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Efficient bioflocculation of chlorella vulgaris with a chitosan and walnut protein extract

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journal contribution
posted on 24.05.2021, 23:40 by K Xu, X Zou, A Mouradov, German Spangenberg, W Chang, Y Li
Bioflocculation represents an attractive technology for harvesting microalgae with the potential additive effect of flocculants on the production of added-value chemicals. Chitosan, as a cationic polyelectrolyte, is widely used as a non-toxic, biodegradable bioflocculant for many algal species. The high cost of chitosan makes its large-scale application economically challenging, which triggered research on reducing its amount using co-flocculation with other components. In our study, chitosan alone at a concentration 10 mg/L showed up to an 89% flocculation efficiency for Chlorella vulgaris. Walnut protein extract (WPE) alone showed a modest level (up to 40%) of flocculation efficiency. The presence of WPE increased chitosan’s flocculation efficiency up to 98% at a reduced concentration of chitosan (6 mg/L). Assessment of co-flocculation efficiency at a broad region of pH showed the maximum harvesting efficiency at a neutral pH. Fourier transform infrared spectroscopy, floc size analysis, and microscopy suggested that the dual flocculation with chitosan and walnut protein is a result of the chemical interaction between the components that form a web-like structure, enhancing the bridging and sweeping ability of chitosan. Co-flocculation of chitosan with walnut protein extract, a low-value leftover from walnut oil production, represents an efficient and relatively cheap system for microalgal harvesting.


This project was supported by the National Natural Science Foundation of China (51478045); the Natural Science Foundation of Shaanxi Province (2020JM-236); the Special Fund for Basic Scientific Research of Central Colleges, Chang’an University (300102299703 and 300102299708), and the China Scholarship Council (201906560054).


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