Solid-state fermentation has the potential to produce inexpensive enzymes for use in high-volume industrial applications. Process parameters such as substrate moisture content and length of fermentation can have a significant effect on the amount and timing of enzyme production. This study was conducted in two stages, a screening stage and an optimization stage, to determine the effects of moisture content of the substrate, surfactant addition upon inoculation, depth of the substrate, and duration of fermentation on xylanase activity produced by Trichoderma longibrachiatum. Screening fermentations were conducted at 25°C, 50 and 75% wet basis moisture content (w.b.), 0.0 and 0.2% v/v surfactant addition, 0.5 and 1.5 cm depth of wheat bran, and 5 and 10 days of fermentation. Optimization fermentations were conducted at 25°C, 45, 55, and 65% moisture content (w.b.), 1.0, 1.5, and 2.0 cm depth of wheat bran, and three and five days of fermentation. Experiments were conducted as full factorial experiments with three replications of each treatment. The optimal values of the process variables were selected based on the units of xylanase activity produced per gram of wheat bran (U/g). Moisture content, depth of substrate, and duration of fermentation had significant main effects on the production of enzyme activity. Surfactant addition upon inoculation had interaction effects with moisture content, and the duration of fermentation by moisture content interaction also was significant. The treatment of 55% moisture content, 1.5 cm depth of substrate, and five days of fermentation resulted in the highest average xylanase activity (716 U/g wheat bran).

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Published in Transactions of the ASAE, v. 41, issue 5, p. 1453-1459.

© 1998 American Society of Agricultural Engineers

The copyright holder has granted the permission for posting the article here.

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The investigation reported in this article (no. 97-05-102) is part of a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.