Effects of ultrasonic waves on filtration performance and fermentation in an internal membrane-filtration bioreactor

Ultrasonic wave technology was employed to improve filtration performance and ethanol production in a bioreactor equipped with an internal ceramic-membrane filter module. The filtration performance was found to depend on the power and the pattern of ultrasonic wave irradiation. Under the optimized conditions (irradiation time: 25 sec, period: 5 min, and ultrasonic power: 60 W), the flux was improved with the periodic-pause method by 200-700% compared with the control (with no irradiation), while the improvement was only 30 to 90% without the periodic-pause method. The final ethanol concentration also increased slightly. However, in a more severe condition (irradiation time: 2.5 min, period: 5 min, and ultrasonic power: 110 W), the irradiation of ultrasonic waves was observed to disturb cell integrity and viability, and thus to decrease ethanol production.