Microalgal Cell Disruption Research Articles

Optimisation of ultrasonication pretreatment on microalgae Chlorella Vulgaris &Nannochloropsis Oculata for lipid extraction in biodiesel production

A wide variety of nutritious products and biofuels can be produced from microalgae. Their applications span across various sectors such as food, medical, and energy industries. Microalgal cell disruption is a crucial aspect in the production processes as it facilitates the extraction of bio-products stored within them. One of the commonly extracted compounds from microalgae is lipids, which constitute a high percentage of their composition. In this study, we conducted ultrasonic pre-treatment on two different microalgae species, namely Chlorella vulgaris and Nannochloropsis oculata. The pre-treatment involved ultrasonic frequencies of 37 and 80 kHz, exposure times of 10, 15, and 20 min, and extraction times of 2, 3, and 4 h. By utilising ultrasonic frequencies, we induced acoustic cavitation to break the microalgae cell walls and extract lipids. The experimental design followed a Response Surface Methodology (RSM) to evaluate the effect of ultrasonication pretreatment parameters on lipid extraction. In comparison to previously published studies, our findings indicate that higher frequencies of ultrasonication lead to increased lipid extraction from microalgae. The highest lipid yield achieved in our study was 11.54% for Chlorella vulgaris and 17.91% for Nannochloropsis oculata, using the input factors of 80 kHz frequency, 20 min of running time, and 4 h of extraction time. Our results contribute to the existing body of knowledge by demonstrating the efficacy of ultrasonic pre-treatment in lipid extraction from microalgae. By providing a quantitative comparison with previous studies, this study highlight the novel aspects of work and its potential implications for the production of biofuels and other valuable products from microalgae.

Enhanced VFAs production from microalgal hydrolytic acidification with ultrasonic-alkali pretreatment

Cell disruption to break the rigid algal cell wall was essential to improve the utilization of resources enriched in microalgae. This study aimed to compare the effects of alkali, ultrasound, and the synergistic effect of ultrasonic and alkali on microalgae disruption and preliminarily investigated the synergistic disruption mechanism. The effect of the above methods on the disruption of microalgal cells was quantified by measuring protein and TOC release. Under the optimized conditions of the UA method (initial pH: 12.0, sound intensity: 6 W/mL, 40 min), the protein release was 360.42 mg/g TS, which were 5.6 and 7.1 times higher than those of alkali and ultrasound, respectively. EEMs spectroscopy showed that org-N compounds were mainly released during UA treatment of Chlorella pyrenoidosa (C. pyrenoidosa), with soluble microbial by-product-like compounds predominating. With free radical detection and particle size analysis, it was found that nutrient release occurred mainly during the microalgal bloom dispersion and individual microalgal micro-fragmented phases. The practical applicability of the synergistic strategy was also investigated. Microalgal hydrolytic acidification after UA pretreatment was suitable for VFAs production. Compared to the blank group, the peak VFAs production (392.5 mg COD/g VSS) increased by 200 % and the time reduced from 11 days to 9 days. These results indicated that synergistic disruption pretreatment was expected to improve the performance of microalgal biomass hydrolytic acidification.

A novel approach for microalgal cell disruption and bioproducts extraction using non-thermal atmospheric plasma (NTAP) technology and chitosan flocculation

