Comparing bioethanol production using buttonwood (Conocarpus erectus) and date palm (Phoenix dactylifera) leaves as raw material

A major obstacle of bioethanol production is finding a renewable and cheap feedstock, which still needs to be addressed. This work focuses on comparing bioethanol production from buttonwood and date palm leaves. Furthermore, cellulase activities were compared from 4 newly isolated cellulase producing Bacillus spp. and optimal temperature, pH and metal ion supplementation conditions to enhance the cellulolytic activity were determined. Finally, the bioethanol yields were compared between a Clostridium aciditolerans sp. (hereafter referred to as AK-1) and Saccharomyces cerevisiae for maximum bioethanol yields. Cellulase activity as high as 372 and 192 U/g substrate were obtained using buttonwood and date palm leaves, respectively, under optimal conditions. Using newly isolated Bacillus strain MI-42 for saccharification, efficiencies of 77.8 and 72.5% were obtained from buttonwood and date palm leaves, respectively. Using AK-1, maximum bioethanol yields of 2.07 and 0.85 g/L were obtained from buttonwood and date palm leaves, respectively, while maximum yields using S. cerevisiae reached 2.12 and 0.9 g/L. However, AK-1 required 96 hours to reach maximum yield, while S. cerevisiae needed just 10 hours. Although buttonwood and date palm leaves could be suitable feedstock, further optimization of the fermentation process is still needed to improve bioethanol yields.