Abstract

The prospect of hydrogen production is one of the most promising ideas for renewable fuel because hydrogen is three times more energy-dense than traditional fuels, as well as more “clean” because it only leaves behind water when it is burned. The goal of this study is to metabolically engineer Rhodobacter Sphaeroides to rewire the chemistry behind hydrogen production using lignocellulosic material. The production of value-added products through a novel “hybrid” fermentation system was also explored by coupling hydrogen production with muconic acid. Conversion of muconic acid to nylon alone accounts for a staggering amount of all nitrous oxide emissions. As the microbes produce muconic acid, the organic acids that suppress muconic acid production were removed as “spent” media and used to boost efficacy of both processes. To maximize efficiency, the Rhodobacter strain (HPCA) that showed the greatest improvement in hydrogen production was used in the hybrid system to maximize hydrogen production to the greatest extent. In the hybrid system, muconate was identified in extremely high titer and an increased hydrogen production efficiency in strain HPCA (13%). Hydrogen production in HPCA was boosted by 34%  compared to the second-highest producing strain (HPC- 140%), totaling to an even larger increase compared to the wild type. The usage of such organic acids for hydrogen production effectively expands the application of this project into waste management as it lowers the COD of plant waste. Overall, this hybrid system has great potential to produce many such value-added products, therefore boosting the viability of scale-up.