Enhancing the production of PHA in Scenedesmus sp. by the addition of green synthesized nitrogen, phosphorus, and nitrogen-phosphorus-doped carbon dots.

Plastic consumption has increased globally, and environmental issues associated with it have only gotten more severe; as a result, the search for environmentally friendly alternatives has intensified. Polyhydroxyalkanoates (PHA), as biopolymers produced by microalgae, might be an excellent option; however, large-scale production is a relevant barrier that hinders their application. Recently, innovative materials such as carbon dots (CDs) have been explored to enhance PHA production sustainably. This study added green synthesized multi-doped CDs to Scenedesmus sp. microalgae cultures to improve PHA production. Prickly pear was selected as the carbon precursor for the hydrothermally synthesized CDs doped with nitrogen, phosphorous, and nitrogen-phosphorous elements. CDs were characterized by different techniques, such as FTIR, SEM, ζ potential, UV-Vis, and XRD. They exhibited a semi-crystalline structure with high concentrations of carboxylic groups on their surface and other elements, such as copper and phosphorus. A medium without nitrogen and phosphorous was used as a control to compare CDs-enriched mediums. Cultures regarding biomass growth, carbohydrates, lipids, proteins, and PHA content were analyzed. The obtained results demonstrated that CDs-enriched cultures produced higher content of biomass and PHA; CDs-enriched cultures presented an increase of 26.9% in PHA concentration and an increase of 32% in terms of cell growth compared to the standard cultures.

Nitrogen and phosphorus removal performance of sequential batch operation for algal cultivation through suspended-solid phase photobioreactor.

Nitrogen (N) and phosphorus (P) absorbed by algae in the suspended-solid phase photobioreactor (ssPBR) have emerged as an efficient pathway to purify the effluent of wastewater treatment plants (WWTPs). However, the key operational parameters of the ssPBR need to be optimized. In this study, the stability of the system after sequential batch operations and the efficiency under various influent P concentrations were evaluated. The results demonstrated that the ssPBR maintained a high N/P removal efficiency of 96 % and 98 %, respectively, after 5 cycles. When N was kept at 15 mg/L and P ranged from 1.5 to 3.0 mg/L, the system yielded plenty of algae products and guaranteed the effluent quality that met the discharge standards. Notably, the carriers were a key contributor to the high metabolism of algae and high performance. This work provided theoretical ideas and technical guidance for effluent quality improvement in WWTPs.

Toxicity of benzyl paraben on aquatic as well as terrestrial life.

Parabens are derivatives of alkyl esters of p-hydroxybenzoic acid and come in different classes. These compounds are primarily used as antimicrobial preservative agents in many commercial products, including cosmetics and pharmaceuticals. Accordingly, Benzyl paraben (BeP) is known to be a potential endocrine disruptor. The aim of this study was to determine the toxicity of benzyl paraben (BeP) on aquatic and terrestrial organisms, specifically Scenedesmus sp., Moina macrocopa, and Eisenia fetida. All the organisms were treated with different concentrations of BeP (0.025 mg/L and 1000 mg/L), and LC25, LC50, and LC90 values were used to measure the toxicity levels. Results showed the LC values of BeP for M. macrocopa (3.3 mg/L, 4.7 mg/L, 7.3 mg/L) and E. fetida (173.2 mg/L, 479.8 mg/L, 1062 mg/L), respectively. Toxicity tests on green algae (Scenedesmus sp.) were conducted, the green algae were subjected to various BeP concentration. At 50 mg/L of BeP, cell viability was reduced to 56.2% and the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay indicated 35.4% viable cells. The chlorophyll value and the biochemical parameters of the algal cells were corroborative with the cell viability test. Lethal indices (LC50) for M. macrocopa and E. fetida were evaluated for their toxicity on biochemical properties and were found to be catalase (0.111 mg/L, 0.5 mg/L), lipid peroxidation (0.072 mg/L, 0.056 mg/L), and total protein (0.309 mg/L, 0.314 mg/L), respectively. Overall, this study demonstrated the toxic impact of BeP on non-target aquatic as well as terrestrial species.

