Scenedesmus Vacuolatus Research Articles

Algal consortia as the flexible bio-system for wastewater treatment: Effect of different light intensities on photosynthetic performance, anti-oxidative system and biodiesel production of consortia

Competence of microalgae consortia-1 (Chlorococcum humicola and Tetradesmus sp.) and consortia-2 (Chlorococcum humicola, Scenedesmus vacuolatus and Tetradesmus sp.) was analyzed by examining their adaptability potential in wastewater under different light intensities (20 W/m2 and 40 W/m2). The results depicted highest decline in nutrients and metal concentration (40–90%) at light intensity of 40 W/m2 by consortia-1 and consortia-2 treated with wastewater (50%, 100%). The result of metal remediation was further confirmed by fourier transform infrared spectroscopy (FTIR) which reflected occurrence of different functional groups in selected consortia. Moreover, light intensity of 40 W/m2 induced neutral-lipid accumulation (1750 cm−1) in consortia-1 as depicted in FTIR spectra. The maximum active photosystem-II reaction center (79.75%), quantum yield (26.17%) and performance index (195.8%) revealed that light intensity (40 W/m2) and wastewater augmented functioning of photosystem-II in consortia-1 than consortia-2. Further, consortia-2 appeared more sensitive to oxidative stress as the concentration of oxidative stress markers (5.73–6.39 folds) was amplified after treatment with wastewater at light intensity of 40 W/m2. The prodigious tolerance potential towards different light intensities and wastewater concentration of consortia-1 may be attributed to increased activity of ascorbic acid (1.16 folds), proline (1.32 folds), cysteine (2.80 folds), superoxide dismutase (3.44 folds), catalase (2.52 folds) and glutathione reductase (1.90 folds). However, abundance of saturated fatty acid (41.34%) together with high cetane number (59.07) indicated that consortia 2 can produce excellent quality biofuel at 20 W/m2 while consortia-2 at 40 W/m2. Overall, consortia 1 appeared competent in terms of photosynthetic performance, remediation efficiency and antioxidant defense mechanism under 20 W/m2 and 40 W/m2 while consortia-2 showed quality biodiesel production at 20 W/m2. Thus, algal consortia based on photosynthetic performance and defense responses along with excellent biodiesel quality under different light intensity and wastewater concentration can serve as the promising biosystem for biomass and bioenergy production.

Heterotrophy Compared to Photoautotrophy for Growth Characteristics and Pigment Compositions in Batch Cultures of Four Green Microalgae.

Four strains of green microalgae (Scenedesmus acutus, Scenedesmus vacuolatus, Chlorella sorokiniana, and Chlamydomonas reinhardtii) were compared to determine growth and pigment composition under photoautotrophic or heterotrophic conditions. Batch growth experiments were performed in multicultivators with online monitoring of optical density. For photoautotrophic growth, light-limited (CO2-sufficient) growth was analyzed under different light intensities during the exponential and deceleration growth phases. The specific growth rate, measured during the exponential phase, and the maximal biomass productivity, measured during the deceleration phase, were not related to each other when different light intensities and different species were considered. This indicates species-dependent photoacclimation effects during cultivation time, which was confirmed by light-dependent changes in pigment content and composition when exponential and deceleration phases were compared. Except for C. reinhardtii, which does not grow on glucose, heterotrophic growth was promoted to similar extents by acetate and by glucose; however, these two substrates led to different pigment compositions. Weak light increased the pigment content during heterotrophy in the four species but was efficient in promoting growth only in S. acutus. C. sorokiniana, and S. vacuolatus exhibited the best potential for heterotrophic biomass productivities, both on glucose and acetate, with carotenoid (lutein) content being the highest in the former.

Competence of algal consortia under municipal wastewater: remediation efficiency, photosynthetic performance, antioxidant defense mechanisms and biofuel production.

