Effects of organic carbon sources on algal biofilm formation and insight into mechanism

Algal biofilm cultivation has great potential in producing high biomass yields and reducing harvesting costs. Organic carbon sources can promote algal growth in suspended cultivation, but their effects on algal biofilm formation and related mechanism have rarely been studied. In this study, we determined the most suitable organic carbon source and its concentration for the formation of algal biofilm, and structure/composition characteristics of extracellular polymeric substances (EPS) from algal biofilm. The results showed that the glycerol concentration of 1000 mg C L-1 in algal biofilm system was the most suitable condition to contribute to the biofilm formation and enhance attached biomass among the treatments. The algal biofilm at the glycerol concentration excreted the contents of relatively high EPS and its protein (EPS-PN), which were beneficial to forming the biofilm. The high EPS-PN content was mainly attributed to the increased hydrophobic proline and alanine contents but declined hydrophilic glutamic acid for improving algal biofilm formation. These findings enhanced our understanding of the formation mechanism of algal biofilm under the organic carbon source condition and provided the theoretical basis for algal biofilm formation.