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

Koita, Khushnuma

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https://hdl.handle.net/2142/34403 Copy

Description

Title

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

Author(s)

Koita, Khushnuma

Issue Date

2012-09-18T21:15:15Z

Director of Research (if dissertation) or Advisor (if thesis)

Rao, Christopher V.

Doctoral Committee Chair(s)

Rao, Christopher V.

Committee Member(s)

• Pack, Daniel W.
• Zhao, Huimin
• Bhalerao, Kaustubh

Department of Study

Chemical & Biomolecular Engr

Discipline

Chemical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(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.

Graduation Semester

2012-08

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http://hdl.handle.net/2142/34403

Copyright and License Information

Copyright 2012 Khushnuma Koita

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