Microalgal cell disruption and bio-product extraction still remain as major challenging steps for biomass downstream processing. In this study, a sustainable approach of using non-thermal atmospheric plasma (NTAP) and chitosan flocculation was developed for microalgal cell disruption and bio-product recovery from wet C. Sorokiniana. For this purpose, the performance of NTAP treatment for cell disruption and extraction of protein, carbohydrate and lipid was investigated by using different applied voltages (8–16 kV). Then, the application of chitosan on recovery of bioproducts from the culture medium was evaluated. Fourier transform infrared (FTIR) analysis, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) images were used to analyze the flocculation mechanism and for flocs characterization. Additionally, the energy consumption and efficiency of the NTAP process were analyzed. According to the NTAP results, the highest cell disruption of 75% was achieved under the applied voltage of 16 kV. However, in the case of bioproducts extraction, the optimal applied voltage was 12 kV which was able to yield 41, 24 and 36 (%CDW) of protein, carbohydrate and lipid, respectively. Adding 100 mg/L chitosan efficiently recovered the released protein (65%) and carbohydrate (85%) from culture medium, while the highest lipid recovery (60%) was achieved at 150 mg/L chitosan addition. This study proved that the utilization of NTAP and chitosan treatment can be considered as a promising approach for valuable products extraction from microalgae.

A rapid, efficient and eco-friendly approach for simultaneous biomass harvesting and bioproducts extraction from microalgae: Dual flocculation between cationic surfactants and bio-polymer

Microalgal biomass harvesting and cell disruption are the main bottlenecks for downstream processing of microalgae such as high-value bioproducts extraction and biofuels production. In this study, we evaluated the performance of dual flocculation between cationic surfactants and bio-polymer of chitosan for simultaneous biomass harvesting and bioproducts extraction from Chlorella sorokiniana microalgae. First, the effects of individual natural flocculants of chitosan and two cationic surfactants: cetyltrimethylammonium bromide (CTAB) and dodecyltrimethylammonium bromide (DTAB) on biomass harvesting were studied. Next, the synergistic effect of dual flocculation between the cationic surfactants and chitosan on harvesting efficiency, time and flocculant dosage was investigated. Finally, we evaluated the potential of high value bioproducts extraction from microalgae after the individual and dual flocculation processes. Zeta potential analysis and microscopic images were employed to achieve mechanistic understanding. Maximum biomass harvesting efficiencies of 85 %, 88 % and 78 % were achieved using individual flocculants of chitosan, CTAB and DTAB, under their optimum dosages of 100, 400 and 4000 mg/L, respectively. A significant synergistic effect of dual flocculation between chitosan (C) and cationic surfactants on biomass harvesting efficiency (CTAB-C: 99 % and DTAB-C: 97 %), settling time (CTAB-C: 2 min and DTAB-C: 5 min) and optimum dosage of surfactants (CTAB-C: 100 mg/L and DTAB-C: 1000 mg/L) was observed. The synergistic effect was associated with multiple flocculation mechanisms of charge neutralization and bridging induced by cationic surfactants and chitosan, respectively. Furthermore, bioproducts recovery efficiencies of 12 %, 25 % and 15 % of cell dry weight were achieved for protein, carbohydrate and lipid, respectively by using dual flocculation of CTAB surfactant and chitosan at much lower dosage of 100 mg/L.

Recovering Microalgal Bioresources: A Review of Cell Disruption Methods and Extraction Technologies.

Microalgae have evolved into a promising sustainable source of a wide range of compounds, including protein, carbohydrates, biomass, vitamins, animal feed, and cosmetic products. The process of extraction of intracellular composites in the microalgae industry is largely determined by the microalgal species, cultivation methods, cell wall disruption techniques, and extraction strategies. Various techniques have been applied to disrupt the cell wall and recover the intracellular molecules from microalgae, including non-mechanical, mechanical, and combined methods. A comprehensive understanding of the cell disruption processes in each method is essential to improve the efficiency of current technologies and further development of new methods in this field. In this review, an overview of microalgal cell disruption techniques and an analysis of their performance and challenges are provided. A number of studies on cell disruption and microalgae extraction are examined in order to highlight the key challenges facing the field of microalgae and their future prospects. In addition, the amount of product recovery for each species of microalgae and the important parameters for each technique are discussed. Finally, pulsed electric field (PEF)-assisted treatments, which are becoming an attractive option due to their simplicity and effectiveness in extracting microalgae compounds, are discussed in detail.

