Solid-state fermintation and its effect on the nutrative value and digestibility of sorghum straw as animal feed [Sudan]

The chemical analysis of sorghum straw showed that it is composed of 38.55 cellulose, 31.15 hemicellulose, 6.50 acid-detergent lignin8.70 crude protein and 3.10 lipids. The alkali pretreatment of sorghum straw increased its digestibility from 24.59 to 51.30 where 2.0 alkali concentration was used in a 1 : 10 solid-liquid ratio and at an incubation temperature of 121 C Daraja for 30 minutes. The main disadvantage of this pretreatment was the complete loss of the proteins and lipids originally present in the straw. In the programme of search for cellulolytic fungi, three strains were isolated from local habitats and were found to possess reasonable cellulase activities as follows: Isolate-F1 gave exoglucanase activity of 0.54 mg/ml at incubation conditions of 50 C Daraja, pH 4.8 and 72 hours, F.P-ase activity of 3.0 unit/ml at 60 C Daraja, pH 5.6 an 180 minutes, and an endoglucanase activity of 3.9 unit/ml at 50 C daraja, pH 4.0 and 90 minutes. Trichoderma sp. gave an activity of 4.6 mg/ml for exoglucanase at 50 C Daraja, pH 4.8 and 72 hours, an activity of 2.4 unit/ml for F .P-ase at 60 C Daraja, pH 5.2 and 180 minutes, and an activity of 3.7 unit/ml for endoglucanase at 40 C Daraja, pH 4.8 for 30 minutes. The Chaetomium sp. showed enzyme activities of 3.8 mg/ml for exoglucanase at 70 C Daraja, pH 5.2 and 72 hours of incubation, and for the other two enzymes the activities were 2.2 unit/ml for F.P-ase at 50 C Daraja, pH 4.0 and 240 minutes and 3.5 unit/ml for endoglucanase at 40 C Daraja, pH 4.0 and 90 minutes. Solid-state fermentatation of the straw with the three fungal isolates resulted in an increase in the crude protein content of the straw to 6.13 with isolate-F1, to 8.20 with Trichoderma sp. and to 7.00 with Chaetomium sp., at 25 C Daraja, pH 5.0 for seven (7) days. Extending of the incubation period to day 10, didn't bring about a significant increase in the protein content of the alkali - pretreated straw to 62.20