Pulsed Electric Field-assisted Extraction Research Articles

Enhancing catechins, antioxidant and sirtuin 1 enzyme stimulation activities in green tea extract through pulse electric field-assisted water extraction: Optimization by response surface methodology approach

Green tea is an economic resource in Thailand because it is derived from smallholder agriculture and has expanded into food production. The purpose of this study is to optimize the parameters of pulsed electric field (PEF) assisted green tea extraction to produce a natural health product. A central composite design was involved to determine the effect of independent variables, including the intensity of electric field (I; 3–5 kV/cm), number of pulses (Np; 1000 to 3000 pulses) and green tea-to-water ratio (GT/W; 0.05–0.15 g/mL) on catechin (C), epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC) and epigallocatechin gallate (EGCG), total phenolic compound, antioxidant and sirtuin 1 enzyme stimulating activities. The results indicated that the Np had the most significant impact (p < 0.05) on the content of catechin and its derivatives and sirtuin 1 enzyme stimulating activity. The observations revealed that the I had a greater impact on antioxidant activities compared to the Np. The optimal conditions for PEF using the response surface method were determined to be I of 5 kV/cm, Np of 3000 pulses, GT/W of 0.14 g/mL and specific energy of 27 kJ/kg. Under the optimized conditions, the content of C, EC, ECG, EGC and EGCG were 7.34 ± 0.33, 11.26 ± 0.25, 3.75 ± 0.13, 7.53 ± 0.77 and 37.78 ± 0.58 mg/g extract, respectively. Furthermore, it was observed that green tea extract exhibited the ability to modulate the deacetylation activity of the sirtuin 1 enzyme, with a value of 22.63 ± 0.17 FIR. The results emphasized that the PEF led to achieving better responses compared to without pre-treatment using the PEF. Therefore, innovative technologies as PEF can be utilized for green tea extraction to produce natural ingredients, which can contribute to improved accessibility to healthcare. Additionally, the implementation of innovation techniques, such as PEF, in the extraction industry can enhance productivity growth and economic development.

Pulsed Electric Field-Assisted Extraction of Inulin from Ecuadorian Cabuya (Agave americana).

Inulin is a carbohydrate that belongs to fructans; due to its health benefits, it is widely used in the food and pharmaceutical industries. In this research, cabuya (Agave americana) was employed to obtain inulin by pulsed electric field-assisted extraction (PEFAE) and FTIR analysis confirmed its presence. The influence of PEFAE operating parameters, namely, electric field strength (1, 3 and 5 kV/cm), pulse duration (0.1, 0.2 and 0.5 ms), number of pulses (10,000, 20,000 and 40,000) and work cycle (20, 50 and 80%) on the permeabilization index and energy expenditure were tested. Also, once the operating conditions for PEFAE were set, the temperature for conventional extraction (CE) and PEFAE were defined by comparing extraction kinetics. The cabuya meristem slices were exposed to PEFAE to obtain extracts that were quantified, purified and concentrated. The inulin was isolated by fractional precipitation with ethanol to be characterized. The highest permeabilization index and the lowest energy consumption were reached at 5 kV/cm, 0.5 ms, 10,000 pulses and 20%. The same extraction yield and approximately the same amount of inulin were obtained by PEFAE at 60 °C compared to CE at 80 °C. Despite, the lower amount of inulin obtained by PEFAE in comparison to CE, its quality was better because it is mainly constituted of inulin of high average polymerization degree with more than 38 fructose units. In addition, TGA analyses showed that inulin obtained by PEFAE has a lower thermal degradation rate than the obtained by CE and to the standard.

Optimization of Four Different Rosemary Extraction Techniques Using Plackett-Burman Design and Comparison of Their Antioxidant Compounds.