Synergistic effect of ultrasound and switchable hydrophilicity solvent promotes microalgal cell disruption and lipid extraction for biodiesel production

To facilitate the lipid extraction from Nannochloropsis oceanica with thick cell wall using switchable hydrophilicity solvent, ultrasound-assisted N, N, N', N'-tetraethyl-1,3-propanediamine (TEPDA) was used to effectively destruct the cell wall. TEPDA cations were adsorbed on the cells via electrostatic force and formed the electron-donor–acceptor (EDA) complex with the hydroxyl groups in cellulose. This broke the hydrogen-bonding interactions between cellulose chains and stripped them from cell wall, thus reducing the cell wall thickness from 141 nm to 68.6 nm. Moreover, TEPDA cations neutralized the negatively charged phospholipid bilayers, decreasing the cell surface zeta potential from −27.5 eV to −14.1 eV. The local electrostatic equilibrium led to cell membrane leakage. The ultrasound promoted the stripping of the cellulose chains at a power intensity of 0.5 W/mL and frequency of 20 kHz, achieving the lipid extraction efficiency of 98.2% within 2 h at a volume ratio of 1:4 of wet microalgae to TEPDA.

Extraction of microalgal starch and pigments by using different cell disruption methods and aqueous two‐phase system

AbstractBACKGROUNDMicroalgae can synthesize starch with productivity higher than conventional terrestrial crops, without the need for arable land. However, little is known about processes to extract starch from microalgae. Here, a biorefinery process is described including microalgal cell disruption followed by extraction of starch and pigments with aqueous two‐phase system (ATPS) using choline chloride and polypropylene glycol 400. Sonication and bead milling were compared for cell disruption rate and starch extraction efficiency.RESULTSA first order kinetic model described well the cell disruption for both the methods, with a rate 2.6 times higher for bead milling than sonication. By applying ATPS on samples with comparable cell disruption (>93%), starch was separated better after sonication (67% recovery in the pellet) than after bead milling, for which it remained equally distributed between pellet (40%) and choline chloride phase. Pigments were extracted with 42–66% yield irrespective of the cell disruption method. Microalgal starch granules had a normal and narrow distribution for size (0.93 ± 0.14 μm) and a gelatinization temperature between 45–55 °C.CONCLUSIONFor the same cell disruption yield, different starch separation efficiencies can be achieved, depending on the cell disruption method applied. Although bead milling was faster than sonication in disrupting cells, it gave worst starch separation efficiency. The properties of the extracted microalgal starch indicate potential technical advantages, with respect to conventional starch sources, for applications in the bioplastic and food sector. © 2021 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Genetic Impairment of Cellulose Biosynthesis Increases Cell Wall Fragility and Improves Lipid Extractability from Oleaginous Alga Nannochloropsis salina.

In microalgae, photosynthesis provides energy and sugar phosphates for the biosynthesis of storage and structural carbohydrates, lipids, and nitrogenous proteins. The oleaginous alga Nannochloropsis salina does not preferentially partition photoassimilates among cellulose, chrysolaminarin, and lipids in response to nitrogenous nutrient deprivation. In the present study, we investigated whether genetic impairment of the cellulose synthase gene (CesA) expression would lead to protein accumulation without the accumulation of storage C polymers in N. salina. Three cesA mutants were generated by the CRISPR/Cas9 approach. Cell wall thickness and cellulose content were reduced in the cesA1 mutant, but not in cesA2 or cesA4 cells. CesA1 mutation resulted in a reduction of chrysolaminarin and neutral lipid contents, by 66.3% and 37.1%, respectively, but increased the soluble protein content by 1.8-fold. Further, N. salina cells with a thinned cell wall were susceptible to mechanical stress, resulting in a 1.7-fold enhancement of lipid extractability. Taken together, the previous and current studies strongly suggest the presence of a controlling mechanism that regulates photoassimilate partitioning toward C and N metabolic pathways as well as the cellulose metabolism as a potential target for cost-effective microalgal cell disruption and as a useful protein production platform.

