Microalgae Biomass Production Research Articles

Microalgae Biomass Production from Rice Husk as Alternative Media Cultivation and Extraction of Phycocyanin Using 3D-Printed Ohmic Heating Reactor.

Phycocyanin is a highly valued pigment present in Spirulina platensis biomass with applications in the food industry in terms of biorefinery concepts; specifically, its antioxidant and antimicrobial capacity are an advantage that could be incorporated into a food matrix. This study aims to use rice husk as an alternative culture medium for S. platensis biomass growth and phycocyanin extraction by ohmic heating processing using a 3D-printed reactor. S. platensis was cultivated in rice husk extract (RHE) from 0-100% (v/v). The highest content of microalgal biomass was 1.75 ± 0.01 g/L, with a specific growth rate of 0.125 ± 0.01 h-1. For the phycocyanin extraction under an ohmic heating process, a 3D-printed reactor was designed and built. To optimize phycocyanin extraction, a central composite rotatable design (CCDR) was evaluated, with three factors: time (min), temperature (°C), and pH. The highest phycocyanin content was 75.80 ± 0.98 mg/g in S. platensis biomass grown with rice husk extract. Ohmic heating is a promising method for rapid phycocyanin extraction, and rice husk as a culture medium is an alternative for the growth of S. platensis biomass in the integration of second- and third-generation biorefineries.

Knocking Out Chloroplastic Aldolases/Rubisco Lysine Methyltransferase Enhances Biomass Accumulation in Nannochloropsis oceanica under High-Light Stress.

Rubisco large-subunit methyltransferase (LSMT), a SET-domain protein lysine methyltransferase, catalyzes the formation of trimethyl-lysine in the large subunit of Rubisco or in fructose-1,6-bisphosphate aldolases (FBAs). Rubisco and FBAs are both vital proteins involved in CO2 fixation in chloroplasts; however, the physiological effect of their trimethylation remains unknown. In Nannochloropsis oceanica, a homolog of LSMT (NoLSMT) is found. Phylogenetic analysis indicates that NoLSMT and other algae LSMTs are clustered in a basal position, suggesting that algal species are the origin of LSMT. As NoLSMT lacks the His-Ala/ProTrp triad, it is predicted to have FBAs as its substrate instead of Rubisco. The 18-20% reduced abundance of FBA methylation in NoLSMT-defective mutants further confirms this observation. Moreover, this gene (nolsmt) can be induced by low-CO2 conditions. Intriguingly, NoLSMT-knockout N. oceanica mutants exhibit a 9.7-13.8% increase in dry weight and enhanced growth, which is attributed to the alleviation of photoinhibition under high-light stress. This suggests that the elimination of FBA trimethylation facilitates carbon fixation under high-light stress conditions. These findings have implications in engineering carbon fixation to improve microalgae biomass production.

Potential use of sludge from El Ferrol Bay (Chimbote, Peru) for the production of lipids in the culture of Scenedesmus acutus (Meyen, 1829)

Despite the extensive development of microalgae biotechnology, it still requires new methodologies to lower production costs, especially in the field of biofuel production. Therefore, innovative methods that facilitate operations and enable cost-effective production are important in driving this industry. In this study, we propose a new low-cost and easy-to-use procedure, addressed to the generation of a culture medium for Scenedesmus acutus. The medium was obtained by thermal reduction of a sludge sample from El Ferrol Bay (Chimbote, Peru), whereby we obtained an aqueous medium. Our results indicated that the aqueous medium incorporates all necessary nutrients for microalgae production; allowing a maximum biomass of 0.75 ± 0.07 g/L with 60% of the medium; while high lipids production (59.42 ± 6.16%) was achieved with 20%. Besides, we quantified, in the experimental medium and at the end of the cultures, the levels of inorganic nutrients such as ammonium, nitrites, nitrates, and phosphates; in addition to COD and TOC, which were significantly reduced (p<\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$p<$$\\end{document} 0.05) after 7 days of culture, mainly in the treatment with 20%. These results suggest tremendous potential for sludge reuse, which also entails a cost reduction in microalgae biomass production, with additional positive impacts on large-scale application over highly polluted environments.

