Algal Biomass Growth Research Articles

Phosphate overplus response in Chlamydomonas reinhardtii: Polyphosphate dynamics to monitor phosphate uptake and turnover

There is widespread interest in using microalgae to sustainably control and recover nutrients from wastewater to meet environmental discharge consents and recycle nutrients into agriculture or other applications. Like bacteria and yeasts, microalgae exhibit a phosphate (Pi) overplus response when Pi-deprived cells are resupplied with this nutrient. Quantitative and qualitative methods were used to follow the dynamics of polyP synthesis and turnover in four strains of Chlamydomonas reinhardtii during Pi deprivation followed by nutrient resupply (either as Pi or complete media). The lowest level of in-cell polyP during Pi deprivation, which correlates with the cessation of growth, is the key parameter for timing Pi resupply to maximise the Pi overplus response. Pi deprivation beyond this point leads to a reduced Pi uptake and reduced overplus response. Additional nutrients do not affect the magnitude of the overplus response but are important for continued growth and maximal Pi removal from the media. One strain tested shows enhanced Pi uptake and increased polyP and total in-cell P, suggesting that strain selection is also important. Although polyP levels are maintained after Pi resupply, the polymer is dynamically remodelled. Inositol hexakisphosphate (IP6) increases during this time but does not precede polyP synthesis as predicted by a model where inositol phosphates switch on polyP synthesis. Tracking polyP allows the correct time for nutrient resupply to be determined and therefore a reproducible Pi overplus response to be achieved. Depending on whether maximum cellular P content or maximum Pi removal is desired different strategies may be required. Pi deprivation until growth cessation then resupplying complete nutrients gives the best trade-off between high in-cell P accumulation, high Pi removal and algal biomass growth. This work provides robust measurements of quantitative physiological parameters, which allows reproducibility in laboratory studies and provides design parameters for algal-based nutrient recovery systems from waste waters.

Engineered algal systems for the treatment of anaerobic digestate: A meta-analysis

The objective of this review was to provide quantitative insights into algal growth and nutrient removal in anaerobic digestate. To synthesize the relevant literature, a meta-analysis was conducted using data from 58 articles to elucidate key factors that impact algal biomass productivity and nutrient removal from anaerobic digestate. On average, algal biomass productivity in anaerobic digestate was significantly lower than that in synthetic control media (p < 0.05) but large variation in productivity was observed. A mixed-effects multiple regression model across study revealed that biological or chemical pretreatment of digestate significantly increase productivity (p < 0.001). In contrast, the commonly used practice of digestate dilution was not a significant factor in the model. High initial total ammonia nitrogen suppressed algal growth (p = 0.036) whereas initial total phosphorus concentration, digestate sterilization, CO2 supplementation, and temperature were not statistically significant factors. Higher growth corresponded with significantly higher NH4–N and phosphorus removal with a linear relationship of 6.4 mg NH4–N and 0.73 mg P removed per 100 mg of algal biomass growth (p < 0.001). The literature suggests that suboptimal algal growth in anaerobic digestate could be due to factors such as turbidity, high free ammonia, and residual organic compounds. This analysis shows that non-dilution approaches, such as biological or chemical pretreatment, for alleviating algal inhibition are recommended for algal digestate treatment systems.

The Hard Reality of Biogas Production through the Anaerobic Digestion of Algae Grown in Dairy Farm Effluents

Much emphasis has been given to algal biomass growth in dairy farm wastewater. Most of the systems examined require productive land to be converted and/or freshwater use to dilute high concentrations of nutrients found in dairy effluent. A rotating algal biofilm (RABR) provides the capacity to grow algae without sacrificing productive land or freshwater. In theory, this system would overcome some of the economic and environmental challenges that other systems have. A combination of theoretical information, nutrient uptake formulas, and economic formulas were used to calculate the potential of biogas production from algae grown in an RABR with dairy effluents. The average nutrient uptake was 0.8 mgN/m2 per day and 0.1 mgP/m2 per day. The maximum methane production from the anaerobic digestion of algae was 112 m3/RABR·year. The minimum and maximum economic scenarios resulted in gross profits of NZD −2101 and −1922. After evaluating this system for the first time in the New Zealand dairy farming context, it was found that biogas production from an RABR is not a feasible option for New Zealand dairy farmers.

