Microalgae Oil Production Research Articles

Extraction of microalgae oil and further production for second-generation biodiesel

Extraction of microalgae oil and further production for second-generation biodiesel

Life cycle assessment of integrated microalgae oil production in Bojongsoang Wastewater Treatment Plant, Indonesia.

This study aims to determine the eco-friendliness of microalgae-based renewable energy production in several scenarios based on life cycle assessment (LCA). The LCA provides critical data for sustainable decision-making and energy requirement analysis, including net energy ratio (NER) and cumulative energy demand (CED). The Centrum voor Milieuwetenschappen Leiden (CML) IA-Baseline was used on environmental impact assessment method by SimaPro v9.3.0.3® software and energy analysis of biofuel production using native polyculture microalgae biomass in municipal wastewater treatment plants (WWTP) Bojongsoang, Bandung, Indonesia. The study was analyzed under three scenarios: (1) the current scenario; (2) the algae scenario without waste heat and carbon dioxide (CO2); and (3) the algae scenario with waste heat and carbon dioxide (CO2). Waste heat and CO2 were obtained from an industrial zone near the WWTP. The results disclosed that the microalgae scenario with waste heat and CO2 utilization is the most promising scenario with the lowest environmental impact (- 0.139kg CO2eq/MJ), positive energy balance of 1.23MJ/m3 wastewater (NER > 1), and lower CED value across various impact categories. It indicates that utilizing the waste heat and CO2 has a positive impact on energy efficiency. Based on the environmental impact, NER and CED values, this study suggests that the microalgae scenario with waste heat and CO2 is more feasible and sustainable to adopt and could be implemented at the Bojongsoang WWTP.

The effect of photobioreactor height/diameter ratio on Chlorella Variabilis microalgae growth and oil production efficiency

The effect of photobioreactor height/diameter ratio on Chlorella Variabilis microalgae growth and oil production efficiency

Innovative Approaches to Enhanced Enzymatic Microalgae‐to Biodiesel Production

AbstractDespite the increasing interest in biodiesel production from microalgae, the high cost of multistage production processes still hinders its commercialization. The high oil productivity of microalgae and their ability to grow rapidly under harsh conditions and in saline water make them a favorable feedstock for biodiesel production. In this review, conventional methods of producing biodiesel from microalgae are thoroughly discussed and compared to state‐of‐the‐art technologies. Considerable emphasis has been put on the adoption of biocatalysts as alternative greener and more effective catalysts. Challenges facing the biocatalytic process and innovative ways to overcome them are also presented. The main focus is on the in‐situ biodiesel production processes, which are promising to pave the way for industrial application of microalgae‐to‐biodiesel process. The use of state‐of the‐art thermoresponsive switchable solvents, coupled with immobilized lipase, for simultaneous cell disruption, oil extraction‐reaction, and product separation in one pot has shown to be highly favorable. Because enzymes are expensive, finding ways to enhance their stability and reusability for a greater number of cycles is essential for the process to be economically viable and competitive.

Efficient method for the determination of the neutral lipid content of oil-producing microalgae strains required for biodiesel

The continued use of petroleum-derived fuels is unsustainable, as these fuels contribute to the environmental accumulation of carbon dioxide. Renewable fuels are necessary for environmental and economic sustainability. Microalgae appear to be the source of renewable biofuel that can meet the global demand for transport fuels. Like plants, microalgae use sunlight to produce oils but they do so more efficiently than crop plants. Oil productivity of many microalgae greatly exceeds the oil productivity of the best producing oil crops. Using microalgae to produce biofuel does not occupy agricultural land will not compromise production of food and other products derived from crops.During the growth of microalgae, the quantitative and qualitative values of produced lipids are constantly changing. Therefore, a laboratory lipid determination method had to be developed. Among the various industrial lipid extraction and purification methods, we only dealt with methods that can also be used in the laboratory. Because only neutral lipid fraction can be used to produce biofuels, an optimized method had to be developed to separate and determine the amount of neutral lipids. Each step was optimized in terms of time, volume, amount of chemical, simplicity and accuracy, these were the main aspects so that the method could be used for a wide range of lipid content and composition. The developed microextraction method enables the examination of a small amount of sample (100 mg) in a small volume (5 mL), in that way many samples can be processed simultaneously. This method saves time, money and chemicals in the laboratory while improving the accuracy of the lipid content determination.

