Corncobs as Substrate for Oleaginous Yeast–Pretreatment via Steam Explosion and Hydrolysis

Corn cobs are a promising lignocellulosic substrate for the production of biofuels like bioethanol via conventional yeast or biodiesel via oleaginous yeast. Pretreatment of the substrate is essential for further hydrolysis and fermentation steps. This study focused on the steam explosion method as pretreatment. Therefore, different steam explosion severities were evaluated. The content of glucan, xylan and Klason lignin was examined. Xylan degraded with increasing severity from 412.7 g·kg-1 (untreated) to a minimum of 127.3 g·kg-1 dry matter (190 °C/30 min). Glucan concentrations increased from 315.1 g·kg-1 (untreated) to a maximum of 371.6 g·kg-1 dry matter (200 °C/20 min). For soluble lignin, an increase could be observed at rising severity, from 145.3 g·kg-1 (untreated) to a maximum of 214.9 g·kg-1 dry matter (190 °C/30 min). Furthermore, the mass recovery was calculated. At harsher pretreatment conditions, a significant mass loss was observed, estimated by the ash content in the recovered dry matter. The lowest recovery rate was observed for SF = 4.13 (190 °C/30 min) with 68.39%. The produced inhibitors were evaluated.