Cell disruption of Nannochloropsis sp. improves in vitro bioaccessibility of carotenoids and ω3-LC-PUFA

The incorporation of microalgae into processed food products is considered a sustainable strategy to enrich food products in omega-3 long chain polyunsaturated fatty acids (ω3-LC-PUFA). However, the microstructural properties of the microalgae might influence the nutrient digestibility and bioaccessibility during consumption. The current study proved the importance of cell disruption of Nannochloropsis sp. for the in vitro lipid digestibility and bioaccessibility of ω3-LC-PUFA and carotenoids. While an incomplete lipid digestion and low bioaccessibility values (1–6% for carotenoids and 13% for ω3-LC-PUFA) were observed for untreated biomass, cell disruption by high pressure homogenization resulted in a complete lipid digestibility and a threefold increase in bioaccessibility. It was shown that the Nannochloropsis sp. cell wall and/or cell membrane act as a natural barrier for (lipophilic) nutrients during in vitro digestion. Hence, microalgal cell disruption is a crucial step in the design of healthy food products enriched with microalgae.

Microalgal cell disruption: Effect on the bioactivity and rheology of wheat bread

The aim of this study is to investigate the potential of the addition of a microalgal biomass to improve nutritional quality of bread. Microalgae contain a substantial amount of nutrients that are naturally encapsulated within cells, namely proteins, polysaccharides, polyunsaturated fatty acids and pigments (chlorophylls and carotenoids), which are capable of resisting harsh conditions during food processing. However, the cell wall integrity may significantly limit nutrient availability, and microalgal cell disruption is potentially required as a pretreatment.A suspension of a fresh Chlorella vulgaris biomass (0.88 g/L) was disrupted in a high-pressure homogenizer at 340 MPa using 1 and 4 passages. The impact of the cell disruption method was evaluated in terms of the reduction in the number of intact cells and average colony diameter of the remaining cells using flow cytometry and microscopy.Since cell disruption promotes the release of intracellular products, it can impart structural modifications to doughs and breads. Therefore, doughs and breads were prepared with the fresh C. vulgaris biomass (1.0 g of Cv/100 g of flour+Cv), the disrupted biomass, or a commercial powder. Doughs were characterized in terms of texture and oscillatory rheology. The texture and colour of breads were also evaluated. Cell wall disruption affected the colour and texture of the breads, resulting in breads with a higher firmness. Furthermore, bioactivity was evaluated, and the reducing power of the bread extracts obtained using the ferric ion reducing antioxidant power assay showed that cell disruption positively modulated the antioxidant capacity.

Disruption of thin- and thick-wall microalgae using high pressure gases: Effects of gas species, pressure and treatment duration on the extraction of proteins and carotenoids

Industrial scale microalgal cell disruption requires low cost, high efficiency and structural conservation of biomolecules for biorefinery. Many cultivated microalgae have thick walls and these walls are barriers for efficient cell disruption. Until recently, despite the high biodiversity of microalgae, little attention has been paid to thin-wall microalgal species in the natural environment for the production and recovery of valuable biomolecules. Instead of developing high power cell disruption devices, utilization of thin-wall species would be a better approach. The present paper describes a simple device that was assembled to evaluate the viability and effectiveness of biomolecule extraction from both thin- and thick-wall species as a proof of concept. This device was tested with high-pressure gases including N2, CO2 plus N2, and air as the disruption force. The highest nitrogen pressure, 110bar, was not able to disrupt the thick-wall microalgal cells. On the other hand, the thin-wall species was disrupted to different degrees using different pressures and treatment durations. In the same treatment duration, higher nitrogen pressure gave better cell disruption efficiency than the lower pressure. However, in the same pressure, longer treatment duration did not give better efficiency than the shorter duration. High pressure CO2 treatments resulted in low soluble protein levels in the media. The best conditions to disrupt the thin-wall microalgal cells were 110bar N2 or air for 1min among these tests. In these conditions, not only were the disruption efficiencies high, but also the biomolecules were well preserved.

