小球藻超音波破壁實驗與數值分析

Cell-wall Fracture Study on Chlorella pyrenoidosa by Sonication Method and Numerical Analysis

莊于瑩(Yu-Ying Chuang)

指導教授 ： 蔡宏營

國立清華大學/工學院/動力機械工程學系/碩士(2013年)

摘要

本研究選擇高油脂含量的微藻類Chlorella pyrenoidosa，簡稱小球藻，作為產製生質柴油的油脂來源，並從眾多細胞破壞萃取藻油方法中採用超音波震盪法來對小球藻壁進行破壞實驗。
實驗設置分為藻體培養與超音波震盪實驗。首先利用非封閉式管狀培養法培養小球藻，培養溫度32℃，通入35 c.c/min的CO2以及空氣1000 c.c/min的氣體，光週期為光照14小時、黑暗10小時，培養時間為8~9天。超音波實驗分單振源及雙振源實驗設計，實驗參數為頻率、功率、震盪時間、細胞濃度及溫度，利用錐藍染劑法、螢光染劑法及半徑縮減率等三種檢測方法來檢測小球藻破壞比例及半徑縮減率，最後單振源實驗中藻種保存時間1.5個月、震盪前未烘烤下，震盪頻率40 kHz、輸入功率300 W、震盪溫度範圍為40~50 ℃以及細胞濃度為1 %的細胞破壞率7 %為最大破壞率，為小球藻的最佳破壞參數。
超音波震盪法的破壞機制為空蝕現象，產生的空泡在爆破時瞬間產生高溫高壓進而對小球藻造成破壞，本研究除了超音波破壁實驗之外，也進行了實驗參數的空泡數值分析，利用Matlab軟體及引用四階Runge-Kutta數值方法求解。數值分析結果中在單振源頻率40 kHz、功率300 W、功率強度為7.639 W/cm^2下，空泡成長的最大半徑約為0.173 mm，最大半徑和初始半徑比可達150倍、爆破壓力可達9.69×〖10〗^7 atm，分析結果與超音波實驗之破壞率相印證。

關鍵字

微藻類 ； 超音波震盪 ； 細胞破壞 ； 空蝕現象

並列摘要

In this study, a species of high lipid content microalgae：Chlorella pyrenoidosa, or called Chlorella sp. is used to be the lipid source of biodiesel production. From the variety of cell disruption and lipid extraction methods, we choose the sonication method to proceed the cell-wall disruption experiments.
There are two parts of experiment set-up, one is microalgae cultivation and another is sonication experiment. We use the open- tube cultivation method to cultivate the Chlorella sp. The temperature is maintained at 32 ℃, the flow rate of CO2 and air are 35 c.c/min and 1000 c.c/min. The light cycle is 14 hours in light, and 10 hours in dark. The cultivation time is 8-9 days. In sonication experiment part, it can be divided to single-frequency part and dual- frequency part. The experiment parameters are frequency, power, sonication time, cell concentration and temperature. We used the Trypan-blue method, fluorescent dye Calcofluor White Stain and the rate of radius reduction to evaluate the experiment results. Finally, we found that the cell disruption rate can reach 7 %, when the sonication parameters are: conservation time in 1.5 month, unbaked algae, sonication frequency at 40 kHz, power at 300 W, temperature between 40 and 50 ℃, and concentration of 1 %, This is the best disruption parameters in single-frequency experiment.
The mechanism of sonication method to disrupt the cell is cavitation. When the cavitation bubbles explode, it can generate the high temperature and pressure so that it can make algae to be disrupted. In addition to sonication experiments, we also do the numerical analysis about the cavitation bubble. The Matlab software and 4-order Runge-Kutta method are applied to solve equation. The results showed that the single frequency parameters with 40 kHz, power of 300 W, and the power intensity of 7.639 W/cm^2, the bubble can reach the maximum radius about 0.173 mm, the ratio of the maximum radius and the initial radius can reach 150, and the collapse pressure can reach 9.69×〖10〗^7 atm. The results of numerical analysis are used to put sonication experiment results to the proof.

並列關鍵字

Microalgae ； Sonication ； Cell disruption ； Cavitation

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