Engineering Commons^™

Improved Fermentation Design And Screening Devices For Biobutanol Production, Garret Christopher Munch

Electronic Thesis and Dissertation Repository

A worldwide increase in demand for renewable fuels has revived interest in fermentatively produced butanol. However, butanol fermentation suffers from low product yields and productivity. The work presented in this thesis addresses part of these research and development needs at three levels: innovative fermentation process design; genetic manipulation for strain enhancement; and the development of a new tool for anaerobic process characterization and optimization.

Product yield could be increased through traditional fermentation engineering. Co-fermentation of butyric acid with glycerol increased the butanol yield from 0.45 mol/mol (mols C in butanol / mol C in substrates) to 0.51 mol/mol. In building …

Autohydrolysis Pretreatment Of Mixed Lignocellulosic Biomass, Claudio Lira

Electronic Thesis and Dissertation Repository

Lignocellulosic biomass, such as agricultural and forestry residues, can be transformed into valuable fuels and chemicals. However, the high cost of feedstock handling and the complex nature of cellulosic biomass processing and conversion remain two major challenges in biorefineries. This thesis aims to tackle these challenges by assessing the transformation of multi-feedstock using autohydrolysis pretreatment.

Corn cobs and stover (residues from corn processing), poplar chips (forestry residue), bagasse and wheat straw (agricultural residues) are abundant and often under-utilized cellulosic residues. These feedstocks were used to investigate the effects of biomass characteristics on the composition of the autohydrolysis pretreatment products. Moreover, …

Enhancing Bioethanol Fermentation Through Removal Of Acetic Acid Using Liquid-Liquid Extraction, Mahdieh Aghazadeh

Open Access Dissertations

The concern for the ever growing human population as well as the depletion of fossil fuel resources and their impact on global warming have long been motivations for the researchers to investigate means for sustainable producing carbon-neutral energy. Second-generation biofuel refers to liquid fuels that are produced from non-food resources and reduce the total greenhouse gas emission by at least 60 %. Acetic acid has been shown to be one of the most ubiquitous fermentation inhibitors in a bioethanol production facility which slows down the bioethanol production and reduces its yield through inhibition of the ethanol producing microorganisms. The use …

The Bifunctional Alcohol And Aldehyde Dehydrogenase Gene, Adhe, Is Necessary For Ethanol Production In Clostridium Thermocellum And Thermoanaerobacterium Saccharolyticum, Jonathan Lo, Tianyong Zheng, Shuen Hon, Daniel G. Olson, Lee Lynd

Dartmouth Scholarship

Thermoanaerobacterium saccharolyticum and Clostridium thermocellum are anaerobic thermophilic bacteria being investigated for their ability to produce biofuels from plant biomass. The bifunctional alcohol and aldehyde dehydrogenase gene, adhE, is present in these bacteria and has been known to be important for ethanol formation in other anaerobic alcohol producers. This study explores the inactivation of the adhE gene in C. thermocellum and T. saccharolyticum. Deletion of adhE reduced ethanol production by >95% in both T. saccharolyticum and C. thermocellum, confirming that adhE is necessary for ethanol formation in both organisms. In both adhE deletion strains, fermentation products shifted from ethanol …

Biohydrogen Production By Thermotoga Neapolitana In Agricultural Media, David Morris

All Theses

In this study the production of hydrogen gas by eubacteria Thermotoga neapolitana was investigated. The organism was grown using varying media of cull peach solids and soybean meal. Hydrogen, co-products, and sugar concentrations were observed and compared.
T. neapolitana grew in medium containing peaches and soybean meal as carbon and nitrogen sources, respectively, and produced hydrogen gas. A standard medium containing glucose and yeast extract produced the most hydrogen at 31.5 mmol H2/L-medium. Withholding the vitamins and minerals from the standard the media had a significant effect on hydrogen production reducing the amount of gas produced to 25.8 mmol H2/L-medium. …

Alkaline Hydrogen Peroxide Pretreatment For Its Use In An On-Farm Bioprocessing Facility, Mary Kathryn Gray

Theses and Dissertations--Biosystems and Agricultural Engineering

Pretreatment is an essential step in biofuel production from lignocellulose. Disruption of the lignin structure gives enzymes and fermentation organisms access to long chains of cellulose and hemicellulose. For this project’s purposes, the pretreatment must work within the framework of an on-farm butanol bioprocessing facility. Alkaline hydrogen peroxide (AHP) is a delignification method that potentially provides several advantages. At the alkaline pH, powerful hydroxyl radicals are formed; which attack lignin. The objectives of this study were to determine if AHP removes substantial lignin for the feedstocks, corn stover, wheat straw, switchgrass and miscanthus, and to determine if AHP acts as …

High Ethanol Titers From Cellulose By Using Metabolically Engineered Thermophilic, Anaerobic Microbes, D. Aaron Argyros, Shital A. Tripathi, Trisha F. Barrett, Stephen R. Rogers, Lawrence F. Feinberg, Daniel G. Olson, Justin M. Foden, Bethany B. Miller, Lee R. Lynd, David A. Hogsett, Nicky C. Caiazza

Dartmouth Scholarship

This work describes novel genetic tools for use in Clostridium thermocellum that allow creation of unmarked mutations while using a replicating plasmid. The strategy employed counter-selections developed from the native C. thermocellum hpt gene and the Thermoanaerobacterium saccharolyticum tdk gene and was used to delete the genes for both lactate dehydrogenase (Ldh) and phosphotransacetylase (Pta). The Δldh Δpta mutant was evolved for 2,000 h, resulting in a stable strain with 40:1 ethanol selectivity and a 4.2-fold increase in ethanol yield over the wild-type strain. Ethanol production from cellulose was investigated with an engineered coculture of organic acid-deficient engineered strains of …

Examining The Effects Of Ethanol Processing And Drying Conditions On The Physical Properties Of Distillers Dried Grains With Solubles (Ddgs), Kurt A. Rosentrater, Brian A. Wrenn

Kurt A. Rosentrater

The production of corn-based ethanol in the U.S. has been dramatically increasing in recent years, and consequently so has the quantity of coproduct materials generated from this processing sector. These streams are primarily utilized as livestock feed, which partially offsets the need for corn in feed rations. Because of its use as an animal feed, considerable research has been conducted into the nutritional properties, and to some extent the physical properties, of commerciallyavailable distillers dried grains with solubles (DDGS). There are, however, occasions when the quality of coproducts is not consistent. Thus questions regarding the influence of production operations on …

Characterizing Volatile Fatty Acids And Other Gases In A Rumen Closed In Vitro Fermentation System Using Solid Phase Microextraction, Jarett P. Spinhirne, Jacek A. Koziel, Norbert K. Chirase

Jacek A. Koziel

A new method for rapid sampling and qualitative characterization of the headspace gases of closed in vitro cultures using solid phase microextraction (SPME) was evaluated for ruminal fluid and ruminal fluid with feed containing a feed additive. Gas sample collection was achieved by exposing a DVB/Carboxen/PDMS 50/30 .m SPME fiber to the headspace of cultures for 1 min every hour. This was followed by immediate analysis on a GC–MS and then reuse of the SPME fiber. Acetic, propionic, isobutyric, butyric, isovaleric, valeric, and hexanoic acids and toluene, dimethyl disulfide, and pentadecane were identified in the headspace. SPME technology facilitated rapid …