Microalgal Biomass Research Articles

Nannochloropsis oceanica IMET1 and its bacterial symbionts for carbon capture, utilization, and storage: biomass and calcium carbonate production under high pH and high alkalinity.

To combat the increasing levels of carbon dioxide (CO2) released from the combustion of fossil fuels, microalgae have emerged as a promising strategy for biological carbon capture, utilization, and storage. This study used a marine microalgal strain, Nannochloropsis oceanica IMET1, which thrives in high CO2 concentrations. A high-pH, high-alkalinity culture was designed for CO2 capture through algal biomass production as well as permanent sequestration through calcium carbonate (CaCO3) precipitation. This was accomplished by timed pH elevation and the addition of sodium bicarbonate to cultures of N. oceanica grown at lab scale (1 L) and pilot scale (500 L) with 10% and 5% CO2, respectively. Our data showed that 0.02 M NaHCO3 promoted algal growth and that sparging cultures with ambient air after 12 days raised pH and created favorable CaCO3 formation conditions. At the 1 L scale, we reached 1.52 g L-1 biomass after 12 days and an extra 9.3% CO2 was captured in the form of CaCO3 precipitates. At the 500 L pilot scale, an extra 60% CO2 was captured (Day 40) with a maximum CO2 capture rate of 63.2 g m-2 day-1 (Day 35). Bacterial communities associated with the microalgae were dominated by two novel Patescibacteria. Functional analysis revealed that genes for several plant growth-promotion traits (PGPTs) were enriched within this group. The microalgal-bacterial coculture system offers advantages for enhanced carbon mitigation through biomass production and simultaneous precipitation of recalcitrant CaCO3 for long-term CO2 storage.IMPORTANCECapturing carbon dioxide (CO2) released from fossil fuel combustion is of the utmost importance as the impacts of climate change continue to worsen. Microalgae can remove CO2 through their natural photosynthetic pathways and are additionally able to convert CO2 into a stable, recalcitrant form as calcium carbonate (CaCO3). We demonstrate that microalgae-based carbon capture systems can be greatly improved with high pH and high alkalinity by providing optimal conditions for carbonate precipitation. Our results with the microalga, Nannochloropsis oceanica strain IMET1, show an extra 9.3% CO2 captured as CaCO3 at the 1 L scale and an extra 60% CO2 captured at the 500 L (pilot) scale. Our optimized system provides a novel approach to capture CO2 through two mechanisms: (i) as organic carbon within microalgal biomass and (ii) as inorganic carbon stored permanently in the form of CaCO3.

Impact of microalgal biomass and microplastics on the sorption behaviour of pesticides in soil: a comparative study

The sustainability of resource recovery and agricultural practices can be enhanced by utilising microalgal biomass from a high-rate algal pond for wastewater treatment to improve soil quality and food yields. However, certain factors should be considered first. The addition of fertilisers and the presence of contaminants such as microplastics (MPs) can modify the behaviour of pesticides, applied to such fields. A sorption study of three model pesticides with different octanol–water partitioning coefficient (log Kow): acetamiprid (ACE, log Kow 0.80), chlorantraniliprole (CAP, log Kow 2.76), and flubendiamide (FLU, log Kow 4.20), was carried out in soils amended with microalgal biomass in the presence and absence of MPs. The surface of the sorbents in the study was characterised by attenuated total reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), water contact angle (CA), and point of zero charge (pHPZC). Overall, the sorption of model pesticides increased with their hydrophobicity: ACE > CAP > FLU. The addition of microalgal biomass to soil increased the sorption of ACE (0.72 ± 0.05 µg g−1), compared to soil only (0.08 ± 0.08 µg g−1). The greater sorption capacity of ACE can be attributed to electrostatic interactions, hydrogen bonding and π–π interactions between ACE moieties and the negatively charged surface of microalgal biomass containing polar functional groups. The presence of MPs (3% w/w, mixture of polyethylene terephthalate (PET), polyethylene (PE), and polystyrene (PS)) did not affect the sorption of ACE, CAP or FLU, regardless of the presence or absence of microalgal biomass. However, FLU sorption was enhanced in the presence of PE and PS in soil, spiked with these individual MP polymers. Microalgal soil amendment can, therefore, influence the behaviour of hydrophilic compounds in soil.

