Research Highlights

Engineered Softwood
Great Lakes Bioenergy researchers and collaborators engineered softwoods to incorporate a key feature of hardwoods. The resulting pine (shown here) processes more easily into pulp and paper.

Great Lakes Bioenergy research consistently results in new discoveries and new technologies. Here, we highlight high-impact research from all three of our research areas.

Study provides guidelines for selecting best lignin isolation techniques for research
Lignin, a complex heterogeneous polymer that forms plant biomass structures, is a promising candidate in the biofuel industry because of its aromatic constitution. Although milled wood, enzymatic, cellulolytic enzyme, and enzymatic mild-acidosis lignins have all been studied on behalf of native lignin, they are all the result of different separation strategies and therefore may have differing structures. This study aimed to compare these separation strategies and determine their effects on lignin structure in softwoods, hardwoods, and grasses.
Flow chart depicting lignin isolation techniques from different biomass sources. The chart starts with three types of biomass: Softwood, Hardwood, and Grass. It then focuses on Hardwood, showing two initial processing methods: Pre-grind and Ball Mill. Pre-grind leads to WCW (Whole Cell-Wall Biomass). Ball Mill produces Milled-Wood Powder, which branches into two paths: Cellulolytic Enzyme Treatment resulting in MWL (Milled-Wood Lignin). Dioxane/Water at R.T., yielding EL (Enzyme Lignin). EL further branch
Patent approved for lignin to polyester precursor conversion process
The cost of manufacturing plant-based biofuels has limited competition with cheaper fossil fuels. By engineering one candidate microbe, Novosphingobium aromaticivorans, to funnel heterogeneous mixtures of lignin-derived aromatic compounds to 2-pyrone-4,6-dicarboxylic acid (PDC), a potential bioplastic precursor, this study aimed to increase its potential market value.
A colorful line graph comparing time and concentration of conversion of phenolics to various substances; PDC has the highest conversion rate
Assessing impacts of supply chain variability on centralized cellulosic biorefinery
Cellulosic biofuels derived from crop residues and dedicated energy crops grown on marginal lands are an attractive alternative to liquid fossil fuels. This study seeks to show how annual fluctuations in biomass production impact the economic and environmental performance of biofuels. 
A green tractor loads large bales of brown material onto a trailer
Terminal enzymes must be co-optimized to relieve MEP bottleneck in Z. mobilis
Many plants and bacteria use the methylerythritol phosphate (MEP) pathway to synthesize precursors for isoprenoids, a diverse class of hydrocarbons that includes natural products, industrial chemicals and biofuels. This research investigates the function of the oxygen-sensitive enzymes IspG and IspH, known bottlenecks in the MEP pathway of the biofuel-producing microbe Zymomonas mobilis.
A curving road leads from magnified bacteria to a biofuel tank. Yield signs read "IspG" and IspH." A green road sign reads "MEP Highway" in the top left corner.
Bioenergy crops shape underground micro-ecosystems​
Results demonstrate striking differences between each vegetal system’s soil pore characteristics, connecting micro-level contrast between large and small soil pores in microbial diversity, composition, and carbon distribution strategies to the structure of hydraulic connections within each system.​
A drawn diagram comparing pore sizes and the nutrients within them
Bacterium converts lignin β-5 linked aromatics into petrochemical alternatives
Lignin contains aromatic subunits joined by various chemical linkages, making it challenging to produce single products from this plant polymer. Microbes can funnel lignin-derived aromatics into target chemicals, but this requires strategies to cleave major inter-unit linkages. This study showed the bacterium Novosphingobium aromaticivorans can catabolize β-5 (phenylcoumaran) linked aromatics, which account for up to 12% of interunit bonds in lignin. 
Catabolic pathway for the β-5 linked aromatic dimer DC-A in N. aromaticivorans represented by chemical structures connected by arrows, indicating the sequence of transformations. The diagram starts with DC-A at the top left, which undergoes several enzymatic reactions (labeled as ADH9, ALDH, and PcdF) to produce various intermediates (DC-L, DC-C, and DC-E-C). The pathway then branches, with one route leading to vanillin through compounds like ferulic acid, while the other leads to 5-CF and ferulic acid.
Rice gene opens up fresh lignin lead
The engineered poplars demonstrated a higher saccharification efficiency than the wild-type poplars. Under the same pretreatment conditions, the researchers observed a greater monosaccharide release from the modified lignin. In addition, the trees produced high-value phenolics that are easily accessible to support other specialty chemical industries.
A poplar stump surrounded by snow and sawdust.
Strategies to improve bioreactor productivity of PDC from aqueous aromatic streams
High aromatic loading rates, hollow-fiber membranes, and NH4OH for pH control contributed to the highest PDC productivities reported to date. Results revealed a trade-off between maximizing high productivity or product titer in the MBR system. 
Illustration of a membrane bioreactor (MBR) system showing components and flow of materials. A poplar tree symbolizes biomass feedstock. Syngric acid and pHBA are represented by blue and red dots, which are converted by the Novosphingobium aromaticivorans microorganism, represented as oblong shapes within the bioreactor vessel. The bioreactor vessel has an input stream of NH4OH. A membrane allows PDC to pass through while bacterial cells are recycled.
Metagenome study suggests common model of microbial community organization
The study demonstrates the potential of microbial communities to produce chemicals from agroindustrial residues, converting organic waste into useful products and contributing to sustainable circular economy. The machine learning tools can be adapted to evaluate other microbial communities in similar reactor settings. 
Flow chart diagram illustrating process used to evaluate microbial communities in various residues
The physiological effects of isobutanol on Zymomonas mobilis
Zymomonas mobilis has properties that make it a good candidate for industrial biofuel production: high catabolic rate, low biomass generation, resistance to inhibitors in lignocellulosic hydrolysates; an a growing set of genetic engineering tools. Recent efforts have targeted Z. mobilis for isobutanol production, but isobutanol toxicity limits growth and productivity. The physiological effects of isobutanol on Z. mobilis are poorly understood.  
The images on the left show bright-field micrographs, while the images on the right display fluorescence micrographs of the same cell samples. Cells in the top frames appear elongated; those in the bottom frames appear more circular.