title: Engineering a thermoregulated intein-modified xylanase into maize for consolidated lignocellulosic biomass processing.
abstract: Plant cellulosic biomass is an abundant, low-cost feedstock for producing biofuels and chemicals. Expressing cell wall-degrading (CWD) enzymes (e.g. xylanases) in plant feedstocks could reduce the amount of enzymes required for feedstock pretreatment and hydrolysis during bioprocessing to release soluble sugars. However, in planta expression of xylanases can reduce biomass yield and plant fertility. To overcome this problem, we engineered a thermostable xylanase (XynB) with a thermostable self-splicing bacterial intein to control the xylanase activity. Intein-modified XynB (iXynB) variants were selected that have <10% wild-type enzymatic activity but recover >60% enzymatic activity upon intein self-splicing at temperatures >59 °C. Greenhouse-grown xynB maize expressing XynB has shriveled seeds and low fertility, but ixynB maize had normal seeds and fertility. Processing dried ixynB maize stover by temperature-regulated xylanase activation and hydrolysis in a cocktail of commercial CWD enzymes produced >90% theoretical glucose and >63% theoretical xylose yields.
authors.affiliation: Agrivida, Inc., Medford, Massachusetts, USA.
authors.forename: Binzhang
authors.initials: B
authors.lastname: Shen
authors.forename: Xueguang
authors.initials: X
authors.lastname: Sun
authors.forename: Xiao
authors.initials: X
authors.lastname: Zuo
authors.forename: Taran
authors.initials: T
authors.lastname: Shilling
authors.forename: James
authors.initials: J
authors.lastname: Apgar
authors.forename: Mary
authors.initials: M
authors.lastname: Ross
authors.forename: Oleg
authors.initials: O
authors.lastname: Bougri
authors.forename: Vladimir
authors.initials: V
authors.lastname: Samoylov
authors.forename: Matthew
authors.initials: M
authors.lastname: Parker
authors.forename: Elaina
authors.initials: E
authors.lastname: Hancock
authors.forename: Hector
authors.initials: H
authors.lastname: Lucero
authors.forename: Benjamin
authors.initials: B
authors.lastname: Gray
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Ekborg
authors.forename: Dongcheng
authors.initials: D
authors.lastname: Zhang
authors.forename: Jeremy C Schley
authors.initials: JC
authors.lastname: Johnson
authors.forename: Gabor
authors.initials: G
authors.lastname: Lazar
authors.forename: R Michael
authors.initials: RM
authors.lastname: Raab
mesh_terms: D001833:Body Temperature Regulation / Q000502:physiology*; D043364:Endo-1,4-beta Xylanases / Q000502:physiology*; D024861:Genetic Enhancement / Q000379:methods*; D047668:Inteins / Q000235:genetics*; D008031:Lignin / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000502:physiology*; D003313:Zea mays / Q000502:physiology*
chemical_list: C036909:lignocellulose; D008031:Lignin; D043364:Endo-1,4-beta Xylanases