Microalgae Biorefinery from Palm Oil Mill Effluent (POME): Bioremediation and Biomass Production

Palm oil processing in Malaysia produces massive amounts of palm oil mill effluent (POME) every day. Effective treatment of POME is in necessity for compliance of regulations and for environmental sustainability. There is a new innovation in effluent treatment which is the application of microalgae for wastewater treatment and biomass production. The present study applied microalgae isolated from POME for the biomass production and bioremediation. The microalgae isolated are identified as Chlorella sorokiniana. Microalga was cultured in bold basal medium (BBM) for 20 days in a total volume of 250 mL, range of pH 6 to 8, with continuous of air supply and light illumination, as well as supplementation. The highest microalgal biomass concentration attained was 3.02 g L-1 at pH 7, white light illumination, and 25 mM of glycerol and urea supplementation. Furthermore, the study has found reduction in chemical oxygen demand (47%), total nitrogen (76%), and color (69%) with 50% POME addition into the microalgal culture medium. Overall, this study is expected to be able to provide information to stakeholders on wastewater technology improvement, the private sector for future investment, and the government sector in making decisions. With that, sustainable POME management can be achieved with environmental sustainability.

Optimizing Anaerobic Co-Digestion Formula of Agro-Industrial Wastes in Semi-Continuous Regime

The actual environmental and energy crises are two of the main problems existing in the world. Among the different technologies that can be implemented is anaerobic digestion, which employs waste and renewable biomass materials. To reach the optimum ratio of different raw materials or substrates in the feed of digesters, laboratory tests are necessary. This work aims to study the increase in the Organic Load Rate (OLR) (1 g VS L−1d−1, 2 g VS L−1d−1, 3 g VS L−1d−1 and 4 g VS L−1d−1, VS: Volatile Solid) and the raw materials number (sorghum (S), pig manure (P), triticale (T), corn stover (C) and microalgae biomass (M)) in the feedstock of the anaerobic digestion process. Mean values of methane yields for the evaluated set were lower in SMP and SMPTC assays (149.80 LCH4 kg VS−1 and 157.15 LCH4 kg VS−1, respectively) than SP, SM and SMPT assays (195.09 LCH4 kg VS−1, 197.69 LCH4 kg VS−1 and 195.76 LCH4 kg VS−1, respectively). Along the experiments, several parameters were evaluated, along with their interactions with OLR and number of raw materials. Two kinetic models were employed to fit the COD (Chemical Oxygen Demand) removal results.

Enhanced Tolerance and Growth of Chlorella vulgaris and Scenedesmus quadricauda in Anaerobic Digestate Food Waste Effluent.

Anaerobic digestate food waste effluent (ADFE) contains high nutrient loads and causes water pollution and waste of resources if discharged without treatment. Microalgae provides a promising strategy for nutrients recovery, biomass production, and CO2 capture. However, due to the characteristics of high ammonia nitrogen and low C/N ratio, it is hard for the original algae to remove N and P in ADFE. Hence, this study investigated the gradient domestication of C. vulgaris and S. quadricauda to enhance their tolerance to high concentrations of ADFE and evaluated their growth and metabolic responses under ADFE concentrations ranging from 20 to 60%. The results revealed that S. quadricauda exhibited better tolerance and growth performance compared to C. vulgaris, with a 42.31% biomass increase in the 40% BG11-diluted ADFE group after domestication. Additionally, extracellular polymeric substances (EPS) secretion increased by 27.66% to help shield algal cells from pollutants. The final removal efficiencies of total nitrogen, total phosphorus, and soluble chemical oxygen demand by S. quadricauda in BG11 dilution group were 37.13%, 40.64%, and 75.45%, respectively, which indicated that domestication alleviated oxidative stress to algal cells. This work demonstrates the simultaneous ADFE treatment and cost-effective microalgal biomass production, providing new insights into microalgal cultivation for the efficient treatment and valorization of nutrient-rich ADFE for sustainability.

