Abstract
In vitro assays were carried out to investigate the solubilization of cell walls and generation of mannan oligosaccharides of a b-mannanase-containing commercial product on SBM. Using commercial dosages of the b-mannanase (500 g per ton of feed) cell wall degradation of mannan in SBM cell walls was visualized and an increase in reducing ends (0.12±0.02 mg/mL) and the generation of mannan oligosaccharides of degree of polymerization 2 and 4 (22.9±3.2 mg/L and 398.8±25.4 mg/L) were also measured using HPLC. Mannan, which is H-bonded to cellulose and xyloglucan, was solubilized using a single monocomponent enzyme, allowing for visualization of the disintegration of the entire SBM cell wall structure. This work is the first of its kind using strictly commercial dosage levels of enzyme for evaluating efficacy of the same microscopically. These data confirm the hypothesis that there most likely is a need for only a single relevant NSP enzyme targeting its specific substrate, independent of the concentration of the latter within the complex polysaccharide matrix in the plant cell wall to experience the beneficial effects of the enzyme both in vitro and in vivo. An analogy to compare our data would be destruction of the foundation (mannan) of a building or a bridge (soybean cell wall) which would inevitably lead to dismantling or demolition the entire building or bridge.
Highlights
Non-starch polysaccharide (NSP) degrading enzymes are added to help increase the metabolizable energy in fiber-containing monogastric diets
Immunofluorescence labelling with monoclonal antibody LM21 b-mannan (Marcus et al, 2010) bound to the cell wall lining overlapping the blue color showing that b-mannan is very closely linked to the b-glucan linkages cellulose and xyloglucan the major NSP in SBM (Figure 1A)
Mannan polysaccharides have been proposed to cross-link cellulose and xyloglucan by means of hydrogen bonds (Schröder et al, 2009). These bonds can only be broken under in vitro conditions by use of high molarity solvents such as guanidinium thiocyanate or KOH (Schröder et al, 2009). Both cellulose and the hemicellulose xyloglucan are the main constituents of the NSP fraction in SBM (Pettersson & Pontoppidan, 2012) whereas mannan is a minor fraction
Summary
Non-starch polysaccharide (NSP) degrading enzymes are added to help increase the metabolizable energy in fiber-containing monogastric diets. Many studies in the past have been conducted to improve the understanding of the mode of action of NSPases or fiber-degrading enzymes for use in animal feed. Addition of NSP-degrading enzymes to the diet modulated the local immune profile of the ileum, increasing IL-1b expression and concentration and decreasing IL-4, IL-17A and IL-11 concentration (Ferrandis et al, 2018). It is claimed NSPases can be considered as tools to train the microbiome to be better able to degrade fiber more effectively especially when they are accompanied initially with oligosaccharides. By breaking down the fiber they produce small amounts of oligosaccharides which have prebiotic effect, and they are postulated to play a role in signaling to the gut microbial population present to develop a higher fiber-degrading capacity (Bedford, 2018)
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