Technoeconomic Evaluation of Microalgae Oil Production: Effect of Cell Disruption Method

Microalgae have a high capacity to capture CO2. Additionally, biomass contains lipids that can be used to produce biofuels, biolubricants, and other compounds of commercial interest. This study analyzed various scenarios for microalgae lipid production by simulation. These scenarios include cultivation in raceway ponds, primary harvest with three flocculants, secondary harvest with pressure filter (and drying if necessary), and three different technologies for the cell disruption step, which facilitates lipid extraction. The impact on energy consumption and production cost was analyzed. Both energy consumption and operating cost are higher in the scenarios that consider bead milling (8.79–8.88 kWh/kg and USD 41.06–41.41/kg), followed by those that consider high-pressure homogenization (HPH, 5.39–5.46 kWh/kg and USD 34.26–34.71/kg). For the scenarios that consider pressing, the energy consumption is 5.80–5.88 kWh/kg and the operating cost is USD 27.27–27.88/kg. The consumption of CO2 in scenarios that consider pressing have a greater capture (11.23 kg of CO2/kg of lipids). Meanwhile, scenarios that consider HPH are the lowest consumers of fresh water (5.3 m3 of water/kg of lipids). This study allowed us to develop a base of multiple comparative scenarios, evaluate different aspects involved in Chlorella vulgaris lipid production, and determine the impact of various technologies in the cell disruption stage.

Investigations of Light Intensities, Nutrient, and Carbon Sources Towards Microalgae Oil Production via Soxhlet Extraction Techniques

Aims: This study was carried out to study the optimized condition for microalgae cultivation in terms of light intensity, and nutrient supply. Also, use of a carbon source was studied to optimize the microalgae growth to produce microalgae with a high biomass productivity and a high lipid content. Background: Algae can be categorized into macroalgae and microalgae. Commonly, microalgae are used to produce biodiesel since microalgae can yield 5000-15000 of oil gallons compared to plant-based biomass as feedstock produced 50-500 oil gallon. Furthermore, microalgae do not face any food crisis and can be cultivated in any wasteland that is not suitable for agriculture throughout the year, compared to crops. Microalgae can also be cultivated in freshwater, saline water and wastewater. Methods: Microalgae cultivation was carried out with microalgae culture labelled as MX1, MX2, MX3, MX4 and were cultivated under high light intensities, whereas MY1, MY2, MY3, MY4 were cultivated under medium light intensity and MZ1, MZ2, MZ3 MZ4 became control culture that was cultivated under high light intensities and no light condition. Results: The effect of light intensity, NPK fertilizer, and glucose on microalgae’s biomass production will be observed simultaneously. At the end of cultivation, MX2 obtained the highest biomass of 97.186 g. The oil extraction yield is 9.66%. GC-MS analysis showed the presence of UFA and PUFA in the oil. Conclusion: Thus, future research is needed to improve the technique to increase the microalgae biomass and lipid to become the potential feedstock for the production of biodiesel.

Carbon flow conversion induces alkali resistance and lipid accumulation under alkaline conditions based on transcriptome analysis in Chlorella sp. BLD

Alkaline environments are abundant globally and cause damage to most organisms, while some microalgae can grow well and accumulate lipids under those conditions. Here the mechanisms of alkali resistance and lipid accumulation in the alkaliphilic microalgae Chlorella sp. BLD were explored using physiological-biochemical and transcriptome analysis. When cultivated at alkaline pH, Chlorella sp. BLD exhibited good alkali-resistance ability and increased biomass (0.97 g L−1). The biochemical composition of Chlorella sp. BLD changed significantly (lipid content increased 39% and protein content decreased 19.5%) compared with pH 7.5. Through transcriptome analysis, we found that pathways related to carbon metabolism such as photosynthesis, glycolysis, and the TCA cycle were significantly regulated under alkaline conditions. Genes that encoding the key enzyme in carbon-related metabolism such as Rubisco, AMY, PK, ME, CS, ACAT, KAS, and DGAT were identified. Transcriptional regulation of these genes results in carbon flow switching from starch and protein to cell wall metabolism, organic acid synthetic and lipid accumulation in response to alkaline conditions. These results reveal the alkali resistance mechanism of Chlorella sp. BLD and provide a theoretical basis for microalgae oil production under alkaline conditions.