Studies on lactose utilization by the microalga Graesiella emersonii in the 3N-BBM-V model medium

ABSTRACT Currently, commercial microalgal biomass production is limited mainly due to high production costs. The use of cheap alternative media, such as dairy industry by-products and wastewater, can facilitate the commercialization of prospective microalgal strains. However, the use of dairy by-products is hampered by poor understanding of mechanisms of lactose utilization, i.e. the main carbon (C) source in such substrates, leading to inconsistent performance of microalgae. This study focuses on the ability of an isolated freshwater axenic microalgal strain Graesiella emersonii MSCL 1718 to utilize lactose and its monomers, i.e. glucose and galactose, in modified Bold’s Basal Medium with triple nitrogen and vitamins (3 N-BBM-V). It aims to develop a better understanding of microalgal interactions with C sources available in dairy by-products. The strain can successfully utilize lactose under mixotrophic and heterotrophic conditions when pH is maintained at approximately 7 and efficiently grow in lactose concentrations up to 30 g l−1. Under mixotrophic cultivation conditions, G. emersonii was capable of utilizing all three tested C sources. However, under heterotrophic cultivation conditions, G. emersonii could not utilize galactose as the main C added to 3 N-BBM-V, highlighting the importance of selecting appropriate cultivation conditions. Additionally, the enzyme β-galactosidase, responsible for lactose hydrolysis, was detected in the microalgal biomass, with activity up to 17.03 ± 1.23 U l−1. FTIR analysis of biomass demonstrated an increase in total lipid content and polyunsaturated fatty acids specifically in the mixotrophic group. Overall, G. emersonii demonstrated features suitable for bioconversion of dairy by-products which should be investigated in further studies.

Total phenolic content and <i>in vitro </i>evaluation of antioxidant activity of microbial extract of defatted biomass of mutant <i>Pseudochlorella pringsheimii</i> EMM2

Microalgal biomass is considered to be a renewable source for organic antioxidants. The present study aimed to evaluate the defatted biomass (DB) of the mutated green microalga Pseudochlorella pringsheimii EMM2 for increasing total phenolic content (TPC) extraction and antioxidant activity via microbial fermentation. Three distinct bacterial strains, Bacillus amyloliquefaciens (Accession number: KT276356), B. stearothermophilus (Accession number: KT282130), and B. subtilis (Accession number: KT282131) were obtained from sago industrial wastewater, utilized the hydrolysate from the DB of P. pringsheimii EMM2 as the exclusive medium for fermentation in this work. Among these bacterial strains, B. stearothermophilus was chosen for further investigation due to its effectiveness in enhancing the extraction of TPC and antioxidant activity of the hydrolysate of DB through fermentation. The fermentation conditions were optimized using a classical method, identifying the optimum physical parameters as a pH of 7.0, a temperature of 55 °C, an agitation speed of 150 rpm, and a fermentation time of 40 hours for maximizing the antioxidant activity of the hydrolysate of DB. Under these optimal conditions, a 6.11-fold increase in DPPH radical scavenging activity was observed in the hydrolysate. Consequently, this study demonstrated that the DB of the mutant microalga P. pringsheimii EMM2 is a valuable source for TPC production through fermentation with B. stearothermophilus.

Valorizing Agro-Industrial By-Products for Sustainable Cultivation of Chlorella sorokiniana: Enhancing Biomass, Lipid Accumulation, Metabolites, and Antimicrobial Potential.

