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

Abstract

Abstract 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.