Scenedesmus Quadricauda Research Articles

Allelopathic effects of three lichen secondary metabolites on cultures of aposymbiotically grown lichen photobionts and free-living alga Scenedesmus quadricauda

In the present work, we studied the influence of lichen secondary metabolites (evernic acid, orcinol, usnic acid) on selected species of algae: Trebouxia erici, photobiont of lichen Cladonia cristatella producing typical lichen secondary metabolites, Coccomyxa solorinae-saccatae, photobiont of lichen Solorina saccata which does not produce typical secondary metabolites of lichens, and free-living alga Scenedesmus quadricauda.For the determination of the cytotoxic effects of these compounds, algae were cultivated on the surface of disks composed of glass microfibers, in quantities of 0.1 mg/disk for each metabolite. After 14-days prolonged cultivation, we analysed selected physiological parameters: growth of algae, chlorophyll a fluorescence, the content of ascorbic acid, content of reduced and oxidized glutathione and contents of selected organic acids. The presence of secondary compounds typically inhibited the growth of tested algae and chlorophyll a fluorescence. In the presence of evernic acid and usnic acid, we observed a decrease of ascorbic acid, glutathione, and significant changes in the composition of organic acids.Lichen metabolites, except for their other biological and ecological roles, may act as phytotoxic substances, causing oxidative stress in photobiont cells. These metabolites may play an important role in the “controlled parasitism” of fungal partner on algal/cyanobacterial partner of symbiosis. Differences in the sensitivity of algal cells from different habitats to lichen compounds are, however, not understood sufficiently.

Spatial and temporal distribution analysis of dominant algae in Lake Taihu based on ocean and land color instrument data

The proliferation of algal blooms can lead to environmental issues. The phytoplankton responsible for these blooms are diverse. Different species of bloom-forming algae have distinct characteristics and hazards, and therefore need different treatment methods. An accurate and quick determination of the spatial and temporal distribution characteristics of different algal species is crucial for lake ecological restoration. Based on the differences in remote sensing reflectance (Rrs) of various typical algae species in eutrophic lakes (including Microcystis aeruginosa, Aphanizomenon sp., and Pseudanabaena sp. in Cyanobacteria and Chlorella sp. and Scenedesmus quadricauda in Chlorophytes), difference index and algae distinguishing index were developed to differentiate algae species. A validation, using an independent dataset from an indoor experiment and in-situ-measured and satellite-image-derived Rrs, showed that the algorithm can provide reliable results (overall accuracies of 81.97%, 81.25%, and 60.42%, respectively). According to Ocean and Land Color Instrument images of Lake Taihu in the period of 2016 to 2020, Microcystis was the dominant algae, followed by Pseudanabaena and Aphanizomenon. The dominance of the two types of Chlorophytes was less pronounced. The proportion of Microcystis as the dominant algae was highest in summer, while the proportion of Pseudanabaena peaked in winter. The proportion of Aphanizomenon varied slightly throughout the year, while the proportion of the two Chlorophytes peaked in winter. In terms of spatial distribution, the patterns in spring and autumn were relatively similar. In summer, approximately 80% of the lake was dominated by Microcystis. In winter, Chlorella and Scenedesmus were more prevalent along the southeastern shore of Lake Taihu. The construction and application of this model can provide a technical support for prediction and prevention of blooms in inland lakes.

ALGINATE BEADS UTILIZATION FOR LONG-TERM STORAGE OF MICROALGAL ISOLATES

Microalgae reckon one of the most promising organisms due to their numerous applications in biotechnology, such as, their biomass utilization to extract various primary and secondary metabolites. These compounds benefit the food and pharmaceutical industries and the energy field, such as, biofuel and hydrogen gas production. Therefore, it is necessary to find various sustainable ways to actively preserve the isolates and productive strains with purity for an extended period without affecting their genetic characteristics and productive ability to grow and regenerate. The latest study aimed to compress several microalgae to form alginate beads using sodium alginate with five types of pure algal cultures, i.e., Scenedesmus quadricauda, Scenedesmus dimorphus, Chlorella vulgaris, Chlorococcum humicola, and Chlamydomonas sp. The vitality and activity of all the strains studied through the storage period showed the success of preparing alginate beads and staying viable for 18 months at 4 °C in the refrigerator under dark conditions. Therefore, encapsulating microalgae with sodium alginate is a possible and helpful method for preserving algae isolates for a prolonged period in a pure form. The survival of algae in alginate beads is an essential step to apply in the future as one of the viable methods to preserve pure algae isolates for a long time.

