New recombinant fibrolytic enzymes for improved in vitro ruminal fiber degradability of barley straw1

Abstract

This study used a high-throughput in vitro microassay, in vitro batch culture, and the Rumen Simulation Technique (RUSITEC) to screen recombinant fibrolytic enzymes for their ability to increase the ruminal fiber degradability of barley straw. Eleven different recombinant enzymes in combination with a crude mixture of rumen enzymes (50% recombinant enzyme:50% crude mixture of rumen enzymes) were compared with the crude mixture of rumen enzymes alone. In the microassay, all treatments were applied at 15 mg of protein load per gram barley straw glucan. Based on the microassay results, 1 recombinant endoglucanase [EGL7A, from the glycoside hydrolase (GH) family 7], 2 recombinant xylanases (XYL10A and XYL10C, from GH10), and a recombinant enzyme mixture were selected and compared with a crude mixture of fibrolytic enzymes from Aspergillus aculeatus for their ability to hydrolyze barley straw. For batch culture, enzymes were applied to barley straw at 2 dosages (100 and 500 µg of protein/g of substrate DM). All enzymes increased (P < 0.05) DM disappearance and total VFA production, but the mixture of recombinant enzymes was not superior to the use of a single recombinant enzyme. Based on positive results (P < 0.05) for total DM disappearance and VFA production in batch culture, 3 enzymes (EGL7A, XYL10A, and XYL10C) were selected and applied to barley straw at 500 µg of protein per gram for further assessment in RUSITECs fed a concentrate:barley straw diet (300:700 g/kg DM). In RUSITECs, the recombinant enzyme XYL10A increased (P < 0.05) barley straw DM, NDF, and ADF disappearance, whereas EGL7A and XYL10C had no effect. The enzymes selected based on the high-throughput in vitro microassay consistently increased barley straw degradation in ruminal batch culture, but not in the semicontinuous culture RUSITEC system.

Pretreatment of Rapeseed Meal Increases Its Recalcitrant Fiber Fermentation and Alters the Microbial Community in an in vitro Model of Swine Large Intestine

“…Torok and colleagues (Torok et al, 2008) investigated changes in gut microbial population in response to the supplementation of an NSP-degrading enzyme (containing βglucanase, xylanase, and protease activities) in a barley-based diet in chickens, and the results showed that microbial composition revealed distinct clusters correlating with un-supplemented and enzyme supplemented birds. Previous research reported that the pre-treatment of feed stuffs with carbohydrases can cause the release of reducing sugars and other hydrolysis materials, promoting chemotactic response in specific bacteria, and stimulating their attachment to feed particles, and thereby growth of these microbes (Beauchemin et al, 2003;Giraldo et al, 2007;Ribeiro et al, 2015Ribeiro et al, , 2018.…”

New mechanistic insight into the digestion of complex dietary fibre by rumen microbiota using combinatorial high-resolution glycomic and transcriptomic analyses

“…Individual bags were then placed in 125 mL serum vials. Rumen uid from 4-5 different sites within rumen was collected from four ruminally cannulated Angus x Hereford heifers fed 50% grass hay, 30% barley straw, 15% corn dried distillers grains plus solubles and 5% mineral/vitamin supplement (DM basis) [13]. Collected rumen uid was strained through cheesecloth and equal volumes from each cow were combined.…”

“…Collected rumen uid was strained through cheesecloth and equal volumes from each cow were combined. The inoculum was prepared by mixing rumen uid 1:4 with mineral buffer [13]. Inoculum (65 mL) was transferred to each vial under a stream of O 2 -free CO 2 .…”

Pretreatment of Rapeseed Meal Increases Its Recalcitrant Fibre Fermentation and Alters the Microbial Community in an in Vitro Model of Swine Large Intestine

“…All the observations above were supported by former reports that feed processed by carbohydrase enzymes could stimulate growth of speci c microbes (Wang et al 2001;Giraldo et al 2007;Giraldo et al 2008). It can be speculated that the pretreatment of feed stuffs with carbohydrases causes the release of hydrolysis materials (presumably oligosaccharides), which promote the chemotactic response of speci c bacteria, and stimulates their attachment to feed particles, thereby leading to growth of these microbes (Giraldo et al 2007;Beauchemin et al 2003;Ribeiro et al 2015;Ribeiro et al 2018).…”

“…Torok and colleagues (Torok et al 2008) investigated changes in gut microbial population in response to the supplementation of an NSP-degrading enzyme (containing β-glucanase, xylanase, and protease activities) in a barley-based diet in chickens, and the results showed that microbial composition revealed distinct clusters correlating with un-supplemented and enzyme supplemented birds. Previous research reported that the pretreatment of feed stuffs with carbohydrases can cause the release of reducing sugars and other hydrolysis materials, promoting chemotactic response in speci c bacteria, and stimulating their attachment to feed particles, and thereby growth of these microbes (Giraldo et al 2007;Beauchemin et al 2003;Ribeiro et al 2015;Ribeiro et al 2018).…”