Combined effect of LED light color and nitrogen source on growth, pigments composition and oxidative stress in Arthrospira platensis

Artificial lighting with light-emitting diodes (LED) is proposed as a suitable solution to reach stable yearly production of high value molecules from microalgae under unfavorable climates. However, available studies are inconsistent regarding the effect of LED color on cultures performance. This study examined the response of Arthrospira platensis to three different LED lighting conditions (white, red, and red-blue 70:30) when is grown in three media with different nitrogen composition. Growth, phycobiliproteins and lipophilic pigments content were determined. In addition, antioxidant enzymes (GST, lipid peroxidation) and morphology were analyzed to enlighten new perspectives on the health status of microalgae production.The highest biomass production (2.13 g/L) was achieved under red LED when Zarrouk medium was supplemented with urea. Regarding pigment production (phycobilins, chlorophyll a and β- carotene), the most desirable combination was red: blue together with urea supplementation. In addition, this combination showed a high biomass production (2.03 g/L) and low expression of antioxidant enzymatic activity. This research shows a novel combination of LED technology and nutrients to enhance microalgae biomass production and high value metabolites with a lower economic cost.

Optimation of the cell density, biomass production, lipid, and carbohydrate content of Nannochloropsis oculata with fluorescein and pH manipulation

Nannochloropsis oculata is a potential marine microalga. However, the mass production of N. oculata encounters several challenges, such as the high costs of resources, contamination, and light absorption optimization. These problems can be solved by pH manipulation and fluorescein induction on culture media. Various studies have shown that pH values manipulation can cause fluctuations in cell density, dry biomass, and carbohydrate and lipid production of microalgae. On the other hand, fluorescein can act as a molecular antenna that improves light absorption. This research is novel because of its focus on its unique attempt to utilize pH manipulation combined with fluorescein induction to enhance the growth and metabolite production of N. oculata. The implications of this research may provide cost-effective, viable, and sustainable development of the algal industry in general. In this research, cultivation was carried out for seven days with four levels of pH (7 – 10) combined with three variations of fluorescein addition (0, 0.15, and 0.3 mL). Every treatment combination had three replications. Cell density and biomass as growth analysis parameters were calculated during the cultivation using the Haemocytometer and gravimetric methods. Bligh &amp; Dyer and phenol sulfate methods were used to analyze lipid and carbohydrate content. Based on the result, the best treatment combination, pH 9 with 0.15 mL of fluorescein, increases cell density and carbohydrate content of N. oculata by 31.45 and 4.4%, albeit not statistically significant.

Enhancing microalgae biomass production: Exploring improved scraping frequency in a hybrid cultivation system

Recently, hybrid systems, such as those incorporating high-rate algal ponds (HRAPs) and biofilm reactors (BRs), have shown promise in treating domestic wastewater while cultivating microalgae. In this context, the objective of the present study was to determine an improved scraping frequency to maximize microalgae biomass productivity in a mix of industrial (fruit-based juice production) and domestic wastewater. The mix was set to balance the carbon/nitrogen ratio. The scraping strategy involved maintaining 1 cm wide stripes to retain an inoculum in the reactor. Three scraping frequencies (2, 4, and 6 days) were evaluated. The findings indicate that a scraping frequency of each 2 days provided the highest biomass productivity (18.75 g total volatile solids m−2 d−1). The species’ behavior varied with frequency: Chlorella vulgaris was abundant at 6-day intervals, whereas Tetradesmus obliquus favored shorter intervals. Biomass from more frequent scraping demonstrated a higher lipid content (15.45%). Extrapolymeric substance production was also highest at the 2-day frequency. Concerning wastewater treatment, the system removed 93% of dissolved organic carbon and ∼100% of ammoniacal nitrogen. Combining industrial and domestic wastewater sources to balance the carbon/nitrogen ratio enhanced treatment efficiency and biomass yield. This study highlights the potential of adjusting scraping frequencies in hybrid systems for improved wastewater treatment and microalgae production.

