Effect of Oligosaccharide Degree of Polymerization on the Induction of Xylan-Degrading Enzymes by Fusarium oxysporum f. sp. Lycopersici

Abstract

Xylan is one of the most abundant carbohydrates on Earth. Complete degradation of xylan is achieved by the collaborative action of endo-β-1,4-xylanases and β-d-xylosidases and a number of accessories enzymes. In filamentous fungi, the xylanolytic system is controlled through induction and repression. However, the exact mechanism remains unclear. Substrates containing xylan promote the induction of xylanases, which release xylooligosaccharides. These, in turn, induce expression of xylanase-encoding genes. Here, we aimed to determine which xylan degradation products acted as inducers, and whether the size of the released oligomer correlated with its induction strength. To this end, we compared xylanase production by different inducers, such as sophorose, lactose, cellooligosaccharides, and xylooligosaccharides in Fusarium oxysporum f. sp. lycopersici. Results indicate that xylooligosaccharides are more effective than other substrates at inducing endoxylanase and β-xylosidases. Moreover, we report a correlation between the degree of xylooligosaccharide polymerization and induction efficiency of each enzyme. Specifically, xylotetraose is the best inducer of endoxylanase, xylohexaose of extracellular β-xylosidase, and xylobiose of cell-bound β-xylosidase.

Bright Side of Fusarium oxysporum: Secondary Metabolites Bioactivities and Industrial Relevance in Biotechnology and Nanotechnology

“…It was found that xylooligo-saccharides were more effective than other substrates at the induction of β-xylosidases and endoxylanases. Moreover, xylotetraose, xylohexaose, and xylobiose were the best inducers of endoxylanase, extracellular β-xylosidase, and cell-bound β-xylosidase, respectively [147].…”

Lignocellulosic Biomass Valorization for Bioethanol Production: a Circular Bioeconomy Approach

“…Xylan is the most known polymer belonging to the hemicellulose polysaccharide family. Xylan molecule has 1–4 xylopyranosyl linked to α-4-O-methyl-D-glucuronopyranosyl units and is a branched-chain polymer having a 5-carbon sugar monomer [ 53 ]. Most of the hemicellulose is soluble in alkaline solvents.…”

Xylo-Oligosaccharide Utilization by Engineered Saccharomyces cerevisiae to Produce Ethanol

“…As mentioned before, complete degradation of xylan is achieved by a variety of modular enzymes. Although many hemicellulolytic enzymes have been studied extensively, little is known about how microorganism cells sense the presence of xylan and uptake hemicellulose-derived products ( Polizeli et al, 2005 ; Delmas et al, 2012 ; Najjarzadeh et al, 2020 ). The induction signal for the synthesis of xylanolytic enzymes is supposed to involve transporters of xylose and short XOS released by the action of little amounts of the enzymes produced constitutively, along with lactose, glucose, and even cellulose, that are able to cross the membrane and induce the regulatory machinery ( Biely and Petráková, 1984 ; Royer and Nakas, 1989 ; Chandra Raj and Chandra, 1995 ; Christakopoulos et al, 1996a , 1996b ; Kulkarni et al, 1999 ), which suggests a complex induction mechanism of xylanases.…”

“…According to their findings, the overall strategy appears to be an induction of a specific, small scale, sensory response by the onset of carbon starvation, mediated at least partially by alleviation of CreA-dependent catabolite repression, that triggers the release of a small subset of degradative enzymes which initiate degradation on a small scale, in turn releasing sugars that cause the fungus to express its full degradative arsenal ( Delmas et al, 2012 ). More recently, Najjarzadeh and collaborators reported that xylotetraose is more effective than other substrates inducing endoxylanase, while xylohexaose and xylobiose are the best inducers of extracellular β-xylosidase, and cell-bound β-xylosidase, respectively ( Najjarzadeh et al, 2020 ).…”