Production of acetone-butanol-ethanol from spoilage date palm (Phoenix dactylifera L.) fruits by mixed culture of Clostridium acetobutylicum and Bacillus subtilis

Spoilage date palm (Phoenix dactylifera L.) fruits were used as substrate for acetone, butanol and ethanol (ABE) production by mixed culture of Clostridium acetobutylicum ATCC 824 and Bacillus subtilis DSM 4451. B. subitlis was used to consume O2 and maintain strict anaerobic conditions for ABE production by the strictly anaerobic C. acetobutylicum ATCC 824. The total ABE production of 21.56 g L−1 was achieved at 75 g L−1 spoilage date fruits homogenate. The maximum ABE productivity of 0.30 g L−1 h−1 and ABE yield of 0.42 were obtained at 75 g L−1 spoilage date fruits homogenate by mixed culture without addition of a reducing agent and N2 flushing. Addition of yeast extract (5 g L−1) or ammonium nitrate (1.6 g L−1) to spoilage date fruits homogenate significantly enhanced ABE production. The combination of yeast extract and ammonium nitrate markedly increased ABE production. These results suggest that spoilage date fruits can be efficiently used for commercial ABE production. The described protocol did not require addition of any costly reducing agent to medium or flushing with N2 to ensure anaerobic conditions. This will makes the anaerobic fermentation of date fruits homogenate more economical and reduces the cost of ABE production.