GLBRC's Conversion Research Area


Research team achieves concentrated stream of sugars, cost savings

GLBRC Conversion research aims to increase the quantity, diversity, and efficiency of energy products derived from plant biomass. Researchers focus on improving biological and chemical methods to convert plant material into advanced biofuels or valuable chemicals that can replace petroleum. Basic research discoveries that enhance the efficiency and sustainability of biomass conversion can break down barriers to developing economically viable biofuels technologies.

Conversion Leadership

Scientific Director, Conversion Lead

Landick is an expert on structure, function and regulation of RNA polymerase, the central engine of gene expression. His work spans disciplines from single-molecule biochemistry to genome-scale mechanisms of gene regulation, and includes devising the first single-molecule observation of nucleic...

Conversion Lead

Hegg’s research team focuses on the variety of ways that nature uses metals to activate and/or produce small molecules such as O2, H2, NO, and H2O2.  In pursuit of this goal, his lab utilizes a combination of mechanistic enzymology, molecular...

Project Overview

Stacks of petri dishes in the Currie Lab

Within the Conversion group, researchers apply a combination of synthetic biology, directed evolution, systems biology, and computational modeling approaches to accelerate the rate and yield of microbial conversion of biomass to fuels. Microbial efforts focus on well-established models and biofuel-producing organisms to identify key genes and pathways that may illuminate opportunities for strain improvement. Chemical routes focus on direct catalytic conversion of biomass-derived sugars and lignin into liquid transportation fuels and/or high-value chemicals.

Specific Conversion projects fall in three categories:

  • Engineering microbe strains to enhance stress tolerance and improve conversion efficiency of sugars to biofuels
  • Developing flexible routes to biofuel production that can be adapted to diverse biomass feedstocks
  • Producing light-driven and lignin-derived advanced biofuels, and using catalytic conversion to convert biomass to biofuels and value-added chemicals


Conversion Publications

A co-solvent hydrolysis strategy for the production of biofuels: process synthesis and technoeconomic analysis

Wangyun Won; Ali H. Motagamwala; James A. Dumesic; Christos T. Maravelias

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We develop an integrated strategy for the production of ethanol from lignocellulosic biomass. Cellulose and hemicellulose fractions are first hydrolyzed into sugars using a mixture of γ-valerolactone (GVL), water, and toluene as a solvent containing dilute sulfuric acid as a catalyst, and the sugars are then co-fermented into ethanol over engineered yeast strains. Separation subsystems are designed to effectively recover GVL and toluene for reuse in biomass hydrolysis, and to recover lignin and humins for heat and power generation. We also develop an alternative process, in which we recover sugars and GVL from the residual biomass. To minimize utility requirements, we conduct heat integration, which allows us to meet all heating requirement using biomass residues. Finally, we perform a range of system-level analyses to identify the major cost and technological drivers. The proposed strategy is shown to be cost-competitive with other strategies.

Biochemical transformation of lignin for deriving valued commodities from lignocellulose

Daniel L. Gall; J. Ralph; Timothy J. Donohue; Daniel R. Noguera

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The biochemical properties of lignin present major obstacles to deriving societally beneficial entities from lignocellulosic biomass, an abundant and renewable feedstock. Similar to other biopolymers such as polysaccharides, polypeptides, and ribonucleic acids, lignin polymers are derived from multiple types of monomeric units. However, lignin’s renowned recalcitrance is largely attributable to its racemic nature and the variety of covalent inter-unit linkages through which its aromatic monomers are linked. Indeed, unlike other biopolymers whose monomers are consistently inter-linked by a single type of covalent bond, the monomeric units in lignin are linked via non-enzymatic, combinatorial radical coupling reactions that give rise to a variety of inter-unit covalent bonds in mildly branched racemic polymers. Yet, despite the chemical complexity and stability of lignin, significant strides have been made in recent years to identify routes through which valued commodities can be derived from it. This paper discusses emerging biological and biochemical means through which degradation of lignin to aromatic monomers can lead to the derivation of commercially valuable products.