Efficient nanowire-assisted electroporation and cellular inclusion release of microalgal cells achieved by a low voltage

A mild and low-energy cell disruption method with high efficiency has growing application potential in both the extraction of high-value microalgal products and the inactivation of microalgal cells. Conventional technologies available have disadvantages including high energy consumption, the use of chemicals and so on. Here, this study developed an efficient microalgal cell disruption method using the copper oxide nanowire (CuONW)-modified three-dimensional (3D) copper foam electrodes with a low applied voltage. Electrodes with nanowires synthesized at 400 °C, the optimal preparation temperature, achieved efficient microalgal cell electroporation. Microalgal cells were completely inactivated and disrupted at the voltage of 2 V with the hydraulic retention time (HRT) of 10 s. Scanning electron microscopy (SEM) images showed obvious electroporation damage on the cell surface upon electroporation-treatment (2 V, 30 s). The amount of released cellular inclusion increased significantly with prolonged HRT and the energy consumption of this technology was only 0.014 kWh/kg via the treatment of 2 V and 10 s. This study provided a novel, energy-efficient and chemical-free technique for both microalgal products extraction and cell inactivation.

Combined effect of ozone and ultrasound on disruption of microalgal cells

ABSTRACTAmong several disruption methods tested so far, ozonation and sonication were distinguished from others by their effective cell rupturing ability. In this study, these disruption methods were combined to enhance the retrieval of biofuel feedstock (carbohydrates and lipids) from microalgae. A mixed microalgal culture was subjected to first ozonation, followed by sonication. Compared to the extraction of 22% of total lipids and 47% of total carbohydrates by sole ozonation, the retrieval of algal metabolites reached 59% and 81% of total lipids and carbohydrates, respectively. The optimum process variables were found by means of a response surface modeling and quadratic programming.

Optimization of Cell Disruption and Transesterification of Lipids from Botryococcus braunii LB572

Several methods including microwave, Frenchpress, autoclave, bead-beating, ultrasonication, and osmotic shock were compared to identify the most effective microalgal cell disruption method. Botryococcus braunii LB572 was cultured in 5 L flasks containing JM medium mixed with oceanic sediment extract for 13 days. Among the methods tested, enhanced lipid extraction was achieved through microwave treatment (2450MHz, 1250W at 150°C for 20 min). Oleic (C18:1), linolenic (C18:3), and palmitic acids (C16:0) were found to be the major fatty acids among the C14-C24 acids from extracted lipid. In addition, the optimal conditions of transesterification were as follows: 70 mL of methanol, 6 mL of sulfuric acid, 8 mL of chloroform, and boiling at 100°C for 30 min; 85.4% of C14-C24 FAME and 78.5% of C16-C18 FAME were esterified from transesterifiable lipids.

Microwave‐Assisted Extraction of Lipids from Wet Microalgae Paste: A Quick and Efficient Method