Enhancing lipid production and sedimentation of Chlorella pyrenoidosa in saline wastewater through the addition of agricultural phytohormones

In this study, the effect of external agricultural phytohormones (mixed phytohormones) addition (1.0, 5.0, 10.0, and 20.0 mg L−1) on the growth performance, lipid productivity, and sedimentation efficiency of Chlorella pyrenoidosa cultivated in saline wastewater was investigated. Among the different concentrations evaluated, the highest biomass (1.00 g L−1) and lipid productivity (11.11 mg L−1 d−1) of microalgae were obtained at 10.0 mg L−1 agricultural phytohormones addition. Moreover, exogenous agricultural phytohormones also improved the sedimentation performance of C. pyrenoidosa, which was conducive to the harvest of microalgae resources, and the improvement of sedimentation performance was positively correlated with the amount of agricultural phytohormones used. The promotion of extracellular polymeric substances synthesis by phytohormones in microalgal cells could be considered as the reason for its promotion of microalgal sedimentation. Transcriptome analysis revealed that the addition of phytohormones upregulated the expression of genes related to the mitogen-activated protein kinase (MAPK)-mediated phytohormone signaling pathway and lipid synthesis, thereby improving salinity tolerance and lipid production in C. pyrenoidosa. Overall, agricultural phytohormones provide an effective and inexpensive strategy for increasing the lipid productivity and sedimentation efficiency of microalgae cultured in saline wastewater.

Biochemical trade-offs and opportunities of commercialized microalgae cultivation under increasing carbon dioxide

Microalgae's exceptional photosynthetic prowess, CO2 adaptation, and high-value bioproduct accumulation make them prime candidates for microorganism-based biorefineries. However, most microalgae research emphasizes downstream processes and applications rather than fundamental biomass and biochemical balances and kinetic under the influence of greenhouse gases such as CO2. Therefore, three distinctly different microalgae species were cultivated under 0% to 20% CO2 treatments to examine their biochemical responses, biomass production and metabolite accumulations. Using a machine learning approach, it was found that Chlorella sorokiniana showed a positive relationship between biomass and chl a, chl b, carotenoids, and carbohydrates under increasing CO2 treatments, while Chlamydomonas angulosa too displayed positive relationships between biomass and all studied biochemical contents, with minimal trade-offs. Meanwhile, Nostoc sp. exhibited a negative correlation between biomass and lipid contents under increasing CO2 treatment. The study showed the potential of Chlorella, Chlamydomonas and Nostoc for commercialization in biorefineries and carbon capture systems where their trade-offs were identified for different CO2 treatments and could be prioritized based on commercial objectives. This study highlighted the importance of understanding trade-offs between biomass production and biochemical yields for informed decision-making in microalgae cultivation, in the direction of mass carbon capture for climate change mitigation.

Effect of natural increase of pH and microalgae cyclical re-cultivation on biomass production and polishing of municipal secondary effluent

A constant source of nutrient pollution that causes eutrophication is municipal wastewater treatment plant (WWTP) secondary effluent. This paper investigates the natural increase of pH, nutrient removal and biomass production from a cyclical re-cultivation system designed to favor the adaptation of microalgae consortia to WWTP secondary effluent. An outdoor experiment was performed with the microalgae consortia MC-10 under 3 sequential batch cycles. The natural pH increase (range 9–10) in the WWTP secondary effluent was established as an operation parameter because it certainly influenced microalgae biomass production (by maintenance and bioavailability of C and P), water treatment and pathogen removal. The increase of pH (9.7, 9.8 and 9.9) during the culture cycles of MC-10 probably generated conditions for fecal bacterial removal below detectable values (i.e., < 2 MPN/100 mL). The treatment of WWTP secondary effluent after batch cycles (cycles 1 to 3) using MC-10 indicated improvements in biomass productivity (66 to 167%) and a great potential for the reduction of total alkalinity (13.1 to 50.3%), NO3–-N (30.9 to 53.6%), PO43–- P (90.4 to 93.0%) and electrical conductivity (EC) (8.5 to 18.1%). Additionally, the harvested biomass showed a high mineral concentration (46.5%) suggesting its potential use as a bio-fertilizer.