Optimization of Bioenergy Production from Algae Using Bioreactor Design

Bioenergy production from algae has gained significant attention due to its potential as a sustainable and renewable energy source. This research investigates the optimization of bioenergy production by focusing on bioreactor design to enhance the efficiency of algal biomass growth and lipid extraction. The study involves analyzing key bioreactor parameters such as light intensity, nutrient concentration, pH levels, and carbon dioxide (CO₂) supply. Experimental results demonstrated a 25% increase in lipid production through optimized conditions, showing promising improvements in biofuel yield. The findings of this research provide valuable insights into the potential scalability of algae-based bioenergy systems.

Aquatic insects balance growth with future supply of algal food resources

Many consumers depend on the contemporaneous growth of their food resources. For example, Tanytarsus gracilentus midges feed on algae, and because midge generation time is much longer than that of algae, individual midges benefit not just from the standing stock but also from the growth of algae during their lifespans. This implies that an intermediate consumption rate maximizes midge somatic growth: low consumption rates constrain midge growth because they do not fully utilize the available food, whereas high consumption rates suppress algal biomass growth and consequently limit future food availability. An experiment manipulating midge presence and initial algal abundance showed that midges can suppress algal growth, as measured by changes in algal gross primary production (GPP). We also found a positive relationship between GPP and midge growth. A consumer–resource model fit to the experimental data showed a hump‐shaped relationship between midge consumption rates and their somatic growth. In the model, predicted midge somatic growth rates were only positively associated with GPP when their consumption rate was below the value that optimized midge growth. Therefore, midges did not overexploit algae in the experiment. This work highlights the balance that consumers which depend on contemporaneous resource growth might have to strike between short‐term growth and future food availability, and the benefits for consumers when they ‘manage' their resources well.

Reverse Salt Flux Effect on Dewatering Chlorella vulgaris in a Forward Osmosis System

Microalgae shows a high potential to produce biofuel and forward osmosis (FO) has been proposed as a promising dewatering process for algal biomass separation from water. However, the effect of reverse salt flux (RSF) on algal biomass during the dewatering process using FO has not been completely explored. This study was to investigate the effect of different types of salt and their concentrations on algal biomass in terms of conductivity, settling velocity, and lipid contents in FS during a simulated FO-driven dewatering of Chlorella vulgaris microalgae. Three draw solution (DS) salts (NaCl, KCl and NH4Cl) were evaluated in RSF-simulating batch tests. The salt diffusion from the DS to the algal feed solution (FS) caused a static growth of algal biomass while increasing lipid content up to 14.8% at 8 mM NH4Cl. With the addition of the different salts, pH was maintained to the optimal algal thriving range (7.2–10.6), but the presence of salt stressed the algal cells and inhibited photosynthesis and algal growth within the experimental conditions. The settling velocity of the algal cells improved with the increase of salt content from 8 to 80 mM of each DS. It seemed that cell division could be accelerated in the presence of NH4Cl, and microscopic images showed a change in the algal cell size distribution, which may negatively affect algal settleability. DS salt in an FO-algal harvesting system should be selected based on the final algal properties and constituents required.

Influence of Different Angles in the Photobioreactor on Algal Biomass Growth with Optimized Poultry Excreta Leachate: A Batch-Scale Study

In this study, the influence of solar inclination angles on biomass growth and the biomolecule profile of Chlorella pyrenoidosa (C. pyrenoidosa) were analyzed in the vertical flat–panel photobioreactor (FPPBR). The growth of C. pyrenoidosa was analyzed at three different solar inclination angles (32.9°, 47.9°, and 90°) in a natural open environment with BG-11 medium and poultry excreta leachate (PEL). The maximum yield of biomass was obtained at 2.40 g/L with PEL and 1.45 g/L with BG-11 medium at a solar inclination angle of 47.9°. The biomass yield with PEL and BG-11 was 5.09–10.26%, 3.94–5.72%, respectively, while biomass productivity with PEL and BG-11 was 5.27–10.63%, 4.06–5.90% higher at a solar inclination angle of 47.9° as compared to 32.9°. The average temperature and radiation of FPPBR were recorded ≈3.90 ± 0.40% and ≈17.28 ± 2.23% higher at a solar inclination angle of 47.9° as compared to a solar inclination angle of 32.9°. The inclined radiation was acquired the maximum area of FPPBR. Results indicated that solar inclination angles enhanced the productivity of algae in FPPBR.

