure of the thesis References 2 Literature review 2.1. Introduction 2.2. Quantum dots and their properties 2.3. Metal Chalcogenide QDs 2.4. Biological metal chalcogenides 2.5. Sulfur based chalcogenides 2.6. Selenium based chalcogenides 2.7. Tellurium based chalcogenides 2.8. Mechanisms of biological synthesis of metal chalcogenides 2.9. Applications of chalcogenide QDs References 3 Biological removal of selenate and ammonium by activated sludge in a sequencing batch reactor3.1. Introduction 3.2. Materials and Methods 3.3. Results 3.4. Discussion 3.5. Conclusion References 4 Effect of heavy metal co-contaminants on selenite bioreduction by anaerobic granular sludge4.1. Introduction 4.2. Materials and methods 4.3. Results 4.4. Discussion 4.5. Conclusion References 5 Biosynthesis of CdSe nanoparticles by anaerobic granular sludge5.1. Introduction 5.2. Materials and Methods 5.3. Results 5.4. Discussion 5.5. Conclusions References 6 Modification of extracellular polymeric substances (EPS) of anaerobic granular sludge used for synthesis of cadmium selenide nanoparticles 6.1. Introduction 6.2. Materials and methods 6.3. Result 6.4. Discussion 6.5. Conclusion References 7 Continuous removal and recovery of tellurium in an upflow anaerobic granular sludge bed (UASB) reactor 7.1. Introduction 7.2. Materials and methods 7.3. Results 7.4. Discussion 7.5. Conclusion References 8A comparison of fate and toxicity of selenite, biogenically and chemically synthesized selenium nanoparticles to the Zebrafish (Danio rerio) embryogenesis 8.1. Introduction8.2. Materials and methods 8.3. Results 8.4. Discussion 8.5. Conclusions References 9 Discussion, conclusions and perspectives 9.1. General discussion 9.2. Synthesis of biogenic chalcogen alloys (e.g. Se/Te) 9.3. Future perspectives References Appendix 1 Biography Publications

Joyabrata Mal was born in 1987 in Kolkata, India. Joy did his bachelor (B.Tech) in Biotechnology at West Bengal University of Technology. He later joined the Indian Institute of Technology, Guwahati, India for his master (M.Tech) of Technology degree in Biotechnology. During this degree, he did his specialization in Environment Biotechnology and worked on synthesis of biohydrogen from carbon monooxide. Joy got admitted into Erasmus Mundus Joint Doctorate Program on Environment Technologies for Contaminated Solids, Soils and Sediments (ETeCoS3) and started as PhD Fellow at UNESCO-IHE from October 2013. As part of program, he also carried out his PhD research at Université Paris-Est.andworked at University of Limoges under a short term scientific mission (STSM, COST Action ES1302). His research was mainly focused on developing novel methods for chalcogens (selenium and tellurium) bioremediation, bioreduction and recovery. He is currently a postdoctoral fellow in University of California Berkeley and working on selenium biogeochemistry.