Background/Objectives: Mixotrophic cultivation of microalgae using agro-industrial by-products as supplements offers a sustainable strategy to enhance biomass production and bioactive compound synthesis. This study aimed to evaluate the effects of different agro-industrial by-products-orange peel extract, Cladophora glomerata macroalgal hydrolysate, and solid-state fungal fermentation hydrolysate-on the growth and bioactivity of Chlorella sorokiniana. Methods: Microalgae were cultivated under mixotrophic conditions with different agro-industrial by-products as organic carbon sources. Biomass accumulation was monitored through dry weight measurements. Lipid extraction was carried out using dimethyl carbonate. The antimicrobial activity of the extracted compounds was assessed against Escherichia coli, Bacillus megaterium, and Bacillus subtilis by determining the minimal inhibitconcentrations. Results: Orange peel extract supplementation resulted in the highest biomass production. It increased dry weight by 13.86-fold compared to autotrophic conditions. Cladophora glomerata macroalgal hydrolysate followed with a 5.79-fold increase, and solid-state fungal fermentation hydrolysate showed a 4.14-fold increase. The lipophilic fraction extracted from microalgal biomass showed high yields. Orange peel extract supplementation achieved the highest extraction yield (274.36 mg/g DW). Antimicrobial activity varied based on the supplement used: biomass cultivated with orange peel extract exhibited superior activity against E. coli, whereas Cladophora glomerata macroalgal hydrolysate biomass demonstrated potent activity against B. subtilis (MIC: 5.67 g/mL). Conclusions: These findings underscore the potential of agro-industrial by-products for enhancing microalgal biomass and metabolite production. The observed antimicrobial properties highlight the application of microalgal-derived compounds in sustainable bioprocesses, supporting their use in pharmaceutical and biotechnological applications.

Carotenoids and biogas recovery from microalgae treating wastewater.

Carotenoids and biogas recovery from microalgae treating wastewater.

A novel structured graphene oxide@microalgae nanohybrids as adsorbents for removal of Cr(VI) ions in aqueous solutions

Novel structured graphene oxide@microalgae-based nanohybrids have been prepared by incorporating green microalgae biomass (Algae) with graphene oxide (GO) or N-doped graphene oxide (NGO) in different ratios (e.g., 3:1, 1:1 and 1:3). Biogenic GO-Algae and NGO-Algae nanohybrids were synthesized via a self-assembly method. Morphological and structural characterizations and adsorption performance of the nanostructured material towards Cr(VI) species were studied extensively. The removal of Cr(VI) species by GO-Algae and NGO-Algae nanohybrids was highly pH dependent, with the maximum adsorption removal occurring at pH 2. The results indicate that the adsorption of Cr(VI) by GO-Algae and NGO-Algae nanohybrids was as follows: GO@Algae-3:1 (90.5%) < GO@Algae-1:1 (98.7%) < GO@Algae-1:3 (99.6%) and NGO@Algae-3:1 (79.2%) < NGO@Algae-1:1 (82.3%) < NGO@Algae-1:3 (92.6%), respectively. The GO: Algae-1:3 and NGO: Algae-1:3 nanohybrids with a high microalgae content ratio exhibited high maximum removal, owing to the presence of more active sites within their lattice compared to their counterparts. On the other hand, pseudo-first-order, pseudo-second-order, intraparticle diffusion, Langmuir, and Freundlich models adequately simulated adsorption mechanisms, suggesting that the adsorption process involved a combination of external mass transfer and chemisorption, with electrostatic and complexation interactions being the dominant mechanisms for Cr(VI) removal. Additionally, GO@Algae-1:3 and NGO@Algae-1:3 displayed outstanding reusability. Therefore, these structured graphene@microalgae-based nanohybrids can simultaneously serve as adsorbents for Cr(VI) removal from wastewater and contaminated water sources.

Mixotrophic Cultivation of Dunaliella tertiolecta in Cheese Whey Effluents to Enhance Biomass and Exopolysaccharides (EPS) Production: Biochemical and Functional Insights.

The rapid growth of the dairy industry has resulted in a significant increase in the generation of effluents, which are characterized by a high organic content that poses environmental challenges. In alignment with sustainable practices and the principles of the circular economy, this study investigates the valorization of cheese whey (CW) effluents through the cultivation of the microalga Dunaliella tertiolecta under mixotrophic conditions. The research aims to utilize cheese whey effluents as a supplemental growth medium to enhance the production of algal biomass and extracellular polymeric substances (EPSs). The results reveal that CW facilitated a 37% improvement in D. tertiolecta growth and led to an approximately eight times greater biomass productivity compared to under photoautotrophic conditions, while the EPS production increased by 30%. Chemical and techno-functional analyses of the microalgal biomass and EPSs suggest promising applications as natural product additives for the food industry. Biomass derived from photoautotrophic culture demonstrated greater antioxidant activity and total polyphenols content. Additionally, the lipid profile revealed 16 distinct fatty acids. On the other hand, biomass from the mixotrophic culture exhibited higher protein levels and eight fatty acids, indicating the influence of the cultivation mode on the biochemical composition. Regarding the EPSs, mixotrophic cultivation resulted in elevated antioxidant activity and total polyphenols content, as well as higher protein and sugar levels. Furthermore, the EPSs produced under mixotrophic conditions exhibited superior techno-functional properties compared to those of the photoautotrophic culture, making them ideal candidates for use as alternative natural food additives.

