| Microorganisms have evolved to degrade and hydrolyze complex matrixes and extreme environmental conditions such as higher temperature, salinity, or pH. With the appropriate inoculum and selective conditions, organisms can be enriched using selective conditions and in order to efficiently degrade a compound of interest. Cellulosic biomass is a renewable resource explored as a feedstock for bioenergy and the microbial mechanisms to hydrolyze the material are discussed in Chapter 1. This research focuses on cellulose and elevated temperatures (52 - 60°C) as a way to select for a microbial consortium able to degrade many plant polymers and generate products of interest, including biohydrogen.;The versatility of the consortium, henceforth called TC52 or TC60 (different by their enrichment temperature) was analyzed by observing growth and metabolic profiles with a variety of substrates. The first portion of the research focused on utilizing the consortium in a microbial fuel cell, Chapter 4. Unfortunately, MFC designs are not sustainable at elevated temperatures so a new design was developed and tested. TC60 was unstable at 60°C with cellulose as a substrate but produced 375 mW/m2 when fed glucose.;The second portion of this research monitored the ability of TC52 and TC60 to adapt and degrade a variety of substrates. In order to monitor short chain fatty acids , a solid phase extraction method (Chapter 2) was developed in order to clean culture samples prior to metabolite analysis with high-performance liquid chromatography. Chapter 3 describes a study where TC60 was enriched on a combination of microalgal biomass and cellulose in order to increase hydrogen yields. Dunaniella tertiolecta and Chlorella vulgaris, two microalgae species, were tested with several ratios of cellulose. Cultures fed a 1:2 ratio of D. tertiolecta and cellulose generated higher hydrogen yields due to lysed microalgae cells. Chapters 7 and 8 show the difference in TC52 metabolite production when grown on commercial paper samples and polysaccharides. Pyrosequencing results indicate that Lutispora thermophilia, Clostridium thermocellum, and Clostridium stercorarium were the dominant microorganisms in many conditions. It must be noted that enrichment was not done on individual substrates, rather, immediate reactions were monitored.;The third portion of this research concerned the effect of the type of substrate, concentration of substrate, and temperature on the metabolism of TC60. Initial substrate concentration (2, 4, 8, 12, 16, 20 g/l), temperature (50, 55, 60°C), and cellulosic substrates (microcrystalline cellulose Sigmacell Type 20 and 50, long fibrous cellulose, and 5 x 5 mm pieces of filter paper) were tested in all possible combinations. Data analyses showed that each individual effect can have a significant affect on metabolite production rates and yields. Also, combined environmental factors can have a combined effect. Statistical analyses were able to reveal which factors played a significant affect on production rates and yields of H2, CO2, ethanol, and acetate. The research and results are outlined and described in Chapters 5 and 6.;This research explored the ability of a consortium to quickly adapt to a change in substrate and the affect this had on metabolite production. This study showed that it is feasible to enrich for a consortium able to generate different forms of bioenergy by changing environmental conditions. |