Effects of black soldier fly oil rich in n-3 HUFA on growth performance, metabolism and health response of juvenile mirror carp (Cyprinus carpio var. specularis)

In the present study, we aimed to assess the effect of dietary black soldier fly oil (BSFO) enriched with n-3 highly unsaturated fatty acids (HUFA) on growth performance, lipid metabolism, inflammation and related gene expression in juvenile mirror carp (Cyprinus carpio var. Specularis). Triplicate cages of juvenile mirror carp were fed one of five isonitrogenous and isolipidic diets for 8 weeks. The control diet contained 25 g kg−1 soybean oil (SO), which was 25%, 50%, 75% or 100% replaced with an n-3HUFA enriched BSFO. This enrichment was done by growing the insects on a by-product of microalgae oil production. The growth and nutrient utilization as well as many health parameters of the fish were significantly improved when fed a 50% or higher replacement of SO with the n-3 HUFA enriched BSFO. A replacement level at 50% or above led to a decreased intra-peritoneal fat index and adipocyte size, accompanied by relevant changes in gene expression. The same replacement levels also led to an improvement in the serum biochemical profile of the fish and showed indications of enhancing immune status. Gene expression results of the liver and head kidney indicates a less inflammatory state in fish fed more than a 50% replacement of SO with BSFO. Overall, this study showed that a 50–100% replacement of SO with this n-3 enriched BSFO positively influences the performance and health status of juvenile mirror carp.

Microalgae Oil Production Using Wastewater in Japan—Introducing Operational Cost Function for Sustainable Management of WWTP

A comparative evaluation of economic efficiency was performed for native polyculture microalgae oil production in an oxidation ditch (OD) process wastewater treatment plant (WWTP). A cost function was developed for the process. The operational cost per 1 m3 of wastewater (w.w.) was 1.34 $/m3-w.w. in the existing scenario, 1.29 $/m3-w.w. in algal scenario A (no cost for CO2 and waste heat) and 1.36 $/m3-w.w. in algal scenario B (no cost for CO2). The conditions were set as follows: hydraulic retention time (HRT): 4 days, microalgal productivity: 0.148 g/L and daily treatment volume: 81.6 m3-w.w./d. The cost differences were related to the increase in polymer flocculants for algae separation (+0.23 $/m3-w.w), carbon credits from CO2 absorption (−0.01 $/m3-w.w), the sales of biocrude (−0.04 $/m3-w.w) and sludge disposal (−0.18 $/m3-w.w). Hence, the introduction of the algae scenario was the same cost-effective as the existing scenario. Microalgae oil production in an OD process WWTP can serve as a new energy system and reduce the environmental load in a society with a declining population.

Immobilised Chlorella vulgaris as An Alternative for The Enhancement of Microalgae Oil and Biodiesel Production

Microalgae are a promising alternative for biodiesel production and a valuable source of fatty acid methyl ester (FAME). In this research, Chlorella vulgaris has been chosen as the suitable microalgae because this species was able to produce highest oils for biodiesel processing. Previously, sodium alginate (SA) was used to entrap the microalgae in the culturing process due to its low toxicity and high transparency. However, SA have some disadvantages such as bead disruption which leading to the loss of microalgae cell. Therefore, this research has been conducted to evaluate the oil production of immobilised Chlorella vulgaris using different matric systems at different ratios which are 0.3:1, 1:1 and 2:1. Currently, six matric systems have been developed, they are SA as a control, a combination of SA and chitosan (SA+CT), SA and carrageenan (SA+CR), SA and gelatin (SA+GT), SA and calcium alginate (SA+CA), and SA and sodium carboxymethylcellulose (SA+CMC). The microalgae was first cultivated, harvested and extracted to produce oil, prior to use in the transesterification process. The SA+GT showed the highest oil yield with 59.14% and a total FAME of 0.56 mg/g. The FAME profile of oil extracted microalgae showed high potential for biodiesel production as it consisted of palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2) and linolenic acid (C18:3). The results proved that the combination of SA+GT had improved the oil yield and fatty acid composition as compared to the other matric systems, which may have useful application for the biodiesel industry. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Improving oil production in plants and microalgae by engineering performance-enhanced diacylglycerol acyltransferase 1

Improving oil production in plants and microalgae by engineering performance-enhanced diacylglycerol acyltransferase 1

Reduction in Energy Requirement and CO2 Emission for Microalgae Oil Production Using Wastewater

