Abstract
Xylanases with high specific activity has been focused with great interest as a useful enzyme in biomass utilization. The production of recombinant GH11 xylanase (MYCTH_56237) from Myceliophthora thermophila has been improved through N-terminal signal peptide engineering in P. pastoris. The production of newly recombinant xylanase (termed Mtxyn11C) was improved from 442.53 to 490.7 U/mL, through a replacement of α-factor signal peptide with the native xylanase signal peptide segment (MVSVKAVLLLGAAGTTLA) in P. pastoris. Scaling up of Mtxyn11C production in a 7.5 L fermentor was improved to the maximal production rate of 2503 U/mL. In this study, the degradation efficiency of Mtxyn11C was further examined. Analysis of the hydrolytic mode of action towards the birchwood xylan (BWX) revealed that Mtxyn11C was clearly more effective than commercial xylanase and degrades xylan into xylooligosaccharides (xylobiose, xylotriose, xylotetraose). More importantly, Mtxyn11C in combination with a single multifunctional xylanolytic enzyme, improved the hydrolysis of BWX into single xylose by 40%. Altogether, this study provided strategies for improved production of xylanase together with rapid conversion of xylose from BWX, which provides sustainable, cost-effective and environmental friendly approaches to produce xylose/XOSs for biomass energy or biofuels production.
Highlights
Xylanases an integral group of hemicelluloses and offers an opportunity of best interest area for researchers on account of their insightful investigation and prospective of industrial applications, especially in the degradation of biomass into fermentable sugars (Basit et al, 2018a)
This study elucidated the improved conversion of xylan into xylose by 40%, when integrated with the multifunctional xylanloytic enzyme (Basit et al, 2019)
The most common signal peptides which are integrated in plasmid of P. pastoris include S. cerevisiae α-mating factor (α-MF), which have been used efficiently for the secretion of various heterologous proteins in P. pastoris (Kommoju et al, 2007)
Summary
Xylanases an integral group of hemicelluloses and offers an opportunity of best interest area for researchers on account of their insightful investigation and prospective of industrial applications, especially in the degradation of biomass into fermentable sugars (Basit et al, 2018a). On account of the heterogeneity and complexity, the complete degradation of xylan necessitates multiple enzymes ( endoxylanases and β-xylosidase) in association with accessory enzymes to interplay in the process, which liberates xylooligosaccharides (XOS) (Gaurav et al, 2017). The enzymatic hydrolysis demonstrates better results and low process energy requirements, the high cost of commercial enzymes and probably enzymes with low activity, creates a bottleneck for complete degradation of hemicelluloses. Improved Production of Xylanase with high activity need to be developed for more economical purposes. Several approaches have been adopted to minimize the expenses of hydrolysis process such as improving enzyme activity and enzyme production (Lin et al, 2017; Zhou et al, 2015; Wang et al, 2012). Recent developments in recombinant protein engineering helped in expressing xylanases in heterologous hosts (Pichia pastoris) for mass production
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