Family 1 carbohydrate binding-modules enhance saccharification rates

Abstract

Cellulose degrading enzymes usually have a two-domain structure consisting of a catalytic domain and a non-catalytic carbohydrate-binding module. Although it is well known the importance of those modules in cell wall degrading process, their function is not yet fully understood. Here, we analyze the cellulose-hydrolysis activity enhancement promoted by the cellobiohydrolase I carbohydrate-binding module from Trichoderma harzianum. It was cloned, expressed, purified and used in combination with either a commercial cellulase preparation, T. reesei cellobiohydrolase I or its separate catalytic domain to hydrolyze filter paper. In all cases the amount of glucose released was increased, reaching up to 30% gain when the carbohydrate-binding module was added to the reaction. We also show that this effect seems to be mediated by a decrease in the recalcitrance of the cellulosic substrate. This effect was observed both for crystalline cellulose samples which underwent incubation with the CBM prior to application of cellulases and for the ones incubated simultaneously. Our studies demonstrate that family 1 carbohydrate-binding modules are able to potentiate the enzymatic degradation of the polysaccharides and their application might contribute to diminishing the currently prohibitive costs of the lignocellulose saccharification process.

Advances in molecular engineering of carbohydrate-binding modules

“…Biomass degradation is necessary as a pretreatment process for the saccharification of lignocellulolytic material, which would aid bioethanol or biofuel production. In addition to their use as components of chimeric enzymes, CBMs have been used as additives in reactions during the saccharification process of crystalline cellulose, increasing the production of glucose up to 30% …”

“…In addition to their use as components of chimeric enzymes, CBMs have been used as additives in reactions during the saccharification process of crystalline cellulose, increasing the production of glucose up to 30%. 79 Lignocellulolytic material is not easily digested into sugars mainly due to the presence of lignin. Low-lignin rice was developed through the expression of a laccasecellulose-binding domain (CBD) fusion protein, and this protein increases saccharification efficiency (up to 1.5fold) and modifications in the cell wall composition.…”

Peer Review #1 of "Insight into plant cell wall degradation and pathogenesis of Ganoderma boninense via comparative genome analysis (v0.1)"

“…Although white rot fungi have been associated with lack of CBMs, G. lucidum and G. boninense contained 10 and 12 out of 16 total families of CBMs, respectively. It is notable that G. boninense possessed high copies of CBM1, an important fungal CBM that uses cellulose and chitin as substrates for polysaccharide-degrading activities (Mello & Polikarpov, 2014;Várnai et al, 2014). Both fungi shared similar GTs except for GT65 and GT41 that were found only in G.…”

Functional expression and characterization of a glucuronoyl esterase from the fungus <i>Neurospora crassa</i>: identification of novel consensus sequences containing the catalytic triad

“…In contrast, Cip2, PcGE1 from P. chrysoporium (Ďuranová et al, 2009b), and CuGE from C. unicolor (d 'Errico et al, 2015) contain type 1 CBM at the N-terminus of the catalytic domain. CBMs are classified into subfamilies based on the amino acid sequence similarity and most of the fungal CBMs in cellulases belong to the family 1, in which three aromatic residues create a planar structure to bind to the crystallized surfaces of chitin/cellulose (Mello and Polikarpov, 2014). When expressed in P. pastoris, a protein of 44 kDa which is nearly equal to the calculated size of myc-and hexahistidine-tagged NcGE was produced.…”