Light-induced aquaculture wastewater valorization, nutrient recovery, and microalgae biomass production in a biocathode-assisted microbial fuel cell

The present study investigates how well the light quality (white, blue, and red light) affects the growth and biochemical profiling of freshwater microalga Scenedesmus obliquus grown on aquaculture wastewater as a nutrient source in a biocathode microbial fuel cell (MFC). The findings show that the electrochemical behaviour of the MFCs varied with the use of different wavelengths, suggesting that light quality and photosynthetic evolved oxygen increased MFC voltage. Sc. obliquus showed the highest percentage of nutrient removal for blue light-operated biocathode MFC. Blue light maximized biomass production with a cell density of 1.54 ± 0.065 OD680 and Chl-a concentration of 12 ± 1.2 mgL−1 during 6-day cultivation. Valorization of aquaculture using MFC proved successful in nutrient recovery and microalgae biomass production, primarily upon exposure to blue light.

Improvement of N and P ratio for enhanced biomass productivity and sustainable cultivation of Chlorella vulgaris microalgae

Microalgae cultivation could contribute to the achievement of several sustainable development goals (SDGs). However, cultivating Chlorella vulgaris, like any other microalgae, is challenging due to various biotic, abiotic and process related factors that can affect its growth and biomass productivity. Nutrient availability, particularly N and P, and their ratio play a crucial role in building cellular structures and maintaining metabolic processes, determining basically the maximum achievable biomass productivity under given circumstances. The present article aims to improve the N and P ratio to enhance the biomass productivity of Chlorella vulgaris microalgae as well as to characterize the biomass growth kinetics that can be used for prediction purposes. The results showed that the nutrient solutions prepared with increased nitrate concentration (T1 – N:P = 55:1 and T3 – N:P = 28:1) promoted chlorophyll formation and significantly outperformed the control sample (BG-11 – N:P = 35:1) with 192% and 183%, leading to higher biomass productivity with 1160 μg L−1 and 1103 μg L−1, respectively. Moreover, a strong positive correlation was revealed (0.81) between phosphate concentration and microalgae activity rate, indicating the role of phosphorous in energy transfer, resulted in stimulated microalgae activity rates with 71.2% and 70.66% in the phosphate-increased nutrient solutions (T2 – N:P = 14:1 and T3 – N:P = 28:1). In addition, an exponential equation was introduced to characterize the biomass growth kinetics, of which the theoretically achievable maximum chlorophyll concentration (CTAM) and the theoretical cultivation time (tcultivation) were determined for the tested nutrient solutions with variable N:P ratio. It was concluded, that the higher the N:P ratio, the higher the CTAM is, nevertheless the absolute concentration of these nutrients need to be considered as well. The introduced two key parameters could provide valuable information for decision makers regarding the optimization of growth conditions, nutrient supplementation, and harvesting, additionally decreasing the production costs and making the cultivation cycles more effective and sustainable.

Microalgae cultivation in flat panel photobioreactor as a method of carbon capture: A review

Biomass is one of the renewable energy technologies that plays a crucial role in fulfilling our energy needs while helping to mitigate carbon release. Microalgae biomass is a valuable product that can be utilized for a variety of applications which are generally high in proteins, carbohydrates, and lipids. In relation to that, photobioreactor (PBR) is known to be the appropriate system for microalgae to grow efficiently under controlled conditions. Nevertheless, handling this system can be challenging due to its complexity since it operates through different physical and chemical processes. This paper describes a systematic review of the recent literature published on flat panel photobioreactor (FPPBR) systems for microalgae cultivation that served as one of the critical technologies for the sustainable production of microalgae biomass and bio-based products. A total of 115 publications have been identified and analyzed from the literature search focusing on identifying different designs of FPPBR that have been developed and validated experimentally and numerically. Ultimately, this review is able to provide valuable insights into the current state of FPPBR implementation for microalgae cultivation that can aid in sorting out new strategies to support climate change attenuation and the commercialization of microalgae-based products.

