Post Doc Shuang Yan Tang
Efficient microbial conversion of biomass into renewable fuels and value-added chemicals remains an important goal in biotechnology.
Xylose, which is the second most abundant sugar in nature and a major constituent of hemicellulose in lignocellulosic biomass and wastes, is a good target for these microbial processes.
Escherichia coli is capable of utilizing a wide range of sugars as carbon and energy sources and producing native metabolites and non-native compounds. In E. coli, xylose uptake occurs primarily through a high-affinity, ATP-binding cassette transporter (xylFGH), although a second, low-affinity proton symporter (xylE) is also present.
The efficiency of xylose utilization in this organism is therefore suboptimal due to energetic requirements for xylose uptake. E. coli has been engineered to uptake xylose and reduce it to xylitol in the presence of glucose by expressing xylose reductase (XR) and a cAMP-independent CRP mutant (CRP*).
These studies showed that while xylose is negligibly metabolized by wild-type E. coli in the presence of glucose (classic diauxic growth), low levels of xylose transport and xylitol production are possible in wild-type E. coli expressing XR. Xylose transport and xylitol production are greatly improved in crp* mutant strains.
These results indicate that either the native xylose transporters are not tightly controlled by CRP or additional transport mechanisms exist.
Graduate Student Hossein Fazelinia
Summary: Computer simulations play an increasingly significant role in
understanding the underlying physical principles that dictate protein
folding, stability and function, and computational advances in this area
have greatly improved protein design predictions. In collaboration with
Costas Maranas we are developing
and testing a computational framework to rationally alter the effector
binding specificity of the bacterial transcriptional regulatory protein
AraC, belonging to the AraC/XylS family of transcriptional regulators.
Graduate Student Jonathin Chin
This research project is aimed at utilizing biomass-derived sugars as sources of energy and carbon backbone for the production of "renewable" chemicals and fuels through metabolic engineering. In collaboration with Costas Maranas, we are studying knowledge-based and model-predicted genetic manipulations in E. coli to develop robust, efficient whole-cell biocatalysts.
One goal is to design bacteria which divert reduced cofactors (generated through central carbon metabolism) away from native electron transport or fermentation pathways and toward desired, heterologous reaction pathways. That is, we aim to maximize the efficiency with which sugars are utilized for driving NAD(P)H-dependent transformations by engineering strains which essentially "respire" on the substrates of these reactions.
Transformations of primary interest are those catalyzed by reductases and oxygenases. Important considerations in this research include the cofactor requirement or specificity for the enzyme of interest, ensuring efficient (low energy) substrate transport and appropriate genetic modifications.
Graduate Student Reza Khankal
Efficient microbial conversion of biomass into renewable fuels and value-added chemicals remains an important goal in biotechnology.
Xylose, which is the second most abundant sugar in nature and a major constituent of hemicellulose in lignocellulosic biomass and wastes, is a good target for these microbial processes.
Escherichia coli is capable of utilizing a wide range of sugars as carbon and energy sources and producing native metabolites and non-native compounds. In E. coli, xylose uptake occurs primarily through a high-affinity, ATP-binding cassette transporter (xylFGH), although a second, low-affinity proton symporter (xylE) is also present.
The efficiency of xylose utilization in this organism is therefore suboptimal due to energetic requirements for xylose uptake. E. coli has been engineered to uptake xylose and reduce it to xylitol in the presence of glucose by expressing xylose reductase (XR) and a cAMP-independent CRP mutant (CRP*).
These studies showed that while xylose is negligibly metabolized by wild-type E. coli in the presence of glucose (classic diauxic growth), low levels of xylose transport and xylitol production are possible in wild-type E. coli expressing XR. Xylose transport and xylitol production are greatly improved in crp* mutant strains.
These results indicate that either the native xylose transporters are not tightly controlled by CRP or additional transport mechanisms exist.
Graduate Student Olubolaji Akinterinwa
This research project is aimed at utilizing biomass-derived sugars as sources of energy and carbon backbone for the production of "renewable" chemicals and fuels through metabolic engineering. In collaboration with Costas Maranas, we are studying knowledge-based and model-predicted genetic manipulations in E. coli to develop robust, efficient whole-cell biocatalysts.
One goal is to design bacteria which divert reduced cofactors (generated through central carbon metabolism) away from native electron transport or fermentation pathways and toward desired, heterologous reaction pathways. That is, we aim to maximize the efficiency with which sugars are utilized for driving NAD(P)H-dependent transformations by engineering strains which essentially "respire" on the substrates of these reactions.
Transformations of primary interest are those catalyzed by reductases and oxygenases. Important considerations in this research include the cofactor requirement or specificity for the enzyme of interest, ensuring efficient (low energy) substrate transport and appropriate genetic modifications.
Graduate Student Lexan Lhu
Isolated from marine sediments, the anaerobe Methanosarcina acetivorans is a methanogenic member of the archaea domain (Sowers, et al., 1984).
M. acetivorans is capable of producing methane from acetate, methanol, and methylamines and was more recently found to produce methane from carbon monoxide (Rother and Metcalf, 2004 ).
Reductions of these substrates to CH4 occur through a succession of methylreductase and methyltransferase reactions using the methyl carrier coenzyme tetrahydrosarcinapterin (THSPT).
Many of the transformations involved in CO metabolism remain poorly characterized.
A better understanding of CO metabolism is critical to balancing the global carbon cycle and to revealing steps behind a metabolic pathway that evolved in primitive life when Earth's atmosphere contained elevated CO levels.