Effect of Glucose Levels and N Sources in Defined Media on Fibrolytic Activity Profiles of Neocallimastix Sp. YQ1 Grown on Chinese Wildrye Grass Hay Or Alfalfa Hay (Report‪)‬

INTRODUCTION The plant cell wall is composed mainly of cellulose, hemicelluloses and lignin. Cellulose is the most abundant polysaccharide, and can be hydrolyzed via a complex process involving cellulases (Beauchemin et al., 2004). The xylan backbone of hemicelluloses can be degraded by xylanase (Wang and McAllister, 2002). Monocotyledonous plants, such as grasses, and dicotyledonous ones, such as alfalfa, have lignin-type compounds within the secondary walls and middle lamella of cell walls. Fungi account for only approximately 8% of the microbial biomass in the rumen (Orpin and Joblin, 1988). However, these rumen fungi play an important role in fibre digestion because they can penetrate both the cuticle and cell wall of lignified tissue (Akin, 1986). Detailed discussions of microbial enzymes have been presented elsewhere (Forsberg et al., 1986; White et al., 1993). Anaerobic fungi possess a broad range of fibrolytic polysaccharide hydrolases, including cellulases, xylanases, and others (Ushida et al., 1997; Ho and Abdulah, 1999). Neocallimastix frontalis has the highest cellulolytic activity of any organism ever reported in the literature (Varga and Kolver, 1997). Borneman et al. (1990, 1991) demonstrated strong activities of ferulic acid esterase (FAE) and _p-coumaric acid esterase (CAE) of two monocentric and three polycentric fungi. The activities of these enzymes can aid in the utilization of low quality roughage by breaking ester bonds in the cross-linkages between lignin and hemicelluloses. These linkages between two ferulic acid molecules on adjacent chains provide cell wall integrity, and, in general, are resistant to enzymatic attack by microorganisms (Iiyama et al., 1994).