Bigelow Timothy A, Xu Jin, Stessman Dan J, Yao Linxing, Spalding Martin H, Wang Tong
Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA; Department of Electrical and Computer Engineering, Iowa State University, Ames, IA 50011, USA.
Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, USA; Department of Engineering, John Brown University, Siloam Springs, AR 72761, USA.
Ultrason Sonochem. 2014 May;21(3):1258-64. doi: 10.1016/j.ultsonch.2013.11.014. Epub 2013 Dec 7.
Efficient lysis of microalgae for lipid extraction is an important concern when processing biofuels. Historically, ultrasound frequencies in the range of 10-40 kHz have been utilized for this task. However, greater efficiencies might be achievable if higher frequencies could be used. In our study, we evaluated the potential of using 1.1 MHz ultrasound to lyse microalgae for biofuel production while using Chlamydomonas reinhardtii as a model organism. The ultrasound was generated using a spherically focused transducer with a focal length of 6.34 cm and an active diameter of 6.36 cm driven by 20 cycle sine-wave tone bursts at a pulse repetition frequency of 2 kHz (3.6% duty cycle). The time-average acoustic power output was 26.2 W while the spatial-peak-pulse-average intensity (ISPPA) for each tone burst was 41 kW/cm(2). The peak compressional and rarefactional pressures at the focus were 102 and 17 MPa, respectively. The exposure time was varied for the different cases in the experiments from 5s to 9 min and cell lysis was assessed by quantifying the percentage of protein and chlorophyll release into the supernate as well as the lipid extractability. Free radical generation and lipid oxidation for the different ultrasound exposures were also determined. We found that there was a statistically significant increase in lipid extractability for all of the exposures compared to the control. The longer exposures also completely fragmented the cells releasing almost all of the protein and chlorophyll into the supernate. The cavitation activity did not significantly increase lipid oxidation while there was a minor trend of increased free radical production with increased ultrasound exposure.
在生物燃料加工过程中，高效裂解微藻以提取脂质是一个重要问题。从历史上看，10 - 40 kHz范围内的超声频率已被用于此任务。然而，如果能使用更高的频率，可能会实现更高的效率。在我们的研究中，我们以莱茵衣藻为模式生物，评估了使用1.1 MHz超声裂解微藻用于生物燃料生产的潜力。超声由一个焦距为6.34 cm、有效直径为6.36 cm的球形聚焦换能器产生，由20个周期的正弦波脉冲串驱动，脉冲重复频率为2 kHz（占空比3.6%）。时间平均声功率输出为26.2 W，每个脉冲串的空间峰值脉冲平均强度（ISPPA）为41 kW/cm²。焦点处的峰值压缩压力和稀疏压力分别为102 MPa和17 MPa。在实验的不同情况下，暴露时间从5秒到9分钟不等，通过量化释放到上清液中的蛋白质和叶绿素的百分比以及脂质提取率来评估细胞裂解情况。还测定了不同超声暴露下的自由基产生和脂质氧化情况。我们发现，与对照组相比，所有暴露的脂质提取率都有统计学上的显著增加。较长时间的暴露也使细胞完全破碎，几乎所有的蛋白质和叶绿素都释放到了上清液中。空化活性并没有显著增加脂质氧化，而随着超声暴露增加，自由基产生有轻微增加的趋势。