Utilizing monoalgal species for wastewater treatment is facing tremendous challenges owing to changing wastewater complexity in terms of physico-chemical characteristic, nutrient and metal concentration. The environmental conditions are also fluctuating therefore, the formation of robust system is of utmost importance for concomitant sustainable wastewater treatment and bioenergy production. In the present study, the tolerance and adaptability potential of algal consortia-1 (Chlorococcum humicola and Tetradesmus sp.) and consortia-2 (Chlorococcum humicola, Scenedesmus vacuolatus and Tetradesmus sp.) treated with municipal wastewater were examined under natural environmental conditions. The results exhibited that consortia-2 was more competent in recovering nitrate-nitrogen (82.92%), phosphorus (70.47%), and heavy metals (31-73.70%) from municipal wastewater (100%) than consortia-1. The results further depicted that total chlorophyll, carbohydrate, and protein content decreased significantly in wastewater-treated consortia-1 as compared to consortia-2. However, lipid content was increased by 4.01 and 1.17 folds in algal consortia-1 and consortia-2 compared to their respective controls. Moreover, absorption peak at 1740.6cm-1reflected higher biofuel-producing potential of consortia-1 as compared to consortia-2 as confirmed through FTIR spectroscopy. The results also revealed that consortia-2 showed the highest photosynthetic performance which was evident from the increment in the active photosystem-II reaction center (1.724 ± 0.068), quantum efficiency (0.633 ± 0.038), and performance index (3.752 ± 0.356). Further, a significant increase in photosynthetic parameters was observed in selected consortia at lag phase, while a noteworthy decline was observed at exponential and stationary phases in consortia-1 than consortia-2. The results also showed the maximum enhancement in ascorbic acid (2.43 folds), proline (3.34 folds), and cysteine (1.29 folds) in consortia-2, while SOD (1.75 folds), catalase (2.64 folds), and GR (1.19 folds) activity in consortia-1. Therefore, it can be concluded that due to remarkable flexibility and photosynthetic performance, consortia-2 could serve as a potential candidate for sustainable nutrient resource recovery and wastewater treatment, while consortia-1 for bio-fuel production in a natural environment. Thus, formation of algal consortia as the robust biosystem tolerates diverse environmental fluctuations together with wastewater complexity and ultimately can serve appropriate approach for environmental-friendly wastewater treatment and bioenergy production.

Synergistic effect of process parameters and nanoparticles on spent lubricant oil waste biodegradation by UV-exposed Scenedesmus vacuolatus: Process modelling, kinetics and degradation pathways

The study examines the impact of process parameters and nanoparticles (NPs) on the degradation of spent coolant waste (SCW) by UV-exposed S. vacuolatus. The model was experimentally optimized using response surface methodology (RSM) with high coefficient of determination (R2) >0.99. Upon validation of the model, total petroleum hydrocarbon (TPH) degradation of 100 % was obtained after 15 days under the optimized conditions of 25 °C temperature, 10 % (v/v) substrate concentration and 10 % (v/v) inoculum concentration. Moreover, the sensitivity of the process parameters on the degradation process assessed using artificial neural network (ANN) revealed high sensitivity of the degradation process to operational temperature. Metabolites obtained provide strong evidence for terminal oxidation and subterminal oxidation metabolic pathways in SCW degradation. In addition, the incorporation of NPs in the SCW degradation significantly enhanced the biodegradation efficiency of UV-exposed S. vacuolatus resulting in shortened degradation period from 15 to 12 days. Likewise, the inclusion of NPs substantially improved UV-exposed S. vacuolatus affinity (1/Ks) for SCW, growth constant (Kg) and maximum specific growth rate (μmax). The degradation kinetics followed the second-order reaction with degradation rate constant (K) in the range of 0.029 to 0.288 m−1 t−1 for monoaromatics and 0.972 to 4.130 m−1 t−1 for PAHs, at half-life (T1/2) ranges of 0.75 to 1.52 day−1 and 0.08 to 0.23 day−1, respectively. This knowledge will enhance the design of waste pollutant degradation towards sustainable green environment.

