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Optimizing pentose sugar utilization in Escherichia coli for the production of biofuels

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Title: Optimizing pentose sugar utilization in Escherichia coli for the production of biofuels
Author(s): Koita, Khushnuma
Director of Research: Rao, Christopher V.
Doctoral Committee Chair(s): Rao, Christopher V.
Doctoral Committee Member(s): Pack, Daniel W.; Zhao, Huimin; Bhalerao, Kaustubh
Department / Program: Chemical & Biomolecular Engr
Discipline: Chemical Engineering
Degree Granting Institution: University of Illinois at Urbana-Champaign
Degree: Ph.D.
Genre: Dissertation
Subject(s): biofuels arabinose efflux pentose transport xylose metabolism strain engineering
Abstract: The hydrolysis of biomass yields a sugar mixture consisting mainly of glucose, arabinose and xylose. Effective metabolism of all sugars in biomass by a microorganism is regarded as essential for commercial biofuel production. However, two of the major challenges that we are currently faced with are the transport of sugars into the microorganism and the co-utilization of these sugars once they are in the cell. In order to engineer simultaneous multiple sugar utilization in Escherichia coli, a better understanding of the pentose sugar pathways is required. In this work, we have investigated the transport of sugars and the regulation of the sugar metabolic pathways within E. coli to engineer a strain most efficient in producing biofuels. While extensive research has been carried out to examine the transport mechanisms of sugars into the cell, this research shows that in addition to transporters that pump sugars into the cell, a number of proteins that pump sugars out of the cell are also expressed by E. coli. Using genetic approaches, we have demonstrated that by either deleting or overexpressing these efflux transporters we can respectively increase or decrease the uptake of pentose sugars, namely arabinose and xylose, which are abundantly present in the hemicellulose of biomass. In addition to examining transport mechanisms, this work has also focused on studying and controlling the metabolism of the pentose sugars. By using a novel targeted approach, we can utilize constitutive promoters and chromosomal integration to control the expression of certain metabolic genes, while relieving repression effects. This enables us to regulate the metabolism of pentose sugars such as xylose that are utilized by the cell less efficiently and allows for simultaneous metabolism of sugars, hence leading to a more efficient biofuel production process.
Issue Date: 2012-09-18
URI: http://hdl.handle.net/2142/34403
Rights Information: Copyright 2012 Khushnuma Koita
Date Available in IDEALS: 2012-09-18
Date Deposited: 2012-08
 

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