How myristyltrimethylammonium bromide enhances biomass harvesting and pigments extraction from Synechocystis sp. PCC 6803

Effect of surfactant's charge properties on behavior, physiology, and biochemistry and the release of microcystins of Microcystis aeruginosa

Surfactant pollution is escalatitheng in eutrophic waters, but the effect of surfactant charge properties on the physiological and biochemical properties of toxin-producing microalgae remains inadequately explored. To address this gap, this study explores the effects and mechanisms of three common surfactants-cetyltrimethylammonium bromide (CTAB, cationic), sodium dodecyl sulfate (SDS, anionic), and Triton X-100 (nonionic)-found in surface waters, on the agglomeration behavior, physiological indicators, and Microcystin-LR (MC-LR) release of Microcystis aeruginosa (M. aeruginosa) by using UV-visible spectroscope, Malvern Zetasizer, fluorescence spectrometer, etc. Results suggest that charge properties significantly affect cyanobacterial aggregation and cellular metabolism. The CTAB-treated group demonstrates a ∼5.74 and ∼9.74 times higher aggregation effect compared to Triton X-100 and SDS (300 mg/L for 180 min) due to strong electrostatic attraction. Triton X-100 outperforms CTAB and SDS in polysaccharide extraction, attributed to its higher water solubility and lower critical micelle concentration. CTAB stimulates cyanobacteria to secrete proteins, xanthohumic acid, and humic acids to maintain normal physiological cells. Additionally, the results of SEM and ion content showed that CTAB damages the cell membrane, resulting in a ∼90% increase in the release of intracellular MC-LR without cell disintegration. Ionic analyses confirm that all three surfactants alter cell membrane permeability and disrupt ionic metabolic pathways in microalgae. This study highlights the relationship between the surface charge properties of typical surfactants and the dispersion/agglomeration behavior of cyanobacteria. It provides insights into the impact mechanism of exogenous surfactants on toxic algae production in eutrophic water bodies, offering theoretical references for managing surfactant pollution and treating algae blooms.

Differentiation and quantification of extracellular polymeric substances from microalgae and bacteria in the mixed culture

Extracellular polymeric substances (EPS) play significant roles in the formation, function, and interactions of microalgal-bacteria consortia. Understanding the key roles of EPS depends on reliable extraction and quantification methods, but differentiating of EPS from microalgae versus bacteria is challenging. In this work, cation exchange resin (CER) and thermal treatments were applied for total EPS extraction from microalgal-bacteria mixed culture (MBMC), flow cytometry combined with SYTOX Green staining was applied to evaluate cell disruption during EPS extraction, and auto-fluorescence-based cell sorting (AFCS) was used to separate microalgae and bacteria in the MBMC. Thermal extraction achieved much higher EPS yield than CER, but higher temperature and longer time reduced cell activity and disrupted the cells. The highest EPS yield with minimal loss of cell activity and cell disruption was achieved using thermal extraction at 55℃ for 30 min, and this protocol gave good results for MBMC with different microalgae:bacteria (M:B) mass ratios. AFCS combined with thermal treatment achieved the most-efficient biomass differentiation and low EPS loss (<4.5 %) for the entire range of M:B ratios. EPS concentrations in bacteria were larger than in microalgae: 42.8 ± 0.4 mg COD/g TSS versus 9.19 ± 0.38 mg COD/g TSS. These findings document sensitive and accurate methods to extract and quantify EPS from microalgal-bacteria aggregates.

A rapid, efficient and eco-friendly approach for simultaneous biomass harvesting and bioproducts extraction from microalgae: Dual flocculation between cationic surfactants and bio-polymer

Microalgal biomass harvesting and cell disruption are the main bottlenecks for downstream processing of microalgae such as high-value bioproducts extraction and biofuels production. In this study, we evaluated the performance of dual flocculation between cationic surfactants and bio-polymer of chitosan for simultaneous biomass harvesting and bioproducts extraction from Chlorella sorokiniana microalgae. First, the effects of individual natural flocculants of chitosan and two cationic surfactants: cetyltrimethylammonium bromide (CTAB) and dodecyltrimethylammonium bromide (DTAB) on biomass harvesting were studied. Next, the synergistic effect of dual flocculation between the cationic surfactants and chitosan on harvesting efficiency, time and flocculant dosage was investigated. Finally, we evaluated the potential of high value bioproducts extraction from microalgae after the individual and dual flocculation processes. Zeta potential analysis and microscopic images were employed to achieve mechanistic understanding. Maximum biomass harvesting efficiencies of 85 %, 88 % and 78 % were achieved using individual flocculants of chitosan, CTAB and DTAB, under their optimum dosages of 100, 400 and 4000 mg/L, respectively. A significant synergistic effect of dual flocculation between chitosan (C) and cationic surfactants on biomass harvesting efficiency (CTAB-C: 99 % and DTAB-C: 97 %), settling time (CTAB-C: 2 min and DTAB-C: 5 min) and optimum dosage of surfactants (CTAB-C: 100 mg/L and DTAB-C: 1000 mg/L) was observed. The synergistic effect was associated with multiple flocculation mechanisms of charge neutralization and bridging induced by cationic surfactants and chitosan, respectively. Furthermore, bioproducts recovery efficiencies of 12 %, 25 % and 15 % of cell dry weight were achieved for protein, carbohydrate and lipid, respectively by using dual flocculation of CTAB surfactant and chitosan at much lower dosage of 100 mg/L.

