Matteo Francavilla

Phytosterols from Dunaliella tertiolecta and Dunaliella salina: A potentially novel industrial application

Sterols have been extracted and analysed from Dunaliellatertiolecta and Dunaliella salina, in order to evaluate a potentially novel industrial exploitation of these microalgae as source of phytosterols. The effect of salt concentration on sterols yields has been studied varying the quantities of NaCl into culture medium. Twelve sterols were identified by Gas-chromatographic MS/MS analysis for both algal strains. The most abundant phytosterols were (22E,24R)-methylcholesta-5,7,22-trien-3beta-ol (ergosterol) and (22E,24R)-ethylcholesta-5,7,22-trien-3beta-ol (7-dehydroporiferasterol). The whole sterol fraction consisted mainly of phytosterols (C(28) and C(29) sterols). Good yields of total sterols were achieved at lower salt concentration (1.3% and 0.89% of dry weight in D. tertiolecta and D. salina, respectively, at 0.6M NaCl), while an increase in salt concentration resulted in a significant decrease in total sterols yield.

The Red Seaweed Gracilaria gracilis as a Multi Products Source

In recent years seaweeds have increasingly attracted interest in the search for new drugs and have been shown to be a primary source of bioactive natural compounds and biomaterials. In the present investigation, the biochemical composition of the red seaweed Gracilaria gracilis, collected seasonally in the Lesina Lagoon (Southern Adriatic Sea, Lesina, Italy), was assayed by means of advanced analytical techniques, such as gas-chromatography coupled with mass spectrometry and spectrophotometric tests. In particular, analysis of lipids, fatty acids, sterols, proteins, phycobiliproteins and carbohydrates as well as phenolic content, antioxidant and radical scavenging activity were performed. In winter extracts of G. gracilis, a high content of R-phycoerythrin together with other valuable products such as arachidonic acid (PUFA ω-6), proteins and carbohydrates was observed. High antioxidant and radical scavenging activities were also detected in summer extracts of the seaweed together with a high content of total phenols. In conclusion, this study points out the possibility of using Gracilaria gracilis as a multi products source for biotechnological, nutraceutical and pharmaceutical applications even although more investigations are required for separating, purifying and characterizing these bioactive compounds.

Efficient and simple reactive milling preparation of photocatalytically active porous ZnO nanostructures using biomass derived polysaccharides

ZnO nanocrystals of different shapes and sizes have been synthesized using an innovative, simple and efficient dry reactive milling methodology using Zn(NO3)2 and various polysaccharides as sacrificial templates. Optimum results were achieved using extracted agar from the red seaweed Gracilaria gracilis. Upon template removal after calcination at 600 °C, the protocol gave rise to a range of porous metal oxide nanomaterials of different shapes and nanoparticle sizes which were found to have excellent photocatalytic properties in aqueous phenol degradation as compared to commercial P25 Evonik titania.

Cascade approach of red macroalgae Gracilaria gracilis sustainable valorization by extraction of phycobiliproteins and pyrolysis of residue

Phycobiliproteins extraction (primary refining) from Gracilaria gracilis seaweed, harvested in Lesina Lagoon (Italy) and further valorization of the residual algal via pyrolysis (secondary refining), were investigated with a cascade biorefinery approach. R-phycoerythrin (7 mg/g d.w.), allophycocyanin (3.5 mg/g d.w.) and phycocyanin (2 mg/g d.w.) were the main phycobiliproteins extracted. Pyrolysis of G.gracilis residue followed, aiming to investigate the production of bio-oil and biochar within a pyrolysis temperature range of 400-600 °C. Results showed that the bio-oil yield is high (∼65 wt%) at pyrolysis temperature ∼500 °C, but its high content in nitrogenous compounds prevents its use as a biofuel, unless some further de-nitrogenation takes place. Biochar yield ranged between 33 wt% (400 °C) and 26.5 wt% (600 °C). Interestingly, inorganic nutrients including P, K, Ca, Fe and Mg were detected in biochar, suggesting its potential use as recovering system of natural mineral resources from the oceanic reservoir.

A mixture of phytosterols from Dunaliella tertiolecta affects proliferation of peripheral blood mononuclear cells and cytokine production in sheep

The aim of this study was to investigate the immunomodulatory and anti-inflammatory role of a mixture of phytosterols extracted from the microalga Dunaliella tertiolecta on peripheral blood mononuclear cells (PBMC) isolated from sheep. PBMC were treated to determine cell proliferation and cytokine production with different sterols: ergosterol (E), a mixture of eleven Algae sterols extracted and purified from D. tertiolecta (Algae Extract, AE), a mixture of ergosterol and 7-dehydroporiferasterol extracted and purified from D. tertiolecta (Purified Extract, PE). Cytokine production (TNF-α, IL-6, IL-1β, and IL-10) was evaluated after cell treatment with Concanavalin A (Con A) and lipopolysaccharide (LPS). The mixture of ergosterol and 7-dehydroporiferasterol extracted and purified from D. tertiolecta showed a suppressive effect on cell proliferation, and a reduction of pro-inflammatory cytokines production. Furthermore, a stimulatory effect on the production of the regulatory cytokine IL-10 was found. The immunosuppressive effect exerted by the mixture of ergosterol and 7-dehydroporiferasterol from D. tertiolecta was dose-dependent both in suppressing cell proliferation and in stimulating IL-10 production. Present results showed that the immunomodulatory and anti-inflammatory activities were more apparent in the purified extract characterized by the mixture of ergosterol and 7-dehydroporiferasterol, and might depend on the existence of a synergic effect of the structures of the two phytosterols. Furthermore, findings from our study suggest that the purified extract characterized by the mixture of ergosterol and 7-dehydroporiferasterol from D. tertiolecta could be used to reduce immune reactions resulting from inflammatory diseases in sheep production systems, and could have innovative implications on the modulation of sheep immune system when used as feed supplements.

