A cascade extraction of active phycocyanin and fatty acids from Galdieria phlegrea

The Undeniable Potential of Thermophiles in Industrial Processes

Extremophilic microorganisms play a key role in understanding how life on Earth originated and evolved over centuries. Their ability to thrive in harsh environments relies on a plethora of mechanisms developed to survive at extreme temperatures, pressures, salinity, and pH values. From a biotechnological point of view, thermophiles are considered a robust tool for synthetic biology as well as a reliable starting material for the development of sustainable bioprocesses. This review discusses the current progress in the biomanufacturing of high-added bioproducts from thermophilic microorganisms and their industrial applications.

Unveiling the potential of Pseudococcomyxa simplex: a stepwise extraction for cosmetic applications

Microalgae are gaining attention as they are considered green fabrics able to synthesize many bioactive metabolites, with unique biological activities. However, their use at an industrial scale is still a challenge because of the high costs related to upstream and downstream processes. Here, a biorefinery approach was proposed, starting from the biomass of the green microalga Pseudococcomyxa simplex for the extraction of two classes of molecules with a potential use in the cosmetic industry. Carotenoids were extracted first by an ultrasound-assisted extraction, and then, from the residual biomass, lipids were obtained by a conventional extraction. The chemical characterization of the ethanol extract indicated lutein, a biosynthetic derivative of α-carotene, as the most abundant carotenoid. The extract was found to be fully biocompatible on a cell-based model, active as antioxidant and with an in vitro anti-aging property. In particular, the lutein-enriched fraction was able to activate Nrf2 pathway, which plays a key role also in aging process. Finally, lipids were isolated from the residual biomass and the isolated fatty acids fraction was composed by palmitic and stearic acids. These molecules, fully biocompatible, can find application as emulsifiers and softener agents in cosmetic formulations. Thus, an untapped microalgal species can represent a sustainable source for cosmeceutical formulations. KEY POINTS: • Pseudococcomyxa simplex has been explored in a cascade approach. • Lutein is the main extracted carotenoid and has antioxidant and anti-aging activity. • Fatty acids are mainly composed of palmitic and stearic acids.

Valuable pigments from microalgae: phycobiliproteins, primary carotenoids, and fucoxanthin

Phycobiliproteins, carotenoids and fucoxanthin are photosynthetic pigments extracted from microalgae and cyanobacteria with great potential biotechnological applications, as healthy food colorants and cosmetics. Phycocyanin possesses a brilliant blue color, with fluorescent properties making it useful as a reagent for immunological essays. The most important source of phycocyanin is the cyanobacterium Arthrospira platensis, however, recently, the Rhodophyta Galdieria sulphuraria has also been identified as such. The main obstacle to the commercialization of phycocyanin is represented by its chemical instability, strongly reducing its shelf-life. Moreover, the high level of purity needed for pharmaceutical applications requires several steps which increase both the production time and cost. Microalgae (Chlorella, Dunaliella, Nannochloropsis, Scenedesmus) produce several light harvesting carotenoids, and are able to manage with oxidative stress, due to their free radical scavenging properties, which makes them suitable for use as source of natural antioxidants. Many studies focused on the selection of the most promising strains producing valuable carotenoids and on their extraction and purification. Among carotenoids produced by marine microalgae, fucoxanthin is the most abundant, representing more than 10% of total carotenoids. Despite the abundance and diversity of fucoxanthin producing microalgae only a few species have been studied for commercial production, the most relevant being Phaeodactylum tricornutum. Due to its antioxidant activity, fucoxanthin can bring various potential benefits to the prevention and treatment of lifestyle-related diseases. In this review, we update the main results achieved in the production, extraction, purification, and commercialization of these important pigments, motivating the cultivation of microalgae as a source of natural pigments.

An Alternative Exploitation of Synechocystis sp. PCC6803: A Cascade Approach for the Recovery of High Added-Value Products

Microalgal biomass represents a very interesting biological feedstock to be converted into several high-value products in a biorefinery approach. In this study, the cyanobacterium Synechocystis sp. PCC6803 was used to obtain different classes of molecules: proteins, carotenoids and lipids by using a cascade approach. In particular, the protein extract showed a selective cytotoxicity towards cancer cells, whereas carotenoids were found to be active as antioxidants both in vitro and on a cell-based model. Finally, for the first time, lipids were recovered from Synechocystis biomass as the last class of molecules and were successfully used as an alternative substrate for the production of polyhydroxyalkanoate (PHA) by the native PHA producer Pseudomonas resinovorans. Taken together, our results lead to a significant increase in the valorization of Synechocystis sp. PCC6803 biomass, thus allowing a possible offsetting of the process costs.