Effect of different temperature regimes on remediation efficiency, photosynthetic performance and fatty acid profile of algal consortia

The present investigation was conducted to examine the adaptability potential of wastewater treated algal consortia (Consortia 1-Chlorococcum humicola and Tetradesmus sp; Consortia 2- Chlorococcum humicola, Scenedesmus vacuolatus and Tetradesmus sp) under temperature regime of 20°C and 40°C. The results exhibited that consortia 1 treated with 25 % wastewater showed highest remediation efficiency than consortia 2. However, maximum specific growth rate (0.064 ± 0.012) and biomass production (2010 ± 14.23 mg/L) was observed in wastewater (50 %) treated consortia 2. The results also revealed highest improvement in different photosynthetic parameters in consortia 1 at 20 °C and 40 °C. Additionally, enrichment of antioxidants and phenolic compounds at 40°C in consortia 1 was evident from FTIR spectroscopy. The results further showed that 40°C enhanced saturated fatty acid percentage (46.99%) in consortia 2. Overall, maximum growth, biomass production, photosynthetic performance and fatty acid profile of selected consortia reflected remarkable adaptability and tolerance towards thermal stress. Thus, employing consortia could serve as the competent bio-system to resolve wastewater complexity and concomitant bio-energy production under temperate and sub-tropical regions.

Effect of ultra-violet light radiation on Scenedesmus vacuolatus growth kinetics, metabolic performance, and preliminary biodegradation study.

This study presents the effect of ultra-violet (UV) light radiation on the process kinetics, metabolic performance, and biodegradation capability of Scenedesmus vacuolatus. The impact of the UV radiation on S. vacuolatus morphology, chlorophyll, carotenoid, carbohydrates, proteins, lipid accumulation, growth rate, substrate affinity and substrate versatility were evaluated. Thereafter, a preliminary biodegradative potential of UV-exposed S. vacuolatus on spent coolant waste (SCW) was carried out based on dehydrogenase activity (DHA) and total petroleum hydrocarbon degradation (TPH). Pronounced structural changes were observed in S. vacuolatus exposed to UV radiation for 24h compared to the 2, 4, 6, 12 and 48h UV exposure. Exposure of S. vacuolatus to UV radiation improved cellular chlorophyll (chla = 1.89-fold, chlb = 2.02-fold), carotenoid (1.24-fold), carbohydrates (4.62-fold), proteins (1.44-fold) and lipid accumulations (1.40-fold). In addition, the 24h UV exposed S. vacuolatus showed a significant increase in substrate affinity (1/Ks) (0.959), specific growth rate (µ) (0.024h-1) and biomass accumulation (0.513g/L) by 1.50, 2 and 1.9-fold respectively. Moreover, enhanced DHA (55%) and TPH (100%) degradation efficiency were observed in UV-exposed S. vacuolatus. These findings provided major insights into the use of UV radiation to enhance S. vacuolatus biodegradative performance towards sustainable green environment negating the use of expensive chemicals and other unfriendly environmental practices.

Cocultivation of White-Rot Fungi and Microalgae in the Presence of Nanocellulose.

ABSTRACTCocultivation of fungi and algae can result in a mutualistic or antagonistic interaction depending on the species involved and the cultivation conditions. In this study, we investigated the growth behavior and enzymatic activity of two filamentous white-rot fungi (Trametes versicolor and Trametes pubescens) and two freshwater algae (Chlorella vulgaris and Scenedesmus vacuolatus) cocultured in the presence of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) oxidized cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC). The growth of fungi and algae was studied in liquid, agar medium, and 3D-printed nanocellulose hydrogels. The results showed that cocultures grew faster under nutrient-rich conditions than in nutrient-depleted conditions. Key cellulose-degrading enzymes, including endoglucanase and laccase activities, were higher in liquid cocultures of T. versicolor and S. vacuolatus in the presence of cellulose compared to single cultures of fungi or algae. Although similar results were observed for cocultures of T. pubescens and C. vulgaris, laccase production diminished over time in these cultures. Fungi and algae were capable of growth in 3D-printed cellulose hydrogels. These results showed that cellulase enzyme production could be enhanced by cocultivating white-rot fungi with freshwater algae under nutrient-rich conditions with TEMPO-CNF and CNC. Additionally, the growth of white-rot fungi and freshwater algae in printed cellulose hydrogels demonstrates the potential use of fungi and algae in hydrogel systems for biotechnological applications, including biofuel production and bio-based fuel cell components.IMPORTANCE Depending on the conditions used to grow fungi and algae in the lab, they can interact in a mutually beneficial or negative way. These interactions could stimulate the organisms to produce enzymes in response to the interaction. We studied how wood decay fungi and freshwater algae grew in the presence and absence of cellulose, one of the basic building blocks of wood. How fungi and algae grew in 3D-printed cellulose hydrogels was also tested. Our results showed that fungi and algae partners produced significantly larger amounts of enzymes that degraded cellulose when grown with cellulose than when grown alone. In addition, fungi and algae were shown to grow in dense nanocellulose hydrogels and could survive the shear conditions during gel structuring while 3D-printing. These cultures could potentially be applied in the biotech industry for applications like energy production from cellulose, biofuel production, and bioremediation of cellulose material.