Nutritional Value of Microalgae and Cyanobacteria Produced with Batch and Continuous Cultivation: Potential Use as Feed Material in Poultry Nutrition.

Recently, the demand for new alternative feedstuffs that do not contain chemical residue and are not genetically modified has been increased for sustainability in poultry production. In this respect, the usage of algae as animal feed is very promising as an alternative feed ingredient that reduces pollutant gases from animal production facilities. The aim of the current study is to investigate the usage possibility of algae, through determining nutritional value and production cost, as a feed ingredient in poultry nutrition. Three microalgae species, including Scenedesmus sp., Ankistrodesmus sp., and Synechococcaceae, were produced with batch and continuous cultivation to determine the difference in the lipid, protein, carbohydrate, fatty acid, and amino acid profiles, as well as the color characteristics and production cost. The highest lipid content of 72.5% was observed in algae biomass produced from Synechococcaceae with batch cultivation, whereas the highest protein level was found in algae biomass produced by Synechococcaceae under continuous cultivation practice (25.6%). The highest content of PUFA was observed in Scenedesmus sp. harvested from both batch and continuous cultivation (35.6 and 36.2%), whereas the lowest content of PUFA was found in Synechococcaceae harvested with continuous cultivation (0.4%). Continuously cultivated of Scenedesmus sp. had higher carbohydrate content than batch-cultivated Scenedesmus sp. (57.2% vs. 50.1%). The algae biomass produced from Synechococcaceae was found to have a higher content of essential amino acids, except lysine and histidine, compared to Scenedesmus sp. and Ankistrodesmus sp. Cultivation practices also affected the amino acid level in each algae species. The continuous cultivation practice resulted in a higher level of essential amino acids, except glycine. Synechococcaceae had richer essential amino acid content except for proline and ornithine, whereas continuous cultivation caused an incremental increase in non-essential amino acids. The lightness value was found to be the lowest (13.9) in Scenedesmus sp. that was continuously cultivated. The current study indicated that Scenedesmus sp. could be offered for its high PUFA and lysine content, whereas Synechococcaceae could have potential due to its high content of methionine and threonine, among the investigated microalgae and Cyanobacteria.

Removal and recovery of nutrients from septic tank wastewater using microalgae: Key factors and practical implications.

Treatment of septic tank wastewater (STWW) with high concentrations of ammonium (NH4+) and total phosphorus (TP), is challenging in decentralized areas. Utilizing microalgae for STWW treatment can simultaneously recover nutrients in the form of high-value microalgal biomass. However, despite the potential benefits, microalgal treatment of STWW is rarely reported. Therefore, this work utilized bench-scale photobioreactors (PBR) to investigate different factors that could affect microalgal cultivation in STWW and treatment efficiency. Accordingly, it was observed that suspended solids present in STWW did not significantly affect the microalgae growth and nutrient removal efficiencies in bubble column PBR. On the other hand, the effect of endemic microorganism could not be verified in this study due to observed fungal contamination and change in nutrient profile of STWW after autoclave. Nevertheless, the highest microalgal growth and nutrient removal efficiencies of NH4+-N = 79.14% and TP = 41.11% were observed within 14 days of photoautotrophic cultivation in raw STWW. Further, 25 days of upscaled photoautotrophic cultivation in 4-L bubble column PBR was performed to study biomass yield, nutrient removal kinetics, and nutrient removal efficiency. Consequently, 0.75 g‧L-1 dry biomass was produced with improved removal efficiency of NH4+-N (96.16%), and TP (69.57%). Elemental analysis of biomass revealed that 62.99 ± 1.46 mg‧L-1 TN and 11.41 ± 1.42 mg‧L-1 TP were recovered. Further, 1.02 geq carbon dioxide (CO2) was bio-fixed with every liter of STWW treated. The findings of this study revealed that microalgae can be successfully utilized for the removal and recovery of nutrients from STWW.