Shedding Light on the Hidden Benefit of Porphyridium cruentum Culture

Microalgae can represent a reliable source of natural compounds with different activities. Here, we evaluated the antioxidant and anti-inflammatory activity of sulfated exopolysaccharides (s-EPSs) and phycoerythrin (PE), two molecules naturally produced by the red marine microalga Porphyridium cruentum (CCALA415). In vitro and cell-based assays were performed to assess the biological activities of these compounds. The s-EPSs, owing to the presence of sulfate groups, showed biocompatibility on immortalized eukaryotic cell lines and a high antioxidant activity on cell-based systems. PE showed powerful antioxidant activity both in vitro and on cell-based systems, but purification is mandatory for its safe use. Finally, both molecules showed anti-inflammatory activity comparable to that of ibuprofen and helped tissue regeneration. Thus, the isolated molecules from microalgae represent an excellent source of antioxidants to be used in different fields.

Inside out Porphyridium cruentum: Beyond the Conventional Biorefinery Concept

Here, an unprecedented biorefinery approach has been designed to recover high-added value bioproducts starting from the culture ofPorphyridium cruentum. This unicellular marine red alga can secrete and accumulate high-value compounds that can find applications in a wide variety of industrial fields. 300 ± 67 mg/L of exopolysaccharides were obtained from cell culture medium; phycoerythrin was efficiently extracted (40% of total extract) and isolated by single chromatography, with a purity grade that allowed the crystal structure determination at 1.60 Å; a twofold increase in β-carotene yield was obtained from the residual biomass; the final residual biomass was found to be enriched in saturated fatty acids. Thus, for the first time, a complete exploitation ofP. cruentumculture was set up.

Chestnut Wood Mud as a Source of Ellagic Acid for Dermo-Cosmetic Applications

Ellagic acid (EA) has long been recognized as a very active antioxidant, anti-inflammatory, and antimicrobial agent. However, its low bioavailability has often hampered its applications in health-related fields. Here, we report a phospholipid vesicle-based controlled release system for EA, involving the exploitation of chestnut wood mud (CWM), an industrial by-product from chestnut tannin production, as a largely available and low-cost source of this compound. Two kinds of CWM with different particle size distributions, indicated as CWM-A and CWM-B (<100 and 32 µm, respectively), containing 5 ± 1% w/w EA, were incorporated into transfersomes. The latter were small in size (~100 nm), homogeneously dispersed, and negatively charged. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing/antioxidant power (FRAP) assays indicated up to three-fold improvement in the antioxidant properties of CWM upon incorporation into transfersomes. The kinetics of EA released under simulated physiological conditions were evaluated by UV-Vis spectroscopy and HPLC analysis. The best results were obtained with CWM-B (100% of EA gradually released after 37 days at pH 7.4). A stepwise increase in the antioxidant properties of the released material was also observed. Cell-based experiments confirmed the efficacy of CWM-B transfersomes as antioxidant agents in contrasting photodamage.

Thermo resistant antioxidants from photoautotrophic microorganisms: screening and characterization

The demand for natural antioxidants to be used in food industry is increasing, as synthetic antioxidants are toxic and have high production costs. Specifically, food processing and preservation require antioxidants resistant to thermal sterilization processes. In this study, twenty-five strains among microalgae and cyanobacteria were screened as antioxidants producers. The species Enallax sp., Synechococcus bigranulatus and Galdieria sulphuraria showed the highest content of chlorophyll a and total carotenoids. In vitro stability and antioxidant activity of the ethanolic extracts were performed. The results revealed that pigments present in the extracts, obtained from the previously mentioned species, were stable at room temperature and exhibited in vitro free radical scavenging potential with IC₅₀ values of 0.099 ± 0.001, 0.048 ± 0.001 and 0.13 ± 0.02 mg mL^-1, respectively. Biocompatibility assay showed that the extracts were not toxic on immortalized cell lines. The antioxidant activity was also tested on a cell-based model by measuring intracellular ROS levels after sodium arsenite treatment. Noteworthy, extracts were able to exert the same protective effect, before and after the pasteurization process. Results clearly indicate the feasibility of obtaining biologically active and thermostable antioxidants from microalgae. Green solvents can be used to obtain thermo-resistant antioxidants from cyanobacteria and microalgae which can be used in the food industry. Thus, the substitution of synthetic pigments with natural ones is now practicable.

