Bioethanol production from lignocellulosicudbiomass: assessing genes linked to acetic acid stress in Saccharomyces cerevisiae

摘要

Lignocellulosic biomass represents a vast and renewable source of fermentable sugar forudproduction of biofuels. However, native lignocellulose—comprised of cellulose,udhemicellulose and lignin—is refractory to degradation because the crystalline cellulose isudnot easily hydrolyzed by cellulases. Standard chemical treatments of lignocellulose toudreduce the crystallinity of cellulose prior to enzymatic hydrolysis also generateudfermentation inhibitors, including acetic and other organic acids, furfural, hydroxymethyludfurfural, and phenolic compounds. To increase the acetic acid resistance of one of theudmajor microorganisms used to ferment lignocellulose-derived sugars, mutations in threeudgenes were introduced and evaluated in a prototrophic laboratory strain ofudSaccharomyces cerevisiae, S288c, and were introduced into the industrial strain D5A.udPrevious work had shown that loss of FPS1, encoding an acetic acid channel, and loss ofudEDE1 and MVB12, encoding proteins involved in endocytosis, increased acetic acidudresistance. Disruption of FPS1 in S288c resulted in somewhat greater resistance at lowudconcentrations (80-120 mM acetic acid) but not at concentrations greater than 120 mM.udCombined genetic and molecular analyses of the disruptions of FPS1, EDE1 and MVB12udin D5A indicated that D5A was diploid, and that only one of the two alleles of each ofudthese genes had been deleted.