This article proposes an easy, quick, and efficient microwave method for the routine laboratory extraction of lipids from wet microalgae paste. A microwave synthesis instrument is used, and time and temperature are optimized using a central composite design. A chloroform/methanol mixture (2:1 v/v) is used as extractor solvent and the ideal condition is 1 min of microwave irradiation at 80 °C using power mode at 300 W. The scanning electron microscopy (SEM) analysis shows extensive cell damage leading to cracking, fragmentation, and large debris in a shorter treatment time. In addition, the fatty acids profile shows that microwave irradiation method has no degrading effect on the extracted fatty acids. The extraction by microwave achieves a significantly higher yield (33.6 ± 2.6%) with only 1 min of extraction time than conventional ultrasonic extraction (20 min, 25 °C, 28.51 ± 0.8% yield) from wet Nannochloropsis oculata biomass. Next, the efficiency of the extraction method in is evaluated in terms of species variation by applying it to the algal paste of Amphora coffeaeformis, Chaetoceros gracilis, and Isochrysis galbana. The lipid content obtained from A. coffeaeformis, C. gracilis, and I. galbana is 16.27 ± 1.5, 22.31 ± 2.5, and 19.87 ± 2.4%, respectively. Thus, the microwave method is successfully applied to algal paste.Practical Applications: The microalgal cell wall disruption is an important and complex stage and effective methods of disruption are fundamental to extracting lipids. This study shows an easy, quick, and efficient microwave method for application in routine laboratory extraction of lipids from wet microalgae pastes. A microwave compact instrument is used and the ideal condition is 1 min of microwave irradiation. The method proves to be robust against variation in mass achieved and significantly higher yield in a shorter time than ultrasonic extraction (conventional method).The microalgal cell disruption is an important and complex stage. The use of microwaves to induce cell disruption in wet biomass proves to be efficient for lipid extraction with only 1 min of extraction time. The method is applied successfully to wet microalgae pastes with different cell walls and the microwave radiation does not degrade the extracted fatty acids.

Microalgal cell disruption via extrusion for the production of intracellular valuables

Abstract The objective of this study was to evaluate the effectiveness of extrusion on cell disruption of a marine alga Nannochloropsis oceanica with a single-screw extruder for the production of intracellular valuables. The effect of operating parameters including feed moisture (15–24%) and screw rotation speed (300–450 rpm) was also determined. Experimental results demonstrated that extrusion was effective in algal cell disruption indicated by direct observation of cell break-up through scanning electron microscope (SEM) and significant increases up to 94.3% and 68.7% in lipid and sugars yield, respectively between treatments and the control (no treatment). It was found that feed moisture (15%) generally improved cell disruption efficiency due to longer residence time of biomass in the extruder. Increasing screw rotation speed from 300 to 450 rpm tended to enhance cell disruption because of stronger shear forces on algae. However, the effectiveness was restricted by residence time of biomass in the extruder because a faster screw rotation speed resulted in a higher biomass flow rate. Thus, the optimal cell disruption was not always achieved at the fastest screw rotation speed; instead, it appeared at the levels depending on specific evaluation indicators (around 350 rpm), therefore the optimal conditions for algal cell disruption were obtained at about 15% of feed moisture and 350 rpm of screw rotation speed. This study also confirmed that extrusion was beneficial for the production of more valuables including polyunsaturated fatty acids (PUFA) and essential amino acids (EAA) from microalgae, for example up to 74.3% increase of PUFA and 20.5% increase of EAA after extrusion compared to the control.

Transcriptional Regulation of Cellulose Biosynthesis during the Early Phase of Nitrogen Deprivation in Nannochloropsis salina

Microalgal photosynthesis provides energy and carbon-containing precursors for the biosynthesis of storage carbohydrates such as starch, chrysolaminarin, lipids, and cell wall components. Under mild nitrogen deficiency (N−), some Nannochloropsis species accumulate lipid by augmenting cytosolic fatty acid biosynthesis with a temporary increase in laminarin. Accordingly, biosynthesis of the cellulose-rich cell wall should change in response to N− stress because this biosynthetic pathway begins with utilisation of the hexose phosphate pool supplied from photosynthesis. However, few studies have characterised microalgal cell wall metabolism, including oleaginous Nannochloropsis sp. microalgae subjected to nitrogen deficiency. Here, we investigated N-induced changes in cellulose biosynthesis in N. salina. We observed that N− induced cell wall thickening, concurrently increased the transcript levels of genes coding for UDPG pyrophosphorylase and cellulose synthases, and increased cellulose content. Nannochloropsis salina cells with thickened cell wall were more susceptible to mechanical stress such as bead-beating and sonication, implicating cellulose metabolism as a potential target for cost-effective microalgal cell disruption.