Effect of different pyrolysis temperatures on biofertilizer properties of microalgal biochar and energy analysis

In this study, Chlorella sp. (Cs), Chlorella vulgaris (Cv), Neochloris conjuncta (Nc), Botryoococcus braunii (Bb), and Scenedesmus obliquus (So) microalgae strains were cultivated in channel type ponds. The microalgal biomasses obtained were divided into two groups (350 and 600 °C). The microalgal biomasses in the first group were biocharized at two different pyrolysis temperatures, while those in the second group were untreated crude microalgal biomasses. As a result of the energy input-output analysis of both groups of microalgal biomasses, the highest net energy gain was calculated in the un-treated Cv strain with 52.41, while the lowest value was calculated in the biocharification process of So and Bb strains at 600°C with 13.03. In all groups, the energy efficiency, energy ratio, and net energy gain of the Cv strain were found to be higher than other microalgae strains. When the bio-fertilizer, biostimulant data, and energy data are evaluated together, it’s concluded that it’s most appropriate to prefer the Cv microalgae strain.

Urban photobioreactor for CO2 sequestration and microalgal biomass production

The growth system of microalgae photobioreactors (PBRs) has drawn a lot of interest as a viable and sustainable method for generating quality biomass for value-added products and biofuels. The objective of this research work is to cultivate micro-algae species Chlorella vulgaris in a photobioreactor that was designed, fabricated, and powered by solar energy system. Three experimental conditions were compared with 1:4 ratios of microalgae culture (40L) and fresh water (10L) having 100mL of media (nutrients) used in each experiment with control sample (ambient air aeration) experiment # 1, injecting 200 g of CO2 for 15 sec (experiment # 2), and 300g of CO2 for 25 sec (experiment # 3) on alternate days during the cultivation period. All experiments showed the reduction of nutrients concentration (orthophosphate and nitrate) and enhancement of biomass productivity with respect to 10 days of cultivation period. Experiments 1, 2 and 3 showed removal of orthophosphate as 50 %, 41.74 % and 60.78 % respectively, whereas nitrate removal was 22 %, 48 % and 58 %. Biomass productivity from experiments 1, 2 and 3 after 10 days of cultivation period were 196.63 mg/L, 203.43 mg/L, 318.76 mg/L respectively. Statistical analysis revealed that supplying CO2 from external source in experiment # 2 and experiment # 3 have same pattern of statistical significance with co-relationship between two groups of means with p-value of 6.306 × . The maximum microalgal biomass was recovered from experiment # 3, with 7.98 % by weight protein content yield and lipid content yield 37.4 % by weight (1.87/ 5 g of dried biomass). Kinetic study showed volumetric mass transfer capacities of and were found to be 1.763× /s and 1.676× /s, with better result of gas transfer capacity of the system. In the extracted lipids favorable qualities of fatty acids for the production of microalgae biodiesel were found such as myristic (C14:0), palmitic (C16:0), palmitoleic (C16:1), oleic (C18:1), linoleic (C18:1), and linolenic acids (C18:3). The use of urban micro-algae photobioreactors is an environmentally sustainable strategy that can contribute significantly to the bio-based economy and reduce the negative effects of traditional fossil fuel usage on the environment.

Enhancing Biomass and Lipid Production in Messastrum gracile Using Inorganic Carbon Substrates and Alternative Solvents for Lipid Extraction.

