The present study aims to investigate the influence of Staphylococcus aureus, Escherichia coli and Enterococcus faecalis in public market wastewater on the removal of nutrients in terms of ammonium (NH4-) and orthophosphate (PO43) using Scenedesmus sp. The removal rates of NH4- and orthophosphate PO43- and batch kinetic coefficient of Scenedesmus sp. were investigated. The phycoremediation process was carried out at ambient temperature for 6 days. The results revealed that the pathogenic bacteria exhibited survival potential in the presence of microalgae but they were reduced by 3-4 log at the end of the treatment process. The specific removal rates of NH4- and PO43- have a strong relationship with initial concentration in the public market wastewater (R2 = 0.86 and 0.80, respectively). The kinetic coefficient of NH4- removal by Scenedesmus sp. was determined as k = 4.28 mg NH4- 1 log10 cell mL-1 d-1 and km = 52.01 mg L-1 (R2 = 0.94) while the coefficient of PO43- removal was noted as k = 1.09 mg NH4- 1 log10 cell mL-1 d-1 and km = 85.56 mg L-1 (R2 = 0.92). It can be concluded that Scenedesmus sp. has high competition from indigenous bacteria in the public market wastewater to remove nutrients, with a higher coefficient of removal of NH4- than PO43.
In this study, the effects of limited and excess nitrate on biomass, lipid production, and fatty acid profile in Messastrum gracile SE-MC4 were determined. The expression of fatty acid desaturase genes, namely stearoyl-ACP desaturase (SAD), omega-6 fatty acid desaturase (ω-6 FAD), omega-3 fatty acid desaturase isoform 1 (ω-3 FADi1), and omega-3 fatty acid desaturase isoform 2 (ω-3 FADi2) was also assessed. It was found that nitrate limitation generally increased the total oil, α-linolenic acid (C18:3n3) and total polyunsaturated fatty acid (PUFA) contents in M. gracile. The reduction of nitrate concentration from 1.76 to 0.11 mM increased the total oil content significantly from 32.5 to 41.85% (dry weight). Palmitic (C16:0) and oleic (C18:1) acids as the predominant fatty acids in this microalgae constituted between 82 and 87% of the total oil content and were relatively consistent throughout all nitrate concentrations tested. The expression of SAD, ω-6 FAD, and ω-3 FADi2 genes increased under nitrate limitation, especially at 0.11 mM nitrate. The ω-3 FADi1 demonstrated a binary up-regulation pattern of expression under both nitrate-deficient (0.11 mM) and -excess (3.55 mM) conditions. Thus, findings from this study suggested that limited or excess nitrate could be used as part of a cultivation strategy to increase oil and PUFA content following media optimisation and more efficient culture methodology. Data obtained from the expression of desaturase genes would provide valuable insights into their roles under excess and limited nitrate conditions in M. gracile, potentially paving the way for future genetic modifications.
Microalgae are promising candidate resources from marine ecology for health-improving effects. Metabolite profiling of the microalgal diatom, Chaetoceros calcitrans was conducted by using robust metabolomics tools, namely ¹H nuclear magnetic resonance (NMR) spectroscopy coupled with multivariate data analysis (MVDA). The unsupervised data analysis, using principal component analysis (PCA), resolved the five types of extracts made by solvents ranging from polar to non-polar into five different clusters. Collectively, with various extraction solvents, 11 amino acids, cholesterol, 6 fatty acids, 2 sugars, 1 osmolyte, 6 carotenoids and 2 chlorophyll pigments were identified. The fatty acids and both carotenoid pigments as well as chlorophyll, were observed in the extracts made from medium polar (acetone, chloroform) and non-polar (hexane) solvents. It is suggested that the compounds were the characteristic markers that influenced the separation between the clusters. Based on partial least square (PLS) analysis, fucoxanthin, astaxanthin, violaxanthin, zeaxanthin, canthaxanthin, and lutein displayed strong correlation to 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging and nitric oxide (NO) inhibitory activity. This metabolomics study showed that solvent extractions are one of the main bottlenecks for the maximum recovery of bioactive microalgal compounds and could be a better source of natural antioxidants due to a high value of metabolites.