Currently Applied Extraction Processes for Secondary Metabolites from Lippia turbinata and Turnera diffusa and Future Perspectives

The poleo (Lippia turbinata Griseb.) and damiana (Turnera diffusa Wild) are two of the most valued species in the Mexican semidesert due to their medicinal uses. The conventional essential oil extraction process is hydrodistillation, and for the extraction of antioxidants, the use of organic solvents. However, these techniques are time-consuming and degrade thermolabile molecules, and the efficiency of the process is dependent on the affinity of the solvent for bioactive compounds. Likewise, they generate solvent residues such as methanol, hexane, petroleum ether, toluene, chloroform, etc. Therefore, in recent years, ecofriendly alternatives such as ohmic heating, microwaves, ultrasound, and supercritical fluids have been studied. These methodologies allow reducing the environmental impact and processing times, in addition to increasing yields at a lower cost. Currently, there is no up-to-date information that provides a description of the ecofriendly trends for the recovery process of essential oils and antioxidants from Lippia turbinata and Turnera diffusa. This review includes relevant information on the most recent advancements in these processes, including conditions and methodological foundation.

Fatty Acids-Enriched Fractions of Hermetia illucens (Black Soldier Fly) Larvae Fat Can Combat MDR Pathogenic Fish Bacteria Aeromonas spp

Aeromonas spp. cause many diseases in aquaculture habitats. Hermetia illucens (Hi) larvae were used as feed-in aquacultures and in eradicating pathogenic fish bacteria. In the present study, we applied consecutive extractions of the same biomass of BSFL fat using the acidic water–methanol solution. The major constituents of the sequential extracts (SEs) were free fatty acids (FFAs), and fatty acids derivatives as identified by gas chromatography spectrometry (GC-MS). Our improved procedure enabled gradual enrichment in the unsaturated fatty acids (USFAs) content in our SEs. The present study aimed to compare the composition and antimicrobial properties of SEs. Among actual fish pathogens, A. hydrophila and A. salmonicida demonstrated multiple drug resistance (MDR) against different recommended standard antibiotics: A. salmonicida was resistant to six, while A. hydrophila was resistant to four antibiotics from ten used in the present study. For the first time, we demonstrated the high dose-dependent antibacterial activity of each SE against Aeromonas spp., especially MDR A. salmonicida. The bacteriostatic and bactericidal (MIC/MBC) activity of SEs was significantly enhanced through the sequential extractions. The third sequential extract (AWME3) possessed the highest activity against Aeromonas spp.: inhibition zone diameters were in the range (21.47 ± 0.14–20.83 ± 0.22 mm) at a concentration of 40 mg/mL, MIC values ranged between 0.09 and 0.38 mg/mL for A. hydrophila and A. salmonicida, respectively. AWME3 MBC values recorded 0.19 and 0.38 mg/mL, while MIC₅₀ values were 0.065 ± 0.004 and 0.22 ± 0.005 mg/mL against A. hydrophila and A. salmonicida, respectively. Thus, the larvae fat from Hermitia illucens may serve as an excellent reservoir of bioactive molecules with good capacity to eradicate the multidrug-resistant bacteria, having promising potential for practical application in the aquaculture field.

Development and fabrication of disease resistance protein in recombinant Escherichia coli

Cyanobacteria and Spirulina produce C-phycocyanin (CPC), a water soluble protein associated pigment, which is extensively used in food and pharmaceutical industries. Other therapeutic proteins might exist in microalgal cells, of which there is limited knowledge. Such proteins/peptides with antibiotic properties are crucial due to the emergence of multi-drug resistant pathogens. In addition, the native expression levels of such disease resistant proteins are low, hindering further investigation. Thus, screening and overexpression of such novel proteins is urgent and important. In this study, a protein which was identified as a putative disease resistance protein (DRP) in the mixture of Spirulina product has been explored for the first time. To improve protein expression, DRP was cloned in the pET system, co-transformed with pRARE plasmid for codon optimization and was significantly overexpressed in E. coli BL21(DE3) under induction with isopropyl-β-d-1-thiogalactopyranoside (IPTG). Furthermore, soluble DRP exhibited intense antimicrobial activity against predominant pathogens, and an inhibition zone of 1.59 to 1.74 cm was obtained for E. coli. At a concentration 4 mg/mL, DRP significantly elevated the growth of L. rhamnosus ZY up to twofold showing probable prebiotic activities. Moreover, DRP showed potential as an effective antioxidant, and the scavenging ability for ROS was in the order of hydroxyl > DPPH > superoxide radicals. A putative disease resistance protein (DRP) has been identified, sequenced, cloned and over-expressed in E. coli as a functional protein. Thus expressed DRP showed potential anti-microbial and antioxidant properties, with promising therapeutic applications.

