Poster Presentation 1B-19

Evaluation of the Performance of Cellulose Preparations

M.J.E.C.van der Maarel,^1* M.A. Kabel,² G. Klip¹ and H.A. Schols²

¹ Innovative Ingredients and Products Department

TNO Nutrition and Food Research

Rouaanstraat 27, 9723 CC Groningen

The Netherlands

Phone: +31 50 3694631

Fax: +31 50 3128891

E-mail: maarel@voedig.tno.nl

² Laboratory of Food Chemistry, Wageningen University, Wageningen, The Netherlands

Cellulose is composed of β1-4 linked glucose molecules. In plant cell walls it is coated with xylans (hemicellulose) and thus contributes to rigid structure of the cell wall. The enzymatic conversion of cellulose/xylans is a complex process involving the concerted action of exo/endocellulases and cellobiases yielding glucose and xylanases yielding xylooligomers and xylose. We analysed a number of commercially available enzyme samples for the amount of cellulase, cellobiase, and xylanase activity, using respectively filter paper, cellobiose, and AZCL-dyed xylan as a substrate. Subsequently, the activity towards more natural substrates was studied. Grass and wheat brans were fractionated into a water unsoluble fraction (WUS), which was free of oligosaccharides and starch, and a cellulose and xylan-rich fraction, obtained by alkaline extraction and centrifugation of the WUS. These fractions were incubated with a relatively high dose of the enzyme samples and after 24h the amount of free glucose and xylose was determined. The results obtained showed that there was a large difference in the performance of the different enzyme samples and that standard activity assays are not always a good indicator for the activity of the enzyme sample on natural substrates.