monomeric sugars (Madadi et al. 2017). Naturally hemicellulolytic enzymes are not
sufficient for the complete hydrolysis of recalcitrance lignocellulosic biomass
(Himmel et al. 2007). Hence, there is a requirement of enzymes, and they are
commercially expensive which will eventually lead to the product loss (Visser
et al. 2015). The only solution for this problem is the efficiency of the enzymes
should be increased (Morone and Pandey 2014) along with the exploitation of
accessory enzymes, e.g. xylanase and β-glucosidase, which can be synergistically
act with cellulases (Berlin et al. 2005). Recently, various reports are found in the
literature based on the improvements of hydrolytic enzymes which has only considered the cellulase and their synergy with hemicellulases (Diogo et al. 2015;
Quiñones et al. 2015; Yang et al. 2018), but very few reports are there focusing on
xylanases individually. Molecular biology aspects which include directed evolution,
library construction strategies, mutagenesis and gene recombination have gained
researchers’ interest to improve the genetic variations on enzymes (McLachlan et al.
2009). The increased hydrolysis of pretreated sugarcane bagasse was reported with
xylanase (Ribeiro et al. 2014). Two xylanase genes (GH10 and GH11) from
Malbranchea cinnamomea, i.e. XYN10A_MALCI and XYN11A_MALCI, respectively, that were expressed in P. pastoris X33 showed improved hydrolysis of
substituted arabinoxylan and unsubstituted xylan. The synergistic action of recombinant xylanase with commercial cellulase resulted in the better hydrolysis of acidand alkali-treated rice straw (Basotra et al. 2018). Similarly, Geobacillus
thermodenitrificans JK1 showed the production of isoforms of xylanase,
i.e. XynA1 and XynA2, acting synergistically with β-xylosidases and
arabinofuranosidase for the improved birchwood xylan hydrolysis (Huang et al.
2017).
7.11 Conclusion
Advancement in the enzyme efficiency and effective hydrolysis is highly required in
the world of biorefinery; for that, scientists must focus on the economic and
eco-friendly processes. Xylanase plays a key role in the biorefinery process;
hence, its production and hydrolytic efficiency must be enhanced by finding new
microorganisms which can produce isoforms of xylanases. Overexpression of new
genes from novel xylanases from different microorganisms can be explored for
future applications. Hence, using the advantage of gene editing and synthetic
biological techniques in the future, with improved characteristics like thermostability, can be a fruitful contribution towards the high demand of biorefinery.
Competing Interests All the authors declare that they have no competing interests.
174
N. Bhardwaj and P. Verma
sufficient for the complete hydrolysis of recalcitrance lignocellulosic biomass
(Himmel et al. 2007). Hence, there is a requirement of enzymes, and they are
commercially expensive which will eventually lead to the product loss (Visser
et al. 2015). The only solution for this problem is the efficiency of the enzymes
should be increased (Morone and Pandey 2014) along with the exploitation of
accessory enzymes, e.g. xylanase and β-glucosidase, which can be synergistically
act with cellulases (Berlin et al. 2005). Recently, various reports are found in the
literature based on the improvements of hydrolytic enzymes which has only considered the cellulase and their synergy with hemicellulases (Diogo et al. 2015;
Quiñones et al. 2015; Yang et al. 2018), but very few reports are there focusing on
xylanases individually. Molecular biology aspects which include directed evolution,
library construction strategies, mutagenesis and gene recombination have gained
researchers’ interest to improve the genetic variations on enzymes (McLachlan et al.
2009). The increased hydrolysis of pretreated sugarcane bagasse was reported with
xylanase (Ribeiro et al. 2014). Two xylanase genes (GH10 and GH11) from
Malbranchea cinnamomea, i.e. XYN10A_MALCI and XYN11A_MALCI, respectively, that were expressed in P. pastoris X33 showed improved hydrolysis of
substituted arabinoxylan and unsubstituted xylan. The synergistic action of recombinant xylanase with commercial cellulase resulted in the better hydrolysis of acidand alkali-treated rice straw (Basotra et al. 2018). Similarly, Geobacillus
thermodenitrificans JK1 showed the production of isoforms of xylanase,
i.e. XynA1 and XynA2, acting synergistically with β-xylosidases and
arabinofuranosidase for the improved birchwood xylan hydrolysis (Huang et al.
2017).
7.11 Conclusion
Advancement in the enzyme efficiency and effective hydrolysis is highly required in
the world of biorefinery; for that, scientists must focus on the economic and
eco-friendly processes. Xylanase plays a key role in the biorefinery process;
hence, its production and hydrolytic efficiency must be enhanced by finding new
microorganisms which can produce isoforms of xylanases. Overexpression of new
genes from novel xylanases from different microorganisms can be explored for
future applications. Hence, using the advantage of gene editing and synthetic
biological techniques in the future, with improved characteristics like thermostability, can be a fruitful contribution towards the high demand of biorefinery.
Competing Interests All the authors declare that they have no competing interests.
174
N. Bhardwaj and P. Verma