M. M. RASHAD, A. M. M. EL-TORKY , M. U. NOOMAN, A. T. KESHTA, H. A. MAHMOUD AND A. E. MAHMOUD
Abstract
The present study was conducted for the possible utilization of water hyacinth plant (Eichhornia crassipes), one of the worst invasive aquatic plants in Egyptian environment, as a substrate for production of microbial xylanase. Among 10 tested microorganisms, Bacillus amyloliquifaciens NRRL B-14393 showed the highest activity of extracellular cellulase-free xylanase under solid-state fermentation of water hyacinth plant (stem & leaves). Distilled water was the most suitable extraction solution. Different fermentation parameters were studied for optimization of production process. Xylanase yield was enhanced 2.33 fold as compared to unoptimized condition (232.37 U/g wet substrate; 4674.4 U/g dry substrate) by growing the bacteria on 10 g of fresh plant supplemented with 0.5% sucrose at 35 °C with initial pH 6.0, 7.0% inoculums size and an initial moisture level of 95% for 24 hours. No nitrogen source or additives were required for enhancing the enzyme yield. The time course for enzymatic degradation of various pre-treated agricultural residues by the produced crude xylanase was studied and maximum hydrolysis was reached after 72 h for mango peel giving reducing sugar 123.9 mg/g dry substrate followed by wheat bran (120.62 mg/g dry substrate) after 24h.