Microalgal Biorefinery for Bulk and High-Value Products: Product Extraction Within Cell Disintegration

Pulsed electric field (PEF) is considered to be a very promising technology for mild cell disruption. The application of PEF for microalgae that have a rigid cell wall, however, is hampered by the presence of that rigid outer cell wall. A cell wall free mutant of C. reinhardtii was used to mimic pretreated microalgae with removed cell wall, to investigate the possibility of using PEF for protein release from microalgae. A complete release of hydrophilic proteins from the cell wall free mutants was observed whereas PEF treatment on the cell wall containing species resulted in substantially lower protein yields. Additional experiments showed that even at low energy input (0.05 kWh/kgbiomass), still about 70% of the proteins could be released with respect to bead beating as reference. These released proteins were water-soluble while the hydrophobic chlorophyll remained mainly entrapped in cell particles. SEM-analysis of these cell particles showed that PEF only opened the cells, instead of completely fragmenting them into smaller particles. These results indicate that PEF is an energy-efficient cell disruption method for selective release of water-soluble proteins, after the microalgal outer cell wall is removed. Enzymatic pretreatment to degrade the cell walls before PEF treatment was shown to be an efficient method to remove the cell wall.

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“…It is therefore reasonable that in general, protein release by means of PEF is limited by the presence of an outer cell wall. 4 …”

Section: Resultsmentioning

confidence: 99%

“…The protein yield was calculated as the increase in water-soluble proteins divided over the total protein concentration: 4 …”

Section: Methodsmentioning

confidence: 99%

Mild and Selective Protein Release of Cell Wall Deficient Microalgae with Pulsed Electric Field

Lam

Kolk

Chordia

et al. 2017

ACS Sustainable Chem. Eng.

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“…Electric field strength, treatment time, and specific energy all influence on the effectivity of PEF treatment. After subjecting a microalgae suspension to a PEF treatment of sufficient intensity, a strong increase in the electrical conductivity of the suspension media and the uptake of propidium iodide can be observed, thereby suggesting that an effective permeabilization of the microalgae has taken place (Kempkes, ; Postma, ‘t Lam et al., ). The critical electric field necessary to achieve electroporation of microalgae cells is lower than that required to electroporate smaller‐sized microorganisms such as bacteria.…”

Section: Pulsed Electric Fields Technology For Enhancing Extraction Omentioning

confidence: 99%

Pulsed electric field‐assisted extraction of valuable compounds from microorganisms

Martínez

Delso

Álvarez

et al. 2020

Comp Rev Food Sci Food Safe

137

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Microorganisms (bacteria, yeast, and microalgae) are a promising resource for products of high value such as nutrients, pigments, and enzymes. The majority of these compounds of interest remain inside the cell, thus making it necessary to extract and purify them before use. This review presents the challenges and opportunities in the production of these compounds, the microbial structure and the location of target compounds in the cells, the different procedures proposed for improving extraction of these compounds, and pulsed electric field (PEF)‐assisted extraction as alternative to these procedures. PEF is a nonthermal technology that produces a precise action on the cytoplasmic membrane improving the selective release of intracellular compounds while avoiding undesirable consequences of heating on the characteristics and purity of the extracts. PEF pretreatment with low energetic requirements allows for high extraction yields. However, PEF parameters should be tailored to each microbial cell, according to their structure, size, and other factors affecting efficiency. Furthermore, the recent discovery of the triggering effect of enzymatic activity during cell incubation after electroporation opens up the possibility of new implementations of PEF for the recovery of compounds that are bounded or assembled in structures. Similarly, PEF parameters and suspension storage conditions need to be optimized to reach the desired effect. PEF can be applied in continuous flow and is adaptable to industrial equipment, making it feasible for scale‐up to large processing capacities.

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“…It is also worth noting from Figure 5a that the amount of water-soluble proteins extracted by the cascade approach was significantly (p ≤ 0.05) smaller than that obtained by the HPH treatment alone, despite inducing a 6-fold increase with respect to PEF treatment alone. This behavior could be attributed to the contact between proteins and ethyl acetate during the lipid extraction phase, which likely triggered proteins degradation/denaturation phenomena, making insoluble a significant fraction of the soluble proteins, with a subsequent loss of their techno-functional properties [13]. Nevertheless, further investigations are strongly recommended in order to confirm this hypothesis.…”

Section: Extraction Yieldsmentioning

confidence: 99%

“…For example, microalgal lipids may serve as a source for biofuels, building blocks in the chemical industry, and value-added edible oils for the functional food and health market [9,10]. Moreover, microalgal proteins, carbohydrates, and pigments may find application in the food, feed, health, and bulk chemical market, or for the production of ethanol and chemicals [11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Application of Pulsed Electric Fields and High-Pressure Homogenization in Biorefinery Cascade of C. vulgaris Microalgae

Carullo

Abera

Scognamiglio

et al. 2022

Foods

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In this study, a cascaded cell disintegration process, based on pulsed electric fields (PEF - 20 kV/cm, 100 kJ/kgSUSP.) and high-pressure homogenization (HPH - 150 MPa, 5 passes) was designed for the efficient and selective release of intracellular compounds (water-soluble proteins, carbohydrates, and lipids) from C. vulgaris suspensions during extraction in water (25 °C, 1 h) and ethyl acetate (25 °C, 3 h). Recovery yields of target compounds from cascaded treatments (PEF + HPH) were compared with those observed when applying PEF and HPH treatments individually. Particle size distribution and scanning electron microscopy analyses showed that PEF treatment alone did not induce any measurable effect on cell shape/structure, whereas HPH caused complete cell fragmentation and debris formation, with an undifferentiated release of intracellular matter. Spectra measurements demonstrated that, in comparison with HPH alone, cascaded treatments increased the selectivity of extraction and improved the yields of carbohydrates and lipids, while higher yields of water-soluble proteins were measured for HPH alone. This work, therefore, demonstrates the feasibility of sequentially applying PEF and HPH treatments in the biorefinery of microalgae, projecting a beneficial impact in terms of process economics due to the potential reduction of the energy requirements for separation/purification stages.

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Microalgal Biorefinery for Bulk and High-Value Products: Product Extraction Within Cell Disintegration

Cited by 9 publications

References 38 publications

Mild and Selective Protein Release of Cell Wall Deficient Microalgae with Pulsed Electric Field

Mild and Selective Protein Release of Cell Wall Deficient Microalgae with Pulsed Electric Field

Pulsed electric field‐assisted extraction of valuable compounds from microorganisms

Application of Pulsed Electric Fields and High-Pressure Homogenization in Biorefinery Cascade of C. vulgaris Microalgae

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