Effects of light quality on microalgae cultivation: bibliometric analysis, mini-review, and regulation approaches.

The ever-increasing concern for energy shortages and greenhouse effect has triggered the development of sustainable green technologies. Microalgae have received more attention due to the characteristics of biofuel production and CO2 fixation. From the perspective of autotrophic growth, the optimization of light quality has the potential to promote biomass production and bio-component accumulation in microalgae at low cost. In this study, bibliometric analysis was used to describe the basic features, identify the hotspots, and predict future trends of the research related to the light quality on microalgae cultivation. In addition, a mini-review referring to regulation methods of light quality was provided to optimize the framework of research. Results demonstrated that China has the greatest interest in this area. The destination of most research was to obtain biofuels and high-value-added products. Both blue and red lights were identified as the crucial spectrums for microalgae cultivation. However, sunlight is the most affordable light resource, which could not be fully utilized by microalgae through the photosynthetic process. Hence, some regulation approaches (e.g., dyes, plasmonic scattering, and carbon-based quantum dots) are proposed to increase the proportion of beneficial spectrum for enhancement of photosynthetic efficiency. In summary, this review introduces state-of-the-art research and provides theoretical guidance for light quality optimization in microalgae cultivation to obtain more benefits.

Removal of Nitrogen and Phosphorous from Synthetic Wastewater by Oscillatoria sp. Cultivated in Vertical Tubular Photobioreactor under Natural Environmental Conditions

A newly isolated cyanobacterium Oscillatoria sp. from the Sub-Himalayan region of India was assessed for nutrient removal efficiencies. It was cultivated in synthetic wastewater under uncontrolled natural environmental conditions. The filaments of cyanobacterium formed entangled mats which easily floated on the surface of the medium. This characteristic feature was exploited for easy harvesting of the biomass that is hitherto a bottleneck for the industrial scale oil production from microalgae. The cultures of Oscillatoria sp. grown in synthetic wastewater removed 93.02% of 76 mg/L nitrate and 94.11% of 51 mg/L phosphate. The fatty acid profiling of 10-day-old cultures showed the dominance of saturated and monounsaturated fatty acids. The percentages of predominant fatty acids found in Oscillatoria sp. were 25.25% myristoleic acid (14:1w5c), 23.3% myristic acid (14:0), 16.81% palmitoleic acid (16:1w7c), 14.88% palmitic acid (16:0) and 4.765% hexadecanoic acid (16:1 w5c). The biomass productivities of 0.065 g/L/day and 0.05 g/L/day were attained by the cultures grown in synthetic wastewater and control BG-11 growth media respectively. This mesocosm study was conducted under the influence of natural sunlight, uncontrolled temperatures and the presence of biological contaminants namely, bacteria and small ciliates. The main objective of the study was to mimic the outdoor conditions, which is the way forward for achieving economic and environmental sustainability in microalgae biomass production.

Microalgae and co-culture for polishing pollutants of anaerobically treated agro-processing industry wastewater: the case of slaughterhouse

