The thermostable β-1,3-1,4-glucanase fromClostridium thermocellumimproves the nutritive value of highly viscous barley-based diets for broilers

Abstract

1. Microbial β-1,3-1,4-glucanases improve the nutritive value of barley-based diets for poultry by effectively decreasing the degree of polymerisation of the anti-nutritive soluble β-glucans. Glycoside hydrolases (GHs) acting on recalcitrant polysaccharides display a modular architecture comprising a catalytic domain linked to one or more non-catalytic Carbohydrate-Binding Modules (CBMs). 2. GHs and CBMs have been classified in different families based on primary structure similarity (see CAZy webpage at http://www.cazy.org ). The role of CBMs is to anchor the appended GHs into their target substrates, therefore eliciting the efficient hydrolysis of structural carbohydrates. 3. Here we describe the biochemical properties of the family 16 GH from Clostridium thermocellum, termed CtGlc16A. CtGlc16A is a thermostable enzyme that specifically acts on β-1,3-1,4-glucans with a remarkable catalytic activity (38000 U/mg protein). 4. CtGlc16A, individually or fused to the family 11 β-glucan-binding domain of cellulase CtLic26A-Cel5E of C. thermocellum, was used to supplement a highly viscous barley-based diet for broilers. 5. The data showed that birds fed on diets supplemented with the recombinant enzymes displayed an improved performance when compared with birds given diets not supplemented with exogenous enzymes. However, inclusion of the non-catalytic CBMs had no influence on the capacity of CtGlc16A to reduce the anti-nutritive effects of soluble β-1,3-1,4-glucans. 6. The data suggest that at elevated dosage rates, CBMs might be unable to potentiate the catalytic activity of appended catalytic domains; this effect may only be revealed when feed enzymes are incorporated at low levels.

Characterizing the avian gut microbiota: membership, driving influences, and potential function

“…When normalized to a proportion of the total cellulolytic gene abundance, predicted proportions of β-1,4-endoxylanase were not significantly different between dietary groupings. Although not necessarily intuitive, these findings are supported by previous observations that the cellulolytic potential of the avian hindgut is minimal (Barnes, 1972; McNab, 1973; Mead, 1989), and correlates with the observation that cellulolytic pre-digestion of feed boosts energy harvest and weight gain (Józefiak et al, 2006; Yu et al, 2008; Cowieson et al, 2010; Mathlouthi et al, 2011; Ghahri et al, 2012; Ribeiro et al, 2012) in farmed broiler chickens. Caution must be taken in interpreting these predictions, as a recent study has shown that the functional capabilities of the gut microbiota are dependent on community membership as well as genetic potential (Berry et al, 2013).…”

Structural analyses and yeast production of the β-1,3-1,4-glucanase catalytic module encoded by the licB gene of Clostridium thermocellum

“…CtLic16A exhibits excellent enzymatic properties when expressed in E. coli [8,10], but expression in an industrial strain is a prerequisite for further commercial applications. Accordingly, the CtLic16A was expressed in the P. pastoris (P-CtLic16A) and its performances were examined and compared to that in E. coli (ECtLic16A).…”

“…Accordingly, CtLic16A is the most thermophilic and thermostable ␤-1,3-1,4-glucanase characterized to date. More recently, the E. coli produced CtLic16A has been proven effective as a commercial enzyme cocktail when supplemented in the broiler daily diet by reducing the digesta viscosity of the feedstuff, indicating that the enzyme is an attractive candidate to be developed as a commercial product [10]. Notably, the catalytic domain of CtLic16A shares a high sequence identity to Bacillus ␤-1,3-1,4-glucanases (38-57%), thus the structural features contributing to its extraordinary thermostability is an interesting topic of research.…”

Overexpression of an Acidic Endo-β-1,3-1,4-glucanase in Transgenic Maize Seed for Direct Utilization in Animal Feed

“…β-1,3-1,4-Glucanase is able to catalyze the hydrolysis of β-glucan into low molecular weight glucose polymers, thus reducing the hydrophilicity and viscosity of chyme and eliminating the anti-nutritional negative effect. Moreover, addition of β-1,3-1,4-glucanase can improve feed intake, enhance animal production, regulate cecal microbiota and increase feed conversion ratio [5]–[8]. Besides, the hydrolysis products from glucans—glucooligosaccharides may serve as fermentable dietary fiber-like substrates and positively affect gastrointestinal tract health [9].…”

“…To date, commercial feed additive β-1,3-1,4-glucanases are generally from microbial expression systems, commonly Aspergillus japonicus [10], Pichia pastoris [11] and Clostridium thermocellum [8]. This process is flexible and convenient, but has disadvantages like high energy consumption, high equipment cost and serious environmental pollution.…”