A comparative evaluation of energy requirement and CO2 emission was performed for native polyculture microalgae oil production in a wastewater treatment plant (WWTP). The wastewater provided nutrients for algae growth. Datasets of microalgae oil production and their details were collected from the Minamisoma pilot plant. Environmental impact estimation from direct energy and material balance was analyzed using SimaPro® v8.0.4. in two scenarios: existing and algal scenarios. In the existing scenario, CO2 emission sources were from wastewater treatment, sludge treatment, and import of crude oil. In the algal scenario, CO2 emission with microalgae production was considered using wastewater treatment, CO2 absorption from growing algae, and hydrothermal liquefaction (HTL) for extraction, along with the exclusion of exhausted CO2 emission for growing algae and use of discharged heat for HTL. In these two scenarios, 1 m3 of wastewater was treated, and 2.17 MJ higher heating value (HHV) output was obtained. Consequently, 2.76 kg-CO2 eq/m3-wastewater in the existing scenario and 1.59 kg-CO2 eq/m3-wastewater in the algal scenario were calculated. In the HTL process, 21.5 MJ/m3-wastewater of the discharged heat energy was required in the algal scenario. Hence, the efficiency of the biocrude production system will surpass those of the WWTP and imported crude oil.

Characterization of Type-2 Diacylglycerol Acyltransferases in the Green Microalga Chromochloris zofingiensis.

Diacylglycerol acyltransferase (DGAT) catalyzes the last and committed step of the acyl-CoA-dependent TAG biosynthesis and thus is a key target for manipulating oil production in microalgae. The microalga Chromochloris zofingiensis can accumulate substantial amounts of triacylglycerol (TAG) and represents a promising source of algal lipids. In this study, C. zofingiensis DGAT2s (CzDGAT2s) were characterized with in silico, in vivo (yeast), and in vitro assays. Putative CzDGAT2s were identified, and their functional motifs and evolutionary relationship with other DGAT2s were analyzed. When CzDGAT2s were individually expressed in a TAG-deficient Saccharomyces cerevisiae strain, only CzDGAT2C could restore the TAG biosynthesis. Further in vitro assays indicated that CzDGAT2C displayed typical DGAT activity, which was fitted to the Michaelis-Menten equation, and N- and C-terminals were important for the enzyme activity. In addition, membrane yeast two-hybrid assay revealed a possible DGAT2 activity modulation via the formation of homodimer/heterodimer among different DGAT2 isoforms.

Microalgae Oil Production: A Downstream Approach to Energy Requirements for the Minamisoma Pilot Plant

This study investigates the potential of microalgae oil production as an alternative renewable energy source, in a pilot project located at Minamisoma City in the Fukushima Prefecture of Japan. The algal communities used in this research were the locally mixed species, which were mainly composed of Desmodesmus collected from the Minamisoma pilot project. The microalgae oil-production processes in Minamisoma consisted of three stages: cultivation, dewatering, and extraction. The estimated theoretical input-energy requirement for extracting oil was 137.25 MJ to process 50 m3 of microalgae, which was divided into cultivation 15.40 MJ, centrifuge 13.39 MJ, drum filter 14.17 MJ, and hydrothermal liquefaction (HTL) 94.29 MJ. The energy profit ratio (EPR) was 1.41. The total energy requirement was highest in the HTL process (68%) followed by cultivation (11%) and the drum filter (10%). The EPR value increased along with the yield in the cultivation process. Using HTL, the microalgae biomass could be converted to bio-crude oil to increase the oil yield in the extraction process. Therefore, in the long run, the HTL process could help lower production costs, due to the lack of chemical additions, for extracting oil in the downstream estimation of the energy requirements for microalgae oil production.

Identification and characterization of an efficient acyl-CoA: diacylglycerol acyltransferase 1 (DGAT1) gene from the microalga Chlorella ellipsoidea

BackgroundOil in the form of triacylglycerols (TAGs) is quantitatively the most important storage form of energy for eukaryotic cells. Diacylglycerol acyltransferase (DGAT) is considered the rate-limiting enzyme for TAG accumulation. Chlorella, a unicellular eukaryotic green alga, has attracted much attention as a potential feedstock for renewable energy production. However, the function of DGAT1 in Chlorella has not been reported.ResultsA full-length cDNA encoding a putative diacylglycerol acyltransferase 1 (DGAT1, EC 2.3.1.20) was obtained from Chlorella ellipsoidea. The 2,142 bp open reading frame of this cDNA, designated CeDGAT1, encodes a protein of 713 amino acids showing no more than 40% identity with DGAT1s of higher plants. Transcript analysis showed that the expression level of CeDGAT1 markedly increased under nitrogen starvation, which led to significant triacylglycerol (TAG) accumulation. CeDGAT1 activity was confirmed in the yeast quadruple mutant strain H1246 by restoring its ability to produce TAG. Upon expression of CeDGAT1, the total fatty acid content in wild-type yeast (INVSc1) increased by 142%, significantly higher than that transformed with DGAT1s from higher plants, including even the oil crop soybean. The over-expression of CeDGAT1 under the NOS promoter in wild-type Arabidopsis thaliana and Brassica napus var. Westar significantly increased the oil content by 8–37% and 12–18% and the average 1,000-seed weight by 9–15% and 6–29%, respectively, but did not alter the fatty acid composition of the seed oil. The net increase in the 1,000-seed total lipid content was up to 25–50% in both transgenic Arabidopsis and B. napus.ConclusionsWe identified a gene encoding DGAT1 in C. ellipsoidea and confirmed that it plays an important role in TAG accumulation. This is the first functional analysis of DGAT1 in Chlorella. This information is important for understanding lipid synthesis and accumulation in Chlorella and for genetic engineering to enhance oil production in microalgae and oil plants.

