餐厨废油脂制备生物柴油过程中的磁性全细胞催化机制研究

Biodiesel derived from waste cooking oil is deemed to be of significance on solving the energy crisis and controlling environmental pollution. Currently, the conventional chemical method suffers from the problem of high energy consumption and greater discharge amount of wastewater. Moreover, extracellular lipases as biocatalysts require complicated purification, recovery, and immobilization. To settle these problems, whole-cell biocatalysts which could directly use lipase-producing microorganism have been of prime interest in the past decade. However, whole-cell biocatalysts also suffer the problems of separation, low mass transport, poor stability and cell loss. Based on these, this project proposed a new and efficient biodiesel production method from waste cooking oil in a magnetically fluidized bed reactor by using magnetic whole-cell biocatalysts (MWCBs), which are constructed by immobilizing cells into magnetic particles. The research would be performed according to the following steps: 1) to establish the synthesis method of MWCBs, to study the relationship between kinetic/thermodynamic factors and the structure/function of MWCBs; 2) to understanding the structure-function relationship of MWCBs, to study the catalytic mechanisms of MWCBs for enzymatic biodiesel production from waste cooking oil; 3) (i) evaluate the influence of parameters, such as flow rate and temperature, on the reaction efficiency and biodiesel yield; (ii) evaluate the influence of external magnetic field on the catalytic activities and mass transfer in the reacting system. The conclusion reached will enrich the theoretical basis about bioconversion of oils and fats and is of real plenitude to environmental biodiesel production with low cost.

发展餐厨废油脂生物柴油技术对于解决能源危机和治理环境污染有重要意义。目前，常用的酸碱催化法需要克服能耗高、废液量大等缺点，而脂肪酶催化法又存在酶提取工艺复杂、成本高等不足。为解决上述难题，全细胞催化法应运而生，但细胞催化剂稳定性差、细胞易流失限制了其发展。因此，本项目提出将超顺磁效应与细胞固定化技术相结合的方法，制备新型磁性全细胞催化剂（MWCB），并在自制的多级磁流化床反应系统中进行油脂催化反应，以达到油脂高效转化的目的。首先研究Fe3O4制备工艺对其表面性质与磁性能的关联机制，明确MWCB的组成、结构及相关特性对其催化活性的影响规律，然后分析MWCB在酯交换过程中的催化反应机理，探讨流速、温度等因素对生物柴油产率的控制规律，揭示外加磁场对MWCB催化活性和反应体系传质过程的影响机制。项目的完成有望进一步丰富和完善油脂转化基础理论体系，对实现生物柴油产业低成本、环保生产具有指导意义。

发展餐厨废油脂生物柴油技术对于解决能源危机和治理环境污染有重要意义。目前，常用的酸碱催化法需要克服能耗高、废液量大等缺点，而脂肪酶催化法又存在酶提取工艺复杂、成本高等不足。为解决上述难题，本项目提出将超顺磁效应与细胞固定化技术相结合的方法，制备新型磁性全细胞催化剂（MWCB），并在磁流化床反应系统中进行油脂催化反应制备生物柴油。首先通过官能团修饰等手段，提高了Fe3O4粒子的分散性、稳定性和生物相容性，探究了Fe3O4制备工艺对其表面性质与磁性能的关联机制，获得的Fe3O4磁滞回线呈典型的 “S”型，颗粒尺寸约10 nm。明确了MWCB的组成、结构及相关特性对其催化活性的影响规律，制得的催化剂直径约4 mm，颗粒表面呈粗糙的多孔结构，饱和磁化强度约20 emu/g，具有超顺磁性，易受外加磁场控制。分析了MWCB在酯交换过程中的催化反应机理，探讨了Fe3O4磁性粒子对催化剂催化活性的影响规律。揭示了催化剂用量、流速、温度等因素对生物柴油产率的控制规律，当催化剂用量为10 wt.%, 流速为 17 mL/min, 磁场强度为 132 Oe，温度35 °C，生物柴油产率可达到89.0±0.6%。通过MWCB重复利用实验，研究了细胞流失程度、催化剂表面物化性质等参数的变化情况，探讨了外加磁场对MWCB催化活性和反应体系传质过程的影响规律。随着磁场强度的逐渐增加，产率不断增加。当磁场强度达到一定数值后，产率逐渐下降。5次循环利用后，MWCB的催化活性基本保持不变，10次循环利用后仍能保持82.5%的生物柴油产率，同步开展的无磁性催化剂对照组产率下降到64.0%。以上研究成果为全细胞催化技术的进一步成熟和未来工业化应用提供基础数据，对实现生物柴油产业低成本、环保生产具有指导意义。