Salinity-Induced Physiochemical Alterations to Enhance Lipid Content in Oleaginous Microalgae Scenedesmus sp. BHU1 via Two-Stage Cultivation for Biodiesel Feedstock.

In the recent past, various microalgae have been considered a renewable energy source for biofuel production, and their amount and extent can be enhanced by applying certain types of stress including salinity. Although microalgae growing under salinity stress result in a higher lipid content, they simultaneously reduce in growth and biomass output. To resolve this issue, the physiochemical changes in microalgae Scenedesmus sp. BHU1 have been assessed through two-stage cultivation. In stage-I, the maximum carbohydrate and lipid contents (39.55 and 34.10%) were found at a 0.4 M NaCl concentration, while in stage-II, the maximum carbohydrate and lipid contents (42.16 and 38.10%) were obtained in the 8-day-old culture. However, under increased salinity, Scenedesmus sp. BHU1 exhibited a decrease in photosynthetic attributes, including Chl-a, Chl-b, Fv/Fm, Y(II), Y(NPQ), NPQ, qP, qL, qN, and ETRmax but increased Y(NO) and carotenoids content. Apart from physiological attributes, osmoprotectants, stress biomarkers, and nonenzymatic antioxidants were also studied to elucidate the role of reactive oxygen species (ROS) facilitated lipid synthesis. Furthermore, elemental and mineral ion analysis of microalgal biomass was performed to evaluate the biomass quality for biofuel and cell homeostasis. Based on fluorometry analysis, we found the maximum neutral lipids in the 8-day-old grown culture at stage-II in Scenedesmus sp. BHU1. Furthermore, the use of Fourier-transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy analyses confirmed the presence of higher levels of hydrocarbons and triacylglycerides (TAGs) composed of saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) in the 8-day-old culture. Therefore, Scenedesmus sp. BHU1 can be a promising microalga for potential biodiesel feedstock.

The growth inhibitory effects and non-targeted metabolomic profiling of Microcystis aeruginosa treated by Scenedesmus sp.

The health of the aquatic ecosystem has recently been severely affected by cyanobacterial blooms brought on by eutrophication. Therefore, it is critical to develop efficient and secure methods to control dangerous cyanobacteria, such as Microcystis aeruginosa. In this research, we tested the inhibition of M. aeruginosa growth by a Scenedesmus sp. strain isolated from a culture pond. Scenedesmus sp. culture filtrate that had been lyophilized was added to M. aeruginosa, and cultivation for seven days, the cell density, chlorophyll a (Chl-a) concentration, maximum quantum yield of photosystem II (Fv/Fm), the activities of superoxide dismutase (SOD), catalase (CAT), and the concentration of malondialdehyde (MDA) and glutathione (GSH) were measured. Moreover, non-targeted metabolomics was carried out to provide light on the inhibitory mechanism in order to better understand the metabolic response. According to the results, M. aeruginosa is effectively inhibited by the lyophilized Scenedesmus sp. culture filtrate at a rate of 51.2%. Additionally, the lyophilized Scenedesmus sp. clearly inhibit the photosystem and damages the antioxidant defense system of M. aeruginosa cells, resulting in oxidative damage, which worsens membrane lipid peroxidation, according to changes in Chl-a, Fv/Fm, SOD, CAT enzyme activities and MDA, GSH. Metabolomics analysis revealed that the secondary metabolites of Scenedesmus sp. significantly interfere with the metabolism of M. aeruginosa involved in amino acid synthesis, membrane creation and oxidative stress, which is coherent with the morphology and physiology outcomes. These results demonstrate that the secondary metabolites of Scenedesmus sp. exert algal inhibition effect by breaked the membrane structure, destroyed the photosynthetic system of microalgae, inhibited amino acid synthesis, reduced antioxidant capacity, and eventually caused algal cell lysis and death. Our research provides a reliable basis for the biological control of cyanobacterial blooms on the one hand, and on other hand supply application of non-targeted metabolome on the study of microalgae allelochemicals.

