A novel method to harvest microalgae biofilms by interfacial interaction

Abstract

Microalgae biofilm-based culture has the advantages of less water requirement and higher biomass productivity. Generally, microalgae biofilms are collected by mechanical scraping, which easily leads to the damage of substrates and low harvest efficiency. In this work, a novel method to harvest microalgae biofilms by interfacial interactions was proposed and studied. The results indicated that N. oculata and Chlorella sp. biofilms could be peeled off from substrates when the biofilm was slowly immersed into liquids with surface tensions higher than 40 mJ·m−2. By developing a model, we found that when the detachment force of liquid applied onto cells was higher than ~60 × 10−6 mN, microalgae biofilms could be peeled off with efficiency of over 94 %. Although water was convenient to peel microalgae biofilms, the biofilms would break into loose pieces in the water within a short time after peeling. We found that saline was suitable to peel off microalgae biofilms and maintain biofilms with a stable structure. This work can provide valuable insights into developing new methods to harvest microalgae biofilms.