Combining genome-scale experimental and computational methods to identify essential genes in Rhodobacter sphaeroides

Brian T. Burger; Saheed Imam; Mattew J. Scarborough; Daniel R. Noguera; Timothy J. Donohue

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Rhodobacter sphaeroides is one of the best-studied alphaproteobacteria from biochemical, genetic, and genomic perspectives. To gain a better systems-level understanding of this organism, we generated a large transposon mutant library and used transposon sequencing (Tn-seq) to identify genes that are essential under several growth conditions. Using newly developed Tn-seq analysis software (TSAS), we identified 493 genes as essential for aerobic growth on a rich medium. We then used the mutant library to identify conditionally essential genes under two laboratory growth conditions, identifying 85 additional genes required for aerobic growth in a minimal medium and 31 additional genes required for photosynthetic growth. In all instances, our analyses confirmed essentiality for many known genes and identified genes not previously considered to be essential. We used the resulting Tn-seq data to refine and improve a genome-scale metabolic network model (GEM) for R. sphaeroides. Together, we demonstrate how genetic, genomic, and computational approaches can be combined to obtain a systems-level understanding of the genetic framework underlying metabolic diversity in bacterial species. IMPORTANCE Knowledge about the role of genes under a particular growth condition is required for a holistic understanding of a bacterial cell and has implications for health, agriculture, and biotechnology. We developed the Tn-seq analysis software (TSAS) package to provide a flexible and statistically rigorous workflow for the high-throughput analysis of insertion mutant libraries, advanced the knowledge of gene essentiality in R. sphaeroides, and illustrated how Tn-seq data can be used to more accurately identify genes that play important roles in metabolism and other processes that are essential for cellular survival.

Contentious relationships in phylogenomic studies can be driven by a handful of genes

Xing-Xing Shen; Chris T. Hittinger; Antonis Rokas

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Phylogenomic studies have resolved countless branches of the tree of life, but remain strongly contradictory on certain, contentious relationships. Here, we use a maximum likelihood framework to quantify the distribution of phylogenetic signal among genes and sites for 17 contentious branches and 6 well-established control branches in plant, animal and fungal phylogenomic data matrices. We find that resolution in some of these 17 branches rests on a single gene or a few sites, and that removal of a single gene in concatenation analyses or a single site from every gene in coalescence-based analyses diminishes support and can alter the inferred topology. These results suggest that tiny subsets of very large data matrices drive the resolution of specific internodes, providing a dissection of the distribution of support and observed incongruence in phylogenomic analyses. We submit that quantifying the distribution of phylogenetic signal in phylogenomic data is essential for evaluating whether branches, especially contentious ones, are truly resolved. Finally, we offer one detailed example of such an evaluation for the controversy regarding the earliest-branching metazoan phylum, for which examination of the distributions of gene-wise and site-wise phylogenetic signal across eight data matrices consistently supports ctenophores as the sister group to all other metazoans.

Effect of ethanol blending on particulate formation from premixed combustion in spark-ignition engines

Stephen Sakai; David A. Rothamer

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Particulate formation due to combustion of a wide range of ethanol-gasoline blends were investigated in an internal combustion engine. The engine used for this study is a single-cylinder research engine, the architecture of which is representative of a modern spark ignited direct injected (SIDI) engine. Instead of direct injection, the engine was fueled using a premixed prevaporized (PMPV) mode, which supplied the fuel to the engine in a well-mixed, gas-phase air-fuel mixture in order to isolate physical effects of the fuel. This created a completely homogenous air-fuel mixture with no pockets of significantly differing equivalence ratio, liquid fuel droplets, or wetted surfaces, ensuring that particulate formation was due to homogenous, gas-phase combustion. The engine was operated at a fixed load and phasing so that the effects of varying equivalence ratio and ethanol content could be examined. The results in this work show that the addition of ethanol results in a consistent decrease in engine-out particulate proportional to ethanol content. Moreover, the critical equivalence ratio, the equivalence ratio at which significant sooting begins, increases in a linear fashion with ethanol addition. It was also shown that the shape of the particulate size distribution (PSD) is affected by ethanol content, with increased ethanol leading to more nucleation-mode dominated distributions.