Multi-pollutants (organic and inorganic) removal potential of scenedesmus species on municipal sewage water and analyzed their phycoremediation mechanisms.

Municipal sledge water is a combination of residential wastewater, industrial effluent, and precipitation water. The water quality parameters analyses results demonstrated that most of the parameters (pH: 5.6 ± 0.3, Turbidity: 102.31 ± 2.8 mg L-1, TH: 946.38 ± 3.7 mg L-1, BOD: 295.63 ± 5.4 mg L-1, COD: 482.41 ± 4.9 mg L-1, Ca: 278.74 ± 1.8 mg L-1, SO42-: 559.64 ± 11.4 mg L-1, Cd: 18.56 ± 1.37 mg L-1, Cr: 31.25 ± 1.49 mg L-1, Pb: 21.45 ± 1.12 mg L-1, and Zn: 48.65 ± 1.56 mg L-1) were considerably increased in quantities with slightly acidic in condition. The in-vitro phycoremediation study was carried out for two weeks with pre-identified Scenedesmus sp. Biomass in different groups of treatments (A, B, C, and D). Interestingly, most of the physicochemical parameters were significantly reduced in group C (4 × 103 cells mL-1) treated municipal sludge water in a shorter treatment period than in the other treatment groups. The phycoremediation percentage of group C were found as pH: 32.85%, EC: 52.81%, TDS: 31.32%, TH: 25.58%, BOD: 34.02%, COD: 26.47%, Ni: 58.94%, Ca: 44.75%, K: 42.74%, Mg: 39.52%, Na: 36.55%, Fe: 68%, Cl: 37.03%, SO42-: 16.77%, PO43-: 43.15%, F: 55.55%, Cd:44.88%, Cr:37.21%, Pb:43.8%, and Zn:33.17%. These findings suggest that increased biomass from Scenedesmus sp. can be used to significantly remediate municipal sludge water and that the obtained biomass and treated sludge can be used as feedstock's for bio fuel as well as bio fertilizer, respectively.

Assessment of the intrinsic bioremediation capacity of a complexly contaminated Yamuna River of India: a algae-specific approach.

Nearly 57 million people depend on Yamuna's water for their daily needs and agriculture. This is the first study of assessment of the Yamuna River for five major pollutants - Nitrate, Sulfate, Phosphate, Silicon, and Chloride, and the role of inhabitant algal species for phycoremediation. Water samples were collected from 11 different locations across three different seasons and it was found that the concentration of these pollutants varies in different locations and seasons. The concentration of Nitrate 392.93 mg/L at ITO Monsoon 2021, Phosphate 86.25 mg/L at Baghpat, Silicon 257.34 mg/L at Faridabad, Sulfate 2165.949 mg/L at ITO during winter 2020, and Chloride 4400.741 mg/L at Old bridge during Monsoon 2021 are found maximum. A significant variation (p < 0.05) in the concentrations of Nitrate, Sulfate, Phosphate, Silicon, and Chloride before and after treatment with microalgae was observed in water samples. All six algae significantly remove all the pollutants, and the maximum pollutants removed are Phosphate and Nitrite. Scenedesmus sp., removes the highest 99.21% Phosphate and 86.31% Nitrate, whereas 78.50% of Sulfate was removed by Klebsormidium sp. The highest 92.77% Silicon and 86.20% Chloride were removed by Oocystis sp. This finding suggests that out of six algae, Scenedesmus sp., in the Yamuna water has grown primarily at all the sites and reduces maximum pollutants. The outcomes from this study confirms that Yamuna River is highly contaminated at all the sites from these five major pollutants and algae are still survive in highly contaminated Yamuna water where no other plants are grown and phycoremediate the water bodies even in the presence of very high-stress condition. These algae can further be utilized for biotreatment of any contaminated water body.

