title: The ACEII recombinant Trichoderma reesei QM9414 strains with enhanced xylanase production and its applications in production of xylitol from tree barks.
abstract: BACKGROUND
  ACEII transcription factor plays a significant role in regulating the expression of cellulase and hemicellulase encoding genes. Apart from ACEII, transcription factors such as XYR1, CRE1, HAP2/3/5 complex and ACEI function in a coordinated pattern for regulating the gene expression of cellulases and hemicellulases. Studies have demonstrated that ACEII gene deletion results in decreased total cellulase and xylanase activities with reduced transcript levels of lignocellulolytic enzymes.
  
  
  RESULTS
  In this study, we have successfully transformed the ACEII transcription factor encoding gene in Trichoderma reesei to significantly improve its degrading abilities. Transformation experiments on parental strain T. reesei QM9414 has resulted in five genetically engineered strains T/Ace2-2, T/Ace2-5, T/Ace2-8, T/Ace5-4 and T/Ace10-1. Among which, T/Ace2-2 has exhibited significant increase in enzyme activity by twofolds, when compared to parental strain. The T/Ace2-2 was cultured on growth substrates containing 2% bark supplemented with (a) sugar free + MA medium (b) glucose + MA medium and (c) xylose + MA medium. The bark degradation efficiency of genetically modified T/Ace2-2 strain was assessed by analyzing the xylitol production yield using HPAEC. By 6th day, about 10.52 g/l of xylitol was produced through enzymatic conversion of bark (2% bark + MA + xylose) by the T/Ace2-2 strain and by 7th day the conversion rate was found to be 0.21 g/g. Obtained results confirmed that bark growth medium supplemented with D-xylose has profoundly increased the conversion rate of bark by T/Ace2-2 strain when compared to sugar free and glucose supplemented growth media. Results obtained from scanning electron microscopy has endorsed our current results. Bark samples inoculated with T/Ace2-2 strain has showed large number of degraded cells with clearly visible cavities and fractures, by exposing the microfibrillar interwoven complex.
  
  
  CONCLUSIONS
  We propose a cost effective and ecofriendly method for the degradation of lignocellulosic biomass such as bark to produce xylitol by using genetically modified T. reesei. Efficient conversion rate and production yield obtained in our current study provides a great scope for the xylitol industries, as our method bypasses the pretreatment of bark achieving clean and low-cost xylitol production.
authors.affiliation: School of Life Science and Engineering, Southwest Jiaotong University, Chengdu City, 610031, Sichuan Province, China.|Department of Biology, Lakehead University, Thunder Bay, ON, P7B 5E1, Canada.
authors.forename: Lili
authors.initials: L
authors.lastname: Xiong
authors.affiliation: Department of Biology, Lakehead University, Thunder Bay, ON, P7B 5E1, Canada.
authors.forename: Ayyappa Kumar Sista
authors.initials: AK
authors.lastname: Kameshwar
authors.affiliation: State Key Laboratory for Agrobiotechnology and College of Biological Sciences, China Agricultural University, Beijing, 100193, China.
authors.forename: Xi
authors.initials: X
authors.lastname: Chen
authors.affiliation: School of Life Science and Engineering, Southwest Jiaotong University, Chengdu City, 610031, Sichuan Province, China.
authors.forename: Zhiyun
authors.initials: Z
authors.lastname: Guo
authors.affiliation: School of Life Science and Engineering, Southwest Jiaotong University, Chengdu City, 610031, Sichuan Province, China.
authors.forename: Canquan
authors.initials: C
authors.lastname: Mao
authors.affiliation: State Key Laboratory for Agrobiotechnology and College of Biological Sciences, China Agricultural University, Beijing, 100193, China.
authors.forename: Sanfeng
authors.initials: S
authors.lastname: Chen
authors.affiliation: Department of Biology, Lakehead University, Thunder Bay, ON, P7B 5E1, Canada. wqin@lakeheadu.ca.
authors.forename: Wensheng
authors.initials: W
authors.lastname: Qin
mesh_terms: D043364:Endo-1,4-beta Xylanases / Q000096:biosynthesis*; D024301:Plant Bark / Q000378:metabolism* / Q000382:microbiology*; D011995:Recombination, Genetic; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014242:Trichoderma / Q000201:enzymology* / Q000235:genetics; D014993:Xylitol / Q000096:biosynthesis*
chemical_list: C432418:ACEII protein, T. reesei; D015534:Trans-Activators; D043364:Endo-1,4-beta Xylanases; D014993:Xylitol
keywords: ACEII gene; Tree barks; Trichoderma reesei; Xylanase; Xylitol