Associated bacterial microbiome responds opportunistic once algal host Scenedesmus vacuolatus is attacked by endoparasite Amoeboaphelidium protococcarum

The interactions of microalgae and their associated microbiomes have come to the fore of applied phycological research in recent years. However, the functional mechanisms of microalgal interactions remain largely unknown. Here, we examine functional protein patterns of the microalgae Scenedesmus vacuolatus and its associated bacterial community during algal infection by the endoparasite Amoeboaphelidium protococcarum. We performed metaproteomics analyses of non-infected (NI) and aphelid-infected (AI) S.vacuolatus cultures to investigate underlying functional and physiological changes under infectious conditions. We observed an increase in bacterial protein abundance as well as a severe shift of bacterial functional patterns throughout aphelid-infection in comparison to NI treatment. Most of the bacterial proteins (about 55%) upregulated in AI were linked to metabolism and transport of amino acids, lipids, coenzymes, nucleotides and carbohydrates and to energy production. Several proteins associated with pathogenic bacterial-plant interactions showed higher protein abundance levels in AI treatment. These functional shifts indicate that associated bacteria involved in commensalistic or mutualistic interactions in NI switch to opportunistic lifestyles and facilitate pathogenic or saprotrophic traits in AI treatment. In summary, the native bacterial microbiome adapted its metabolism to algal host die off and is able to metabolize nutrients from injured cells or decompose dead cellular material.

Biopolymer treatment of ammonium-rich industrial effluents for the mass cultivation of microalgae

Although wastewater reutilization for microalgae culturing can meet the dual goals of wastewater treatment and biomass production, some effluents with high contaminant concentrations are toxic to microalgae, necessitating pretreatment protocols to lower the toxicity before bioremediation. The present study aimed to bioremediate the industrial effluents of El Delta Co. for Fertilizers and Chemical Industries (Mansoura, Egypt), using sodium alginate as a pretreatment to enable reuse as a growth medium for microalgae culturing. Various water quality parameters signified the inferior state of the effluent with an ammonia-N concentration of 185.76 mg L−1. Toxicity investigations of the raw industrial effluents revealed toxicity to Chlorella sorokiniana, Scenedesmus vacuolatus and Pseudokirchneriella subcapitata. Effluent bioremediation was adopted using different concentrations of the biopolymer sodium alginate, and 1.0 g L−1 sodium alginate resulted in the highest removal of both ammonia-N and heavy metals. Chlorella sorokiniana and S. vacuolatus successfully grew in the 1.0 g L−1 alginate-treated effluent. Chlorella sorokiniana removed 87.8% of the ammonia-N, 75% of the copper, and 100% of the phosphorus. Scenedesmus vacuolatus consumed 85.7% of the ammonia-N, 66.7% of the copper, and 100% of the phosphorus. Adjusting the N:P mass ratio to 9.9 resulted in high tolerance of C. sorokiniana and S. vacuolatus to the effluent toxicity, with an EC50 > 100%. The 1.0 g L−1 sodium alginate-treated effluent stimulated C. sorokiniana and S. vacuolatus growth relative to the control. Additionally, C. sorokiniana and S. vacuolatus had the highest biomass production and protein content, reaching 1.42 and 0.74 g L−1 and 57.04 ± 0.04% and 52.19 ± 0.02%, respectively, in the treated effluent. Therefore, it was concluded that this bioremediation approach using the 1.0 g L−1 alginate pretreatment followed by microalgal cultivation (C. sorokiniana and S. vacuolatus) successfully treated the industrial effluent, representing a promising protocol for bioremediation practices.

