Strategies of xylanase supplementation for an efficient saccharification and cofermentation process from pretreated wheat straw.

Ethanol production from lignocellulosic raw materials includes a pretreatment step before enzymatic hydrolysis (EH). Pretreated substrates contain complex hemicelluloses in the solid fraction that can protect the cellulose from enzymatic attack. In addition, soluble xylooligomers are contained in the pretreated materials and may have an inhibitory effect on cellulase activity. In this context, several approaches for xylanase supplementation have been studied to increase EH yields. In this study, the whole slurry obtained after steam explosion pretreatment of wheat straw has been used as substrate. EH experiments were performed using commercial cellulase preparations supplemented with an endoxylanase (XlnC) from Aspergillus nidulans. Among different strategies of XlnC supplementation, the 24-h xylanase treatment before cellulase addition yielded an increase of 40.1 and 10.1% in glucose and xylose production, respectively. Different XlnC addition strategies were integrated in a simultaneous saccharification and cofermentation process (SSCF) using the xylose fermenting strain Saccharomyces cerevisiae F12. Ethanol production in SSCF was 28.4% higher when comparing to a simultaneous saccharification and fermentation process.