Effect of nutrient starvation on nutrient uptake and extracellular polymeric substance for microalgae cultivation and separation

Abstract

A B S T R A C TThe purpose of the present study is to investigate the effects of nutrient starvation of microalgae on its nitrogen (N) and phosphorus (P) uptake, characteristics of extracellular polymeric substances (EPS), and algal sedimentation. An experiment was carried out by starving the wastewater-tolerant microalgae Chlorella sp. ADE4. The algal cultivation was put under various conditions of nutrient starvation in order to enhance nutrient removal and algal cell separation. The experimental results showed that 40 h of nutrient starvation prior to the cultivation did affect nutrient removal of Chlorella sp. ADE4. When using synthetic wastewater, the N-starved algae was the most effective in removing 82% of N in 48 h and 92% of P in 24 h. However, the starvation conditions did not cause noticeable removal improvement when microalgae were tested with real wastewater effluent. N and P removal efficiencies of 57 and 100%, respectively, were achieved in 48 h in real wastewater effluent. The lower N removal efficiency was caused by P limitation in the real sewage effluent. EPS were analyzed to evaluate if they play a role in algal cell agglomeration and subsequent microalgal separation. Carbohydrates and protein were indicated as major components in soluble and bound EPS. It was found that starvation of microalgae for 40 h could induce higher EPS production. Interestingly, the N-starved microalgae contained a large protein fraction in their EPS and low N content in their biomass. However, a significant correlation between EPS content and sedimentation efficiency was not observed in this study.

Evaluation of the effect of agitation speed on the growth and high‐value LC‐PUFA formation of Porphyridium cruentum based on basic rheological analysis

“…Meanwhile, higher biomass concentrations led to greater EPS secretion and large amounts of EPS were formed within a solid biofilm around each cell, 47 which was beneficial to capture nutrients for cells from the culture medium. 32 Consequently, the nutrients, especially N and P, were assimilated more easily under maximum biomass or EPS production (150 and 300 rpm), as shown in Fig. 2(A,B).…”

“…Isolation and extraction of EPS were performed according to the method of Boonchai et al 32 Briefly, a certain volume of microalgae broth was centrifuged at 10000 rpm (11 962 × g) for 15 min at 4 ∘ C and washed with distilled water for thrice. The washing water and supernatant were collected and filtered for solution EPS.…”

Microbial Extracellular Polymeric Substances: Ecological Function and Impact on Soil Aggregation

“…Initially, EPS were used as an abbreviation for “extracellular polysaccharides,” “exopolymers,” or “exopolysaccharides.” EPS can be produced by bacteria, cyanobacteria, microalgae ( Parikh and Madamwar, 2006 ; Boonchai et al, 2014 ), yeasts ( Pavlova and Grigorova, 1999 ), fungi ( Hwang et al, 2004 ; Elisashvili et al, 2009 ), and protists ( Jain et al, 2005 ; Lee Chang et al, 2014 ). EPS are biosynthetic polymers composed mainly of polysaccharides, structural proteins, enzymes, nucleic acids, lipids, and other compounds such as humic acids ( Wingender et al, 1999a , b ; Flemming and Wingender, 2010 ).…”

Benthic hotspots in the pelagic zone: Light and phosphate availability alter aggregates of microalgae and suspended particles in a shallow turbid lake

“…Extracellular polymeric substances (EPS), including polysaccharides, proteins, glycoproteins, glycolipids, and extracellular DNA (Flemming et al ), can enhance the formation of aggregates (Kiørboe et al ; Passow et al ; Chow et al ). Various marine and freshwater microalgae have been found to increase the production of EPS under nutrient limitation (Guerrini et al ; Magaletti et al ; Urbani et al ; Abdullahi et al ; Boonchai et al ). In general, this is interpreted as the release of excess photosynthate when the production of carbohydrates by microalgae exceeds the consumption of carbohydrates by microalgae due to nutrient‐limited growth requirements (Fogg ; Wood and Van Valen ).…”