title: Automated UV-C mutagenesis of Kluyveromyces marxianus NRRL Y-1109 and selection for microaerophilic growth and ethanol production at elevated temperature on biomass sugars.
abstract: The yeast Kluyveromyces marxianus is a potential microbial catalyst for fuel ethanol production from a wide range of biomass substrates. To improve its growth and ethanol yield at elevated temperature under microaerophilic conditions, K. marxianus NRRL Y-1109 was irradiated with UV-C using automated protocols on a robotic platform for picking and spreading irradiated cultures and for processing the resulting plates. The plates were incubated under anaerobic conditions on xylose or glucose for 5 mo at 46 °C. Two K. marxianus mutant strains (designated 7-1 and 8-1) survived and were isolated from the glucose plates. Both mutant strains, but not wild type, grew aerobically on glucose at 47 °C. All strains grew anaerobically at 46 °C on glucose, galactose, galacturonic acid, and pectin; however, only 7-1 grew anaerobically on xylose at 46 °C. Saccharomyces cerevisiae NRRL Y-2403 did not grow at 46 °C on any of these substrates. With glucose as a carbon source, ethanol yield after 3 d at 46 °C was higher for 8-1 than for wild type (0.51 and 0.43 g ethanol/g glucose, respectively). With galacturonic acid as a carbon source, the ethanol yield after 7 d at 46 °C was higher for 7-1 than for wild type (0.48 and 0.34 g ethanol/g galacturonic acid, respectively). These mutant strains have potential application in fuel ethanol production at elevated temperature from sugar constituents of starch, sucrose, pectin, and cellulosic biomass.
authors.affiliation: United States Department of Agriculture (USDA), Agricultural Research Service (ARS), National Center for Agricultural Utilization Research (NCAUR), Renewable Product Technology (RPT) Research Unit, Peoria, IL, USA. Stephen.Hughes@ars.usda.gov
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Hughes
authors.forename: Sookie S
authors.initials: SS
authors.lastname: Bang
authors.forename: Elby J
authors.initials: EJ
authors.lastname: Cox
authors.forename: Andrew
authors.initials: A
authors.lastname: Schoepke
authors.forename: Kate
authors.initials: K
authors.lastname: Ochwat
authors.forename: Rebecca
authors.initials: R
authors.lastname: Pinkelman
authors.forename: Danielle
authors.initials: D
authors.lastname: Nelson
authors.forename: Nasib
authors.initials: N
authors.lastname: Qureshi
authors.forename: William R
authors.initials: WR
authors.lastname: Gibbons
authors.forename: Cletus P
authors.initials: CP
authors.lastname: Kurtzman
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Bischoff
authors.forename: Siqing
authors.initials: S
authors.lastname: Liu
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Cote
authors.forename: Joseph O
authors.initials: JO
authors.lastname: Rich
authors.forename: Marjorie A
authors.initials: MA
authors.lastname: Jones
authors.forename: David
authors.initials: D
authors.lastname: Cedeño
authors.forename: Joy
authors.initials: J
authors.lastname: Doran-Peterson
authors.forename: Nestor M
authors.initials: NM
authors.lastname: Riaño-Herrera
authors.forename: Nelson
authors.initials: N
authors.lastname: Rodríguez-Valencia
authors.forename: Juan C
authors.initials: JC
authors.lastname: López-Núñez
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D057205:Automation, Laboratory; D001709:Biotechnology / Q000379:methods; D004736:Energy-Generating Resources; D000431:Ethanol / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007716:Kluyveromyces / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D046210:Microfluidic Analytical Techniques; D016297:Mutagenesis, Site-Directed / Q000379:methods*; D012371:Robotics / Q000639:trends; D012641:Selection, Genetic; D013696:Temperature; D014466:Ultraviolet Rays
chemical_list: D000431:Ethanol; D005947:Glucose
keywords: Kluyveromyces marxianus yeast; biomass sugars; thermotolerant ethanologenic yeast; yeast UV-C mutagenesis