Microalgae show promise as a biomass and bioproduct for applications in various industries. The cultivation of microalgae plays a crucial role in optimizing biomass yield and bioproduct accumulation. The provision of inorganic carbon substrates substantially enhances microalgal growth and lipid biosynthesis, resulting in marked increases in the production of biofuels and other bioproducts. This study examined biomass and lipid accumulation in Messastrum gracile IFRPD 1061 under inorganic stress conditions, previously unreported. M. gracile IFRPD 1061 was subjected to varying conditions of inorganic carbon substrates, 1-3 g·L-1 sodium carbonate and bicarbonate concentration, to enhance biomass and lipid accumulation. Optimal productivity levels were observed with sodium bicarbonate addition of 3 g·L-1 and 1 g·L-1 for biomass and lipids, resulting in productivities of 392.64 and 53.57 mg·L-1·d-1, respectively. Results underlined the effectiveness of sodium carbonate and bicarbonate as inorganic carbon sources for stimulating microalgal growth and enhancing the production of high-value products. The extraction of lipids from freeze-dried biomass of M. gracile IFRPD 1061 demonstrated optimal yield using methanol/hexane solvents compared with the control experiments. Lipid extraction yields using methanol/hexane were 42.18% and 46.81% from oven-dried and freeze-dried biomass, respectively. Lipids extracted from oven-dried M. gracile IFRPD 1061 using methanol/hexane/chloroform solvents indicated the potential of methanol/hexane as a solvent for lipid extraction from dry microalgal biomass using an ultrasonic-assisted technique. This study contributes valuable insights into maximizing biofuel and bioproduct production from microalgae, highlighting A. gracilis as a promising candidate for industrial applications.

Ammoniation of filter residues from corn straw filtering the microalgae cultured in urine wastewater.

Ammoniation of filter residues from corn straw filtering the microalgae cultured in urine wastewater.

Microalgae biomass–A source of sustainable dietary bioactive compounds towards improved health and well-being

Microalgae biomass–A source of sustainable dietary bioactive compounds towards improved health and well-being

Co-metabolism of Norfloxacin by Chlorella pyrenoidosa: Carbon source effects, biotransformation mechanisms, and key driving genes.

Co-metabolism of Norfloxacin by Chlorella pyrenoidosa: Carbon source effects, biotransformation mechanisms, and key driving genes.

Is it possible to shape the microalgal biomass composition with operational parameters for target compound accumulation?

Microalgae, as photosynthetic microorganisms, offer a sustainable source of proteins, lipids, carbohydrates, pigments, vitamins, and antioxidants. Leveraging their advantages, such as fast growth, CO2 fixation, cultivation without arable land, and wastewater utilisation, microalgae can produce a diverse range of compounds. The extracted products find applications in bioenergy, animal feed, pharmaceuticals, nutraceuticals, cosmetics, and food industries. The selection of microalgal species is crucial, and their biochemical composition varies during growth phases influenced by environmental factors like light, salinity, temperature, and nutrients. Manipulating growth conditions shapes biomass composition, optimising the production of target compounds. This review synthesises research from 2019 onwards, focusing on stress induction and two-stage cultivation in microalgal strategies. This review takes a broader approach, addressing the effects of various operating conditions on a range of biochemical compounds. It explores the impact of operational parameters (light, nutrient availability, salinity, temperature) on biomass composition, elucidating microalgal mechanisms. Challenges include species-specific responses, maintaining stable conditions, and scale-up complexities. A two-stage approach balances biomass productivity and compound yield. Overcoming challenges involves improving upstream and downstream processes, developing sophisticated monitoring systems, and conducting further modelling work. Future efforts should concentrate on strain engineering and refined monitoring, facilitating real-time adjustments for optimal compound accumulation. Moreover, conducting large-scale experiments is essential to evaluate the feasibility and sustainability of the process through techno-economic analysis and life cycle assessments.

Microalgal biofilm cultivation on lignocellulosic based bio-carriers: Effects of material physical characteristics on microalgal biomass production and composition

Microalgal biofilm cultivation on lignocellulosic based bio-carriers: Effects of material physical characteristics on microalgal biomass production and composition

Biosorption of heavy metals by microalgae: Hazardous side effects for marine organisms.

Biosorption of heavy metals by microalgae: Hazardous side effects for marine organisms.