POLYSACCHARIDE RELEASE BY APHANOTHECE HALOPHYTICA INHIBITS CYANOBACTERIA/CLAY FLOCCULATION¹

Abstract

Many microalgae release polysaccharides, but the effects of the polysaccharides on mutual flocculation of microalgae and clay in aquatic environments have not been well studied. Aphanothece halophytica Frémy is a bloom-forming cyanobacterium in salterns and can release large amounts of polysaccharide (AH-RPS). In the present study, we investigated the effect of AH-RPS on mutual flocculation of cyanobacterium and clay and further explored the mechanisms by which AH-RPS affected mutual flocculation. We determined that AH-RPS possessed clay-dispersing activity as defined as the ability to inhibit the flocculation and sedimentation of clay suspensions in water. Supplementation of AH-RPS in cyanobacterial cell suspensions and in the culture media containing the same kaolin clay concentration dose dependently decreased flocculation of cyanobacterial cells and increased clay-dispersing activity. These findings indicate that the clay-dispersing activity of AH-RPS was related to its inhibitory effect on mutual flocculation of cyanobacterial cells and clay particles. Moreover, the clay-dispersing activity of AH-RPS was stable from pH 3 to pH 10 and was increased by adding NaCl, MgCl 2 , CaCl 2 , or low concentrations of KCl (up to 0.4 M). Taken together, our data suggest that AH-RPS might maintain its clay-dispersing activity and inhibit mutual flocculation of microalgae and suspended clay in saltern brine.

Flocculating activities of polysaccharides released from the marine mat-forming cyanobacteria Microcoleus and Lyngbya

“…might facilitate the survival and growth of the benthic cyanobacteria in the saltern. By contrast, in our previous report, Aphanothece halophytica, a cyanobacterium forming surface bloom in the saltern, was found to produce RPS with claydispersing activity, which inhibits mutual flocculation of the cyanobacterium and clay particles and may prevent the sedimentation of the cyanobacterium in the brine (Chen et al 2010 …”

Effects of Synthetic Copolymer and Algae-Exopolysaccharides for the Sedimentation and Dehydration of Organic Waste

“…When ApEPS was included with the 6% kaolin suspension, the decrease of interfacial sedimentation was the same to that of water ( Figure 1A, open triangle). Li et al (2010) reported that ApEPS has clay-dispersing activity which is stable at the pH range 3-10 and inhibit flocculation. Our data are consistent with the results of Li et al (2010).…”

“…The other is extracellular polysaccharide from a halotolerant cyanobacterium Aphanothece halophytica (ApEPS). Previously, Chen et al (2010) [5] reported that A. halophytica often forms algal blooms in salterns in summer of China and releases large amounts of polysaccharide. ApEPS was shown to have a unique property of claydispersing activity which was stable during the pH range 3.0-10.0 (Li et al 2001;Chen et al 2010) [5,6].…”

“…Previously, Chen et al (2010) [5] reported that A. halophytica often forms algal blooms in salterns in summer of China and releases large amounts of polysaccharide. ApEPS was shown to have a unique property of claydispersing activity which was stable during the pH range 3.0-10.0 (Li et al 2001;Chen et al 2010) [5,6]. Our A. halophytica was isolated from Dead Sea and can grow at high external NaCl concentrations up to 3 M and at alkaline pH 11 (Takabe et al 1988;Laloknam et al 2006) [7,8].…”

Biodesalination: A Case Study for Applications of Photosynthetic Bacteria in Water Treatment

“…The aggregation of cells within a biofilm is known to be aided by the favorable interactions between physicochemistry of the cell surface and the EPS (Karunakaran and Biggs, 2011). However, when using coagulants, especially polyvalent metal salts, to induce aggregation, EPSs of Aphanothece halophytica and Microcystis aeruginosa increase coagulant demand (Takaara et al, 2007(Takaara et al, , 2010Chen et al, 2009Chen et al, , 2010Henderson et al, 2010). On the other hand, the presence of EPSs, without the use of metal salts, can induce aggregation.…”