Author ORCID Identifier

https://orcid.org/0000-0001-5057-7703

Year of Publication

2019

Degree Name

Master of Science in Chemical Engineering (MSChE)

Document Type

Master's Thesis

College

Engineering

Department

Chemical and Materials Engineering

First Advisor

Dr. Dibakar Bhattacharyya

Abstract

The movement towards a more sustainable energy economy may require not only the generation of cleaner fuel sources, but the conversion of waste streams into value-added products. Phototrophic purple non-sulfur bacteria are capable of metabolizing VFAs (volatile fatty acids)and generate hydrogen as a byproduct of nitrogen fixation using energy absorbed from light. VFAs are easily produced from dark anaerobic fermentation of food, agricultural, and municipal wastes, which could then be fed into photobioreactors of purple bacteria for hydrogen production.

The process of photofermentation by purple bacteria for hydrogen production remains attractive due to the capability of reaching high substrate conversions under mild operating conditions, but increasing the efficiency of converting light energy into hydrogen remains challenging. Purple bacteria cannot utilize the entire solar spectrum, and the dominant region of absorption lies in the near-infrared region above 800 nm.

In this work, the model purple non-sulfur bacteria Rhodopseudomonas palustris was used to study different strategies to increase light utilization and hydrogen production. Near-infrared LED arrays were selected to match the target bacteriochlorophyll absorption range, and were tested to be used as a sole illumination source for photofermentation. Additionally, plasmonic nanoparticles with resonant frequencies matching bacterial absorbance were added in solution to increase light utilization through scattering and near field electric enhancement effects at intensities around 100 W/m2 . Both of these approaches proved to increase cellular growth rate and hydrogen production, which opens the door to utilizing more advanced photonic structures for use in bacterial phototrophic processes.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2019.332

Funding Information

National Science Foundation EAGER Grant 1700091

NSF EPSCoR grant 1355438

Southern Company

Available for download on Saturday, August 01, 2020

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