Implication of municipal wastewater on growth kinetics, biochemical profile, and defense system of Chlorella vulgaris and Scenedesmus vacuolatus

In the present investigation, the growth pattern, cellular modification, oxidative stress markers, and defense responses in Chlorella vulgaris and Scenedesmus vacuolatus were analyzed after treatment with municipal wastewater (25%–100%). The main aim was to compare the Chlorella vulgaris and Scenedesmus vacuolatus on account of remediation efficiency, lipid production and defense responses under different concentrations of wastewater. The results revealed that the nutrients (93.28%) and heavy metal (92.08%) removal was highest at 25% of wastewater concentration while maximum specific growth rate (0.0708 day−1), total chlorophyll (0.118 mg g−1 fw), and carbohydrate content (24.06 mg L−1 fw) was observed with Scenedesmus vacuolatus at 50% concentration of wastewater. Additionally, fourier transform infrared spectroscopy showed 100% concentration of wastewater enhanced lipid accumulation in Scenedesmus vacuolatus than Chlorella vulgaris. The lesser accumulation of thiobarbituric acid reactive species and hydrogen peroxide while increment in antioxidants activity (1.87–15.63 folds) may be responsible for imparting tolerance to Scenedesmus vacuolatus against different concentrations of municipal wastewater. Overall, the study revealed that 50% and 100% wastewater concentration was suitable for excellent growth and lipid accumulation in Scenedesmus vacuolatus, respectively. Thus, due to high nutrients reutilization potential, metal removal rate, growth profile, lipid production, and anti-oxidative responses, Scenedesmus vacuolatus seems more effective and tolerant than Chlorella vulgaris. Therefore, exploiting Scenedesmus vacuolatus may be the successful step towards sustainable management of wastewater and lipid production.

Toxicological effects of active and inert ingredients of imazethapyr formulation Verosil® against Scenedesmus vacuolatus (Chlorophyta)

Imazethapyr, a selective systemic herbicide, is widely used in agriculture and it is frequently detected in water bodies close to application areas. Like other agrochemicals, imazethapyr is commercialized in formulations containing a mixture of additives that increase the effectiveness of the active ingredient. These complex mixtures may cause adverse effects on non-target primary producers, such as microalgae, when they reach freshwater bodies. The aim of this study was to assess the effects, separately, of the formulation Verosil®, the formulation additives, and technical-grade imazethapyr, in the acidic form or as ammonium salt, on the microalga Scenedesmus vacuolatus (Chlorophyta). Verosil®, formulation additives, and acid imazethapyr significantly inhibited the growth of S. vacuolatus (Verosil® > formulation additives > acid imazethapyr) and caused morphological alterations from 2mg L-1, 4mg L-1, and 60mg L-1 onwards, respectively. Verosil® and formulation additives caused the most adverse effect including membrane disorganization, cytoplasm contraction, cell wall thickening, thylakoidal membrane disaggregation, and starch granule accumulation. In addition, Verosil® and formulation additives increased the chl a/chl b ratio, indicating possible alterations in photosystems as a stress response. The carotene/chl a ratio was also increased in microalgae exposed to both Verosil® and formulation additives, suggesting an antioxidant response to these toxic compounds. All these results support the hypothesis that the formulation additives contribute significantly to the toxicity and alterations caused by the commercial formulation Verosil® on S. vacuolatus.

Effects of leachates from UV-weathered microplastic on the microalgae Scenedesmus vacuolatus

Plastics undergo successive fragmentation and chemical leaching steps in the environment due to weathering processes such as photo-oxidation. Here, we report the effects of leachates from UV-irradiated microplastics towards the chlorophyte Scenedesmus vacuolatus. The microplastics tested were derived from an additive-containing electronic waste (EW) and a computer keyboard (KB) as well as commercial virgin polymers with low additive content, including polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), and polystyrene (PS). Whereas leachates from additive-containing EW and KB induced severe effects, the leachates from virgin PET, PP, and PS did not show substantial adverse effects in our autotrophic test system. Leachates from PE reduced algae biomass, cell growth, and photosynthetic activity. Experimental data were consistent with predicted effect concentrations based on the ionization-corrected liposome/water distribution ratios (Dlip/w) of polymer degradation products of PE (mono- and dicarboxylic acids), indicating that leachates from weathering PE were mainly baseline toxic. This study provides insight into algae toxicity elicited by leachates from UV-weathered microplastics of different origin, complementing the current particle- vs. chemical-focused research towards the toxicity of plastics and their leachates.Graphical abstract

