Pulsed electric field‐assisted extraction of valuable compounds from microorganisms

Abstract

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.

Pulsed Electric Fields-Assisted Extraction of Valuable Compounds From Arthrospira Platensis: Effect of Pulse Polarity and Mild Heating

“…In particular, A. platensis is an excellent source of C-phycocyanin (C-PC), a water-soluble pigmented protein, which has gained importance in many applications in the food, cosmetic and pharmaceutical sectors, thanks to its blue color and its therapeutic properties, as well as for its potential use as a fluorescent marker in biomedical research (Fernández-Rojas et al, 2014). In A. platensis, C-PC serves as a light-harvesting pigment for the photosynthetic activity of this cyanobacteria, in which it is assembled, along with other phycobiliproteins, in the thylakoid membranes of chloroplast (Martinez et al, 2020), and may represent more than 20% of its dry weight (Martinez et al, 2017).…”

“…In general, the recovery of intracellular compounds of interest from algal biomass via conventional solvent extraction techniques is hampered by the presence of the rigid cell wall and membranes, which act as a barrier that greatly limits the penetration of the solvent into the cytoplasm and the diffusion of the solubilized intracellular compounds during the extraction process (Martinez et al, 2020). For these reasons, to recover a substantial amount of valuable compounds, the conventional extraction techniques may require the use of a large amount of solvent, long extraction time and relatively high temperature that may cause losses of labile compounds, as well as lead to the co-extraction of undesirable components (Günerken et al, 2015;Poojary et al, 2016).…”

Natural Pigments of Microbial Origin

“…In order to minimize the use of organic solvents and preserve as much as possible the qualitative and quantitative compositions of the pigmented molecules, ecofriendly methodologies have been investigated. Although these techniques have been employed for extraction of many bioactive substances, their effective application for extraction microbial pigments should be further exploited (Kalra et al, 2020;Martínez et al, 2020). Some characteristics, advantages and disadvantages of these green methodologies are detailed in Table 2.…”

“…The employment of SFE for carotenoids extraction from diverse substrates from laboratory to the commercial scale have been reported (Kitada et al, 2009;Goto et al, 2015). In addition, pressurized liquid extraction (PLE; also known as accelerated solvent extraction-ASE) (Lebeau et al, 2017), pulsed electric field (PEF)-assisted extraction (Martínez et al, 2020), and ionic liquids (IL)-assisted extraction (Mussagy et al, 2019) have been described as efficient and feasible green methods to improve the extraction yield of pigments from microbial biomass. All these techniques have pros and cons ( Table 2) and despite the advances in extraction methodologies, improved green methods are still necessary.…”

Improved Extraction Efficiency of Antioxidant Bioactive Compounds from Tetraselmis chuii and Phaedoactylum tricornutum Using Pulsed Electric Fields

“…Most of the studies evaluating the application of PEF focus on the use of aqueous suspensions of microalgae, thus mainly allowing extraction of water-soluble compounds [ 12 , 13 ], whereas the extraction of non-polar pigments (e.g., chlorophylls or carotenoids) is limited under these conditions. Some previous studies evaluated the use of supplementary extractions using 96% ethanol, obtaining considerable higher yields of pigments extracted from the PEF-pretreated microalgae Chlorella vulgaris [ 14 ].…”