The ACEII recombinant Trichoderma reesei QM9414 strains with enhanced xylanase production and its applications in production of xylitol from tree barks. Issue 1 (December 2016)

• Record Type: Journal Article
• Authors: Xiong, Lili; Kameshwar, Ayyappa; Chen, Xi; Guo, Zhiyun; Mao, Canquan; Chen, Sanfeng; Qin, Wensheng
• Is Part Of: Microbial cell factories. Volume 15:Issue 1(2016)
• Page Start: 1
• Page End: 18
• Publication Date: 2016-12
• Subjects: Xylitol -- Tree barks -- ACEII gene -- Xylanase -- Trichoderma reesei; Microbial biotechnology -- Periodicals; Recombinant proteins -- Synthesis -- Periodicals; 660.62
• DOI: 10.1186/s12934-016-0614-4
• Languages: English
• ISSNs: 1475-2859

Abstract

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 inTrichoderma reesei to significantly improve its degrading abilities. Transformation experiments on parental strainT. reesei QM9414 has resulted in five genetically engineered strainsT /Ace2-2, T/ Ace2-5, T /Ace2-8, T /Ace5-4 andT/ Ace10-1. Among which, T /Ace2-2 has exhibited significant increase in enzyme activity by twofolds, when compared to parental strain. TheT /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 modifiedT /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 theT /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 withd -xylose has profoundly increased the conversion rate of bark byT /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 withT /Ace2-2 strain has showed large number of degraded cells with clearly visible cavities and fractures, by exposing the microfibrillar interwoven complex. Conclusion We propose a cost effective and ecofriendly method for the degradation of lignocellulosic biomass such as bark to produce xylitol by using genetically modifiedT. 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.