Attachment Behavior Of Chlamydomonas Microsphaera In Bioelectrochemical Systems

As,Microalgae,one of the photosynthetic microorganisms,have been widely applied in bioelectrochemical systems due to its high nitrogen and phosphorus utilization,photosynthetic efficiency and fast proliferation.However,the behavior process and mechanistic understanding of microalgae adhesion onto electrode is still sketchy.Therefore,we use Chlamydomonas microsphaera as model microalgae,and try to analyze how environmental factors affect the attachment of microalgae..Based on the exploration ofcell motility and EPS secretion in microalgae attachment,we can provide theoretical and data support for microalgae collection and bioelectrochemical system improvement.In the model bioelectrochemical systems,the effects of nutrient concentration,applied voltagewere studied.The main conclusions are as follows:Firstly,changes in nutritional conditions affected on the attachment of Chlamydomonas microsphaera.As the concentration of nitrogen and phosphorus increasing,the attachment of Chlamydomonas microsphaera rised first to a peak of15.74% and 16.59% at 1/10 N and 1/10 P dilution,repectively.At the same time,the cell velocity of Chlamydomonas microsphaera increased from 13.94 μm/s at the initial moment to 27.56 μm/s.The analysis of extracellular polymers secreted correlated tightly with the attachment of microalgae.Furthermore,nutritional conditions changed the Zeta potential of the solution,with the values increased from the initial-20.50 m V to-15.20 m V,indicating that the repulsion between microalgal cells decreased and tended to aggregate at this time.According to the principal component analysis,the velocity of movement of microalgae,the amount of extracellular protein secretion and the Zeta potential of the solution all promote the adhesion of Chlamydomonas microsphaera.Secondly,without nutrient limitation,the applied voltage affected the adhesion of Chlamydomonas microsphaera.With the increase of the applied voltage,the attachment rate of Chlamydomonas microsphaerathe increased significantly,and reached a peak of 19.67% at 0.4 V.At this time,the stimulation of the applied voltage accelerated the movement of the microalgaejumping from 23.99 μm/s to 54.82 μm/s,thereby promoting the adhesion of the microalgae.The proper applied voltage will also promote the secretion of microalgae EPS,which helps the adhesion ofmicroalgae.Further increasing the applied voltage can inhibit tthe velocity of movement of microalgae and the secretion of EPS,thereby inhibiting the attachment behavior of microalgae.According to the principal component analysis of the above components,the influence of each factor on the adhesion of microalgae is as follows:extracellular protein> polysaccharide> velocity of movement.Thirdly,the effect of gradient applied voltage on microalgae attachment behavior under limiting nutrient conditions shows that,the adhesion rate of microalgae attached with a peak value of 20.65% at 0.4 V,which was remarkably higher than that from nutrient sufficient tests..Meanwhile,the microalgae enhanced both its EPS secretion ability and velocity of movement,reaching a maximum of 68.55 μm/s,either of them higher than the velocity of movement of the microalgae under nutrient sufficient tests.Comparisively,the effects of applied voltage on nutrient adsorption capacity of carbon felt,velocity of movement and EPS secretion capacity of microalgae showed similar impact on cell attachment under restrictive nutrient conditions,whereas the nutrition was sufficient,and the results of principal component analysis were similar.It indicated that the double restriction condition was more favorable to the attachment of microalgae,where the applied voltage was the dominant factor.