Microalgae are known as a rich source of bioactive compounds which exhibit different biological activities. Increased demand for sustainable biomass for production of important bioactive components with various potential especially therapeutic applications has resulted in noticeable interest in algae. Utilisation of microalgae in multiple scopes has been growing in various industries ranging from harnessing renewable energy to exploitation of high-value products. The focuses of this review are on production and the use of value-added components obtained from microalgae with current and potential application in the pharmaceutical, nutraceutical, cosmeceutical, energy and agri-food industries, as well as for bioremediation. Moreover, this work discusses the advantage, potential new beneficial strains, applications, limitations, research gaps and future prospect of microalgae in industry.
Microalgae are the major photosynthesizers on earth and produce important pigments that include chlorophyll a, b and c, β-carotene, astaxanthin, xanthophylls, and phycobiliproteins. Presently, synthetic colorants are used in food, cosmetic, nutraceutical, and pharmaceutical industries. However, due to problems associated with the harmful effects of synthetic colorants, exploitation of microalgal pigments as a source of natural colors becomes an attractive option. There are various factors such as nutrient availability, salinity, pH, temperature, light wavelength, and light intensity that affect pigment production in microalgae. This paper reviews the availability and characteristics of microalgal pigments, factors affecting pigment production, and the application of pigments produced from microalgae. The potential of microalgal pigments as a source of natural colors is enormous as an alternative to synthetic coloring agents, which has limited applications due to regulatory practice for health reasons.
Astaxanthin, a carotenoid pigment found in several aquatic organisms, is responsible for the red colour of salmon, trout and crustaceans. In this study, astaxanthin production from freshwater microalga Chlorella sorokiniana and marine microalga Tetraselmis sp. was investigated. Cell growth and astaxanthin production were determined spectrophotometrically at 620 and 480 nm, respectively. Astaxanthin was extracted using acetone and measured subsequent to biomass removal. Aerated conditions favoured astaxanthin production in C. sorokiniana, whereas Tetraselmis sp. was best cultured under unaerated conditions. C. sorokiniana produced more astaxanthin with the highest yield reached at 7.83 mg/l in 6.0 mM in nitrate containing medium compared to Tetraselmis sp. which recorded the highest yield of only 1.96 mg/l in 1.5 mM nitrate containing medium. Production in C. sorokiniana started at the early exponential phase, indicating that astaxanthin may be a growth-associated product in this microalga. Further optimization of astaxanthin production was performed using C. sorokiniana through a 2(3) full factorial experimental design, and a yield of 8.39 mg/l was achieved. Overall, the study has shown that both microalgae are capable of producing astaxanthin. Additionally, this research has highlighted C. sorokiniana as a potential astaxanthin producer that could serve as a natural astaxanthin source in the current market.
This study was undertaken to investigate the effects of different nitrate concentrations in culture medium on oil content and fatty acid composition of Chlorella vulgaris (UMT-M1) and Chlorella sorokiniana (KS-MB2). Results showed that both species produced significant higher (p<0.05) oil content at nitrate ranging from 0.18 to 0.66 mM with C. vulgaris produced 10.20-11.34% dw, while C. sorokiniana produced 15.44-17.32% dw. The major fatty acids detected include C16:0, C18:0, C18:1, C18:2 and C18:3. It is interesting to note that both species displayed differentially regulated fatty acid accumulation patterns in response to nitrate treatments at early stationary growth phase. Their potential use for biodiesel application could be enhanced by exploring the concept of binary blending of the two microalgae oils using developed mathematical equations to calculate the oil mass blending ratio and simultaneously estimated the weight percentage (wt.%) of desirable fatty acid compositions.