Recovery of polymeric substances from excess sludge: Surfactant-enhanced ultrasonic extraction and properties analysis

The recovery of polymeric substances from excess sludge is gaining significant research interest in future wastewater treatment technologies. We present a surfactant-enhanced ultrasonic method to extract mixed polymeric substances with typical functional groups from excess sludge. Four potential reasons were revealed for the higher efficiency upon ultrasonication with surfactant: low surface tension, damage of non-covalent bonds between extracellular polymeric substances and cells, enhanced dissolution of polymeric substances, and release of intracellular polymeric substances caused by cell lysis. The increase in extraction efficiency after the addition of cetyltrimethylammonium bromide and sodium dodecyl sulfate reached the maximum of 76.5% and 53.1%, respectively. The contents of polysaccharides, proteins, and DNA were approximately 50% of the total polymeric substances, and the content of protein was higher than that of polysaccharide; the concentration change of the surfactant had a minimal effect on these contents. For the polymeric substances extracted via ultrasonication with surfactant, the size was smaller than that for the non-surfactant extraction; moreover, the contents of metals decreased significantly (Al: 0.18% → 0%; Na: 0.15% → 0%; Ca: 0.24% → 0.11%), which was probably caused by the interaction between the surfactant and metal ions in the excess sludge. The surfactant had a negligible effect on the properties of polymeric substances, adsorption capacity of polymeric substances for heavy metal ions, and dewatering performance of sludge. The recycled polymeric substances may be used as a substitute for commercial adsorbents of heavy metal ions. Thus, the obtained results provide further insight into the recovery of polymeric substances from excess sludge via the surfactant-enhanced ultrasonic method.

Simultaneous harvesting and extracellular polymeric substances extrusion of microalgae using surfactant: Promoting surfactant-assisted flocculation through pH adjustment

In this research, the use of four different types of surfactants on biomass harvesting and extracellular polymeric substances (EPS) extrusion of Chlorella sorokiniana sp was investigated. The synergy between cationic surfactants and pH was tested to improve flocculation efficiency through the combined mechanism of charge neutralization, bridging and sweeping. Zeta potential and microscopic images were used to gain mechanistic understanding. The harvesting efficacy correlated positively with the biomass zeta potential and the surfactants alkyl-chain length; i.e., CTAB (88%) > DTAB (66%) > triton X-100 (41%) > SDS (11%). When the pH increased from 8 to 12, the harvesting efficiency was improved 12% and 39% for CTAB and DTAB, respectively. More interestingly, pH adjustment dramatically reduced the optimal dosages of CTAB and DTAB from 400 to 50 and 1000 to 300 mg/L, respectively. All selected surfactants could successfully release high value components of EPS such as protein and polysaccharide.

Self-Assembled Quaternary Ammonium-Containing Comb-Like Polyelectrolytes for the Hydrolysis of Organophosphorous Esters: Effect of Head Groups and Counter-Ions

The aim of this work was to increase the efficiency of catalytic systems for the hydrolytic cleavage of 4-nitrophenyl esters of phosphonic acids. Quaternary ammonium-containing comb-like polyelectrolytes («polymerized micelles») with ester cleavable fragments and a low aggregation threshold were used as catalysts. The synthesis of poly(11-acryloyloxyundecylammonium) surfactants with different counterions (Br^- , NO₃ ^- , CH₃ C₆ H₄ SO₃ ^- ) and head groups was realized by micellar free-radical polymerization. Molecular weight, critical association concentration, particle sizes and solubilization properties toward Orange OT were determined. Self-assemblies organized by poly(11-acryloyloxyundecyltrimethyl ammonium) bromide successfully catalyze the hydrolysis of 4-nitrophenyl butylchloromethylphosphonate up to two orders of magnitude compared to aqueous alkaline hydrolysis. The development of these catalysts is promising for industrial applications and organophosphorus compound detoxification.

Revealing the role of adsorption in ciprofloxacin and sulfadiazine elimination routes in microalgae

Pharmaceutical and Personal Care Products (PPCPs) removal coupling with bioenergy production by microalgae has attracted growing attention. However, the biological interactions between PPCPs and microalgae are unclear during microalgal biosorption and biodegradation of PPCPs. In this study, an optimal ciprofloxacin (CIP) and sulfadiazine (SDZ) removal efficiency were achieved 100% and 54.53% with carbohydrate productivity of >1000 mg L^-1 d^-1 by Chlamydomonas sp. Tai-03, respectively. The elimination routes indicated that CIP removal was mainly achieved by biodegradation (65.05%) whereas SDZ was mainly removed by photolysis (35.60%). The visualization evidence of microscopic imaging Raman spectrometer supported the favorable biosorption of CIP due to its positive charge (+10.20 mV). Meanwhile, the tendency for gradual reduction of CIP in extracellular polymeric substances (EPS) indicated that suspended microalgal cell facilitated CIP uptake and biodegradation. Furthermore, photolysis and biodegradation pathways were thoroughly analyzed to demonstrate that intermediates were less toxic and had no adverse effect on the subsequent ethanol conversion. This study provides valuable information for the development of a novel microalgal PPCPs removal. These findings reveal the possible biological mechanisms of biosorption and biodegradation of PPCPs in microalgae, which could further enhance the feasibility of microalgal applications for simultaneous PPCPs remediation and alternative energy production.