A review on plankton as a bioindicator: A promising tool for monitoring water quality

AbstractBioindicators have become increasingly popular and have contributed significant amounts of useful information to the process of managing water resources. The ability of a species (or species assemblage) to adapt to a certain range of chemical, physical, and biological conditions is one criterion that can be used to assess the quality of its surrounding environment. Planktons that react quickly to changes in their environment have proven to be particularly valuable, and the identification of certain indicator species has become increasingly common in the process of determining the quality of the water. The “health” of an aquatic system can be inferred from the presence or absence of plankton, which act as early warning signals. When compared with the expense of assessing harmful contaminants, the overall cost of conducting routine monitoring of biological communities is far lower and has a higher degree of reliability. The ability of bioindicators to identify indirect biotic effects of pollutants, which is something that many physical or chemical tests are unable to do, is another advantage of using bioindicators. Different aquatic species as bioindicators tolerate different environmental conditions, and their different tolerances to particular environments help in identifying a particular environmental condition. Phytoplankton species like Euglena viridis, Oscillatoria limosa, Nitzschia palea, and Scenedesmus quadricauda, and zooplankton species like Branchionus sp., Molina sp., Keratella cochlearis, Daphnia sp., and Cyclopus sp. indicate water pollution. This review's objective is to highlight some recent research on planktons, focusing on their capabilities and opportunities for application as bioindicators of water quality.

Evaluation of Growth and Production of High-Value-Added Metabolites in Scenedesmus quadricauda and Chlorella vulgaris Grown on Crude Glycerol under Heterotrophic and Mixotrophic Conditions Using Monochromatic Light-Emitting Diodes (LEDs).

This study aimed to examine the impact of crude glycerol as the main carbon source on the growth, cell morphology, and production of high-value-added metabolites of two microalgal species, namely Chlorella vulgaris and Scenedesmus quadricauda, under heterotrophic and mixotrophic conditions, using monochromatic illumination from light-emitting diodes (LEDs) emitting blue, red, yellow, and white (control) light. The findings indicated that both microalgae strains exhibited higher biomass yield on the mixotrophic growth system when compared to the heterotrophic one, while S. quadricauda generally performed better than C. vulgaris. In mixotrophic mode, the use of different monochromatic illumination affected biomass production differently on both strains. In S. quadricauda, growth rate was higher under red light (μmax = 0.89 d-1), while the highest biomass concentration and yield per gram of consumed glycerol were achieved under yellow light, reaching 1.86 g/L and Yx/s = 0.18, respectively. On the other hand, C. vulgaris demonstrated a higher growth rate on blue light (μmax = 0.45 d-1) and a higher biomass production on white (control) lighting (1.34 g/L). Regarding the production of metabolites, higher yields were achieved during mixotrophic mode in both strains. In C. vulgaris, the highest lipid (26.5% of dry cell weight), protein (63%), and carbohydrate (20.3%) contents were obtained under blue, red, and yellow light, respectively, thus indicating that different light wavelengths probably activate different metabolic pathways. Similar results were obtained for S. quadricauda with red light leading to higher lipid content, while white lighting caused higher production of proteins and carbohydrates. Overall, the study demonstrated the potential of utilizing crude glycerol as a carbon source for the growth and metabolite production of microalgae and, furthermore, revealed that the strains' behavior varied depending on lighting conditions.

