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.
Use of nanostructure-initiator mass spectrometry (NIMS) to deduce selectivity of reaction in glycoside hyrolases
The enzymatic hydrolysis of plant cell wall material is a formidable task due to its complexity. Enzyme cocktails containing multiple classes of polysaccharide-degrading enzymes are used in several existing cellulosic ethanol plants to hydrolyze plant biomass into fermentable sugars. These enzymes are classified into families in the carbohydrate active enzyme (CAZy) database, and they include glycoside hydrolases (GHs), pectic lyases (PLs), carbohydrate esterases (CEs), and others. Due to several experimental limitations, only a small fraction of the enzymes included in CAZy have a function assigned by biochemical analysis.
Lignin, a complex polyphenolic constituent of plant secondary cell walls, is one of the most abundant biopolymers on the planet and is an immensely important global carbon sink. The chemical recalcitrance of lignin, however, poses a major challenge for industrial biomass processing, most notably in pulp and paper production and in the emerging cellulosic biofuels industry.
Valorization of lignin from biomass is challenging and research efforts have lagged behind the upgrading of sugar streams. Yet lignin comprises a substantial portion of lignocellulosic biomass (15-30% by weight), is the most energy dense fraction, and is a rich source of aromatic compounds.
A valuable ‘new’ compound is available from lignin ‘waste’ streams. Lignin, a complex phenylpropanoid polymer in the plant cell wall, is synthesized via oxidative radical coupling reactions from three prototypical monolignols. Several novel monomers, all deriving from the monolignol biosynthetic pathway, have been found to incorporate into lignin in wild-type and transgenic plants; these findings imply that plants are quite flexible in being able to use a variety of monomers during lignification to form the heterologous lignin polymer.
Soil microbial communities are an important component of ecosystems because of their key roles in nutrient cycling, influence on plant community composition, regulation of plant productivity, and decomposition of organic matter. The recovery of these communities is an important element in the process of returning a restored ecosystem to its desired structure and function, but this recovery often lags behind changes in land use and management.
The recalcitrance of plant cell walls to biological degradation, deconstruction, or conversion is the most critical challenge in developing successful bioprocessing technologies for lignocellulose conversion to renewable fuels and chemicals.
CGR2 and CGR3 are likely methyltransferases critical for pectin methylesterification and plant growth
By providing mechanical strength and enabling reception and transmission of developmental and environmental cues, the plant cell wall serves as a critical interface between the protoplast and the surrounding environment. The diverse roles of the cell wall are maintained by a complex yet dynamic combination of lignin and polysaccharides, which comprise cellulose, hemicellulose, pectin and lignin.
Lignocellulose-derived hydrolysates contain several different inhibitors (collectively called lignotoxins or LTs) that arise during pre-treatment of biomass. Determining the mechanisms by which yeast or bacteria are adversely affected by LTs is a key step toward improving the efficiency of fermentation and bioconversion.
A major barrier to efficient conversion of lignocellulosic materials to biofuels is sensitivity of microbes to inhibitory compounds formed during biomass pretreatment.
The prospect of converting large tracts of the Midwest’s marginal farming land to perennial biofuel crops carries with it some key unknowns, including how such a change could affect the balance of water between rainfall inputs, evaporation losses, and movement of soil water to the groundwater.