Anand Sanjeev, Singh Diwakar, Avadhanula Mallika, Marka Sowmya
Midwest Dairy Foods Research Center, Dairy Science Dept., South Dakota State Univ., Brookings, SD 57007, U.S.A.
Compr Rev Food Sci Food Saf. 2014 Jan;13(1):18-33. doi: 10.1111/1541-4337.12048.
Membrane fouling is a major operational problem that leads to reduced membrane performance and premature replacement of membranes. Bacterial biofilms developed on reverse osmosis membranes can cause severe flux declines during whey processing. Various types of biological, physical, and chemical factors regulate the formation of biofilms. Extracellular polymeric substances produced by constitutive microflora provide an effective barrier for the embedded cells. Cultural and microscopic techniques also revealed the presence of biofilms with attached bacterial cells on membrane surfaces. Presence of biofilms, despite regular cleaning processes, reflects ineffectiveness of cleaning agents. Cleaning efficiency depends upon factors such as pH of the cleaning agent, temperature, pressure, cleaning agent dose, optimum cleaning time, and cross-flow velocity during cleaning. Among different cleaning agents, surfactants help to prevent bacterial attachment to surfaces by reducing the surface tension of water and interfacial tension between the layers. Enzymes mixed with surfactants and chelating agents can be used to penetrate the biofilm matrix formed by microbes. Recent studies have shown the role of quorum-sensing-based cell-to-cell signaling, which provides communication within bacterial cells to form a mature biofilm, and also the role of applying quorum inhibitors to prevent biofilm formation. Major cleaning applications are also summarized in Table .
膜污染是一个主要的运行问题，会导致膜性能下降以及膜的过早更换。反渗透膜上形成的细菌生物膜会在乳清加工过程中导致通量严重下降。多种生物、物理和化学因素调节生物膜的形成。组成型微生物群产生的胞外聚合物为嵌入的细胞提供了有效的屏障。培养和显微镜技术也揭示了膜表面存在附着细菌细胞的生物膜。尽管有定期的清洗过程，但生物膜的存在反映了清洗剂的无效性。清洗效率取决于清洗剂的pH值、温度、压力、清洗剂剂量、最佳清洗时间以及清洗过程中的错流速度等因素。在不同的清洗剂中，表面活性剂通过降低水的表面张力和层间界面张力来帮助防止细菌附着在表面。与表面活性剂和螯合剂混合的酶可用于穿透微生物形成的生物膜基质。最近的研究表明了基于群体感应的细胞间信号传导的作用，它在细菌细胞内提供通信以形成成熟的生物膜，以及应用群体抑制剂来防止生物膜形成的作用。主要的清洗应用也总结在表中。
