Producing bioethanol from pretreated-wood dust by simultaneous saccharification and co-fermentation process

•The effects of various pretreatment processes on wood dust hydrolysis and the production of bioethanol were studied.•The effects of the cocultivation of T. reesei and A. niger on wood dust hydrolysis and the production of bioethanol were investigated.•The effects of wood dust concentration on the production of bioethanol were determined.•A modified bioreactor was applied to improve the production of bioethanol.

The aim of this study was to utilize a new and highly effective bioreactor system, i.e., simultaneous saccharification and fermentation (SSCF), for bioethanol production by the cocultivation of Trichoderma reesei, Aspergillus niger, and Zymomonas mobilis by using a direct conversion process of pretreated-wood dust medium. Wood dust has been effectively used to obtain reducing sugars (glucose, xylose, and other byproducts) through the use of either a supercritical fluid extraction (SFE) or steam explosion (SE) pretreatment step. In addition, experimental results showed that polyurethane as a porous carrier could enhance total saccharification enzyme activity at an inoculum proportion of 1/1 of T. reesei, and A. niger and at a total inoculum concentration of 6.5 × 106 spores/ml. Furthermore, the concentration of alginate beads (3%) and immobilized proportion of Z. mobilis to alginate beads (1:4) were also examined. In accordance with previous reports, bioethanol production was carried out in a SSCF bioreactor by the cocultivation of T. reesei and A. niger in the polyurethane carrier and Z. mobilis immobilized in alginate beads using pretreated-wood dust medium. Experimental results revealed that, after 24 h of cultivation, the yield of bioethanol produced using pretreated-wood dust medium (1%) were 0.069 g/g and 0.049 g/g, for SFE and SE, respectively. Meanwhile, the sugar conversion rate reached 20.72% and 24.39% for SFE and SE, respectively. Thus, the results of this study show that pretreated-wood dust medium has significant potential for use in bioethanol production.

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