Anaerobically treated slaughterhouse effluent is rich in nutrients, organic matter, and cause eutrophication if discharged to the environment without proper further treatment. Moreover, phosphorus and nitrogen in agro-processing industry wastewaters are mainly removed in the tertiary treatment phase. The objective of this study is to evaluate the pollutant removal efficiency of Chlorella and Scenedesmus species as well as their co-culture treating two-phase anaerobic digester effluent through microalgae biomass production. The dimensions of the rectangular photobioreactor used to conduct the experiment are 15 cm in height, 20 cm in width, and 30 cm in length. Removal efficiencies between 86.74–93.11%, 96.74–97.47%, 91.49–92.91%, 97.94–99.46%, 89.22–94.28%, and 91.08–95.31% were attained for chemical oxygen demand, total nitrogen, nitrate, ammonium, total phosphorous, and orthophosphate by Chlorella species, Scenedesmus species, and their co-culture, respectively. The average biomass productivity and biomass yield of Chlorella species, Scenedesmus species, and their co-culture were 1.4 ± 0.1, 1.17 ± 0.12, 1.5 ± 0.13 g/L, and 0.18, 0.21, and 0.23 g/L*day, respectively. The final effluent quality in terms of chemical oxygen demand, total nitrogen, and total phosphorous attained by Chlorella species and the co-culture were below the permissible discharge limit for slaughterhouse effluent standards in the country (Ethiopia). The results of the study showed that the use of microalgae as well as their co-culture for polishing the nutrients and residual organic matter in the anaerobically treated agro-processing industry effluent offers a promising result for wastewater remediation and biomass production. In general, Chlorella and Scenedesmus species microalgae and their co-culture can be applied as an alternative for nutrient removal from anaerobically treated slaughterhouse wastewater as well as biomass production that can be used for bioenergy.Graphical

Machine learning-based optimisation of microalgae biomass production by using wastewater

Microalgae biomass a valuable resource for energy source and fertilisers. Among all available media sources, wastewater serves as cost-efficient media for microalgae biomass production. However, improvements are still needed to increase microalgae biomass productivity in wastewater, particularly optimising cultivation parameters, including light intensity, CO2 content, and initial inoculum level. Machine learning algorithms can easily optimise the cultivation parameters by analysing the microalgae-based wastewater treatment dataset without experimental runs. In the present work, a machine learning algorithm, Decision Tree, was used to analyse microalgae-based datasets and predict different optimised combinations of descriptor variables leading to high growth rate and microalgae biomass production. The decision tree model presented 18 combinations of descriptor variables leading to increased biomass production with a general accuracy of 81.25%. Seven of them were experimentally verified by using two newly isolated strains that predicted a 10% error after experimental verification. Models also revealed that the medium's initial inoculum level and nitrogen/phosphorus ratio highly influence microalgae growth as compared to other parameters. Results obtained in the analysis can be easily implemented at pilot and industrial scales without any laboratory experiments.

Cobalamin and Thiamine Effect on Microalgae Biomass Production in the Glagah Consortium

The Glagah consortium is a mixed culture of various microalgae and bacteria isolated from Glagah Beach, Yogyakarta. Cobalamin and thiamine, which are given by symbiotic bacteria, are assumed will increase biomass. This study aimed to determine the effect of cobalamin and thiamine on microalgae biomass production in the Glagah consortium. The microalgae of Glagah consortium were cultivated for 10 days with vancomycin and gentamicin antibiotic as treatment and without antibiotics as a control. The parameters measured included the number of bacterial colonies, cobalamin and thiamine levels measured by LC-MS, chlorophyll a and b levels, cell density of microalgae and dry biomass. The highest level of cobalamin and thiamine was in the Glagah consortium without antibiotics. Cobalamin and thiamine increased in the exponential phase along with the increasing Staphylococcus sp. colonies. The Quantity of Staphylococcus sp. colonies in the exponential phase was 62.105 (cfu/mL). The level of cobalamin in the exponential phase was 2.33 µg/L and the level of thiamine in the exponential phase was 49.71 µg/L. The highest productivity dried weight biomass was 0.0134 g/L/day in the day-6th on the Glagah consortium without antibiotics. This result showed that microalgae and bacterial interaction was mutualism symbiosis involving cobalamin and thiamine that increased in the exponential phase along with the increasing Staphylococcus sp. colonies. This interaction was able to increase biomass microalgae.

