Monday, April 30, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
The mesophilic fungus Aspergillus flavus is described in the literature as cosmopolitan and able to grow or degrade different substrates, such as plants, animal and vegetable waste. This microorganism showed an arsenal of holocelulases able to degrade cell wall polysaccharides of plants, especially when grown with lignocellulosic wastes (banana stem, dirty cotton residue and sugar cane bagasse) as carbon source in submerged cultivation. This fungus, with three days of submerged cultivation in these carbon sources, produced significant amounts of xylanase and pectinase activities, as induction curve held for approximately thirty days of cultivation. A. flavus stood out in the production of pectinases in cultures with all sources of lignocellulosic wastes aforementioned, showing activity in a wide pH range, especially above 8.0 in Tris-HCl buffer and temperature range of 50-65°C. The activities of xylanase and mannanase in lignocellulosics were also relevant, with higher values of pH and temperature in the acidic range and 50°-60°C, respectively. Fractionation of holocellulases by ultrafiltration, gel filtration chromatography on Sephacryl S-400 and ion exchange chromatography on CM-sepharose and Q-Sepharose showed profiles of enzymatic activities present in the same fractions. Banana stem was one of lignocellulosic carbon sources that most stimulated the production of holocellulases. The process of enzymatic hydrolysis of bagasse from cane sugar (pre-treated or untreated) showed about 5% conversion of polysaccharides into sugars. The holocellulase showed affinity to the substrate avicel when analyzing the carbohydrate-binding module (CBM) for endoglucanase and xylanase activities.