Multi-copy expression of a protease-resistant xylanase with high xylan degradation ability and its application in broilers fed wheat-based diets.

The acidic thermostable xylanase (AT-xynA) has great potential in the feed industry, but its low activity is not conductive to large-scale production, and its application in poultry diets still needs to be further evaluated. In Experiment1, AT-xynA activity increased 3.10 times by constructing multi-copy strains, and the highest activity reached 10,018.29 ± 91.18 U/mL. AT-xynA showed protease resistance, high specificity for xylan substrates, xylobiose and xylotriose were the main hydrolysates. In Experiment2, 192 broilers were assigned into 3 treatments including a wheat-based diet, and the diets supplemented with AT-xynA during the entire period (XY-42) or exclusively during the early stage (XY-21). AT-xynA improved growth performance, while the performance of XY-21 and XY-42 was identical. To further clarify the mechanism underlying the particular effectiveness of AT-xynA during the early stage, 128 broilers were allotted into 2 treatments including a wheat-based diet and the diet supplemented with AT-xynA for 42 d in Experiment3. AT-xynA improved intestinal digestive function and microbiota composition, the benefits were stronger in younger broilers than older ones. Overall, the activity of AT-xynA exhibiting protease resistance and high xylan degradation ability increased by constructing multi-copy strains, and AT-xynA was particularly effective in improving broiler performance during the early stage.

High-level expression of an acidic thermostable xylanase in Pichia pastoris and its application in weaned piglets.

An acidic thermostable xylanase (AT-xynA) which was stable at low pH and high temperature was considered to have great potential in animal feed. For large-scale production, AT-xynA activity was enhanced about 1-fold in Pichia pastoris by constructing a double-copy expression strain in this study. Furthermore, impacts of different AT-xynA levels on growth performance, nutrient digestibility, short-chain fatty acids, and bacterial community in weaned piglets were determined. Compared with the control group, ADFI and ADG were higher for the pigs fed 4,000 or 6,000 U/kg AT-xynA (P < 0.05). AT-xynA supplementation also significantly increased the digestibility of OM, GE, and DM (P < 0.05). AT-xynA supplementation increased the concentrations of acetate in ileal (P < 0.01) and cecal digesta (P < 0.05). Isobutyrate (P < 0.05) and valerate (P < 0.05) concentrations in colonic digesta also significantly increased compared with the control group. AT-xynA supplementation increased the abundance of Lactobacillus in the ileal, cecal, and colonic digesta of weaned piglets (P < 0.05). AT-xynA alleviated anti-nutritional effects of nonstarch polysaccharides (NSP) by preventing the growth of Pateurella and Leptotrichia in the ileum (P < 0.05). AT-xynA increased the abundance of NSP-degrading bacteria, such as Ruminococcaceae, Prevotella in the cecum and colon (P < 0.05). In summary, AT-xynA addition could improve the growth performance of weaned piglets by altering gut microbiota.