Algal consortia based metal detoxification of municipal wastewater: Implication on photosynthetic performance, lipid production, and defense responses

The present investigation was carried out to assess the competence of artificially engineered microalgal consortia i.e. consortia 1 (Scenedesmus vacuolatus + Chlorococcum humicola), consortia 2 (Tetradesmus sp. + Scenedesmus vacuolatus), and consortia 3 (Chlorococcum humicola + Scenedesmus vacuolatus + Tetradesmus sp.) for municipal wastewater treatment and lipid production under laboratory conditions. The purpose of the present study was to screen the competent microalgae consortia based on wastewater remediation, photosynthetic performance, and antioxidant defense responses. The outcome based on nutrient reutilization (78.98–98%), metal detoxification (50–94%), and biomass production (1.43–1.65 folds) reflected greater adaptability and tolerance of consortia 2 against different concentrations of wastewater. The photosynthetic performance parameters such as active photosystem II reaction centre, the quantum yield, and photosynthetic performance index were increased by 1.20–2.35 folds in consortia 2 after treatment with different concentrations of wastewater. Additionally, Fourier transform infrared spectroscopy peak showed at 1750 cm−1 confirmed neutral lipid accumulation in consortia 2 at 100% concentration of wastewater. The measurement of oxidative stress markers such as thiobarbituric acid reactive species and hydrogen peroxide showed considerable decline in consortia 2 as compared to consortia 1 and 3. Interestingly, increased non–enzymatic (1.02–2.44 folds) and enzymatic antioxidant (1.05–4.14 folds) activity in consortia 2 reflected that oxidative stress was attenuated by the amplified activity of ascorbic acid, proline, cysteine, superoxide dismutase, catalase, and glutathione reductase. Overall, photosynthetic performance, lipid production, and antioxidants activity represented that the consortia 2 can be effectively used for sustainable wastewater treatment and lipid production. Thus, the synergistic association of two microalgae may be the superior and neoteric paradigm with multilevel benefits such as sustainable nutrient resource utilization, metal detoxification, and lipid production.

Comparison of biodegradative efficiency of wildtype versus mutagenised Scenedesmus vacuolatus of spent coolant waste: dehydrogenase activity and total petroleum degradation studies

ABSTRACT This study aims to compare the biodegradability efficiency of spent coolant waste by wild-type microalga versus mutagenised Scenedesmus vacuolatus. The biodegradation efficiency of both groups microalgae was evaluated using dehydrogenase activity (DHA) and total petroleum hydrocarbon (TPH) degradation using gas chromatography and mass spectrometry (GCMS). The DHA of both microalgae was conducted in relation to the triphenyl formazan production (TPF). The TPH of extracellular hydrocarbon degradation and intracellular hydrocarbons were analysed using GCMS. The data obtained from DHA and GCMS were analysed using analysis of variance at a 5% level of significance (0 < 0.05). The wild-type and mutagenised S. vacuolatus showed biodegradation of spent coolant waste after five weeks. The highest TPF produced by wild-type microalgae after five weeks was 1.139 mg/mL ± 0.009. The highest TPF produced by mutagenised S. vacuolatus after five weeks was 1.771 mg/mL ± 0.006 which was 1.55-fold higher than the TPF produced by the wild-type microalgae in the treatment weeks. The highest TPH degraded by wild-type after five weeks was 85.87% ± 0.20, while the highest TPH degradation of 100% was observed for the mutagenised S. vacuolatus after five weeks of spent coolant waste treatment. These results suggest that the mutagenised S. vacuolatus was better in utilising and degrading spent coolant waste and, therefore, can be used to mitigate spent oil pollution.