Rosemary has many medicinal and therapeutic properties and therefore it is important to study how to maximize the recovery of its bioactive compounds. In the present study, four different extraction techniques were used, namely stirring extraction (STE), pulsed electric field-assisted extraction (PEF), ultrasound probe-assisted extraction (UPAE), and ultrasound bath-assisted extraction (UBAE). First, some primary experiments were carried out in order to optimize each technique individually through the Plackett-Burman design. Then, each technique was applied under optimal conditions and the results were compared with each other. The optimal total polyphenol content (TPC) of STE is ~19 mg gallic acid equivalents per gram of dry weight (dw), while the antioxidant activity of the extract is 162 μmol ascorbic acid equivalents (AAEs) per gram of dw via FRAP and ~110 μmol AAE per gram of dw via DPPH. As for PEF, the optimal TPC is ~12 mg GAE/g dw, and the FRAP and DPPH values are ~102 and ~70 μmol AAE per gram of dw, respectively. When it comes to UPAE, the optimal TPC is ~16 mg GAE/g dw and the antioxidant capacity of the extract is ~128 μmol AAE/g dw through FRAP and ~98 μmol AAE/g dw through DPPH. UBAE optimal extract yielded ~17 mg GAE/g dw TPC, ~146 μmol AAE/g dw for FRAP, and ~143 μmol AAE/g dw for DPPH. The highest flavonoid content (~6.5 mg rutin equivalent/g dw) and DPPH (~143 μmol ascorbic acid equivalent/g dw) is obtained through UBAE. UPAE has been shown to be more efficient in recovering ascorbic acid (~20 mg/g dw). Additionally, the chlorophyll-to-carotenoid ratios of UPAE and UBAE were 2.98 and 2.96, respectively, indicating that the extracts had a generally positive impact on health. Considering the environmental impact of each extraction technique but also which antioxidant factor needs to be maximized, the most suitable extraction technique will be chosen.

Pulsed electric field-assisted extraction of hesperidin from tangerine peel and its technological optimization through response surface methodology.

Tangerine peel is rich in flavonoids, particularly hesperidin, which has anti-inflammatory, antioxidant and anticancer biological activities. However, it is often wasted during citrus processing. The current common extraction method for hesperidin is solvent extraction, which has the characteristics of low extraction rate and high contamination. The aim of this study was to investigate the effect of pulsed electric field-assisted alkali dissolution extraction, followed by an acidification precipitation method, on the extraction rate and structure of hesperidin from tangerine peel. The results showed that the selected factors (material/liquid ratio, electric field intensity and pulse number) had a significant effect on the extraction yield. An optimum condition of 66.00 mL g-1, 4.00 kV cm-1 and 35.00 pulses gave the maximum amount (669.38 μg mL-1), which was consistent with the theoretically predicted value by software (672.10 μg mL-1), indicating that the extraction process was feasible. In addition, the purified extract was further identified as hesperidin from UV and NMR spectra. An appropriate strength of pulsed electric field-assisted alkali dissolution extraction followed by an acidification precipitation method can effectively improve the extraction rate of orange peel, and the purity of the extracted orange peel is higher. Compared with the traditional extraction, the pulsed electric field-assisted extraction method may be a potential technology for hesperidin extraction, which is beneficial for the high-value utilization of citrus resources. © 2024 Society of Chemical Industry.

Pulsed electric field-assisted extraction of carotenoids from Chlorella zofingiensis

The present work aimed to evaluate the use of PEF as a pretreatment to carotenoid and chlorophyll extraction from two different C. zofingiensis biomasses, green (non-stressed) and orange (stressed). PEF treatment was performed by varying the electric field strength (15, 20, 25 kV/cm) and the treatment time (30, 75, 150 μs). The effect of incubation in a pH 7 buffer for 24 h after PEF and before extraction was also evaluated. The application of an intermediate intensity combined with higher number of pulses (20 kV/cm with 50 pulses) was sufficient to promote the extraction, yielding the highest contents of carotenoids and chlorophylls. The incubation promoted higher extraction yields for treatments performed with shorter treatment times and with mild electric field strengths. Overall, the findings of this study suggest that the application of PEF combined with ethanol could represent a suitable approach for the extraction of carotenoids and chlorophylls from Chlorella zofingiensis biomass.

Essential Components from Plant Source Oils: A Review on Extraction, Detection, Identification, and Quantification.

Oils derived from plant sources, mainly fixed oils from seeds and essential oil from other parts of the plant, are gaining interest as they are the rich source of beneficial compounds that possess potential applications in different industries due to their preventive and therapeutic actions. The essential oils are used in food, medicine, cosmetics, and agriculture industries as they possess antimicrobial, anticarcinogenic, anti-inflammatory and immunomodulatory properties. Plant based oils contain polyphenols, phytochemicals, and bioactive compounds which show high antioxidant activity. The extractions of these oils are a crucial step in terms of the yield and quality attributes of plant oils. This review paper outlines the different modern extraction techniques used for the extraction of different seed oils, including microwave-assisted extraction (MAE), pressurized liquid extraction (PLE), cold-pressed extraction (CPE), ultrasound-assisted extraction (UAE), supercritical-fluid extraction (SFE), enzyme-assisted extraction (EAE), and pulsed electric field-assisted extraction (PEF). For the identification and quantification of essential and bioactive compounds present in seed oils, different modern techniques-such as high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared spectroscopy (FTIR), gas chromatography-infrared spectroscopy (GC-IR), atomic fluorescence spectroscopy (AFS), and electron microscopy (EM)-are highlighted in this review along with the beneficial effects of these essential components in different in vivo and in vitro studies and in different applications. The primary goal of this research article is to pique the attention of researchers towards the different sources, potential uses and applications of oils in different industries.

