The algal extracellular substances (AESs), mainly excreted in the lag and stationary phases, inhibited the algal growth and culture recycle. The AESs consisted of protein-like substances and saccharides, which restrained the algal lipid and protein biosynthesis. Moreover, the increasing reactive oxygen species and anti-oxidative enzymes caused by AESs led to the oxidative damage and suppressed the cell activity. The AESs affected the cells through two possible ways: one is the AESs adhered to the cell surfaces; another is the cells yielded signal molecules in response to the AESs. Fortunately, the ultrasound degraded the AESs into small molecules, which clearly alleviated the limitation and recovered the algal biomass and metabolism. This study demonstrated that ultrasonication is a promising way to alleviate the AESs, which facilitating the medium recycle for long-term continuous microalgae production.

藻类细胞外物质（AES）主要在滞后期和固定相中排泄，抑制了藻类的生长和培养循环。AES由类蛋白物质和糖类组成，它们抑制了藻类脂质和蛋白质的生物合成。此外，由AES引起的增加的活性氧和抗氧化酶导致氧化损伤并抑制细胞活性。AES通过两种可能的方式影响细胞：一种是AES附着在细胞表面。另一个是细胞响应AES产生信号分子。幸运的是，超声波将AES降解为小分子，从而明显减轻了局限性并恢复了藻类生物量和代谢。这项研究表明，超声处理是缓解AES的一种有前途的方法，