Elephant grass pretreated by steam explosion for inducing secretion of cellulases and xylanases by Penicillium echinulatum S1M29 solid-state cultivation

Abstract

One of the bottlenecks in the production of second-generation ethanol is the high cost of the enzymes used for the hydrolysis of lignocellulosic biomass. One way to reduce this cost is to use local biomass, such as elephant grass (Pennisetum purpureum), but for this use the lignocellulosic material must be pretreated. Among the pretreatments that have been studied, steam explosion has been the most efficient. In this study, it was evaluated the production of cellulases and xylanases by Penicillium echinulatum S1M29 in solid-state cultivation using elephant grass pretreated by steam explosion at different temperatures (180, 190 and 200°C) and residence times (6, 8, 10min). In culture media, it was used 100% elephant grass that was pretreated by steam explosion (washed and unwashed after the process) or in combination with wheat bran (50%). It was found that the untreated elephant grass is superior to wheat bran for Filter Paper Activity (FPA) with values of 23.38±0.10IUg−1. The replacement of 50% wheat bran with elephant grass that was pretreated by steam explosion and washed favoured the production of enzymes with maximal activities of 32.93±0.58IUg−1 for FPA, 205.83 6.85±IUg−1 for endoglucanase, and 148.96±0.00IUg−1 for β-glucosidases. For xylanase production, untreated elephant grass proved more effective because the combination of substrates provided the greatest enzymatic activity in a sample that was not subjected to washing, reaching values of 571.74±27.14IUg−1.