This is the first study of assessment of five major pollutants and role of inhabitant algal species of Yamuna River for Phycoremediation.

Scenedesmus sp. strain SD07 cultivation in municipal wastewater for pollutant removal and production of lipid and exopolysaccharides.

In this study, an efficient microalgal strain SD07 was isolated from pond wastewater and identified as Scenedesmus sp. using the 18S rRNA gene sequence analysis. The strain SD07 was grown in a variety of concentrations (25-100%) of municipal wastewater. Scenedesmus sp. strain SD07 grown in 75% diluted wastewater produced a higher amount of biomass (1.93 ± 0.10 g L-1), and removal of chemical oxygen demand (COD), ammonium (NH4+), total nitrogen (TN) and total phosphate (TP) by 91.36%, 88.41%, 93.26% and 96.32%, respectively from wastewater. The harvested strain SD07 biomass has protein, carbohydrate and lipid contents of 35%, 20.4% and 33%, respectively. Fatty acid profiles revealed that the strain SD07 lipids mainly consist of palmitic acid (40.5%), palmitoleic acid (19%), linoleic acid (17%) and oleic acid (13.2%). Furthermore, strain SD07 cultured in 75% diluted wastewater produced 378 mg L-1 of exopolysaccharides (EPS). The EPS was utilized as a biostimulant in the cultivation of Solanum lycopersicum under salinity stress. In summary, these findings suggest that this Scenedesmus sp. strain SD07 can be employed for wastewater treatment as well as the production of valuable biomass, high-quality algal oil and EPS.

A Two-Stage Culture Strategy for Scenedesmus sp. FSP3 for CO2 Fixation and the Simultaneous Production of Lutein under Light and Salt Stress.

In this study, Scenedesmus sp. FSP3 was cultured using a two-stage culture strategy for CO2 fixation and lutein production. During the first stage, propylene carbonate was added to the medium, with 5% CO2 introduced to promote the rapid growth and CO2 fixation of the microalgae. During the second stage of cultivation, a NaCl concentration of 156 mmol L-1 and a light intensity of 160 µmol m-2 s-1 were used to stimulate the accumulation of lutein in the microalgal cells. By using this culture method, high lutein production and CO2 fixation were simultaneously achieved. The biomass productivity and carbon fixation rate of Scenedesmus sp. FSP3 reached 0.58 g L-1 d-1 and 1.09 g L-1 d-1, with a lutein content and yield as high as 6.45 mg g-1 and 2.30 mg L-1 d-1, respectively. The results reveal a commercially feasible way to integrate microalgal lutein production with CO2 fixation processes.

Municipal Landfill Leachate Treatment and Sustainable Ethanol Production: A Biogreen Technology Approach.

Sustainable material sources are an important agenda to protect the environment and to meet human needs. In this study, Scenedesmus sp. was used to treat municipal landfill leachate via batch and continuous cultivation modes to protect the environment and explore sufficient biomass production for bioethanol production using Saccharomyces cerevisiae. Physicochemical characteristics of leachate were determined for the phases before, during, and after the process. Batch and continuous cultivation were used to treat raw leachate to determine optimum conditions for treatment. Then, the biomass of Scenedesmus sp. with and without sonication was used as a substrate for ethanol production. Sonication was carried out for biomass cell disruption for 20 min at a frequency of 40 kHz. Through batch cultivation mode, it was found that pH 7 was the optimum condition for leachate treatment. Continuous cultivation mode had the highest removal values for COD, phosphorus, and carbohydrate, namely 82.81%, 79.70%, and 84.35%, respectively, among other modes. As for ethanol production, biomass without sonication with 9.026 mg·L-1 ethanol, a biomass concentration of 3.300 µg·L-1, and pH 5 were higher than biomass with sonication with 5.562 mg·L-1 ethanol, a biomass concentration of 0.110 µg·L-1, and pH 5. Therefore, it is evident that the leachate has the potential to be treated by Scenedesmus sp. and converted to bioethanol in line with the concept of sustainable materials.