Valorisation of food processing wastes using PEF and its economic advances – recent update

SummaryFood processing is an emerging industrial sector that applies new technologies to process foods efficiently. During processing, food industries produce a substantial amount of by‐products as waste. Disposal of these wastes remains a problem and causes environmental pollution and greenhouse gas emissions. However, novel food processing technology like pulsed electric field‐assisted extraction (PEFAE) has the potential to utilise these wastes as a source of bioactive compounds and extract valuable compounds in a shorter period with minimal use of solvents and energy. This review covers the basics of pulsed electric field (PEF) and its effect on bioactive compound extraction yield and quality. Furthermore, the article compares the PEF treatment energy and extraction efficiency with other non‐conventional extraction methods to better make the reader understand in terms of selecting the suitable processing method. However, the extraction yield and process efficiency depend highly on the processing parameters. Hence, the article also explains the various kinetic models involved in PEF‐assisted food waste valorisation to control the process parameters during treatment.

Effect of pulsed electric field parameters on the alkaline extraction of valuable compounds from perilla seed meal and optimization by central composite design approach

Perilla seed meal (PSM) is the by-product of the oil extraction industry and a potential source of bioactive compounds. Pulsed electric field, a non-thermal technology, can be used to recover heat labile bioactive compounds from plant materials such as perilla seed meal. This study found that pulsed electric field (PEF) assisted alkaline extraction influenced the protein content and antioxidant activity of perilla seed meal (PSM). Among all PEF parameters, electric field strength (EFS) and pulse width (PW) were found to be the most significant as judged by F-value. Consequently, a central composite rotatable experimental design was applied to investigate the effect of electric field strength (EFS) and pulse width against protein content, antioxidant activity, and total phenolic content (TPC) of PEF treated PSM extract. Compared to conventional alkaline extraction, an increase in the yield of protein content by 10.58%, antioxidant activity by 7.48%, and total phenolic content by 21.59% was recorded at the optimal values of electric field strength (4 kV/cm) and pulse width (120 µs). Moreover, Karl pearson correlational analysis revealed a strong relationship (linear, R2=0.963) between antioxidant activity and total phenolic content. The validation was done at 95% confidence level for which the predicted values were compared with the actual experimental values, and the means were found to be insignificantly different from each other (p > 0.05). Industrial relevanceNon-thermal extraction techniques such as pulsed electric field used in this study can be used for the recovery of valuable compounds from the food materials especially heat sensitive compounds. PEF treatment increased the extractability of the water-soluble compounds from the perilla seed meal (PSM) samples and increased the recovery of valuable compounds from PSM while maintaining the nutritional and functional viability. Hence, this technology is having the potential to be used as assistant technology for the extraction of heat sensitive components from the plant cells which may find its applications in neutraceutical and pharmaceutical industries.

Lycopene extraction from industrial tomato processing waste using emerging technologies, and its application in enriched beverage development

SummaryThe present study aimed to extract lycopene from the industrial tomato processing waste (peel) using emerging technologies such as power ultrasound‐assisted extraction (UAE), low‐temperature microwave‐assisted extraction (MAE), pulsed electric field (PEF)‐assisted extraction (PAE), combined low‐temperature microwave‐power ultrasound‐assisted extraction (MUAE) and combined ultrasound‐pulsed electric field‐assisted extraction (UPAE). A green solvent (ethanol: ethyl acetate, 2:3, v/v) was used for the recovery of lycopene and a mass transfer kinetic approach was used to understand the extraction kinetics of various extraction methods. The highest extraction yield was observed for UPAE treatment with the lycopene yield of 3.56% followed by MUAE with 3.49%. UPAE had the highest antioxidant capacity (87.09% DPPH) compared to other methods. Thus, the green solvent and combination UPAE technology are environmentally sustainable techniques and present a good scope for lycopene recovery. Further, the extracted lycopene was entrapped in oil in water emulsion to develop an enriched lemon juice beverage.