Natural porous agar materials from macroalgae

Porous agar materials have been prepared from marine macroalgae species using a simple microwave-assisted extraction/drying methodology, providing a new family of polysaccharide derived porous solids. The microwave-assisted extraction allows a more efficient and less time-consuming extraction of the polysaccharide compared to conventional extraction protocols based on conventional heating. DRIFT and (13)C NMR results indicated that the internal agar structure (based on d-galactose and 3,6-anhydro-l-galactose linked units) was preserved after the extraction methodology, which opens a wide range of future possibilities and applications for this new family of porous polysaccharides. The extracted agar materials, which have already applications per se due to their high purities, could be subsequently transformed into a novel family of attractive mesoporous agar materials that could be used as natural templates for the production of nanocrystals of metal oxides.

Microwave-induced low temperature pyrolysis of macroalgae for unprecedented hydrogen-enriched syngas production

An efficient methodology based on low temperature microwave-induced pyrolysis has been developed for syngas production from macroalgae. The protocol provided unprecedented hydrogen production, with switchable H2/CO ratios depending on pyrolysis conditions which were found to remarkably improve conventional pyrolysis experiments even at significantly higher temperatures (400 vs. 800 °C). Arcing effects under microwave irradiation, which result in an interesting observed pseudo-catalytic effect promoted by the metal oxides contained in macroalgae, seem to account for the improved results.

Tunable microwave-assisted aqueous conversion of seaweed-derived agarose for the selective production of 5-hydroxymethyl furfural/levulinic acid

A simple, highly efficient and tunable microwave-assisted conversion of seaweed-derived agarose into 5-hydroxymethyl furfural (5-HMF) or levulinic acid (LA), depending on the reaction conditions, is reported. The proposed system could be fine-tuned for the selective production of 5-HMF (ca. 51% yield) in the absence of any catalyst or alternatively to levulinic acid (64% yield) with the simple addition of 1% v/v sulfuric acid, both under optimized aqueous microwave irradiation conditions (10 min, 180 °C). Additionally, galactose could also be generated as the main product (45–77%) depending on the temperature and the addition of catalytic amounts of sulfuric acid. A plausible reaction mechanism is provided in which the formation of intermediates from the hydrolysis of agarose is critical to obtain 5-HMF and LA as final products.

Bioremediation of aquaculture wastewater from Mugil cephalus (Linnaeus, 1758) with different microalgae species

ABSTRACT Current aquaculture practices have a detrimental impact on the environment, in particular due to the release of high concentration of nitrogen and phosphorus that can induce eutrophication. This study investigates and compares the capacity of three microalgae species Tetraselmis suecica, Isochrysis galbana and Dunaliella tertiolecta, in the bioremediation of grey mullet Mugil cephalus wastewater. The experiment was conducted in batch conditions for 7 days using completely mixed bubble column photobioreactors. After two days, T. suecica and D. tertiolecta were able to remove more than 90% of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorous (DIP), whereas I. galbana removed only 32% and 79% of DIN and DIP, respectively. A higher biomass yield resulted for T. suecica (603 ± 34 mg/L, mean ± SE). This study confirms the potential to employ T. suecica in an Integrated Multi-Trophic Aquaculture system for bioremediation of wastewater and identifies D. tertiolecta as another valid candidate species. Moreover, these species can growth in unsterilized culture media, and this reduces energy consumption, costs and efforts.

Inoculum pre-treatment affects the fermentative activity of hydrogen-producing communities in the presence of 5-hydroxymethylfurfural

To enhance the productivity of mixed microbial cultures for fermentative bio-hydrogen production, chemical-physical pre-treatments of the original seed are needed to suppress the activity of hydrogen (H2)-consuming microbes. This approach might influence negatively the composition and diversity of the hydrogen-producing community with consequences on the functional stability of the H2-producing systems in case of perturbations. In this study, we aimed at investigating the effect of different types of pre-treatment on the performance of hydrogen production systems in the presence of an inhibitor, such as 5-hydroxymethylfurfural (HMF). The efficiency and the microbial community structure of batch reactors amended with HMF and inoculated with non-pretreated and pretreated (acid, heat shock, and aeration) anaerobic sludge were evaluated and compared with control systems. The type of pre-treatments influenced the microbial community assembly and activity in inhibited systems, with significant effect on the performance. Cumulative H2 production tests showed that the pre-aerated systems (control and HMF inhibited) were the most efficient, while the difference of the lag phase of the pre-acidified control and HMF-added test was negligible. Analyses of the structure of the enriched microbial community in the systems through PCR-denaturing gradient gel electrophoresis (DGGE) followed by band sequencing revealed that the differences in performance were mostly related to shifts in the metabolic pathways rather than in the predominant species. In conclusion, the findings suggest that the use of specific inoculum pre-treatment could contribute to regulate the metabolic activity of the fermentative H2-producing bacteria in order to enhance the bio-energy production.