Biological carbon monoxide conversion for hydrogen production and environmental applications

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Industrial development and rampant population growth has resulted in energy crisis, global climate change, environmental degradation and health problems. Thus, increasing focus is being placed on clean energy supply and environmental protection for an overall sustainable development. In this context, biotechnological products and processes are considered more economical and feasible than physico-chemical processes due to several advantages, such as low energy requirement, environment friendly, low investment cost etc. This study, therefore, focused on biological carbon monoxide (CO) conversion for biohydrogen and environmental applications.Initially, the inherent capability of anaerobic biomass collected from five different sources which were mainly large scale sewage treatment plants located at different parts of India, was examined to utilize CO as the sole carbon source. These different bacterial biomass were screened for their ability to utilize CO at pH 7 and temperature 30oC. The results revealed that granular anaerobic biomass form upflow anaerobic sludge blanket (UASB) reactor treating sewage was capable of converting CO to methane and carbon dioxide as the main products along with small amount of hydrogen. Further, effect of CO partial pressure, temperature, inoculum size and biomass pre-treatment using taguchi experimental design revealed the robustness of the raw biomass for CO conversion and sulfate reduction. Experiments with 2-bromoethanosulfonate to inhibit methanogenic activity of the biomass showed the CO conversion to methane was via hydrogenotrophic route and methane formation can be avoided by using 10 mmol/L of BES which resulted in a significant increase in final H2 concentration. Metagenomic analysis of the anaerobic biomass from Kavoor STP revealed that bacteria belongs to Methanomicrobia, Clostridia, Acidobacteria, Gammaproteobacter, Bacteroidia classes are predominantly present in the biomass. Presence of Desulfovibrio sp. was also detected in small quantity indicating its role in biological sulfate reduction.
Supervisor: Kannan Pakshirajan