Comparative Phycoremediation Performance of Three Microalgae Species in Two Different Magnitude of Pollutants in Wastewater from Farmhouse

The cultivation of microalgae using urban wastewater as a nutrient substrate represents a promising bio-refinery concept that can serve multiple purposes; indeed, it allows for the generation of biomass, which can be used for various applications while meanwhile removing nutrients from wastewater. In this study, the potential of urban wastewater collected at two different time periods in a farmhouse as a nutrient substrate for microalgal growth was assessed. Wastewater samples were treated on a laboratory scale, inoculating reactors with two common species, Chlorella vulgaris (CV) and Scenedesmus quadricauda (SQ), and with an autochthonous strain of Klebsormidium sp. K39 (Kleb), directly isolated from effluents of the same system. The main aim of the study was to compare the microalgae’s performances in terms of wastewater re-mediation and biomass productivity. In the first case study, which involved an effluent with a lower pollutant level, microalgal cultivation showed removal efficiencies in the range of 57–63% for total nitrogen, 65–92% for total phosphorous, 94–95% for COD, and 100% for E. coli. In the second case study, involving an effluent with a higher pollutant level, the remediation performances of the three microalgae strains ranged from 93 to 96% for total nitrogen, from 62 to 74% for total phosphorous, from 96 to 97% for COD, and 100% for E. coli. At the end of the experimental trials, treated waters showed values of pollutants suitable for irrigation use, in accordance with environmental and national legislation, which established specific thresholds for irrigation purposes.

Keystone microalgae species determine the removal efficiency of sulfamethoxazole: a case study of Chlorella pyrenoidosa and microalgae consortia.

In recent years, antibiotics pollution has caused serious harm to the aquatic environment, and microalgae mediated degradation of antibiotics has attracted increasing attention. However, the potential toxicity of antibiotics to keystone microalgae species or their microalgae consortia, and the impact of microalgal diversity on antibiotic removal need to be further studied. In this study, we investigated the removal efficiency and tolerance of five freshwater microalgae (Chlorella pyrenoidosa, Scenedesmus quadricauda, Dictyosphaerium sp., Haematoccocus pluvialis, and Botryococcus braunii) and their microalgae consortia to sulfamethoxazole (SMX). We found that the removal efficiency of SMX by C. pyrenoidosa reached 49%, while the other four microalgae ranged between 9% and 16%. In addition, C. pyrenoidosa, S. quadricauda, and Dictyosphaerium sp. had better tolerance to SMX than H. pluvialis, and their growth and photosynthesis were less affected. At 10 and 50 mg/L SMX, the removal capacity of SMX by mixed microalgae consortia was lower than that of C. pyrenoidos except for the consortium with C. pyrenoidos and S. quadricauda. The consortia generally showed higher sensitivity towards SMX than the individual species, and the biochemical characteristics (photosynthetic pigment, chlorophyll fluorescence parameters, superoxide anion (O2 -), superoxide dismutase activity (SOD), malondialdehyde (MDA) and extracellular enzymes) were significantly influenced by SMX stress. Therefore, the removal of antibiotics by microalgae consortia did not increase with the number of microalgae species. Our study provides a new perspective for the selection of microalgal consortia to degrade antibiotics.

Effect of Selenomethionine and Concentration on Growth and Chlorophyll-a of Scenedesmus quadricauda

Selenium is an essential element for all living organisms. Since its deficiency can cause health problems, it is supplied from the outside during nutrition through foods or supplements. Microalgae have become vector organisms among aquatic organisms during their transportation to the final consumer human in the food chain. However, selenium is an important supplement that should be consumed in sufficient proportions, and since its consumption at high levels will create a toxic effect, the doses to be provided must be consumed by considering factors such as age and gender. The upper selenium concentration is toxic for microalgae culture. For this reason, the effect of adding selenomethionine at 50, 75, 100 and 250 mg/L concentrations in the culture medium of Scenedesmus quadricauda on microalgae growth and chlorophyll-a content was investigated. According to the results obtained that the highest chlorophyll-a and cell number were measured as 0.593±0,1µg/L and 64±4,9 x106cells/mL using 50 mg/L selenomethionine in the culture. It has been detected the highest selenomethionine concentrations caused toxic for Scenedesmus quadricauda culture.