Characteristics of pigment complex of sphagnum mosses of south-belomorian bogs on example of Ilas bog massif

Sphagnum mosses play a significant role in the plant communities of the south-belomorian bogs. The adaptation of these plants to environmental conditions can be traced through changes in the pigment complex. In this work, the content of chlorophylls a and b and carotenoids was determined in some ridge species (Sphagnum fuscum, S. rubellum) and hollow species (S. lindbergii and S. majus) in June and September. An increase in total pigments in species growing on ridges is observed in autumn and that can be explained by the formation of comfortable conditions for photosynthesis. The growth of algal biomass can cause a decrease in the pigment content in the species of hollows.

Growth dependent carbon sequestration proficiency of algal consortium grown in carbon dioxide enriched simulated greenhouse

Biological carbon sequestration gaining more impetus day by day, where algae is the main backbone as a biological agent. Thus, the present study focused on the evaluation of algal biomass growth, collected from the polysheet wall of green house chamber, along with its carbon capture potentiality. The experiment were conducted in three different atmospheric conditions viz. (i) inside the green house chamber where temperature and carbon dioxide concentration was higher; (ii) in the normal atmospheric condition under full sunlight, and (iii) in closed room condition where light intensity was fixed. Maximum carbon accumulation was found (834.59±2.09 mg C/g) inside the green house chamber where mean temperature and carbon dioxide concentration were 41 °C and 705 ppm respectively. Collective effect of temperature and carbon dioxide concentration also facilitate in the maximum growth of the algal biomass (8693.68 mean number of cell/mL) in the greenhouse chamber.

Leachate treatment using sequential microwave and algal photo-bioreactor: Effect of pretreatment on reactor performance and biomass productivity

The present study aims to design a lab-scale hybrid reactor, primarily focused on the removal of organics, nutrients, heavy metal and other toxic compounds, thereby, minimizing risk associated with the disposal of landfill leachate. The potential of a designed hybrid treatment system (i.e., sequential microwave (MW) with algal bioreactor) with and without pretreatment, i.e., coagulation-flocculation (CF), was evaluated based on several parameters. The CF pretreatment under optimized conditions has resulted in 90% turbidity and 76% COD removals from leachate; furthermore, the MW treatment achieved 91% ammonia removal from raw leachate. As a result, substantial algal growth was observed in the preliminary algal batch experiment conducted with MW and MW-CF treated samples. Subsequently, leachate treatment was carried out using sequencing batch reactor (SBR) systems, i.e., MW-algal SBR and CF-MW-algal SBR. Algal biomass growth and increment in DO level were observed in algal-SBR experiments. Under the optimized reactor conditions, TN and TP removal rates in the algal-SBR were found to be 1.67–20 mg/L/d and 0.6–9.6 mg/L/d, respectively. The majority of heavy metals present in the leachate were removed due to algal-uptake (mainly Zn2+) and bio-sorption (total-Fe, Cu2+ and Pb2+). Meanwhile, some amount of energy can be recovered from algal biomass as inferred from the cost benefit analysis. Overall, the hybrid treatment combining MW and algal-SBR has shown immense potential for sustainable leachate treatment.

