Enzymic Release of Reducing Sugars from Oat Hulls by Cellulase, as Influenced by Aspergillus Ferulic Acid Esterase and Trichoderma Xylanase

Abstract

Hydroxycinnamic acids, mainly ferulic and p-coumaric acids, are believed to be inhibitory to ruminal biodegradability of complex cell wall materials such as oat hulls. Previous studies have shown that a novel enzyme, Aspergillus ferulic acid esterase, and Trichoderma xylanase act synergistically to break the ester linkage between ferulic acid and the attached sugar of feruloyl polysaccharides, releasing ferulic acid from oat hulls. In this paper, we examined the enzymic release of reducing sugars from oat hulls by the actions of individual enzymes (Aspergillus ferulic acid esterase at 13 mU, 6.4 U, and 4678.4 U/assay; cellulase at 20 levels, ranging from 7.8 mU to 2772.7 U/assay; Trichoderma xylanase at 20 levels, ranging from 7.8 mU to 4096 U/assay) and by the combined action of cellulase at six levels (62.5 mU, 2 U, 16 U, 128 U, 1024 U, and 2772.7 U/assay), Aspergillus ferulic acid esterase at 13 mU/assay, and Trichoderma xylanase at two levels (1 U and 256 U/assay). The amount of total acid-extractable reducing sugars in the oat hulls used in this study was 793.8 +/- 8.0 microg/mg. The results show that after a 24-h incubation with Aspergillus ferulic acid esterase alone, no reducing sugars were observed to be released from oat hulls. With cellulase as the sole enzyme, as the concentration increased from 7.8 mU to 2772.7 U/assay, the release of reducing sugars increased (P < 0.01) from 0 to 39% of the total present, with the highest release at 512 U/assay. With Trichoderma xylanase alone, as the concentration increased from 7.8 mU to 4096 U/assay, the release of reducing sugars increased (P < 0.01) from 4.9 to 33%, with the highest release at 2048 U/assay. When incubated together with Trichoderma xylanase (1 U or 256 U/assay) and Aspergillus ferulic acid esterase (13 mU/assay), cellulase at all six levels (62.5 mU, 2 U, 16 U, 128 U, 1024 U and 2772.7 U/assay) significantly increased the release of reducing sugars (P < 0.01) from 8 to 69%. These results indicate that the synergistic interaction between Aspergillus ferulic acid esterase and Trichoderma xylanase on the release of ferulic acid from feruloyl polysaccharides of oat hulls makes the remainder of the polysaccharides open for further hydrolytic attack and facilitates the accessibility of the main chain of polysaccharides to cellulase. This action extends the cell wall hydrolysis, thus releasing a higher yield of reducing sugars. Such enzymic pretreatment of oat hulls may provide a unique advantage to rumen microorganisms for the biodegradation of the complex cell walls of byproduct feeds such as oat hulls.

Production of cellulolytic enzymes containing cinnamic acid esterase from Schizophyllum commune

“…Treatment with this enzyme preparation can effectively release the cinnamic acid derivatives. Some studies have demonstrated that a combination of ferulic acid esterase and endoxylanase released ferulic acid from de-starched wheat bran (Faulds and Williamson, 1991) and oat hulls (Yu et al, 2002(Yu et al, , 2003. Therefore, the fi ndings of the present study indicate enzyme preparations from S. commune may provide a novel method for utilization of unused agricultural wastes.…”

Action of Designer Cellulosomes on Homogeneous Versus Complex Substrates

“…The total acid-extractable reducing sugar content was determined according to Ref. 22 with some modifications: 300 mg (dry matter) were incubated for 1 h with 12 M H 2 SO 4 at 35°C. The sample was diluted 12 times with distilled water and autoclaved at 120°C for 1 h. The pH was adjusted to 7 with NaOH, and the suspension was centrifuged for 15 min at 8000 ϫ g. The reducing sugar content of the supernatant was determined using the Park and Johnson method (23), and the glucose content was examined using the glucose oxidase method (24).…”

Use of ‘natural’ products as alternatives to antibiotic feed additives in ruminant production

“…Notwithstanding, enzymes hydrolysing hemicelluloses are often positively correlated to increases in substrate degradation, e.g., xylanase and esterase activities (Nsereko et al, 2000b;Colombatto et al, 2003b;Yu et al, 2005). Exogenous ferulic acid esterase and arabinofuranosidase have been shown to act in synergy with xylanases and cellulases (Yu et al, 2003;Koukiekolo et al, 2005). Similarly, the synergy of exogenous and rumen-derived enzymes has been shown to be one important mode of action of feed enzyme additives .…”