Role of Environmental Biotechnology in Remediation of Heavy Metals by Using Fungal-Microalgal Strains

Bioremediation is a branch of biotechnology that employs the use of living organisms, like microalgae and fungi, in the removal of contaminants, pollutants, and toxins from soil, water, and other environments. The experiment was designed to evaluate the efficiency of microorganisms to remove heavy metals by using, two fungi (Aspegillus niger and Candida albicans) with two microalgae (Scenedesmus quadricauda and Tetradesmus nygaardi), in removing heavy metals from liquid media during study period (20 days). For this study, cadmium and lead were selected by different concentrations (5, 15, 35, and 50ppm) of such heavy metals. The results indicate that fungi and microalgae effectively removed a significant amount of heavy metals. With respect to Pb and Cd, the maximum removal of lead for all concentrations (5-50ppm) were, (94, 90, 86.28 and 81.6%) respectively, and maximum cadmium removal were (88, 86.66, 84.57 and 79%) recorded by consortium culture of Scenedesmus quadricauda and Tetradesmus nygaardi on day 20th of the experiment. Statistically there were significant difference (p≤0.05) between control and all treatments for both tested heavy metals.

Enhancing Nature-Based Solutions: Efficient Removal of Hydroxytyrosol in Olive Mill Wastewater Treatment for Value Creation

This study aimed to investigate the potential use of the microalgae Chlorella sorokiniana and Scenedesmus quadricauda for the bioremediation of olive mill wastewater (OMW), which is a major environmental issue and a waste product of olive oil production. The study investigated the effects of different dilutions (10% and 50%) of OMW on the growth of the microalgae and their ability to remove the phenolic component hydroxytyrosol (OH-Tyr) and enhance their antioxidant properties. The results indicated that, although the growth on OMW was not enhanced, both microalgae strains were able to remove OH-Tyr from OMW, with Chlorella sorokiniana showing higher removal efficiency than Scenedesmus quadricauda. Moreover, the antioxidant activity of the microalgal extracts increased after 96 h of exposure to OMW. These findings suggest that microalgae-based treatment of OMW could be a promising approach for the bioremediation of this waste product and the production of value-added products. Overall, the use of microalgae for the treatment of OMW could provide a sustainable solution for the management of this waste product while generating potential economic benefits for olive producers.

Using Microalga Scenedesmus quadricauda for the Improvement of Municipal Wastewater Quality

Microalgae culture is an interesting step in wastewater treatment since it provides a tertiary biotreatment while also producing potentially valuable biomass that may be used for a variety of applications. Microalgae cultures, with their ability to utilize inorganic nitrogen and phosphate for growth, provide an elegant solution to tertiary and quaternary treatments. Scenedesmus quadricauda culture was employed with three different doses, 2g/l, 1g/l, and 0.2g/l, to investigate the impacts of microalgae in wastewater. Standard procedures were used to measure samples for physicochemical parameters such as pH, EC, PO4, NO3, NO2, NH4 and BOD5 every third day for 21 days. Results showed that a higher dose of 2g.l-1 was the most effective for removing the highest rate of nutrients. It was confirmed by significant differences (p≤0.05) between all doses. Ammonium pass had the highest removal percentage of 97%, followed by NO3 with 95.7%, and BOD5 with a range of 90.3 to 93.5 %. Decreases in nutrients were accompanied by a rise in chlorophyll content, with the greatest biomass of 1.52 mg. l-1 on the 17th day of the experiment. The purpose of this paper is to provide an overview of the methods that microalgae use to bioremediate organic contaminants in aquatic ecosystems.