Microalgae selection and improvement as oil crops: GM vs non-GM strain engineering

Despite being established as a sustainable feedstock for biofuel production with tremendous potential, the microalgae biofuel industry still struggles to make large-scale production economically viable. An overriding aspect in microalgae oil production is strain selection, as it affects nearly all stages of production. This chapter presents the key traits that microalgae should possess for successful lipid production, as well as suitable isolation and selection strategies. It highlights the various metabolic engineering methods that are currently available for the biological improvement of microalgae strains, comparing GM vs non-GM approaches.

Environmental impact of CO2-expanded fluid extraction technique in microalgae oil acquisition

Environmental impact of CO2-expanded fluid extraction technique in microalgae oil acquisition was quantitatively analyzed using life cycle assessment (LCA) method and compared with other available extraction techniques. It was found that CO2-expanded fluid extraction technique exhibited only one-tenth of environmental impact over other extraction methods, particularly on organic respiratory and climate change. Achieved low environmental impact was mainly attributed to the high extraction efficiency that further allows it for operating in mild pressure and shortened period of time, which dramatically decreases the energy consumption and afterwards environmental impacts. Utilizing renewable energy for CO2-expanded fluid extraction would further lower its environmental impact by minimizing carbon footprint resulting from electricity generation. Importantly, based on water-energy nexus consideration, the low environmental impact along with low energy consumption of CO2-expanded fluid extraction technique arises an opportunity to regard microalgae oil an energy storage vessel in response to the intermittent nature of renewable energy. This would be a new incentive for the development of microalgae oil production.

Parametric analysis for an algal oil production process

Microalgae are considered to be one of the most feasible options that have the potential to serve as a major feedstock for biofuels and bio-products production. However, the economic viability of commercial scale production remains questionable by many researchers and investors. There are several uncertainties in the technology for microalgae growing and harvesting, and the extraction of algal oil, which makes it difficult to identify the technology most suitable for minimizing cost and maximizing profits. Therefore, there is a need to carry out parametric analyses to identify the influence of system configuration and process on the economic viability. This study establishes an economic analysis for a microalgae oil production pathway to determine the minimum cost of producing algal oil. Taking the capital and operating costs parameters from the economic analysis, some of the key parameters are changed across a range of values and their influence on the final cost of algal oil is analysed. Each of the parameters is analysed across a range of production scale from 5 to 75 g/m 2 /d. The results show that the most important cost-driving parameters are the pond cost (especially the liners) and the harvesting costs, and that the costs can be reduced from £1.87/L to £1.58/L for a growth rate of 25 g/m 2 /d and £1.34/L for a growth rate of 50 g/m 2 /d. This ultimately suggests that to achieve economic viability,

Opportunities to improve the areal oil productivity of microalgae

Microalgae are often considered as a promising alternative source of vegetable oils. These oils can be used for food and biofuel applications. Productivities that are projected for large-scale microalgal oil production are, however, often poorly supported by scientific evidence and based on too optimistic assumptions. To facilitate the inclusion of the microalgal physiology in these projections, existing knowledge and novel scientific insights were condensed into a mechanistic model that describes photosynthesis and carbon partitioning during nitrogen starvation. The model is validated using experimental data from both wild-type and a starchless mutant of Scenedesmus obliquus. The model is subsequently used to quantify how reactor design, process design, and strain improvement can improve the oil productivity from 2.1 to up to 10.9gm−2day−1. These projected productivities are used to reflect on commonly assumed oil productivities and it is concluded that the microalgal oil productivity is often overestimated several folds.