泡沫分离-渗透汽化耦合发酵连续生产表面活性剂的规律研究

Microbial enhanced oil recovery (MEOR) is the most promising and environment friendly oil recovery technique. Lower oil-water interfical tension reduced by biosurfactant is the main oil-displacement mechanism of MEOR，however, high production cost and low productivity are the main factors restricting the development and application of biosurfactant. It is estimated that the cost of biosurfactant separation is about 60% of the total cost of production. To reduce biosurfactant separation cost and relieve metabolite inhibition on microorganism, foam fractionation and pervaporation are combined to integrate with biosurfactant fermentation in the continuous and closed circulating fermentation mode. Effect laws of in situ removal of biosurfactant and metabolic by-products on microbial growth and metabolism will be investigated. Moreover, the kinetic mathematical model of fermentation-separation coupling will be constructed, and the inherent relationship between biosurfactant productivity and affecting factors will be investigated, aiming to reveal the crucial factors affecting biosurfactant production and provide scientific guide for biosurfactant producing and regulating.

微生物采油是三次采油中最具前景、绿色环保的原油采收技术。表面活性剂降低油水界面张力是微生物采油技术的主要机理，然而高成本低产率严重制约了生物表面活性剂的发展和应用。据估计，生物表面活性剂的产物分离成本高达生产总成本的60%左右。为实现产物浓缩以降低后续的分离成本,并同时降低代谢物对于微生物细胞的抑制作用以提高表面活性剂产量，本项目首次结合泡沫分离和渗透汽化分离技术，采用连续封闭循环发酵模式生产表面活性剂；研究产物和副产物原位分离对微生物生长代谢的影响规律；并建立系统发酵-分离的耦合动力学模型，揭示表面活性剂产量与各影响因素间的内在关系，确定影响表面活性剂生产的关键控制因素，为微生物采油中表面活性剂的生产和调控提供指导。

生物表面活性剂应用十分广泛，但生产效率低下且分离成本高。为了减轻产物抑制和降低分离成本，本研究在表面活性剂发酵系统中引入泡沫分离和渗透汽化。采用自行筛选的铜绿假单胞菌，对其适用碳源、氮源和初始pH进行优化后，将其用于发酵制备表面活性剂，经鉴定，所制备的表面活性剂属于鼠李糖脂类同系物的混合物，并且在温度20-100℃，pH6-12，盐度2-20%范围内具有很好的表界面稳定性。将泡沫分离-发酵耦合生产鼠李糖脂，总产量达到3.574g/L，是分批发酵最大产量的2.7倍。且发酵时长约为批发酵的2倍。对菌株进行紫外诱变，能将鼠李糖脂产量进一步提高到4.744g/L。而且经泡沫分离，泡沫液中鼠李糖脂浓度均超过10g/L,且回收率可达到72.89%，表明生物表面活性剂可以被有效的分离和浓缩。研究发现伴随着泡沫分离有细胞的夹带损失，以活性炭、PUF、玉米芯为载体进行固定化发酵，证明固定化能固定细胞并且强化发酵。将渗透汽化-发酵耦合生产鼠李糖脂，耦合发酵的时长为对照组的1.9倍，鼠李糖脂产量为2.588g/L.，是未耦合发酵组的1.53倍，表明渗透汽化对副产物的分离能有效降低其对细胞的抑制。将鼠李糖脂应用于钻井油泥清洗，经响应面优化，获得最佳的清洗条件为：鼠李糖脂浓度325mg/L，pH=10.70，温度63℃，转速450r/min，时间35min，液固比5:1，其油泥的脱油率高达70.92%，使油泥的含油量从10.18%下降到2.96%。