Abstract:Phenylpropanoid metabolism yields a mixture of monolignols that undergo chaotic, non-enzymatic reactions such as free radical polymerization and spontaneous selfassembly in order to form the polyphenolic lignin which is a barrier to cost-effective lignocellulosic biofuels. Post-synthesis lignin integration into the plant cell wall is unclear, including how the hydrophobic lignin incorporates into the wall in an initially hydrophilic milieu. Self-assembly, self-organization and aggregation give rise to a comple… Show more
“…A physicochemical approach was developed to cutin synthesis that proposes that cutin could be the result of spontaneous, nonprotein-mediated, chemical interactions and reactions in a supramolecular self-assembling process [67]. Similar processes have been reported in the formation of other plant barrier biopolymers, such as sporopollenin [68,69] and lignin [70].…”
“…A physicochemical approach was developed to cutin synthesis that proposes that cutin could be the result of spontaneous, nonprotein-mediated, chemical interactions and reactions in a supramolecular self-assembling process [67]. Similar processes have been reported in the formation of other plant barrier biopolymers, such as sporopollenin [68,69] and lignin [70].…”
“…(e) Lignin, 10-30% of plant biomass [51], is a polyphenolic created through radical, oxidative coupling of monolignols. This mechanism causes multifarious structural linkages to be formed which are so diverse it has been hypothesized that no two lignin molecules are identical [52]. Lignin strengthens the cell wall by crosslinking with the polysaccharide fraction [53].…”
“…Although lignocellulose stored within the cell wall of plants is one of the largest reserves of convertible energy on the planet, extraction of this resource remains a challenge because of the recalcitrance of the plant cell wall to degradation (2,3). Cellulose and hemicellulose polysaccharides, the sources of fermentable sugars, are semicrystalline in nature and deeply embedded within a complex network of highly stable lignin polymers (4,5). Pretreatment of feedstock can remove lignin and reduce cellulose crystallinity, which is critical for improving subsequent saccharification of polysaccharides by enzymes derived from lignocellulolytic microorganisms (6).…”
To process plant-based renewable biofuels, pretreatment of plant feedstock with ionic liquids has significant advantages over current methods for deconstruction of lignocellulosic feedstocks. However, ionic liquids are often toxic to the microorganisms used subsequently for biomass saccharification and fermentation. We previously isolated Enterobacter lignolyticus strain SCF1, a lignocellulolytic bacterium from tropical rain forest soil, and report here that it can grow in the presence of 0.5 M 1-ethyl-3-methylimidazolium chloride, a commonly used ionic liquid. We investigated molecular mechanisms of SCF1 ionic liquid tolerance using a combination of phenotypic growth assays, phospholipid fatty acid analysis, and RNA sequencing technologies. Potential modes of resistance to 1-ethyl-3-methylimidazolium chloride include an increase in cyclopropane fatty acids in the cell membrane, scavenging of compatible solutes, up-regulation of osmoprotectant transporters and drug efflux pumps, and down-regulation of membrane porins. These findings represent an important first step in understanding mechanisms of ionic liquid resistance in bacteria and provide a basis for engineering microbial tolerance.osmotic stress | osmolytes | membrane lipids | differential gene expression | whole genome metabolic reconstruction
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