Pulsed electric field‐ultrasonic assisted extraction combined with macroporous resin for the preparation of flavonoids from Pericarpium Citri Reticulatae

Pericarpium Citri Reticulatae (PCR) has long been perceived as a condiment and medicine in East Asian countries especially China. To establish a cost-effective method with the potential for industrial implementation to enhance extraction and purification of PCR flavonoids, four extraction methods (hot water extraction (HWE), ultrasound-assisted extraction (UAE), pulsed electric field-assisted extraction (PEF-AE), pulsed electric field combined with ultrasound-assisted extraction (PEF-UAE)) and five macroporous resins (AB-8, NKA-9, D-101, HPD-100 and HPD-950) were investigated and compared in this study. Results of total flavonoid content (TFC) and monomer flavonoid composition revealed that PEF-UAE was the most efficient extraction process. Response surface methodology (RSM) was employed to determine the optimum conditions of PEF-UAE (ultrasonic power 340 W, ultrasonic time 30 min, electric field strength 3 kV/cm and 81 pulses). Under the optimum conditions, the PCR flavonoids extracted by PEF-UAE yielded the highest contents of total flavonoid, nobiletin and tangeretin in all PCR flavonoids samples. Among the five macroporous resins, AB-8 was used to purify PCR flavonoids due to its higher adsorption and desorption capacities. A maximum purification efficiency was achieved under 6 h of adsorption time and 298 K of temperature, indicated by 2.47-fold, 2.78-fold and 2.43-fold increases in the contents of hesperidin, nobiletin and tangeretin respectively. The purified PEF-UAE flavonoid extract also demonstrated the superior α-glucosidase inhibitory and radical scavenging activities. This study offered a prerequisite for the future utilization of PEF-UAE and AB-8 to produce PCR flavonoids for food and medicine applications.

Efficient and green strategy based on pulsed electric field coupled with deep eutectic solvents for recovering flavonoids and preparing flavonoid aglycones from noni-processing wastes

The recovery of flavonoids and preparation of flavone aglycones from pomace waste are accompanied by the use of acidic organic solvents and high energy consumption, which lead to environmental pollution. This study aimed to develop an efficient and eco-friendly method based on pulsed electric field-assisted extraction (PEF-AE) combined with deep eutectic solvents (DESs) to recover flavonoids from noni pomace. The feasibility of using pulsed electric fields (PEF) combined with DESs as an alternative to conventional enzymatic, acidic, and pyrolytic methods, for the conversion of flavone glycosides to flavone aglycones was also evaluated. The results showed that, by using PEF-AE combined with DESs, the recovery efficiencies of the two main flavonoids (rutin and quercetin) in noni pomace were significantly superior to those of conventional organic extraction. Choline chloride/ethylene glycol (Ch/Eth) and choline chloride/oxalic acid (Ch/Oxa) were found to be optimal extractants for the recovery of rutin and quercetin. After response surface methodology optimisation, the highest extraction amounts of rutin and quercetin were 16.21 mg/g and 19.85 mg/g, respectively. During the extraction process, it was found that almost 100% of degraded rutin can be converted to quercetin in Ch/Oxa. Under identical treatment time and temperature, the rutin conversion efficiency of PEF was 25.4–206.4 folds higher than that of hot-water treatment (HWT). An excellent rutin conversion efficiency (8.72%/min) for PEF was achieved by adjusting the key reaction conditions. Overall, PEF-AE combined with DESs is an efficient, selective, and sustainable method for recovering flavonoids from noni pomace waste. This study also demonstrated that PEF coupled with DESs is a promising method for the efficient and eco-friendly preparation of flavone aglycones.

Alternative Methods of Bioactive Compounds and Oils Extraction from Berry Fruit By-Products—A Review

Berry fruit by-products are a source of polyphenol compounds and highly nutritious oils and can be reused to fulfill the requirements of the circular economy model. One of the methods of obtaining polyphenol-rich extracts or oils is extraction. Applying conventional solvent extraction techniques may be insufficient to reach high polyphenol or lipid fraction yields and selectivity of specific compounds. Alternative extraction methods, mainly ultrasound-assisted extraction, pulsed electric field-assisted extraction, microwave-assisted extraction and supercritical fluid extraction, are ways to improve the efficiency of the isolation of bioactive compounds or oils from berry fruit by-products. Additionally, non-conventional techniques are considered as green extraction methods, as they consume less energy, solvent volume and time. The aim of this review is to summarize the studies on alternative extraction methods and their relationship to the composition of extracts or oils obtained from berry waste products.