An aqueous two-phase system (ATPS) with ionic liquids (ILs) was used for the isolate of C-phycocyanin (CPC) from Spirulina platensis microalga. Various imidazolium ILs and potassium salts were studied. The effect of ILs-ATPS on the extraction efficiency of CPC was also studied. The experimental parameters like pH, loading volume, algae concentration, temperature, and alkyl chain length of IL were well-covered in this report. The experimental results showed that the extraction efficiency, the partition coefficient, and the separation factor for CPC were 99%, 36.6, and 5.8, respectively, for an optimal pH value of 7 and a temperature of 308 K. The order of extraction efficiency for CPC using IL-ATPS was: 1-octyl-3-methylimidazolium bromide (C8MIM-Br) > 1-hexyl-3-methylimidazolium bromide (C6MIM-Br) > 1-butyl-3-methylimidazolium bromide (C4MIM-Br). The isolation process followed the pseudo second-order kinetic model and the thermodynamic results were obviously spontaneous.
The unceasing rise of greenhouse gas emission has led to global warming and climate change. Global concern on this phenomenon has put forward the microalgal-based CO2 sequestration aiming to sequester carbon back to the biosphere, ultimately reducing greenhouse effects. Microalgae have recently gained enormous attention worldwide, to be the valuable feedstock for renewable energy production, due to their high growth rates, high lipid productivities and the ability to sequester carbon. The photosynthetic process of microalgae uses atmospheric CO2 and CO2 from flue gases, to synthesize nutrients for their growth. In this review article, we will primarily discuss the efficiency of CO2 biosequestration by microalgae species, factors influencing microalgal biomass productions, microalgal cultivation systems, the potential and limitations of using flue gas for microalgal cultivation as well as the bio-refinery approach of microalgal biomass.
Chlorella sorokiniana CY-1 was cultivated using palm oil mill effluent (POME) in a novel-designed photobioreactor (NPBR) and glass-made vessel photobioreactor (PBR). The comparison was made on biomass and lipid productions, as well as its pollutants removal efficiencies. NPBR is transparent and is developed in thin flat panels with a high surface area per volume ratio. It is equipped with microbubbling and baffles retention, ensuring effective light and CO2 utilization. The triangular shape of this reactor at the bottom serves to ease microalgae cell harvesting by sedimentation. Both biomass and lipid yields attained in NPBR were 2.3-2.9 folds higher than cultivated in PBR. The pollutants removal efficiencies achieved were 93.7% of chemical oxygen demand, 98.6% of total nitrogen and 96.0% of total phosphorus. Mathematical model revealed that effective light received and initial mass contributes toward successful microalgae cultivation. Overall, the results revealed the potential of NPBR integration in Chlorella sorokiniana CY-1 cultivation, with an aim to achieve greater feasibility in microalgal-based biofuel real application and for environmental sustainability.
Biodiesel with improved yield was produced from microalgae biomass under simultaneous cooling and microwave heating (SCMH). Nannochloropsis sp. and Tetraselmis sp. which were known to contain higher lipid species were used. The yield obtained using this novel technique was compared with the conventional heating (CH) and microwave heating (MWH) as the control method. The results revealed that the yields obtained using the novel SCMH were higher; Nannochloropsis sp. (83.33%) and Tetraselmis sp. (77.14%) than the control methods. Maximum yields were obtained using SCMH when the microwave was set at 50°C, 800W, 16h of reaction with simultaneous cooling at 15°C; and water content and lipid to methanol ratio in reaction mixture was kept to 0 and 1:12 respectively. GC analysis depicted that the biodiesel produced from this technique has lower carbon components (<19 C) and has both reasonable CN and IV reflecting good ignition and lubricating properties.
Fish meal is currently the major protein source for commercial aquaculture feed. Due to its unstable supply and increasing price, fish meal is becoming more expensive and its availability is expected to face significant challenges in the near future. Therefore, feasible alternatives to fish meal are urgently required. Microalgae have been recognized as the most promising candidates to replace fish meal because the protein composition of microalgae is similar to fish meal and the supply of microalgae-based proteins is sustainable. In this study, an indigenous microalga (Chlorella vulgaris FSP-E) with high protein content was selected, and its feasibility as an aquaculture protein source was explored. An innovative photobioreactor (PBR) utilizing cold cathode fluorescent lamps as an internal light source was designed to cultivate the FSP-E strain for protein production. This PBR could achieve a maximum biomass and protein productivity of 699 and 365 mg/L/day, respectively, under an optimum urea and iron concentration of 12.4 mM and 90 μM, respectively. In addition, amino acid analysis of the microalgal protein showed that up to 70% of the proteins in this microalgal strain consist of indispensable amino acids. Thus, C. vulgaris FSP-E appears to be a viable alternative protein source for the aquaculture industry.