Physiological and Biochemical Responses of Bicarbonate Supplementation on Biomass and Lipid Content of Green Algae Scenedesmus sp. BHU1 Isolated From Wastewater for Renewable Biofuel Feedstock.

In the present study, different microalgae were isolated from wastewater environment and evaluated for higher growth and lipid accumulation. The growth adaptability of all the isolated microalgae were tested for carbon source with supplementation of sodium bicarbonate in BG-11 N+ medium. Further based on the uptake rate of sodium bicarbonate and growth behavior, microalgal strains were selected for biofuel feedstock. During the study, growth parameters of all the isolates were screened after supplementation with various carbon sources, in which strain Scenedesmus sp. BHU1 was found highly effective among all. The efficacy of Scenedesmus sp. BHU1 strain under different sodium bicarbonate (4-20 mM) concentration, in which higher growth 1.4 times greater than control was observed at the concentration 12 mM sodium bicarbonate. In addition, total chlorophyll content (Chl-a + Chl-b), chlorophyll fluorescence (Fv/Fm, Y(II), ETR max, and NPQmax), and biomass productivity were found to be 11.514 µg/ml, 0.673, 0.675, and 31.167 µmol electrons m-2 s-1, 1.399, 59.167 mg/L/day, respectively, at the 12 mM sodium bicarbonate. However, under optimum sodium bicarbonate supplementation, 56.920% carbohydrate and 34.693% lipid content were accumulated, which showed potential of sodium bicarbonate supplementation in renewable biofuel feedstock by using Scenedesmus sp. BHU1 strain.

Attached cultivation of microalgae on rational carriers for swine wastewater treatment and biomass harvesting.

Attachment effects of six carrier materials on the cultivation of high-value microalga Scenedesmus sp. LX1 in diluted swine wastewater were investigated. The results showed that when the initial algal densities were 5×105 cells/mL and 1×106 cells/mL in sterilized wastewater with 20-fold dilution, the biomass of microalgae attaching to geotextile was the highest. The contact angle and surface structure of the material affected the attachment of microalgae. Further, among the four dilutions, the highest attached biomass on geotextile was 414.47 mg/L in the sterilized wastewater at 20-fold, but the pollutants removal rate and attached biomass were higher in the non-sterile wastewater in the other three dilutions (original wastewater, 5-fold, 10-fold). Next, the microalgae were able to remove pollutants with the highest removal rates of COD, TN, NH4+-N and TP reaching to 86.92%, 60.75%, 71.81% and 96.13%. Moreover, the microalga was found to accumulate high-value products especially protein as high as 44.57%.

Elucidating the bioremediation mechanism of Scenedesmus sp. IITRIND2 under cadmium stress.

Cadmium (Cd) is a non-biodegradable pollutant that has become a global threat due to its bioaccumulation and biomagnification in higher trophic levels of the food chain. Green technologies such as phycoremediation is an emerging approach and possess edge over conventional methods to remediate Cd from the environment. The present investigation elucidates the adaptive mechanism of a freshwater microalga, Scenedesmus sp. IITRIND2 under Cd stress. The microalga showed excellent tolerance to Cd stress with IC50 value of ~32 ppm. The microalga showed phenomenal removal efficiency (~80%) when exposed to 25 ppm of Cd. Such a high uptake of Cd by the cells was accompanied with increased total lipid content (~33% of dry cell weight). Additionally, the elevated level of ROS, lipid peroxidation, glycine-betaine, and antioxidant enzymes evidenced the activation of efficient antioxidant machinery for alleviating the Cd stress. Further, analysis of the fatty acid methyl ester (FAME) presented a steady increase in saturated and polyunsaturated fatty acids with biodiesel properties complying the American and European fuel standards. The study proposes an integrated approach for bioremediation of toxic Cd using hyper-tolerant microalgal strains along with biodiesel production from the generated algal biomass.