Calcium sulfite oxidation activated by ferrous iron integrated with membrane filtration for removal of typical algal contaminants

Oxidation treatment of algae-laden water may cause cells rupture and emission of intracellular organics, thus restricting its further popularization. As a moderate oxidant, calcium sulfite could be slowly released in the liquid phase, thus exhibiting a potential to maintain the cells integrity. To this end, calcium sulfite oxidation activated by ferrous iron was proposed integrated with ultrafiltration (UF) for removal of Microcystis aeruginosa, Chlorella vulgaris and Scenedesmus quadricauda. The organic pollutants were significantly eliminated, and the repulsion between algal cells was obviously weakened. Through fluorescent components extraction and molecular weights distribution analyses, the degradation of fluorescent substances and the generation of micromolecular organics were verified. Moreover, the algal cells were dramatically agglomerated and formed larger flocs under the premise of maintaining high cell integrity. The terminal normalized flux was ascended from 0.048–0.072 to 0.711–0.956, and the fouling resistances were extraordinarily decreased. Due to the distinctive spiny structure and minimal electrostatic repulsion, Scenedesmus quadricauda was easier to form flocs, and its fouling was more readily mitigated. The fouling mechanism was remarkably altered through postponing the formation of cake filtration. The membrane interface characteristics including microstructures and functional groups firmly proved the fouling control efficiency. The reactive oxygen species (i.e., SO4•− and 1O2) generated through the principal reactions and Fe–Ca composite flocs played dominant roles in alleviating membrane fouling. Overall, the proposed pretreatment exhibits a brilliant application potential for enhancing UF in algal removal.

The use of an algal bioindicator in the assessment of different chemical remediation strategies for PAH-contaminated soils and sediments

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous petroleum-derived pollutants that tend to accumulate in soils and sediments. Among the in situ chemical oxidation technologies applied at PAH-contaminated sites are Fenton reagent (FN), persulfate ion (PS) and permanganate ion (PM). The natural phytoplankton of an aquatic environment is useful as a biological indicator of the treatment efficacy of pollutant degradation. The objective of this work was to assess the use of an algal species, native from Los Barreales Reservoir (Argentina), as an efficacy indicator of the chemical remediation of PAH-contaminated soils and sediments. Oxidations with FN, PS or PM were carried out on soils and sediments previously contaminated with two types of PAHs (phenanthrene (Ph) or Benzo(a)anthracene (Ba)), analysing pH, residual oxidant, PAH degradation and heterotrophic bacteria abundance in soils or sediments after 7 days. Then, a bioassay was carried out by incubating the obtained soils or sediments, and the native alga Scenedesmus quadricauda (Turpin, Brébisson), analysing its abundance after 7 days. S. quadricauda abundance was related to PAH degradation efficacy, residual oxidants and changes in system pH. In this sense, the application of PS produced the lowest growth of the indicator in assays both with soils and sediments. Fenton reaction results varied depending on the contaminating PAH, with the best percentages of PAH degradation and growth of S. quadricauda for Ba. PM oxidation resulted in the best development of the indicator. This study constitutes a first approach to the use of S. quadricauda as an efficiency indicator of soil/sediment chemical remediation.

The effect of carbon nanodots and graphene quantum dots on the green microalga Scenedesmus quadricauda

The effect of carbon nanodots and graphene quantum dots on the green microalga Scenedesmus quadricauda

Enhanced growth and auto-flocculation of Scenedesmus quadricauda in anaerobic digestate using high light intensity and nanosilica: A biomineralization-inspired strategy

Coupling municipal anaerobic digestate (MAD) treatments with microalgal cultivation can concomitantly achieve nutrient removal and microalgal bioenergy production. However, the high cost caused by dilution water and microalgal harvesting is a great challenge. In this study, Scenedesmus quadricauda was screened as the most appropriate algae strain due to its potential for growth and auto-flocculation, and the MAD diluted 5-fold with WWTP effluent was demonstrated as an ideal medium for S. quadricauda growth. Moreover, inspired by naturally generated silica shells of diatoms, a low-cost and biomimetic auto-flocculation strategy that combined high light intensity induction and microalgal silicification was proposed to accelerate the auto-flocculation process. Compared with low light intensity groups, this strategy imparted diatom-like features to S. quadricauda cells, and contributed to 3.07-fold higher auto-flocculation efficiency within 30 min. It was attributed to the fact that the high light intensity of 150 μmol·m − 2·s − 1 stimulated the extracellular polymeric substances (EPS) secretion and induced the variation in property and composition of EPS, especially the protein secondary structures, which allowed silica nanoparticles to spontaneously attach onto S. quadricauda cells in the presence of viscous EPS. Furthermore, this strategy significantly increased microalgal biomass yield to a dry weight of 1.37 g·L − 1, accompanied by 93.78%, 96.39% and 91.36% removals of NH4+-N, TP, and COD, respectively. The productivity of valuable by-products, including lipid, carbohydrate, protein, and pigment, reached 56.30, 101.35, 30.39 and 11.28 mg·L − 1·d − 1, respectively. Overall, this study supplies a novel approach for low-cost microalgal bioenergy production from MAD and energy-efficient microalgae harvest by auto-flocculation.