Municipal sludge dewatering properties and heavy metal distribution: Effects of surfactant and hydrothermal treatment

Extracellular polymeric substances (EPS) play an important role in reducing moisture content and removing heavy metals from municipal sludge. In this study, cetyl trimethyl ammonium bromide (CTAB) and primary alcohol ethoxylate (AEO₉) were used to prepare complex surfactants. Municipal sludge was treated with mixed surfactants and hydrothermal treatment (HTT) to test the sludge dewatering and heavy metal adsorption performance of EPS treated with varying proportions and contents of surfactants. The results showed that EPS with different proportions had different adsorption capacities for major heavy metals in sludge was 20.48%-29.82%. The adsorption capacity of EPS on heavy metals is significantly positively correlated with protein content (R² = 0.9266, P = .00). There is no significant correlation between polysaccharides (R² = 0.0092, P = .00) and nucleic acids (R² = 0.0638, P = .00) and heavy metal adsorption capacity. Combined treatment of 10% CTAB, 15% AEO₉, and HTT produced the minimal bound water content in treated sludge, zeta potential increased by 49.2 mV and sludge specific resistance is only 0.66% of the raw sludge.

Use of microalgae based technology for the removal of antibiotics from wastewater: A review

The antibiotic resistance induced by the release of antibiotics to the environment has urged research towards developing effective technologies for antibiotic removal from wastewater. Traditional technologies such as activated sludge processes are not effective for antibiotic removal. Recently, microalgae-based technology has been explored as a potential alternative for the treatment of wastewater containing antibiotics by adsorption, accumulation, biodegradation, photodegradation, and hydrolysis. In this review, the toxicities of antibiotics on microalgae, the mechanisms of antibiotic removal by microalgae, and the integration of microalgae with other technologies such as ultraviolet irradiation (photocatalysis), advanced oxidation, and complementary microorganism degradation for antibiotic removal were discussed. The limitations of current microalgae-based technology and future research needs were also discussed.

Promoting waste activated sludge reduction by linear alkylbenzene sulfonates: Surfactant dose control extracellular polymeric substances solubilization and microbial community succession

Short-time aerobic digestion (STAD) was proved to promote the reduction of waste activated sludge (WAS). This study systematically disclosed the influential characteristics and mechanisms of linear alkylbenzene sulfonates (LAS) dosage on the reduction of WAS in STAD system. Flow cytometer (FC) combined with SYTOX Green (SG) dye was used to differentiate extracellular polymeric substances (EPS) release and cell lysis of WAS during STAD process. LAS lower than 0.10 g/g total suspended solids (TSS) brought about EPS solubilization and the decrease of sludge floc size, and the accumulated soluble microbial products (SMP) could be biodegraded by heterotrophs. Moreover, the activity of microorganisms (denoted as specific oxygen uptake rate (SOUR)) and proportion of bacteria functional for LAS and SMP biodegradation dramatically increased, leading to a high LAS biodegradation rate (k_LAS) and increased WAS biodegradation rate (k_{COD, WAS}). Even more LAS (> 0.10 g/g TSS) caused cell lysis, leading to the decreased k_TCOD and k_LAS, and therefore inhibit the reduction of WAS. High WAS reduction and LAS biodegradation rate were achieved at the LAS dosage of 0.10 g/g TSS in STAD system. This study lays the foundation for improving WAS reduction by optimizing surfactant dose in STAD system.

Simultaneously enhanced biopolymers production and sludge dewaterability of waste activated sludge by synergetic integration process of short-time aerobic digestion with cocoamidopropyl betaine and calcium oxide

Waste activated sludge (WAS) has seriously threatened the environment safety and the public health due to its rapid growth and complex components. Simultaneously enhanced the biopolymers production and the sludge dewaterability of WAS were investigated by synergetic integration process of the short-time aerobic digestion (STAD) with cocoamidopropyl betaine (CAPB) and calcium oxide (CaO). STAD could improve the biopolymers production by biosynthesis. CAPB could further significantly enhance the biopolymers production and optimized the constituents. CaO (0.1-0.2 g/g TSS) could dramatically enhance the sludge dewaterability by forming a multi-grid skeleton in WAS, while the biopolymers production could almost remain stable. Especially, the synergetic integration process of STAD with 0.1 g CAPB/g TSS for 8 h and 0.1 g CaO/g TSS could cost-effectively enhance both the biopolymers production and the sludge dewaterability. The produced biopolymers showed strong adsorbability for heavy metals (eg, 375 mg Cu²⁺/g biopolymers). Accordingly, the developed novel process is of big significance for resource utilization and volume reduction of WAS.