Using ozone for microalgal cell disruption to improve enzymatic saccharification of cellular carbohydrates

In this study, ozone was used as a pretreatment method to improve the yield in enzymatic saccharification of microalgal carbohydrates by increasing the disruption of microalgal cells. Different ozone doses (0.25–2.0 g O3 g−1 dry weight biomass (DWB)) were applied to the algal suspensions before the enzymatic hydrolysis process, which was performed at various enzyme concentrations, enzymatic hydrolysis times and biomass concentrations. The highest glucose yield obtained was 80.6% (w/w) of total carbohydrates under the conditions of 2.5 g L−1 biomass concentration and 4 h hydrolysis time for 0.5 g O3 g−1 DWB ozone dose and 1.2 mL−1 g−1 DWB enzyme concentration. In addition to ozone pretreatment, the same algal culture was subjected to acid, alkaline and ultrasonic pretreatments. It was observed that application of ozone increased the glucose yield much higher than the other three pretreatment methods, indicating its great potential in production of bioethanol from microalgae.

Protic ionic liquid-assisted cell disruption and lipid extraction from fresh water Chlorella and Chlorococcum microalgae

Protic ionic liquids (PILs) with their ability to host labile protons and form hydrogen bonds are likely to be efficient catalyst for bioprocessing. This is one of the first reports investigating PIL-assisted microalgal cell disruption and lipid extraction. The applicability of several PILs with butyrolactam, caprolactam, propylammonium and hydroxypropylammonium cations in combination with formate, acetate and hexanoate anions for cell disruption and lipid extraction from fresh water Chlorella and Chlorococcum sp. have been evaluated in this study. The investigations were performed with de-watered wet microalgae under ambient temperatures and hence do not require any energy intensive drying and/or processing steps. The PILs with formate and hexanoate anions when compared with conventional pre-treatment techniques: sonication, microwave and cellulase provided better microalgal cell disruption efficiencies. The FESEM analysis for the Butyrolactam hexanoate (BTH) treated cells show extensive pattern of microalgal cell disruption. The fluorescence imaging analysis coupled with culturing experiments indicates a near-complete disruption and loss in viability of the PIL-treated microalgal cells. The lipid yield from the formate and hexanoate anions-PILs was statistically comparable and/or higher to the Bligh & dyer control method. Among the PILs, BTH recorded 1.86 and 1.72 folds higher lipid yields than the control method with Chlorella and Chlorococcum sp. respectively. The lipids show predominance of C16 and C18 fatty acids similar to lipid profile obtained with the control method. Furthermore, the PILs were also found to have a beneficial role in reducing the chlorophyll pigments in the final lipid product. Overall, the results show PILs with formate and hexanoate anions can be utilized for a relatively energy efficient, one-step cell disruption and lipid extraction process from wet microalgae.

Evaluation on H2O2‐aided ultrasonic pretreatment for cell disruption of Chlorella pyrenoidosa

AbstractIn this work, Chlorella pyrenoidosa was chosen as model microalgae, and several pretreatments, including hydroxyl‐peroxide‐aided ultrasonic pretreatments and mono‐ultrasonication (US), were used to rupture the microalgal cells for extracting cellular inclusion. The disruption efficiency and the energy consumption of each technique were estimated through measuring the amount of released protein from cells and the microscopic images after pretreatment. Results showed that the combined pretreatments obtained a much higher lysis efficiency than did the US (over twofold). However, the concentration of H2O2 used (ranging from 0.1 to 5 mM) failed to influence the lysis efficiency significantly (P < 0.05). Additionally, the acoustic energy efficiency was increased with the initial cell concentration treated, but the coefficient of utilization of algal biomass was decreased significantly. Therefore, an ideal initial cell concentration (13.4 × 107 cells/mL) was gained in terms of the higher coefficient of utilization of algal biomass. This research suggested that a synergistic technique could be an effective pretreatment for microalgal cell disruption and downstream comprehensive utilization. © 2017 Curtin University of Technology and John Wiley & Sons, Ltd.