Unprecedented biodesalination rates–Shortcomings of electrical conductivity measurements in determining salt removal by algae and cyanobacteria

Phormidium keutzingianum performed biodesalination of brackish water (10 g/L). The electrical conductivity (EC) was measured to evaluate the salt concentration over 80 days of cyanobacterial inoculation. Anion concentrations were measured using ion chromatography to estimate salt removal. EC-based measurements showed ∼8–10% removal efficiency in the first 20 days. However, the removal efficiency based on chloride ion concentration showed ∼40% removal in the same time frame. The pH increase was observed with growth of algal biomass. The increasing pH proposes the formation of hydroxyl and carbonate ions. Sulfuric acid was added at day 110 to neutralize them. At pH 4, the EC reduced significantly to about ∼37% confirming the chloride removal. EC should not be used to measure salt reduction as it is an obscure parameter, and therefore, EC is not the best choice to measure salinity removal using algae. Some recently published studies used only EC to estimate biodesalination, and it is anticipated that salt removal is misrepresented in those studies.

Biocircular platform for third generation biodiesel production: Batch/fed batch mixotrophic cultivations of microalgae using glycerol waste as a carbon source

The green microalga, Scenedesmus incrassulatus PPAY1 was cultivated in vertical tubular photobioreactor under batch/fed-batch modes. Biodiesel derived glycerol waste (BDGW) was applied as a cheap main nutrient source. For batch cultivation (BC), maximum biomass concentration was reached at 2.83 gL-1when 20 gL-1 BGW was used. In contrast, in the case of fed-batch cultivation (FBC), the maximum algae and lipid contents were achieved at 5.65 gL-1 and 58.27%, respectively when 30 and 20 gL-1 BDGW were applied. The highest lipid yield of 2.94 gL-1was found at 30 gL-1 BDGW. The analysis of the fatty acid content revealed that palmitic acid-, oleic acid- and linoleic acid- were mainly found in both BC and FBC conditions. As expected, FBC was in a better culture strategy than BC. BDGW could be used directly without any pretreatment in both algal biomass growth and microalgal oil accumulation which simplifies cultivation and reduces operating costs during biodiesel production.

Natural attenuation of metals by algal mat from acid mine drainage at Malanjkhand copper mine

Filamentous macroscopic green algae are observed in acidic (pH 4.47–5.75) and metal-enriched discharges from the Malanjkhand copper mine (India), which is the largest one in Asia. The genuses of the algae are identified as Microspora and Ulothrix. The Microspora occurs as the most dominant one and thrives in wide range of pH. The pH of the water and precipitation of the secondary metal-(oxy)hydroxides in the bottom sediment are found to be the controlling factors for the occurrence and growth of algal biomass. The concentration of Cu, Fe, Ni, Pb, and Zn in mine discharges has been reduced by many folds in downstream of the algal site. The algal biomass contains very high concentration of metals, particularly Fe and Cu; the order of the metal content is Fe > Cu > Zn > Ni > Pb. This study also demonstrates the influence of pH on distribution of metals in algae. The concentration of Fe and Cu ranges from 0.95 to 9.14% and 1.74 to 3.66%, respectively. Based on this study, it is found that Microspora can be used as bioindicator of acid mine drainage (AMD) impact around copper mine. Due to the exceptionally high metal accumulation potential, Microspora-dominated algal biomass can be used for bioremediation of the AMD and recovery of Cu in particular.

Integration of ozone with co-immobilized microalgae-activated sludge bacterial symbiosis for efficient on-site treatment of meat processing wastewater

Direct discharge of high concentration meat processing wastewater (MPW) into municipal sewage system will cause serious shock loading and reduce wastewater treatment efficiency, thus, efficient on-site pretreatment is usually required. Purpose of this study is to integrate ozone with microalgal biotreatment to achieve effective removal of both organic compounds and nutrients with one-step biodegradation and obtain high quality effluent dischargeable to municipal sewage system. Results showed that ozone pretreatment removed 35.0–90.2% color and inactivated 1.8–4.7 log CFU/mL bacteria in MPW. In post biotreatment using microalgae co-immobilized with activated sludge (ACS) bacteria, bacterial growth in ozone pretreated wastewater (7.1–8.1 log CFU/mL) were higher than non-pretreated control (6.0 log CFU/mL) due to enhanced biodegradability of wastewater pollutants. Algal biomass growth in wastewater pretreated with 0.5 (2489.3 mg/L) and 1 (2582.0 mg/L) minute's ozonation were improved and higher than control (2297.1 mg/L). Ozone pretreatment significantly improved nutrients removal. Following ozone pretreatment of 0.5 min, microalgal biotreatment removed 60.1% soluble chemical oxygen demand (sCOD), 79.5% total nitrogen (TN) and 91.9% total phosphate (PO43−) which were higher than control (34.4% sCOD, 63.4% TN, 77.6% total PO43−). Treated effluent contained 342.3 mg/L sCOD, 28.8 mg/L TN, 9.9 mg/L total PO43− and could be discharged into municipal sewage system. However, excessive ozone pretreatment displayed adverse impact on algal growth and sCOD removal. Therefore, integration of 0.5 min's ozone pretreatment with microalgae-based biotreatment is an efficient on-site treatment to simultaneously remove organic compounds and nutrients with one-step biodegradation.

