【作者】 徐嘉杰；

【导师】 李树君； 韩鲁佳；

【作者基本信息】 中国农业大学 ， 农产品加工及贮藏工程， 2014， 博士

【摘要】 全球正面临着能源紧张及其价格持续上涨,微藻是具有替代石油等化石能源潜力的生物质资源,可用于生产运输用燃料。然而微藻能源发展至今,成本问题始终制约着产业的发展。另一方面,随着养殖业的迅猛发展,畜禽粪便发酵产生大量沼液,属高污染物,无法直接排放至环境中。随着废水养殖微藻技术的出现,利用沼液进行小球藻的培养,不仅对其进行无害化处理、资源化利用,而且降低微藻生物能源生产成本,实现废物的能源化利用。本研究针对奶牛场沼液培养小球藻,通过分离纯化小球藻,并对其扩大培养,建设一定规模的示范基地,并研究后续收集、破壁和提油过程。本文的主要研究内容及结论如下：研究了小球藻(Chlorella sp.)在沼液中的生长以及沼液中有机物的清除情况。结果显示：小球藻在培养第6d生长速率达到0.307,生物量最大为1.30g/L,表明小球藻能够很好的适应沼液环境；处理14d后,沼液中有机物含量均有明显的降低。规模化养殖发现小球藻能够有效的利用沼液中的氨氮、磷等元素,可以实现净化处理。同时以聚合氯化铝(Polyaluminium Chloride, PAC)作为絮凝剂,探讨了其对小球藻的絮凝效果及其动力学模型,并对其实际应用的成本进行了评价。结果显示：5种不同剂量PAC在8min内均能高效絮凝小球藻,絮凝效率在86%以上,浓度为123.5mg/L时絮凝效率达到了98.6%,随着PAC浓度增大,小球藻的絮凝效率也提高,絮凝1t小球藻,絮凝剂成本为300-460元。针对沼液培养小球藻进行油脂含量、灰分、蛋白、脂肪酸组成、挥发性成分及在不同加热温度下的组分鉴别进行测定和研究。结果显示,所得小球藻干基油脂含量为10.14%。脂肪酸组成主要为多不饱和脂肪酸,含量为84.76%。通过挥发性组分的测定,主要包括烃类、醛类、酮类、醇类、酸类、胺类、杂环化合物等化合物。利用电子鼻对小球藻在不同温度下的气体成分变化进行研究,发现在60℃到90℃气体变化较小,然而继续加热成分明显变化。提出湿法超高压有机溶剂同步作用提取小球藻油脂,并与其他方法(超声波、高压均质和微波处理)进行比较。结果显示：超高压作用能达到最高细胞破碎率和油脂得率(10.02%和86.80%),且油脂提取和细胞破碎率均随着压力的增强而提高。总结四种破壁提取方法,细胞破碎率水平依次为超高压、高压均质、超声波和微波处理。油脂得率水平依次为超高压、超声波、高压均质和微波处理。探索小球藻细胞破壁和油脂提取同步完成工艺。实验结果显示,超高压效果最佳,细胞破碎率和油脂得率分别达到11.24%和92.75%。将同步法与分步法进行比较,发现同步法提取油脂和细胞破碎率均明显高于分步法。并对湿法超高压油脂同步提取小球藻油脂工艺进行响应面分析,得出最佳条件：压力580MPa,作用时间699s,溶剂比1：2.25。更多还原

【Abstract】 The use of fossil energy has economic and environmental consequences including increased energy prices from growing shortages, and detrimental emissions to the environment. Yet, fuels derived from algae can be used to displace fossil fuels without competing with food and crop production, which is a major drawback of first-generation biofuels. However, because of its high cost, algal biodiesel production at a commercial scale is not yet feasible. Algae production requires the input of macronutrients, and this can be a major operational expense when synthetic fertilizers are used. Agricultural wastes and other wastewaters containing sufficient nitrogen and phosphorus concentrations may be used in their place to offset these costs, while preventing these nutrients from entering the environment.In this study, Chlorella was grown using anaerobic digested dairy manure, and later separated, purified, and enriched. Using this growth culture, we then investigated the collection, pre-treatment, and oil extraction from the algae biomass. During cultivation of Chlorella sp, the growth rate and maximum biomass yield reached0.307/d and1.30g/L, and entered the stable phase within6days, which suggested this wastewater was a suitable substrate for Chlorella cultivation. After14days, the amount of available nutrients and organic carbon in the growth medium significantly decreased. With the enriched culture, the removal rate of TN, TP, NH4-N, NO3-N, POP and COD was53.95%,99.67%,78.81%,98.22%and85.88%, respectively. These results demonstrated that Chlorella can be used to effectively assimilate wastewater nutrients and reduce COD, while simultaneously generating commercially valuable microalgae products.Also, magnesium chloride (PAC) was used to test flocculation efficiency and kinetics. An economic evaluation was then performed using these data. Different dosages of PAC were added into microalgae suspensions. After stirring at200rpm for lmin, the contents of Chlorophyll were recorded at different times. The results showed that5different dosages of PAC exhibited flocculation efficiencies as high as over86%after8min. The flocculation efficiency was98.6%when the dosage of PAC was123.5mg/L. The flocculation efficiency increased significantly along with the dosage of PAC. And the cost was300-460Yuan when flocculating microalgae biomass was1ton. The results indicated that the flocculation of PAC obeyed second-order kinetics.We tested the fat content, ash, protein, fatty acid composition, and identification of volatile components in different temperatures of microalgae cultured in anaerobic digested dairy manure. The results show that the lipid content of dry Chlorella was10.14%and fatty acid content accounted for84.76%, mainly as polyunsaturated fatty-acids. The volatile components included hydrocarbons, aldehydes, ketones, alcohols, acids, amines, heterocyclic compounds and similar compounds. The gas compositions of Chlorella at different temperatures were identified by electronic nose, and the results indicated minimal changes over temperatures of60℃to90℃. At higher temperatures, composition changed significantly.Compared to other oil extraction methods, the results show that ultra high pressure achieves the highest cell breakage rate and oil extraction rate, which were10.02%and86.80%respectively. Oil extraction and cell disruption rate increased with increasing pressure. Regarding the cell disruption rates with four extraction methods, ultra high pressure was greatest, followed by high pressure homogenizer, ultrasonic and microwave. For oil extraction, the order was ultra high pressure, ultrasound, high pressure homogenization and microwave processing.Finally, we explored the possibility of combining the pre-treatment and extraction process into synchronous step. Experimental results show that at an optimum high pressure, cell disruption and oil extraction rates reached11.24%and92.75%respectively. Compared to separated pre-treatment and extraction, the cell disruption rates using the one-step approach were significantly higher. Thus, synchronous step can effectively improve the crushing ratio and oil extraction rate, reduce processing steps, particularly when ultra-high pressure is used. After analysis response surface, we received an optimum condition:pressure580MPa, time699s and solvent rate1:2.25.更多还原