Microalgae have received much interest as a biofuel feedstock in response to the uprising energy crisis, climate change and depletion of natural sources. Development of microalgal biofuels from microalgae does not satisfy the economic feasibility of overwhelming capital investments and operations. Hence, high-value co-products have been produced through the extraction of a fraction of algae to improve the economics of a microalgae biorefinery. Examples of these high-value products are pigments, proteins, lipids, carbohydrates, vitamins and anti-oxidants, with applications in cosmetics, nutritional and pharmaceuticals industries. To promote the sustainability of this process, an innovative microalgae biorefinery structure is implemented through the production of multiple products in the form of high value products and biofuel. This review presents the current challenges in the extraction of high value products from microalgae and its integration in the biorefinery. The economic potential assessment of microalgae biorefinery was evaluated to highlight the feasibility of the process.
The world at large is facing a new threat with the emergence of the Coronavirus Disease 2019 (COVID-19) pandemic. Though imperceptible by the naked eye, the medical, sociological and economical implications caused by this newly discovered virus have been and will continue to be a great impediment to our lives. This health threat has already caused over two million deaths worldwide in the span of a year and its mortality rate is projected to continue rising. In this review, the potential of algae in combating the spread of COVID-19 is investigated since algal compounds have been tested against viruses and algal anti-inflammatory compounds have the potential to treat the severe symptoms of COVID-19. The possible utilization of algae in producing value-added products such as serological test kits, vaccines, and supplements that would either mitigate or hinder the continued health risks caused by the virus is prominent. Many of the characteristics in algae can provide insights on the development of microalgae to fight against SARS-CoV-2 or other viruses and contribute in manufacturing various green and high-value products.
Microalgal-bacterial granular sludge (MBGS) process has become a focal point in treating municipal wastewater. However, it remains elusive whether the emerging process can be applied for the treatment of aquaculture wastewater, which contains considerable concentrations of nitrate and nitrite. This study evaluated the feasibility of MBGS process for aquaculture wastewater treatment. Result showed that the MBGS process was competent to remove respective 64.8%, 84.9%, 70.8%, 50.0% and 84.2% of chemical oxygen demand, ammonia-nitrogen, nitrate-nitrogen, nitrite-nitrogen and phosphate-phosphorus under non-aerated conditions within 8 h. The dominant microalgae and bacteria were identified to be Coelastrella and Rhodobacteraceae, respectively. Further metagenomics analysis implied that microbial assimilation was the main contributor in organics, nitrogen and phosphorus removal. Specifically, considerable nitrate and nitrite removals were also obtained with the synergy between microalgae and bacteria. Consequently, this work demonstrated that the MBGS process showed a prospect of becoming an environmentally friendly and efficient alternative in aquaculture wastewater treatment.
Natural antioxidants from sustainable sources are favoured to accommodate worldwide antioxidant demand. In addition to bioprospecting for natural and sustainable antioxidant sources, this study aimed to investigate the relationship between the bioactives (i.e. carotenoid and phenolic acids) and the antioxidant capacities in fucoxanthin-producing algae. Total carotenoid, phenolic acid, fucoxanthin contents and fatty acid profile of six species of algae (five microalgae and one macroalga) were quantified followed by bioactivity evaluation using four antioxidant assays. Chaetoceros calcitrans and Isochrysis galbana displayed the highest antioxidant activity, followed by Odontella sinensis and Skeletonema costatum which showed moderate bioactivities. Phaeodactylum tricornutum and Saccharina japonica exhibited the least antioxidant activities amongst the algae species examined. Pearson correlation and multiple linear regression showed that both carotenoids and phenolic acids were significantly correlated (p<0.05) with the antioxidant activities, indicating the influence of these bioactives on the algal antioxidant capacities.
