中国科学院过程工程研究所机构知识库

利用封闭式光生物反应器培养微藻，可以对培养体系的各种因素（如温度、光强等）进行精确的控制，对光能和CO2的利用率高，有效减少水分的蒸发，而且还能防止被外界物种的侵扰，减少污染率，实现高密度培养并提高微藻培育成功率。塑料薄膜材料最为常用的光生物反应器材料，具有易于加工和成本低等优点，但其在使用过程中的表面污染是塑料薄膜材料在光生物反应器中应用中难以避免的一个问题，藻液体系中的藻细胞、胞外多糖、胞外蛋白等有机物以及其它无机物等共同作用，引起反应器材料表面的生物附着现象，造成光生物反应器透光率下降，培养环境的恶化和微藻产量的下降。因此，针对光生物反应器的生物污损问题，本文提出通过制备两亲性两性离子共聚物涂层改善光生物反应器的抗生物污损性能，为光生物反应器的表面改性提供一种简单快速、可应用于工业大规模生产的方法，达到抑制或减少微藻在反应器表面附着的目的。要点如下：本文通过种子半连续聚合法合成了一系列不同亲疏水单体比例的两亲性两性离子共聚物（ASC），对乳液的固含量、单体转化率、平均粒径和zeta电位、耐钙离子稳定性、耐低温稳定性、耐溶剂性和吸水率等基本物化性质进行了测定，得到如下结果：ASC乳液的固含量在28%-35%之间，单体转化率均达到了80%以上，耐钙离子和耐低温稳定性良好，平均粒径和吸水率随着亲水单体的添加量的增大出现先减小后增大的趋势，都在ASC-5（亲水单体：疏水单体=2:1）处出现最小值，分别为155.1 nm和7.84%;利用上述两亲性两性离子共聚物对乙烯-醋酸乙烯共聚物（EVA）薄膜上进行涂覆改性，得到EVA涂覆改性膜（EVA-ASC），利用红外衰减全反射-傅里叶变换（ATR-FTIR）、X射线光电子能谱（XPS）测定了EVA-ASC改性薄膜表面组成，利用静态接触角仪测定了改性薄膜在去离子水中浸泡不同时间的接触角，结果发现EVA-ASC在空气中的接触角在76°-100°之间，亲水性较差，但在水环境中SBMA则表现出优异的与水结合能力，第15天时EVA-ASC-5的接触角为48°，亲水性优异；利用考马斯亮蓝法和耗散型石英晶体微天平（Quartz Crystal Microbalance with Dissipation，QCM-D）法测定了改性薄膜表面的抗蛋白吸附性能，结果发现：与EVA未改性薄膜相比，ECA-ASC改性薄膜的抗吸附性能大幅提升，EVA-ASC-4（亲水单体：疏水单体=1.8:1）的蛋白吸附量为8.63 μg/cm2，减少了92.1%，利用QCM-D法证明了改性薄膜表面的蛋白吸附是可逆吸附；利用苯酚硫酸法对改性薄膜表面的抗多糖吸附能力进行测试，其变化趋势与蛋白吸附实验中变化趋势基本一致，EVA-ASC-4的多糖吸附量为24.09 μg/cm2，与EVA薄膜相比减少了48.1%；以小球藻为藻种，考察了改性薄膜在小球藻培养环境中抗附着性能，结果表明：在小球藻培养液中浸泡培养一周后，EVA薄膜在显微镜观察下看到了明显的微藻附着，而EVA-ASC-4改性薄膜表面只观察到了微量附着，细胞附着数量在第7天时达到1.0875×105 cells/cm2，是EVA薄膜表面细胞数量的一半。本文为实现提高塑料薄膜反应器材料表面抗生物附着性能提供了一条简单、高效的途径。;The closed photobioreactors can be used for microalgae culture, due to its precisely control of various factors (such as temperature, light intensity, etc.). They have advantages including high utilization of light energy and CO2, effective reduction of pollution rate and the evaporation of water, prevention of external intruder, which work together to achieve high-density culture and increase the success rate of microalgae cultivation. Plastic films are used commonly for photobioreactors, for its easy processing and low cost. However, biofouling behaviour is an inevitable problem in the application of plastic film materials for microalgae culture. Algae cells, extracellular polysaccharides, extracellular proteins and other organic and inorganic substances in the algae liquid system adhered to the surface of the films, leading to a decrease in light transmittance of photobioreactors and deterioration of the culture environment. Therefore, in view of the biofouling problem of photobioreactors, the purpose of this paper is to prepare an amphiphilic zwitterionic copolymer coating, which provides a simple and rapid method for surface modification of photobioreactors, and can be applied for industrial large-scale production. The main points are as follows:In this paper, a series of amphiphilic zwitterionic copolymers (ASC) with different proportions of hydrophilic and hydrophobic monomers were synthesized by semi-continuous seeded polymerization process. The solid content, monomer conversion, average particle size, zeta potential, calcium ion resistance, low temperature stability, solvent resistance and water absorption of the ASC were measured, and the following results were obtained: the solid contents of ASC emulsion were between 28% and 35%, and the monomer conversion rates were more than 80%. ASC had good resistance to calcium ions and low temperature resistance. The average particle size and water absorption rate rose down at first and then rose up with the increasing amount of the hydrophilic monomer and the minimum value appears at ASC-5 (when the ratio of hydrophilic and hydrophobic monomers was 2:1), which were 155.1 nm and 7.84%.The ethylene-vinyl acetate copolymer (EVA) films were coated by ASC emulsion and obtained modified EVA films (EVA-ASC). The surface composition of EVA-ASC films were determined by Attenuated Total Reflection-Fourier Transform Infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The contact angle changes of EVA-ASC films, which immersed in deionized water for a week were measured by static contact angle meter. The contact angles of EVA-ASC in air were between 76°-100°, performed poor hydrophilicity. However, SBMA showed good water-binding properties in aquatic environment. EVA-ASC-5 had the contact angle of 48° and showed excellent hydrophilicity.The protein resistance properties of EVA-ASC films were tested by Coomassie Brilliant Blue and Quartz Crystal Microbalance with Dissipation (QCM-D) methods. It was found that the anti-adsorption properties were greatly improved of EVA-ASC films compared with EVA unmodified films. The adsorption of EVA-ASC-4 (when the ratio of hydrophilic and hydrophobic monomers was 1.8:1) had a minimum value of 8.63 μg/cm2, which reduced by 92.1%. The QCM-D method was used to prove that the protein adsorption on the surface of EVA-ASC films were reversible adsorption.The anti-polysaccharide adsorption capacity of EVA-ASC films were measured by phenol-sulfuric acid method. The variation trend was basically the same as that in the protein adsorption experiment. The minimum adsorption value happened at EVA-ASC-4, which was 24.09 μg/cm2 and decreased by 48.1% compared with EVA films. Using Chlorella sp. as a model algae, the anti-biofouling properties of EVA-ASC films in the culture environment of Chlorella sp. were investigated. The results showed that obvious microalgae biofouling behaviour happened in EVA films, which was observed under microscope after immersion for a week in Chlorella sp. culture system. Slightly adhesion behaviour was observed on the surface of the EVA-ASC-4 film and the cell number of Chlorella sp. reached 1.0875×105 cells/cm2 on the 7th day, which was half of the adhesion cell number on EVA films surface.This paper provided a simple and efficient way to improve the anti-biofouling properties of plastic films for photobioreactors.