Ultrasonic cavitation of lignocellulosic raw materials as effective method of preparation for butanol production

Abstract

Six types of native and ultrasonic cavitation-treated non-cereal plant biomass as a substrate for cultivation of the butanol-producing strain Clostridium sp. IMB B-7570 were studied. During the research, an ultrasonic bath with emitters with a total power of 720 W and an ultrasound frequency of 28 kHz was used. The weighted average size of the straw particles was 78 μm. As a result of the research, the accumulation of butanol in the culture liquid after 72 hours of fermentation was determined. After fermentation of the producer strain Clostridium sp. IMB B-7570 all three products of the acetone-butanol-ethanol process were detected in the culture liquid. It was established that cultivation of the strain on pre-treated biomass significantly increases the accumulation of butanol in the culture liquid. The highest accumulation of butanol (0.7 g·l-1) was obtained using crushed rape biomass as a substrate. In this case, ethanol and acetone were present in small quantities – 0.05 g·l-1 and 0.02 g·l-1, respectively. A significant increase in the yield of biobutanol compared to untreated experiments is the result of the mechanical destruction of the lignocellulosic structure of plant biomass due to the cavitation effect of ultrasound, which is confirmed by numerous experiments on various types of raw materials. A comparative analysis of the research results established that the accumulation of solvents after ultrasonic cavitation of the non-grain part of plants correlates with acid-enzymatically prepared substrate, but ultrasonic cavitation is more effective than hydrolysis, and therefore this method of preliminary preparation of biomass for fermentation can be more competitive in industrial conditions.