English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Background   Aspergillus niger , along with many other lignocellulolytic fungi, has been widely used as a commercial workhorse for cellulase production. A fungal cellulase system generally includes three major classes of enzymes i.e., β-glucosidases, endoglucanases and cellobiohydrolases. Cellobiohydrolases (CBH) are vital to the degradation of crystalline cellulose present in lignocellulosic biomass. However,  A. niger  naturally secretes low levels of CBH. Hence, recombinant production of  A. niger  CBH is desirable to increase CBH production yield and also to allow biochemical characterisation of the recombinant CBH from  A. niger .    Methods  In this study, the gene encoding a cellobiohydrolase B ( cbh B) from  A. niger  ATCC 10574 was cloned and expressed in the methylotrophic yeast  Pichia pastoris  X-33. The recombinant CBHB was purified and characterised to study its biochemical and kinetic characteristics. To evaluate the potential of CBHB in assisting biomass conversion, CBHB was supplemented into a commercial cellulase preparation (Cellic ®  CTec2) and was used to hydrolyse oil palm empty fruit bunch (OPEFB), one of the most abundant lignocellulosic waste from the palm oil industry. To attain maximum saccharification, enzyme loadings were optimised by response surface methodology and the optimum point was validated experimentally. Hydrolysed OPEFB samples were analysed using attenuated total reflectance FTIR spectroscopy (ATR-FTIR) to screen for any compositional changes upon enzymatic treatment.    Results  Recombinant CBHB was over-expressed as a hyperglycosylated protein attached to  N -glycans. CBHB was enzymatically active towards soluble substrates such as 4-methylumbelliferyl-β-D-cellobioside (MUC),  p -nitrophenyl-cellobioside ( p NPC) and  p -nitrophenyl-cellobiotrioside ( p NPG3) but was not active towards crystalline substrates like Avicel ®  and Sigmacell cellulose. Characterisation of purified CBHB using MUC as the model substrate revealed that optimum catalysis occurred at 50 °C and pH 4 but the enzyme was stable between pH 3 to 10 and 30 to 80 °C. Although CBHB on its own was unable to digest crystalline substrates, supplementation of CBHB (0.37%) with Cellic ®  CTec2 (30%) increased saccharification of OPEFB by 27%. Compositional analyses of the treated OPEFB samples revealed that CBHB supplementation reduced peak intensities of both crystalline cellulose I α  and Iβ in the treated OPEFB samples.    Discussion  Since CBHB alone was inactive against crystalline cellulose, these data suggested that it might work synergistically with other components of Cellic ®  CTec2. CBHB supplements were desirable as they further increased hydrolysis of OPEFB when the performance of Cellic ®  CTec2 was theoretically capped at an enzyme loading of 34% in this study. Hence,  A. niger  CBHB was identified as a potential supplementary enzyme for the enzymatic hydrolysis of OPEFB.

Cellobiohydrolase B ofAspergillus nigerover-expressed inPichia pastorisstimulates hydrolysis of oil palm empty fruit bunches