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

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2012

Author dc:creator

• Koita, Khushnuma

Contributors dc:contributor

• Rao, Christopher V.
• Pack, Daniel W.
• Zhao, Huimin
• Bhalerao, Kaustubh

• biofuels
• arabinose efflux
• pentose transport
• xylose metabolism
• strain engineering

Statement dc:rights

• Copyright 2012 Khushnuma Koita

Language dc:language

en

Handle dc:identifier

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

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/34403