Role of Microalgae in Environmental Biotechnology to Remove Heavy Metals

The objective of the study is to evaluate the role of microalgae in heavy metal remediation (Pb and Cd). Three microalgae species were used (Tetradesmus nygaardi, Scenedesmus quadricauda, and Coelastrella sp.) with four concentrations of both tested heavy metals (lead and cadmium) were, (5, 15, 35, and 50 ppm). Samples were analyzed every 4th day during the experimental study for 20 days. The result showed that during experimental days the lower concentration (5ppm) has the highest reduction percent for Pb and Cd by all microalgal species (Tetradesmus nygaardi, Scenedesemus quadricauda, and Coellastrella sp.). Whereas Coellastrella sp. had the highest efficiency for Pb and Cd uptake in all concentrations (5, 15, 35, and 50 ppm) for Pb removal percent were (86.8%, 86%, 82.85%, 78%) respectively, while for Cd were (84%, 80.66%, 77.14%, 76.94%) respectively. The lead had a higher reduction percent for all concentrations (5-50ppm) in comparison with cadmium by all microalgal strains during 20 days of the experiment. The removal of Cd and Pb by microalgal strains by order, Coellastrella sp. > Tetradesmus nygaardi > Scenedesemus quadricauda.

Interactive effects of temperature and bisphenol A on phytoplankton growth and community structure.

Environmental contamination of bisphenol A (BPA) is a widespread and multifaceted issue with vast ecological, social and economic consequences. Thus, understanding how local environmental conditions, such as temperature, interact with BPA to affect populations and community dynamics remain important areas of research. Here, we conduct laboratory experiments aimed at understanding how environmental gradients of both temperature and BPA concentration influence freshwater phytoplankton population growth and community structure. We exposed phytoplankton assemblages comprised of three common species of green algae (Chlorella vulgaris, Ankistrodesmus braunii and Scenedesmus quadricauda) as well as isolates of each individual species to three BPA concentrations (0, 2, 13mg/L BPA) and three temperatures (18, 23, 27°C) monitoring population growth and community structure (via biovolume). We observed antagonistic interactions between BPA and warmer temperatures, such that when warmer temperatures decreased growth (observed with A. braunii), high concentrations of BPA elevated growth at these warm temperatures; however, when warmer temperatures increased growth (C. vulgaris, S. quadricauda), high BPA concentrations diminished these gains. Although BPA exposure inhibited the growth of most C. vulgaris populations, growth was not reduced in A. braunii or S. quadricauda populations exposed to 2mg/L BPA. Phytoplankton assemblage evenness (Pielou evenness index) decreased as BPA concentration increased and was consistently lowest under 27°C. Community composition was similar in assemblages cultured under 0 and 2mg/L BPA under 18 and 23°C but was most similar between assemblages cultured under 2 and 13mg/L BPA under 27°C. These results indicate that local environmental temperatures can mediate the consequences of BPA for freshwater phytoplankton growth rates and community structure and that BPA can diminish potential gains of increased growth rate for warm-adapted phytoplankton species at high environmental temperatures.

