School of Civil Engineering, Guangzhou University, Guangzhou, 510006, PR China; State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150090, PR China.
School of Environment, Harbin Institute of Technology, Harbin, 150090, PR China; State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150090, PR China.
Chemosphere. 2022 Sep;302:134841. doi: 10.1016/j.chemosphere.2022.134841. Epub 2022 May 4.
Lysozyme hydrolysis can accelerate waste-activated sludge (WAS) solubilisation, which can significantly shorten the process and promote the efficiency of anaerobic digestion. This study investigated the impact of divalent cations on lysozyme-induced solubilisation of WAS. The performance of lysozyme pretreatment was dramatically inhibited by Mg and Ca. Compared to the control group, the amount of net SCOD, protein, and polysaccharides released to the supernatant were reduced by 36.6%, 44.7%, and 35.8%, respectively, in the presence of divalent cations. The extracellular polymeric substance (EPS) matrix became tightly bound, resulting in fewer proteins and polysaccharides being extracted from loosely-bound EPS (LB-EPS) with divalent cations, which was detrimental to the solubilisation of WAS. Divalent cations decreased the surface electronegativity of sludge particles and prolonged the adsorption of lysozymes by sludge flocs. More than 16.6% of total lysozymes remained in the liquid phase of WAS after 240 min Mg and Ca strengthened the binding among proteins and polysaccharides and promoted the intermolecular cross-linking of polysaccharides. The EPS matrix formed a dense spatial reticular structure that blocked the transfer of lysozymes from the EPS matrix to the pellet. As a result, the lysozymes accumulated in LB-EPS rather than hydrolysing the microorganism's cell wall. This study provides a new perspective on the restriction of WAS pretreatment with lysozymes and optimises the method of lysozyme-induced solubilisation of WAS.
溶菌酶水解可以加速剩余活性污泥（WAS）的溶解，从而显著缩短处理过程并提高厌氧消化的效率。本研究探讨了二价阳离子对溶菌酶诱导 WAS 溶解的影响。Mg 和 Ca 显著抑制了溶菌酶预处理的性能。与对照组相比，在存在二价阳离子的情况下，上清液中净 SCOD、蛋白质和多糖的释放量分别减少了 36.6%、44.7%和 35.8%。细胞外聚合物（EPS）基质变得紧密结合，导致更多的蛋白质和多糖从松散结合的 EPS（LB-EPS）中被提取出来，这对 WAS 的溶解不利。二价阳离子降低了污泥颗粒的表面电负性，并延长了污泥絮体对溶菌酶的吸附。在 240 分钟后，超过 16.6%的总溶菌酶仍留在 WAS 的液相中。Mg 和 Ca 增强了蛋白质和多糖之间的结合，并促进了多糖的分子间交联。EPS 基质形成了致密的空间网状结构，阻止了溶菌酶从 EPS 基质向颗粒的转移。结果，溶菌酶在 LB-EPS 中积累，而不是水解微生物细胞壁。本研究为溶菌酶预处理 WAS 的限制提供了新的视角，并优化了溶菌酶诱导 WAS 溶解的方法。