Identification, characterization, and lipid profiling of microalgae Scenedesmus sp. NC1, isolated from coal mine effluent with potential for biofuel production.

An autoflocculating microalgal strain was isolated from coal mine effluent wastewater which was named as Scenedesmus sp. NC1 after morphological and molecularly characterization. Further analysis of internal transcribed spacer 2 (ITS2) and compensatory base changes (CBCs) showed it does not belong to the clade comprising Scenedesmus sensu stricto. In stationary phase of growth, Scenedesmus sp. NC1 exhibited excellent autoflocculation efficiency (> 88 %) within 150 min of setting. Temperature, pH, and inorganic metals exhibited minor influence on the autoflocculation activity of Scenedesmus sp. NC1. The fatty acid profiling of Scenedesmus sp.NC1 showed that palmitic acid (C16:0), oleic acid (C18:1), and stearic acid (18:0) accounted for more than 68 % of total fatty acids. Moreover, Scenedesmus sp. NC1 demonstrated significant bioflocculation potential over non-flocculating freshwater microalgae, Chlorella sp. NCQ and Micractinium sp. NCS2. Hence, Scenedesmus sp. NC1 could be effective for economical harvesting of other non-flocculating microalgae for productions of biodiesel and other metabolites.

Bioprospecting of wild type ethanologenic yeast for ethanol fuel production from wastewater-grown microalgae.

BACKGROUND: Wild-type yeasts have been successfully used to obtain food products, yet their full potential as fermenting microorganisms for large-scale ethanol fuel production has to be determined. In this study, wild-type ethanologenic yeasts isolated from a secondary effluent were assessed for their capability to ferment saccharified microalgae sugars. RESULTS: Yeast species in wastewater were identified sequencing the Internal Transcribed Spacers 1 and 2 regions of the ribosomal cluster. Concurrently, microalgae biomass sugars were saccharified via acid hydrolysis, producing 5.0 ± 0.3 g L-1 of fermentable sugars. Glucose consumption and ethanol production of yeasts in hydrolyzed-microalgae liquor were tested at different initial sugar concentrations and fermentation time. The predominant ethanologenic yeast species was identified as Candida sp., and glucose consumption for this strain and S. cerevisiae achieved 75% and 87% of the initial concentration at optimal conditions, respectively. Relatively similar ethanol yields were determined for both species, achieving 0.45 ± 0.05 (S. cerevisiae) and 0.46 ± 0.05 g ethanol per g glucose (Candida sp.). CONCLUSION: Overall, the results provide a first insight of the fermentation capacities of specific wild-type Candida species, and their potential role in ethanol industries seeking to improve their cost-efficiency.

Effect of olive mill wastewaters on Scenedesmus sp. growth, metabolism and polyphenols removal.

BACKGROUND: The three-phase extraction process of olive oil produces highly contaminated wastewater (OMW). The elimination of this toxic by-product is an important environmental issue that requires the development of an appropriate management solution. The cultivation of microalgae using OMW as growth medium was therefore studied using single (the culture medium was formed by 0% to 80% ultrafiltered olive mill wastewater (OMUF) or OMW added to BG11) and two-stage strategies (microalgae were firstly cultivated in the BG11 medium. In the second stage, 40% and 80% of OMUF and OMW were added to the culture). In this work, biodegradation of OMW and subsequent extraction of lipid and antioxidant molecules was investigated as an ecofriendly method for the bioremediation and valorization of OMW. RESULTS: For two-stage cultivation, OMUF and OMW stress enhanced the intracellular amount of polyphenol accumulated in Scenedesmus sp. and exhibited the highest 2, 2-diphenyl-1- picrylhydrazyl radical (DPPH) and 2,2'-azino-bis (3-ethylbenzoline-6-sulfonate) radical (ABTS) scavenging ability compared with single-stage cultivation. Moreover, the lipid profile is dominated by polyunsaturated acids. In the single-stage cultivation, the Ch a, Ch b, carotenoid, carbohydrate and lipid content of 2.57, 7.4, 1.69, 368, and 644 g kg-1 were observed in 40% OMUF added culture, respectively, along with high biomass productivity and 58% of polyphenol removal. Moreover, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that the biomass of Scenedesmus sp. cultured on 40% OMUF did not show any toxic effect, making it an efficient strategy. CONCLUSION: The results indicate that Scenedesmus sp. is a promising microalga for the biotreatment of OMW and the extraction of bioactive metabolites. © 2021 Society of Chemical Industry.