Effects of polystyrene nanoplastics on the physiological and biochemical characteristics of microalga Scenedesmusquadricauda

The contamination of the aquatic environment with microplastics has become a global environmental concern. Microplastic particles can be shredded to form smaller nanoplastics, and knowledge on their impacts on phytoplankton, especially freshwater microalgae, is still limited. To investigate this issue, the microalga Scenedesmus quadricauda was exposed to polystyrene nanoplastics (PS-NPs) of five concentrations (10, 25, 50, 100, and 200 mg/L). The growth; the contents of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD); the chlorophyll content; and concentrations of soluble protein and soluble polysaccharide were accordingly measured. The results showed that the microalgal density increased with the increase of the polystyrene nanoplastic concentrations, and the physiological features of alga were enhanced after the stimulation of nanoplastics. Furthermore, a high concentration (200 mg/L) of nanoplastics increased the contents of chlorophyll, soluble protein, and polysaccharide (P < 0.05). The antioxidant enzyme activities of Scenedesmus quadricauda were significantly activated by nanoplastics. Lastly, we propose three possible algal recovery mechanisms in response to nanoplastics in which Scenedesmus quadricauda was tolerant with PS-NPs by cell wall thickening, internalization, and aggregation. The results of this study contribute to understanding of the ecological risks of nanoplastics on freshwater microalgae.

Removal of Nutrients by Using Green Microalgae from Lab-Scale Treated Palm Oil Mill Effluent

The use of microalgae for the removal of contaminants such as total phosphorus (TP), total nitrogen (TN), chemical oxygen demand (COD), and other pollutants from palm oil mill effluent (POME) has recently received much attention. This study aimed to investigate the impact of POME as a nutrient on microalgal growth and the rate at which nutrients were removed. Three green microalgae species were isolated from Penang, Malaysia’s palm oil mill. The polyphasic approach, which combines morphological and molecular observations, was used for species identification. The three green microalgae were identified as Chlorella sorokiniana, Scenedesmus quadricauda, and Chlorococcum oleofaciens. All three green microalgae were cultivated in 25%, 50%, and 75% (v/v) of lab-scale palm oil mill effluent (LABT-POME) to investigate the growth of these three green microalgae in 100 mL of BBM. Under a light microscope and a scanning electron microscope (SEM), the morphological changes of those three green microalgae (before and after cultivation in 25%, 50%, and 75% dilution of (LABT-POME)) were observed. When cultivated in LABT-POME, C. oleofaciens showed the highest growth rate compared to the other two species of green microalgae. C. oleofaciens was able to remove more than 90% of total phosphorus (TP), total nitrogen (TN), and ammonia nitrogen from LABT-POME, as well as minimise soluble chemical oxygen demand (SCOD) by about 65%. The growth of C. oleofaciens was well fitted to the Verhulst growth kinetic model with an R2 value of 0.99 and a growth rate of 0.3195 day−1 (d−1). The results of this study show the ability of newly isolated green microalgae to remove nutrients (TP, TN, NH3–N, and SCOD) from POME, which could be used as an effective and environmentally friendly method to remove pollutants.

Effects of N-acyl homoserine lactone on immobilized Scenedesmus quadricauda bead using Ca-alginate for wastewater treatment

During wastewater treatment using microalgae, microalgae are inevitably exposed to bacteria and their autoinducers (AIs). There is limited evidence regarding the interaction between microalgae and AIs in wastewater treatment processes. In this study, the effect of N-acyl homoserine lactone (AHL), an AI of Gram-negative bacteria, on the immobilization of Scenedesmus quadricauda using calcium alginate was investigated and compared between heterotrophic and mixotrophic conditions. AHL did not affect the performance of the microalgal bead reactors under heterotrophic and mixotrophic conditions. Removal efficiencies of chemical oxygen demand, nitrogen, and phosphorus under mixotrophic conditions were 96 ± 1.2 %, 39 ± 6.5 %, and 95 ± 5.4 %, respectively (n = 18). Aggregation of microalgae was observed in reactors fed with AHL. The cell concentration of microalgae in the effluent was decreased by 42–44 %. The cell concentration of microalgae in the bead was increased by 16 % under mixotrophic conditions, and the disruption of beads was only 0.8 % of total microalgal beads during the time of study. Furthermore, microalgal aggregate formation was more effective under mixotrophic conditions.