Surface physicochemical properties of selected single and mixed cultures of microalgae and cyanobacteria and their relationship with sedimentation kinetics

Abstract

Background: Microalgae are photosynthetic microorganisms presenting a diversity of biotechnological applications. However, microalgal cultivation systems are not energetically and economically feasible. Possible strategies that can be applied to improve the feasibility of microalgal production include biofouling control in photobioreactors, the use of attached growth systems and bioflocculation. These processes are ruled by surface physicochemical properties. Accordingly, the surface physicochemical properties of Chlorella vulgaris, Pseudokirchneriella subcapitata, Synechocystis salina and Microcystis aeruginosa were determined through contact angle and zeta potential measurements. Additionally, mixed cultures of the selected microorganisms were performed. Sedimentation kinetics of the studied cultures was also evaluated to understand how surface physicochemical properties influence microalgal recovery. Results: All studied microorganisms, except S. salina, presented a hydrophilic surface. The co-culture of S. salina with the other studied microorganisms resulted in a more hydrophobic algal suspension. Regarding zeta potential determinations, all studied suspensions presented a negatively charged surface (approximately -40.8 ± 4.4 mV). Sedimentation experiments have shown that all microalgal suspensions presented low microalgal recovery efficiencies. However, a negative linear relationship between microalgal removal percentage and free energy of hydrophobic interaction was obtained. Conclusions:The evidence of a relationship between microalgal removal percentage and free energy of hydrophobic interaction demonstrates the importance of surface physicochemical properties on microalgal settling. However, the low recovery efficiencies achieved, as well as the high net zeta potential values determined, indicate that another factor to consider in microalgal settling is the ionic strength of the culture medium, which play an important role in suspensions' stability.

The effect of growth phase on the surface properties of three oleaginous microalgae (Botryococcus sp. FACGB-762, Chlorella sp. XJ-445 and Desmodesmus bijugatus XJ-231)

“…Higher values determined for γ s - indicate that the studied microalgae showed a strong electron-donating property. It should be stated that similar results were obtained in previous studies by Ozkan and Berberoglu (2013) and Gonçalves et al (2015) [ 3 , 29 ]. In addition, γ s + values close to zero are in accordance with the Oss et al (2008) model, which predicts almost the non-existence of electron acceptor parameters [ 3 ].…”

Quantitative Criterion to Predict Cell Adhesion by Identifying Dominant Interaction between Microorganisms and Abiotic Surfaces

“…However, it should be noted that, in some applications, the surface characteristics of the abiotic substrata could be affected by the roughness, heterogeneity, and adsorption of molecules. ,, However, the surface characteristics of the cell could be affected by the extracellular polymeric substances pili and flagella , and might change in response to the changes in the culture conditions and different stages of cell cultivation . In some applications, mixed cultivation might exist, thus, the species interactions might also significantly influence the cell adhesion . Although these differences might affect the accuracy of the criterion, the study demonstrated that the criterion was still valuable for the prediction of adhesion in the majority of cases.…”

“…44 In some applications, mixed cultivation might exist, thus, the species interactions might also significantly influence the cell adhesion. 49 Although these differences might affect the accuracy of the criterion, the study demonstrated that the criterion was still valuable for the prediction of adhesion in the majority of cases. Follow-up studies would be conducted to amend the criterion for better applicability.…”

The extracellular polysaccharide determine the physico-chemical surface properties of Microcystis

“…The discrepancy may contribute to the differential occurrence of Microcystis blooms in different seasons. Notably, during the logarithmic phase, the contact angles of Microcystis with solvent were smaller than that of M. aeruginosa LEGE 91344 (less than 90°; Gonçalves et al, 2015 ), and A. variabilis (greater than 90°; Volpe and Siboni, 1997 ; Ozkan and Berberoglu, 2013 ; Hao et al, 2017 ). Compared with other freshwater cyanobacteria, S. salina LEGE 06079, Synechocystis sp., and A. variabilis are all hydrophobic ( Table 1 ).…”