Pulsed electric field-assisted extraction of phenolic antioxidants from tropical almond red leaves

The main objective of this study is to compare the extraction efficiency, phenolic composition and antioxidant activity of fallen red leaves of the tropical almond (Terminalia catappa) using two extraction methods. The leaf was extracted under different conditions: soaking (12 and 24 h) and pulse electric fields (0.5 and 0.75 kV/cm). The results demonstrated that the highest total phenolic content (TPC) and higher antioxidant activity were related to the 50% concentration of red leaf extract. The evaluation of the two extraction methods revealed that the extract of red leaf obtained via PEF with 0.75 kV/cm field strength had the highest TPC and antioxidant activity (DPPH). Finally, red leaf phenolic compounds were identified and reported by HPLC.

Physicochemical properties, antioxidant and antiproliferative activities of polysaccharides from Morinda citrifolia L. (Noni) based on different extraction methods

The influences of different extraction methods on the yields, physicochemical properties, antioxidant activities and antiproliferative abilities of polysaccharides from Morinda citrifolia L. (Noni) were investigated and compared. Three extraction methods were applied to extract Noni polysaccharides (NP), which include hot water extraction (HWE), pulsed electric field-assisted extraction (PEFAE) and ultrasonic-assisted extraction (UAE). The extraction yields, sugar contents, uronic acid contents, molecular weights, monosaccharide proportions, antioxidant activities and antiproliferative abilities of three NP samples were significantly different. However, their preliminary structural characteristics and monosaccharide types were similar. More specifically, UAE-NP had the highest extraction yield, the smallest molecular weight and the best antioxidant activities. Especially, UAE-NP showed excellent antiproliferative abilities. Compared with HWE-NP and PEFAE-NP, the IC50 value of UAE-NP on HepG2 cells reduced by 45.45% and 33.14%, respectively. The highest antioxidant activities of the UAE-NP might be attributed to its smaller molecular weight, lower Gal content and higher Fuc content. The strongest antiproliferative effects of the UAE-NP might be related to the low molecular weight. Overall, UAE could be a potential technique for the extraction of high-quality NP due to its high yield, high efficiency and notable bioactivities.

Optimization of high-intensity pulsed electric field-assisted extraction of procyanidins from Vitis amurensis seeds using response surface methodology

Procyanidins (PC) from Vitis amurensis seeds was extracted using high-intensity pulsed electric field (PEF). The process parameters including pulse number, electric field strength, ratio of material to liquid and ethanol concentration were studied using response surface methodology, and extraction yield of the extracts were determined. Antioxidant activity of the extracts by PEF, ultrasonic-assisted extraction (UAE), microwave-assisted extraction (MAE) and ethanol extraction (EAE) were compared based on total antioxidant capacity, DPPH radical scavenging capacity and ferrous ion chelating activity. The results revealed that the optimization of conditions of PEF are: pulse number 10; electric field strength 25 kV/cm; ratio of material to liquid 1:21 g/mL; ethanol concentration 63% (v/v), and the PC yields reached 8.23% under this condition. The PEF resulted in a highest extraction yield of PC among the four extraction methods. There was no significant difference in total antioxidant capacity of PC obtained by four methods, the DPPH radical scavenging capacity and ferrous ion chelating activity of PC extracted by PEF were close to that of UAE and MAE, which were superior to EAE. These showed that PEF was an effective method for extracting PC.

Optimization of the pulsed electric field -assisted extraction of functional compounds from cinnamon

Abstract Effective components from cinnamon were extracted by pulsed electric field-assisted extraction (PEF) technology. A response surface method was used to investigate the effects of independent process variables (voltage of pulsed electric field: 2, 4 and 6 kV/cm and number of pulsed electric field: 20, 40 and 60 n) on the yield (Y) and antioxidant characteristics: total phenolic compounds (TPC), 1,1- diphenyl -2- picrylhydrazyl free radical scavenging (DPPHsc) and half maximal of radical-scavenging activity (EC50) of cinnamon extract. Experimental results were fitted to a second-order polynomial model where multiple regression analysis and analysis of variance were used to determine fitness of the model and optimal conditions for investigated responses. The optimal conditions based on both individual and combinations of all process variables (voltages and the pulse numbers) were determined by Derringer's desired function methodology. At this optimum condition, the quality and quantity characteristics of Y, TPC, DPPHSC, and EC50 of the cinnamon extract were found to be (5.06%), (505.9 mg k/g), (91.7%) and (0.51 mg/mL), respectively which were well matched with the predicted values.