Evaluation and Characterization of Microalgae from Kalaburagi Region as a Potential Source of Biomass Production

Microalgaes are considered for a large number of applications such as biomass and energy production due to their increased capability of biomass production. Various biotic and abiotic factors influence the growth of microalgae. Among the abiotic factors include the temperature, light intensity, pH of the medium, salinity, and nutritional conditions play the major role. Ten samples of microalgae were collected from different sites of water bodies from Gulbarga University campus. The microalgae isolated were identified and characterized using light microscope, SEM and PCR based 18s rRNA. Influence of cultural conditions such as carbon and nitrogen sources, pH, temperature and salinity on biomass production were studied and analyzed. Among the strains identified, a novel species was isolated and identified as Scenedesmus vacuolatus AK1. The maximum growth rate and biomass productivity can be achieved by providing glucose as carbon source and urea as nitrogen sources at an optimum of 0.5gm/l and 0.1mg/l irrespectively. It was also observed that the strain showed a good growth profile and increase in biomass production at an optimum alkaline pH of 8. Maximum biomass productivity of 0.6g/l was observed at an optimum temperature of 30˚C in BG-11 medium. Maximum biomass yield of 1.45g/l was observed at 5mM NaCl concentration.

A multi-omics concentration-response framework uncovers novel understanding of triclosan effects in the chlorophyte Scenedesmus vacuolatus

In aquatic ecosystems, the biocide triclosan represents a hazard for the non-target microalgae. So far, algal responses were mainly investigated at apical levels hampering the acquisition of a holistic view on primary, adaptive, and compensatory stress responses. We assessed responses of the chlorophyte Scenedesmus vacuolatus to triclosan at apical (growth, photosynthesis) and molecular (transcriptome, metabolome) levels for comparative pathway sensitivity analysis. For each responsive signal (contigs, metabolites), a concentration-response curve was modeled and effect concentrations were calculated leading to the setting of cumulative sensitivity distributions. Molecular responses showed higher sensitivity than apical observations. The functional annotation of contigs and metabolites revealed 118 metabolic pathways putatively impaired by triclosan, highlighting a wide repercussion on the algal metabolism. Metabolites involved in the lipid metabolism showed decreasing trends along the concentration gradient and a globally highest sensitivity, pointing to the primary target of triclosan. The pathways involved in xenobiotic degradation and membrane transporters were mainly regulated in the transcriptome with increasing response trends comprising compensatory responses. The suggested novel approach, combining apical and multi-omics analyses in a concentration-response framework improves mechanistic understanding and mode of action analysis on non-targeted organisms and is suggested to better implement high-throughput multi-omics data in environmental risk assessment.

Plant Growth-Promoting Methylobacteria Selectively Increase the Biomass of Biotechnologically Relevant Microalgae.

Microalgae, a diverse group of single-celled organisms exhibiting versatile traits, find broad applications in industry. However, high production costs require further efforts to optimize their production and to enhance biomass yields. In the present study, co-occurrence of algae and methylobacteria was observed when naturally occurring microalgae biofilms were subjected to 16S rRNA gene fragment amplicon sequencing. This bacterial group is so far less explored than other microalgae-associated bacteria in terms of mutualistic relationships that might be exploitable for biotechnological applications. In order to assess the potential of four plant growth-promoting strains from the genus Methylobacterium for increased algae biomass production, co-cultivation experiments were conducted with three industrially relevant microalgae (Chlorella vulgaris, Scenedesmus vacuolatus, and Haematococcus lacustris). For S. vacuolatus and H. lacustris, a significant increase in algal biomass formation of 1.3-fold to up to 14-fold was observed after 7 days of co-incubation. Visualization of mixed cultures using confocal laser scanning microscopy revealed a high abundance of methylobacteria in the phycosphere of H. lacustris and S. vacuolatus, visually attached to the algae’s surface forming a biofilm-like assemblage. Genome analyses revealed that features attributable to enhanced algal growth include genes involved in the synthesis of vitamins, siderophores and plant hormones. Our results provide evidence for the constructability of novel symbiotic algae-bacteria relationships with inter-kingdom supportive capacities, underlining the potential of microbial consortia as promising tool for sustainable biotechnology and agriculture.

