Abstract An integrated membrane process for green sugarcane juice purification is promising but its application is limited by serious membrane fouling, especially biofouling. For the first time, this work investigated the effect of pH, temperature and sugar concentration on the growth of L. mesenteroides subsp. dextranicum, which is a main bacterium consisting in cane juice leading to serious biofouling during decoloration of cane juice by nanofiltration (NF). It was found that acidic pH, lower temperature and sucrose concentration increased bacterial growth, and more dextran was produced at faster bacterial growth, resulting in severer fouling during membrane filtration. Biofouling behavior and enzymatic/chemical cleaning efficiency were compared in dead-end and cross-flow filtrations of synthetic solution or cane juice (in virtue of membrane fouling resistance, permeate flux decline, permeability recovery, surface morphology and chemistry characterizations), showing that dextran was not only the main foulant but also the adhesive among the other foulants as well as between foulants and membrane. Moreover, a compact dextran layer would cover or enwrap other foulants such as protein, pigments, cell debris and bacteria, protecting them from chemical cleaning. Therefore, the dextranase degradation followed by an alkaline cleaning with surfactant was the most effective strategy to remove the biofouling layer and recover the membrane permeability. This work not only elucidated the fouling mechanisms during decoloration of cane juice by NF, but also offered an effective cleaning strategy for biofouling control in the practical application.

中文翻译：

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纳滤膜精制甘蔗汁中的生物污垢：污垢机理与清洗

摘要 一种用于绿色甘蔗汁纯化的集成膜工艺具有前景，但其应用受到严重的膜污染，尤其是生物污染的限制。这项工作首次研究了 pH、温度和糖浓度对 L. mesenteroides subsp. 生长的影响。葡聚糖是甘蔗汁中的主要细菌，在通过纳滤 (NF) 对甘蔗汁进行脱色过程中会导致严重的生物污染。结果发现，酸性 pH 值、较低的温度和蔗糖浓度会增加细菌的生长，并且在细菌生长较快的情况下会产生更多的葡聚糖，导致膜过滤过程中更严重的污染。在合成溶液或甘蔗汁的死端和错流过滤中比较了生物污染行为和酶/化学清洁效率（凭借膜污染阻力、渗透通量下降、渗透率恢复、表面形态和化学特征），表明葡聚糖不仅是主要污垢，而且是其他污垢之间以及污垢与膜之间的粘合剂。此外，紧密的葡聚糖层将覆盖或包裹其他污染物，如蛋白质、色素、细胞碎片和细菌，保护它们免受化学清洗。因此，葡聚糖酶降解后用表面活性剂进行碱性清洗是去除生物污垢层和恢复膜渗透性的最有效策略。