Pulsed electric field-assisted extraction of carotenoids from fresh biomass of Rhodotorula glutinis

Abstract The aim of this study was to demonstrate the potential of PEF for inducing autolysis of R. glutinis, with the purpose of designing a more efficient and ecofriendly carotenoid extraction process: an extraction from fresh biomass, using cheaper, non-toxic, environmental-friendly solvents. Propidium iodide uptake and release of intracellular components revealed the irreversible electroporation of R. glutinis by PEF. Flow cytometry measurements detected morphological changes in PEF-treated R. glutinis cells during incubation caused by the autolysis triggering effect of electroporation. After submitting the fresh biomass to a PEF treatment (15 kV/cm, 150 μs) that irreversibly electroporated more than the 90% of the cells, ethanol proved ineffective for extracting carotenoids from fresh biomass of R. glutinis. However, after incubating the PEF-treated fresh biomass for 24 h at 20 °C in a pH 7 buffer, ca. 240 μg/g d.w. of carotenoids were recovered after 1 h of extraction in ethanol. The highest amount of carotenoids extracted (375 μg/g d.w.) from the PEF-treated cells of R. glutinis was obtained after having incubated them at 25 °C for 24 h in a medium of pH 8.0. The improvement in carotenoid extraction by incubating the R. glutinis cells after PEF treatment seems to be caused by PEF-triggered autolysis, which tends to disrupt the association of carotenoids with other molecules present in the cytoplasm, and causes a degradation of the cell wall.

Recent Advances on Application of Ultrasound and Pulsed Electric Field Technologies in the Extraction of Bioactives from Agro-Industrial By-products

Agro-industrial by-products are rich sources of natural bioactive compounds and their valorisation is a must for global food sustainability. Along with conventional techniques, numerous novel methods have been developed and optimised to facilitate extraction of the bioactives in sustainable and efficient manner. This review summarises the recent advances in the application of novel extraction technologies for various classes of bioactive molecules from agro-industrial by-products with special emphasis on two emerging techniques, i.e. ultrasound- and pulsed electric field-assisted extraction. These two technologies have shown promising extraction efficacy with reduced usage of extraction solvents, thus saving time and cost. The mechanism through which these techniques aid extraction, the various parameters affecting their efficacy, integration with other novel techniques, and promising applications for by-product valorisation are discussed.

Alternative and efficient extraction methods for marine-derived compounds.

Marine ecosystems cover more than 70% of the globe’s surface. These habitats are occupied by a great diversity of marine organisms that produce highly structural diverse metabolites as a defense mechanism. In the last decades, these metabolites have been extracted and isolated in order to test them in different bioassays and assess their potential to fight human diseases. Since traditional extraction techniques are both solvent- and time-consuming, this review emphasizes alternative extraction techniques, such as supercritical fluid extraction, pressurized solvent extraction, microwave-assisted extraction, ultrasound-assisted extraction, pulsed electric field-assisted extraction, enzyme-assisted extraction, and extraction with switchable solvents and ionic liquids, applied in the search for marine compounds. Only studies published in the 21st century are considered.

Extraction and conversion pathways for microalgae to biodiesel: a review focused on energy consumption

Numerous life cycle analysis (LCA) studies of microalgae to fuel have been released over the past 3 years in an attempt to determine the environmental sustainability of this novel concept. Despite numerous issues with these LCA studies, they have highlighted that cultivation and dewatering/drying for extraction and conversion are major energy sinks within the process. This paper provides a critical review of extraction and conversion methods discussed in literature and under commercial investigation. The basis of this review is energy consumption, with its purpose to highlight methods that deserve further attention in research and development. This review concludes with an energetic assessment of four conversion processes including pulsed electric field-assisted extraction followed by transesterification, in situ acid catalysed esterification of dry biomass, in situ hydrolysis and esterification of wet biomass and hydrothermal liquefaction. The analysis highlighted that energetically feasible methods do exist for the conversion of microalgal biomass to fuel; however, all require further research to be applied at commercial scale.