Effects of Ultrasonic Stimulation and Light Intensity on the Growth Rate and Biomass Productivity of Chlorella ellipsoidea in a Closed-Batch Cultivation System

Microalgae exhibit high nutritional value as animal feed in aquatic animal nurseries. Therefore, approaches to enhance biomass productivity are of great economic significance. This study aimed to evaluate the effect of ultrasonic wave stimulation on the specific growth rate and biomass yield of Chlorella ellipsoidea strain TISTR 8260. C. ellipsoidea stimulated by ultrasonic waves at 50 Hz for 1, 5, and 10 min were cultivated in a closed-batch cultivation system with varying light intensities. Data revealed that stimulation for 1 min and rearing at 71.43 μmol m−2 s−1 resulted in the highest biomass productivity and specific growth rates, with averages of 0.89±0.008 g/L/day and 0.59±0.009 per day, respectively. The findings of this study emphasize the usefulness of ultrasonic waves in enhancing the biomass productivity of microalgae.

Solar bioreactors used for the industrial production of microalgae.

Microalgae are excellent sources of biomass containing several important compounds for human and animal nutrition-proteins, lipids, polysaccharides, pigments and antioxidants as well as bioactive secondary metabolites. In addition, they have a great biotechnological potential for nutraceuticals, and pharmaceuticals as well as for CO2 sequestration, wastewater treatment, and potentially also biofuel and biopolymer production. In this review, the industrial production of the most frequently used microalgae genera-Arthrospira, Chlorella, Dunaliella, Haematococcus, Nannochloropsis, Phaeodactylum, Porphyridium and several other species is discussed as concerns the applicability of the most widely used large-scale systems, solar bioreactors (SBRs)-open ponds, raceways, cascades, sleeves, columns, flat panels, tubular systems and others. Microalgae culturing is a complex process in which bioreactor operating parameters and physiological variables closely interact. The requirements of the biological system-microalgae culture are crucial to select the suitable type of SBR. When designing a cultivation process, the phototrophic production of microalgae biomass, it is necessary to employ SBRs that are adequately designed, built and operated to satisfy the physiological requirements of the selected microalgae species, considering also local climate. Moreover, scaling up microalgae cultures for commercial production requires qualified staff working out a suitable cultivation regime. KEY POINTS: • Large-scale solar bioreactors designed for microalgae culturing. • Most frequently used microalgae genera for commercial production. • Scale-up requires suitable cultivation conditions and well-elaborated protocols.

Bioremediation of domestic wastewaters integrated with enhanced biodiesel production using Desmodesmus sp. mutated by atmospheric and room temperature plasma

In this work, we analyzed the biochemical changes and cultivation feasibility of microalgae Desmodesmus sp. mutated by atmospheric and room temperature plasma (ARTP) technology in mixed wastewater. The mutant strain AT151 was cultivated in different types of pretreated wastewaters for suitable pretreatment, resulting in the highest biomass content of > 354 mg/L, with a > 52% increase in lipid production in the filtered wastewater, and the difference between 0.22-μm and 0.45-um filtration was not significant (P > 0.05). The fatty acids of AT151 indicated a majority of C16 and C18 at > 86%, and the monounsaturated fatty acid content exceeded 18%, which was beneficial for high-quality biodiesel. Nutrient removal was found to be visible in wastewater by cultivating mutant microalgae AT151. The removal rates of total nitrogen (TN), total phosphorus (TP), and total organic carbon (TOC) for AT151 cultivated in wastewater were more than 87%, 94% and 47%, respectively. Furthermore, the relationship between the microalgae and bacteria was studied, showing significant differences in bacterial community (P < 0.05). The obvious phenomenon consisted of dominant bacteria changes, where Brevundimonas balnearis and Synechocystis sp. served as stable strains during cultivation, forming a symbiotic relationship with mutant microalgae AT151. The dominant bacteria showed obvious metabolism according to functional KEGG prediction, mainly affecting the factors of amino acids, carbohydrates, and growth factor metabolism. Therefore, enhancing microalgae biomass and lipid production through wastewater cultivation holds both scientific significance and practical feasibility.