Predictive model development and simulation of photobioreactors for algal biomass growth estimation

Abstract In the current scenario of energy requirement and the commercialization aspect of algal biofuel and biomass, it is important that means of predicting the production be available. In this paper, the mathematical models are developed for the tubular, bubble column and airlift photobioreactors to predict the productivity of the algal biomass. A modified Monod kinetic equation, incorporating the effect of nutrient and CO2 concentrations, light availability and oxygen built-up, is used to the estimate specific growth rate of the biomass. The light availability inside the reactor is defined in terms of the modified Beer–Lambert’s law as a function of distance from the surface where light is incident and the cell mass concentration. This allows a more accurate measurement of the shading effect. The equations are solved for different reactor types and their estimated productivities are successfully validated against values available in published literature. The model predicts comparatively better productivity for the tubular reactor (1.5 g/L day) than the bubble column and airlift reactor (1.42 and 1.35 g/L day respectively) because tubular reactor has shorter light/dark cycles and better light availability. The analysis is also done to identify the effect of nutrient, carbon dioxide, light and hydrodynamics on the overall productivity.

Experimental Investigation of Chlorella vulgaris and Enterobacter sp. MN17 for Decolorization and Removal of Heavy Metals from Textile Wastewater

The present study evaluated the performance of microalgae Chlorella vulgaris in an Enterobacter sp. MN17-assisted textile industry wastewater treatment system for decolorization, removal of heavy metals (Cu, Cr, Pb, and Cd), and chemical oxygen demand (COD). Different dilutions (5, 10, and 20%) of wastewater were prepared to decrease the pollutant toxicity for culturing microalgae and bacteria. Reduction of color, COD, and metal contents by microalgal treatment of wastewater varied greatly, while removal efficiency (RE) was significantly enhanced when endophytic bacterial strain MN17 inoculum was applied. Most notable, results were found at a 5% dilution level by Enterobacter sp. MN17-inoculated C. vulgaris medium, as chromium (Cr), cadmium (Cd), copper (Cu), and lead (Pb) concentrations were decreased from 1.32 to 0.27 mg L−1 (79% decrease), 0.79–0.14 mg L−1 (93% decrease), 1.33–0.36 mg L−1 (72% decrease), and 1.2–0.25 mg L−1 (79% decrease), respectively. The values of COD and color were also significantly decreased by 74% and 70%, respectively, by a C. vulgaris–Enterobacter sp. MN17 consortium. The present investigation revealed that bacterial inoculation of microalgae significantly enhanced the removal of coloring agents and heavy metals from textile wastewater by stimulating the growth of algal biomass. This study manifested the usefulness of microalgae–bacterial mutualism for the remediation of heavy metals, COD, and color in industrial effluents. Microalgae consortia with growth promoting bacteria could be a breakthrough for better bioremediation and bioprocess economy. Thus, further studies are needed for successful integration of microalgae–plant growth promoting bacterial (PGPB) consortium for wastewater treatments.