Towards green extraction methods from microalgae learning from the classics

Microalgae started receiving attention as producers of third generation of biofuel, but they are rich in many bioactive compounds. Indeed, they produce many molecules endowed with benefic effects on human health which are highly requested in the market. Thus, it would be important to fractionate algal biomass into its several high-value compounds: this represents the basis of the microalgal biorefinery approach. Usually, conventional extraction methods have been used to extract a single class of molecules, with many side effects on the environment and on human health. The development of a green downstream platform could help in obtaining different class of molecules with high purity along with low environmental impact. This review is focused on technical advances that have been performed, from classic methods to the newest and green ones. Indeed, it is fundamental to set up new procedures that do not affect the biological activity of the extracted molecules. A comparative analysis has been performed among the conventional methods and the new extraction techniques, i.e., switchable solvents and microwave-assisted and compressed fluid extractions.

Green Compressed Fluid Technologies To Extract Antioxidants and Lipids from Galdieria phlegrea in a Biorefinery Approach

A green cascade approach was used to recover phycocyanins, carotenoids and lipids from Galdiera phlegrea. Phycocyanin extraction was performed by high pressure homogenization and purified by ultrafiltration, whereas carotenoids were obtained by a pressurized liquid extraction and lipids by supercritical fluid extraction. The second step of this innovative, green, and cost-effective procedure is able to improve the recovery of zeaxanthin and β-carotene up to 40%, without affecting the quality of compounds and avoiding the use of organic solvents and the drying processes. The isolated carotenoids were active as antioxidants, as clearly shown by their protective activity on a cell-based model. The lipid yield was increased by 12% with respect to conventional methods.

Biomass and phycobiliprotein production of Galdieria sulphuraria, immobilized on a twin-layer porous substrate photobioreactor

The extremophile red alga Galdieria sulphuraria was successfully grown immobilized in a twin-layer porous substrate bioreactor (TL-PSBR). A maximal biomass growth rate of 10 g dry weight m^-2 day^-1 was measured at a photon fluence rate of 200 μmol photons m^-2 s^-1 with addition of 1% CO₂ and a temperature of 34 °C. Under these conditions, a maximal biomass value of 232 g m^-2 was attained after 33 days of growth. Phycobilin productivity, however, was highest at a lower photon fluence rate of 100 μmol photons m^-2 s^-1 and reached a phycobilin value of 14 g m^-2, a phycobilin content in the biomass of 63 mg g^-1 and a phycobilin growth rate of 0.28 g m^-2 day^-1 for phycocyanin and 0.23 g m^-2 day^-1 for allophycocyanin. Addition of CO₂ was essential to enhance growth and phycobilin production in G. sulphuraria and further optimization of the cultivation process in the TL-PSBR appears possible using a multi-phase approach, higher growth temperatures and optimization of nutrient supply. It is concluded that autotrophic cultivation of G. sulphuraria in a TL-PSBR is an attractive alternative to suspension cultivation for phycobilin production and applications in bioremediation.

A thermophilic C-phycocyanin with unprecedented biophysical and biochemical properties

C-phycoyanins are abundant light-harvesting pigments which have an important role in the energy transfer cascade of photosystems in prokaryotic cyanobacteria and eukaryotic red algae. These proteins have important biotechnological applications, since they can be used in food, cosmetics, nutraceutical, pharmaceutical industries and in biomedical research. Here, C-phycocyanin from the extremophilic red alga Galdieria phlegrea (GpPC) has been purified and characterized from a biophysical point of view by SDS-PAGE, mass spectrometry, UV-Vis absorption spectroscopy, circular dichroism and intrinsic fluorescence. Stability against pH variations, addition of the oxidizing agent hydrogen peroxide and the effects of temperature have been also investigated, together with its in cell antioxidant potential and antitumor activity. GpPC is stable under different pHs and unfolds at a temperature higher than 80 °C within the pH range 5.0-7.0. Its fluorescence spectra present a maximum at 650 nm, when excited at 589 nm. The protein exerts interesting in cell antioxidant properties even after high temperature treatments, like the pasteurization process, and is cytotoxic for A431 and SVT2 cancer cells, whereas it is not toxic for non-malignant cells. Our results assist in the development of C-phycocyanin as a multitasking protein, to be used in the food industry, as antioxidant and anticancer agent.