Resumo

Interest in xylanolytic enzymes has increased in recent years due to their potential application in biotechnology. Xylanolytic enzymes have applications in conversion of lignocellulosic materials to chemicals and fuels, animal feed digestion, food and textile industries, and as bleaching agents in the pulp and paper processing. Since many agro-industrial wastes are a potentially valuable resource for industrial exploitation, this work aimed to evaluate the xylanase production by Penicillium glabrum using different agro-industrial wastes and establish the best fungal growing conditions for xylanase production with the best substrate. Xylanase activity was assayed at 50 °C using 1.0 % (w/v) birchwood xylan in McIlvaine buffer pH 6.5. The reducing sugars released were quantified by the dinitrosalicylic acid method, using xylose as standard. Total protein was determined by modified Bradford method, using bovine serum albumin as standard. Among the agricultural and agro-industrial wastes, highest xylanase production was observed with brewer’s spent grain (34.32 U/mL and 102.65 U/mg protein). These values were higher than those obtained with oat spelt xylan. Xylanase activity was also observed in the presence of wheat bran, oat bran and rice straw. In standing culture with brewer’s spent grain, the highest xylanase production was verified in 6.0 day-old cultures (42.45 U/mL), whereas in shaking condition, lower levels of xylanase activity was observed, reaching the maximum on 3.5-day-old cultures (25.85 U/mL). The highest activity was observed at initial pH 5.5, corresponding to the values of 48.54 U/mL and verified when P. glabrum grown at 25 ºC, corresponding to 51.43 U/mL. The use of brewer’s spent grain, an abundant and low-cost residue, as substrate for fungal growth and xylanase production can not only add value and decrease the amount of this waste, but also substantially reduce the xylanase production cost.