title: Production of biorenewable styrene: utilization of biomass-derived sugars and insights into toxicity.
abstract: Fermentative production of styrene from glucose has been previously demonstrated in Escherichia coli. Here, we demonstrate the production of styrene from the sugars derived from lignocellulosic biomass depolymerized by fast pyrolysis. A previously engineered styrene-producing strain was further engineered for utilization of the anhydrosugar levoglucosan via expression of levoglucosan kinase. The resulting strain produced 240 ± 3 mg L(-1) styrene from pure levoglucosan, similar to the 251 ± 3 mg L(-1) produced from glucose. When provided at a concentration of 5 g L(-1), pyrolytic sugars supported styrene production at titers similar to those from pure sugars, demonstrating the feasibility of producing this important industrial chemical from biomass-derived sugars. However, the toxicity of contaminant compounds in the biomass-derived sugars and styrene itself limit further gains in production. Styrene toxicity is generally believed to be due to membrane damage. Contrary to this prevailing wisdom, our quantitative assessment during challenge with up to 200 mg L(-1) of exogenously provided styrene showed little change in membrane integrity; membrane disruption was observed only during styrene production. Membrane fluidity was also quantified during styrene production, but no changes were observed relative to the non-producing control strain. This observation that styrene production is much more damaging to the membrane integrity than challenge with exogenously supplied styrene provides insight into the mechanism of styrene toxicity and emphasizes the importance of verifying proposed toxicity mechanisms during production instead of relying upon results obtained during exogenous challenge.
authors.affiliation: Bioeconomy Institute, Iowa State University, Ames, IA, 50011-2230, USA.
authors.forename: Jieni
authors.initials: J
authors.lastname: Lian
authors.affiliation: Chemical Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University, Phoenix, AZ, USA.
authors.forename: Rebekah
authors.initials: R
authors.lastname: McKenna
authors.affiliation: Bioeconomy Institute, Iowa State University, Ames, IA, 50011-2230, USA.
authors.forename: Marjorie R
authors.initials: MR
authors.lastname: Rover
authors.affiliation: Chemical Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University, Phoenix, AZ, USA.
authors.forename: David R
authors.initials: DR
authors.lastname: Nielsen
authors.affiliation: Department of Food Science and Human Nutrition, Iowa State University, Ames, IA, USA.
authors.forename: Zhiyou
authors.initials: Z
authors.lastname: Wen
authors.affiliation: Department of Chemical and Biological Engineering, Iowa State University, 3051 Sweeney Hall, Ames, IA, 50011-2230, USA. ljarboe@iastate.edu.
authors.forename: Laura R
authors.initials: LR
authors.lastname: Jarboe
mesh_terms: D018533:Biomass; D050260:Carbohydrate Metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D005947:Glucose / Q000031:analogs & derivatives / Q000378:metabolism; D008031:Lignin / Q000737:chemistry / Q000378:metabolism*; D008560:Membrane Fluidity / Q000187:drug effects; D020058:Styrene / Q000378:metabolism* / Q000494:pharmacology / Q000633:toxicity*
chemical_list: C036909:lignocellulose; D020058:Styrene; C014989:1,6-anhydro-beta-glucopyranose; D008031:Lignin; D005947:Glucose
keywords: Biocatalyst inhibition; Laccase; Levoglucosan kinase; Membrane damage; Styrene