Microalgae cultivation for the treatment of anaerobically digested municipal centrate (ADMC) and anaerobically digested abattoir effluent (ADAE).

The successful cultivation of microalgae in wastewater establishes a waste to profit scenario as it combines treatment of a waste stream with production of valuable end-products. Here, growth and nutrient removal efficiency of three different locally isolated microalgal cultures (Chlorella sp., Scenedesmus sp., and a mixed consortium) cultivated in anaerobically digested municipal centrate (ADMC) and anaerobically digested abattoir effluent (ADAE) was evaluated. No significant differences (P > 0.05) in specific growth rate and biomass productivity were recorded between Chlorella monocultures and the mixed culture grown in both effluents. Scenedesmus sp. monocultures was found incapable of growth in both ADMC and ADAE throughout the cultivation period resulting in the collapse of cultures and no further measurements on the growth, biomass production and nutrient removal efficiency of this alga in both effluent. Fq´/Fm´ values which represent the immediate photo-physiological status of microalgae found to be negatively inhibited when Scenedesmus sp. was grown in both effluents throughout the cultivation period. Fq´/Fm´ values of Chlorella sp. monocultures and the mixed cultures recovered back to normal (≈0.6) after an initial drop. Ammonium removal rates was found to be significantly higher (≈2 folds) for Chlorella sp. monocultures grown in both ADMC and ADAE when compared to the mixed cultures. Nonetheless, no significant differences were observed in the removal of phosphate for both cultures in the different effluents. The total protein and carbohydrate content of the biomass produced was similar for both microalgae cultures grown using ADAE and ADMC. However, chlorophyll a and total carotenoids content were found to be higher (P < 0.05) for the cultures grown in ADAE than ADMC. Overall, Chlorella sp. monoculture was the most efficient option for treating both ADMC and ADAE while simultaneously generating protein rich biomass (up to 49%) that can be potentially exploited as aquaculture feedstock.

Immobilized algae-based treatment of herbicide-contaminated groundwater.

Scenedesmus species, immobilized on alginate gel, was found effective in removing nitrate, atrazine, magnesium, phosphorus, zinc, oxadiazon, and triallate from groundwater in a continuous flow reactor. The laboratory-scale experiments with synthetic groundwater, made of 8.8 mg/L NO3 -N and 90 µg/L atrazine, were performed at a hydraulic retention time of 7 days and the temperatures of 20 and 35°C. The highest uptake of nitrate and atrazine was observed at 20°C (97% and 70%, respectively). When tested in actual groundwater, 92% of nitrate, 100% of magnesium, 99.9% of phosphorus, and 92% of zinc were successfully removed at the end of 29 days' treatment operations. The algal beads removed 100% of oxadiazon and triallate in the first 10 days, but some of the herbicides diffused back into the solution toward the end of the treatment process. PRACTITIONER POINTS: Immobilized algae-alginate beads can remove nitrate, atrazine, oxadiazon, and triallate from groundwater in continuous flow reactor. The uptake rate of nitrate and atrazine is higher in room temperature (20°C). Same algae beads could be reused for herbicide uptake for the average of 10 days. The immobilized system is a natural sustainable alternative that can be used in groundwater pump and treat.