Evaluating the effect of hydraulic retention time on fouling development and biomass characteristics in an algal membrane photobioreactor treating a secondary wastewater effluent

Coupling algal biomass growth to wastewater treatment is a promising alternative for the simultaneous removal and recovery of nutrients. This study aims to evaluate the effects of the Hydraulic Retention Time (HRT) on the fouling behavior and biomass characteristics of C. Vulgaris in a Membrane Photobioreactor (MPBR), fed with a secondary synthetic wastewater effluent. The changes in the algal cell characteristics and in their metabolic products were assessed at three different HRTs (12 h, 24 h and 36 h). Experimental results showed that higher loading rates led to a broader Particle Size Distribution (PSD) resulting from looser and less stable algal flocs. In contrast, bigger and homogeneously distributed particles observed at lower loading rates, led to a porous layer with lower fouling rates and organic removal. The presence of smaller particles and dissolved organics resulted in a more compact and less porous layer that increased the removal of small-MW organics.

Integration of sodium hypochlorite pretreatment with co-immobilized microalgae/bacteria treatment of meat processing wastewater

Wastewater with 0.2, 0.4, 0.8, 1.0 mg/L free chlorine was biologically treated using co-immobilized microalgae/bacteria. In contrast, non-pretreated wastewater was treated with beads (control) and blank beads (blank) under the same operating condition. Results showed that NaClO pretreatment removed 8–33% total nitrogen (TN), 31–45% true color and 0.7–2.5 log CFU/mL aerobic-bacteria. At the end of treatment, maximum algal biomass (2,027 dry weight mg/L) was achieved with 0.2 mg/L free chlorine. Bacterial growth in wastewater was decreased by NaClO pretreatment before reaching 7.2–7.7 log CFU/mL on the fifth day. Beads with microorganisms (control) removed 15% more chemical-oxygen-demand (COD), 16% more TN, and 13% more total phosphate (PO43−) than blank. Pretreatment with 0.2 mg/L free chlorine increased TN removal from 75% to 80% while pollutants removal was substantially decreased with 0.4–1.0 mg/L free chlorine. Considering algal biomass growth and pollutants removal, 0.2 mg/L free chlorine pretreatment was recommended for microalgae/bacteria co-immobilized system.

Design of Photobioreactors for Algal Biomass Growth

The present energy scenario of depleting sources of fossil fuel, increasing the cost of processed fuel and geopolitical policies have made it imperative that alternate energy sources and processes that reduce greenhouse gas emissions be identified. Biofuels from algae, in recent times, have emerged as a potential alternative to fossil fuels, as it can be easily produced, stored, and used as transportation fuels. Here, mathematical design models are developed for tubular, bubble column, and airlift photobioreactors to calculate their productivity for the growth of algal biomass. A modified Monod kinetic equation is used to estimate the specific growth rate of the biomass. The model equations are solved for tubular reactor systems and the estimated productivities are successfully validated against values available in published literature. It is found that the tubular reactor has productivity, around 2.1 g/L.day. The analysis is also done to identify the effect of light, nutrient, and carbon dioxide on overall productivity.

Optimization and scale-up of an LED-illuminated microalgal photobioreactor for wastewater treatment.

The use of light-emitting diode (LED)-illuminated photobioreactors with microalgae has been extensively studied for wastewater treatment. Most studies have used isolated microalgae species; however, this practice does not match the reality of conditions in wastewater treatment plants. Operational conditions that promote greater growth of algal biomass and that remove pollutants most effectively are disputed in the literature. In this context, LED-illuminated photobioreactors with microalgae were evaluated using multivariate analysis in order to optimize removal of pollutants (nitrogen, phosphorus, and carbonaceous organic matter). Three variables were evaluated: operating time, LED wavelength, and luminous flux intensity. A microalgae consortium was used in the photobioreactor. In addition to the LED-illuminated photobioreactors, control photobioreactors illuminated by sunlight were also operated. Using the results obtained in the optimization, a scaled-up reactor approximately 8.5 times larger in volume was operated to evaluate if the behavior would be maintained. The best operational conditions for the removal of pollutants were observed in LED-illuminated photobioreactors operated under a light intensity of 700 μmol·m-2s-1 for 15 days. Under these conditions, it was possible to remove 89.97% of carbonaceous organic matter, 86.50% of nitrogen, and 30.64% of phosphorus. The scaled-up photobioreactor operated with similar performance.