The anaerobic fungus Neocallimastix sp. strain L2,isolated from the feces of a llama, was tested for growth on a range ofsoluble and insoluble carbohydrate substrates. The fungus was able to fermentglucose, cellobiose, fructose, lactose, maltose, sucrose, soluble starch,inulin, filter paper cellulose, and Avicel. No growth was observed onarabinose, galactose, mannose, ribose, xylose, sorbitol, pectin, xylan,glycerol, citrate, soya, and wheat bran. The fermentation products aftergrowth were hydrogen, formate, acetate, ethanol, and lactate. Thefermentation pattern was dependent on the carbon source. In general, higherhydrogen production resulted in decreased formation of lactate and ethanol.Recovery of the fermented carbon in products at the end of growth ranged from50% to 80%. (Hemi)cellulolytic enzyme activities were affectedby the carbon source. Highest activities were found in filtrates fromcultures grown on cellulose. Growing the fungus on inulin and lactose yieldedthe lowest cellulolytic activities. Highest specific activities foravicelase, endoglucanase, beta-glucosidase, and xylanase were obtained withAvicel as the substrate for growth (0.29, 5.9, 0.57, and 13IU · mg-1 protein, respectively). Endoglucanase activitybanding patterns after SDS-PAGE were very similar for all substrates. Minordifferences indicated that enzyme activities may in part be the result ofsecretion of different sets of isoenzymes.