Effect of Hydrocarbon-Polluted Seawater on the Cell Density of Microalgae Scenedesmus vacuolatus Shihira &amp; Krauss

Study about the effect of hydrocarbon-polluted seawater on the cell density of microalgae Scenedesmus vacuolatus has been done. Hydrocarbon pollution derived from oil in the sea can inhibit photosynthesis process of microalgaes. This might impact the density of microalgae cells. The purposes of this study are to determine the effect of the concentration of hydrocarbon-polluted seawater on the density of Scenedesmus vacuolatus microalgae cells and to determine the optimum treatment to reduce total petroleum hydrocarbons (TPH) levels. Sampling of hydrocarbon-polluted seawater was taken at Kali Adem port, Jakarta. The treatment done in this research used Walne medium with the addition of 25% hydrocarbon-polluted seawater (A), 50% (B), 75% (C), and 100% (D). Control is Walne medium with sterile seawater that was not from the Kali Adem port. The results showed the highest average density of Scenedesmus vacuolatus cells was in the control sample. This can be seen from the results of the average cell density at peak time of 29.48 x 105 cells / mL, as well as the log phase length of Scenedesmus vacuolatus. Measurement of TPH levels showed decreases of TPH in all treatments. The optimum treatment to reduce TPH levels is on treatment B with reduction percentage of 70.62%. Key words: Kali Adem port, Scenedesmus vacuolatus, total petroleum hydrocarbon (TPH), Walne medium

The use of response surface methodology for improving fatty acid methyl ester profile of Scenedesmus vacuolatus.

The present study has been designed to optimise certain important process parameters for Scenedesmus vacuolatus to achieve efficient carbon dioxide extenuation as well as suitable fatty acid profile in context to improve biodiesel properties. The effect of varying sodium bicarbonate concentration was evaluated in single and multicomponent system such as nitrate, phosphate, inoculum size to observe interactive effects on algae biomass production, carbon dioxide (CO2) removal efficiency and fatty acid methyl ester (FAME) profile. Maximum biomass productivity of 117.0 ± 7.7mg/L/day with 3g/L of sodium bicarbonate was obtained i.e. approximately 2 folds higher than the control. Under multicomponent exposure, maximum biomass of 1701.5 ± 88.8mg/L and maximum chlorophyll concentration of 15.3 ± 6.4mg/L were achieved on 14th day at 3g/L sodium nitrate, 0.1g/L dipotassium hydrogen phosphate, 2g/L of sodium bicarbonate and initial cell density of 0.3 (N3P0.1B2OD0.3). FAME content of 46.1mg/g of biomass was obtained at this combination which is approximately 3 folds higher than the FAME content obtained under nitrogen and phosphate deprivation (16.6mg/g at N0P0B2OD0.3). Confocal microscopy images confirmed the results with enhanced lipid droplet accumulation at high bicarbonate concentration as compared with the control. This interactive study concluded the variability in FAME profile along with the exposure to varying nutrient concentrations.

Comparison of biodegradation of lubricant wastes by Scenedesmus vacuolatus vs a microalgal consortium

Locally, the petroleum, aluminum and steel milling industries have expressed considerable interest in the utilization of bioremediation as a means for reducing their lubricant waste. Since hydrocarbons accumulate within microalgae, the aim of this study was to determine the efficiency of Scenedesmus vacuolatus vs a microalgal consortium (Chlamydomonas pitschmannii, Trebouxia australis and Pectinodesmus pectinatus) in the biodegradation lubricant waste products; from which these indigenous microalgae were originally isolated. To determine the biodegradation capability of these microalgae, dehydrogenase activity tests were carried out and indicated by % TPF values. Samples that tested positive for dehydrogenase activity, were analyzed using gas chromatography/mass spectrometry, to track the biotransformation of hydrocarbons intracellularly and extracellularly. Results were analyzed statistically with SPSS, p < 0.05. Dehydrogenase activity for both the coolant rolling oil (0.058 ± 0.001 mg/mL), and the spent rolling emulsion (0.047 ± 0.002) was higher for the microbial consortium compared to S. vacuolatus, 0.046 ± 0.001 mg/mL. Weekly, gas chromatography/mass spectrometry biotransformations, indicated no hydrocarbons present after five weeks, confirming 100% biodegradation. Irrespective of the use of either a single isolate or a microalgal consortium; complete biodegradation after just five weeks, makes the use of microalgae for bioremediation a viable strategy.