The extensive amount of available information on global warming suggests that this issue has become prevalent worldwide. Majority of countries have issued laws and policies in response to this concern by requiring their industrial sectors to reduce greenhouse gas emissions, such as CO2. Thus, introducing new and more effective treatment methods, such as biological techniques, is crucial to control the emission of greenhouse gases. Many studies have demonstrated CO2 fixation using photo-bioreactors and raceway ponds, but a comprehensive review is yet to be published on biological CO2 fixation. A comprehensive review of CO2 fixation through biological process is presented in this paper as biological processes are ideal to control both organic and inorganic pollutants. This process can also cover the classification of methods, functional mechanisms, designs, and their operational parameters, which are crucial for efficient CO2 fixation. This review also suggests the bio-trickling filter process as an appropriate approach in CO2 fixation to assist in creating a pollution-free environment. Finally, this paper introduces optimum designs, growth rate models, and CO2 fixation of microalgae, functions, and operations in biological CO2 fixation.
In this era of globalization, various products and technologies are being developed by the industries. While resources and energy are utilized from processes, wastes are being excreted through water streams, air, and ground. Without realizing it, environmental pollutions increase as the country develops. Effective technology is desired to create green factories that are able to overcome these issues. Wastewater is classified as the water coming from domestic or industrial sources. Wastewater treatment includes physical, chemical, and biological treatment processes. Aerobic and anaerobic processes are utilized in biological treatment approach. However, the current biological approaches emit greenhouse gases (GHGs), methane, and carbon dioxide that contribute to global warming. Microalgae can be the alternative to treating wastewater as it is able to consume nutrients from wastewater loading and fix CO2 as it undergoes photosynthesis. The utilization of microalgae in the system will directly reduce GHG emissions with low operating cost within a short period of time. The aim of this review is to discuss the uses of native microalgae species in palm oil mill effluent (POME) and flue gas remediation. In addition, the discussion on the optimal microalgae cultivation parameter selection is included as this is significant for effective microalgae-based treatment operations.
Effective optimization of microalgae-to-bioethanol process systems hinges on an in-depth characterization of key process parameters relevant to the overall bioprocess engineering. One of the such important variables is the biomass particle size distribution and the effects on saccharification levels and bioethanol titres. This study examined the effects of three different microalgal biomass particle size ranges, 35 μm ≤ x ≤ 90 μm, 125 μm ≤ x ≤ 180 μm, and 295 μm ≤ x ≤ 425 μm, on the degree of enzymatic hydrolysis and bioethanol production. Two scenarios were investigated: single enzyme hydrolysis (cellulase) and double enzyme hydrolysis (cellulase and cellobiase). The glucose yield from biomass in the smallest particle size range (35 μm ≤ x ≤ 90 μm) was the highest, 134.73 mg glucose/g algae, while the yield from biomass in the larger particle size range (295 μm ≤ x ≤ 425 μm) was 75.45 mg glucose/g algae. A similar trend was observed for bioethanol yield, with the highest yield of 0.47 g EtOH/g glucose obtained from biomass in the smallest particle size range. The results have shown that the microalgal biomass particle size has a significant effect on enzymatic hydrolysis and bioethanol yield.
Reserve lipids of microalgae are promising for biodiesel production. However, economically feasible and sustainable energy production from microalgae requires optimization of cultivation conditions for both biomass yield and lipid production of microalgae. Biomass yield and lipid production in microalgae are a contradictory problem because required conditions for both targets are different. Simultaneously, the mass cultivation of microalgae for biofuel production also depends extremely on the performance of the microalgae strains used. In this study a green unicellular microalgae Chlorella sorokiniana (DS6) isolated from the holding tanks of farm wastewater treatment plant using multi-step screening and acclimation procedures was found high-lipid producing facultative heterotrophic microalgae strain capable of growing on dairy farm effluent (DFE) for biodiesel feedstock and wastewater treatment. Morphological features and the phylogenetic analysis for the 18S rRNA identified the isolated strains. A novel three stage cultivation process of facultative strain of C. sorokiniana was examined for lipid production.