Streptomycetes as Microbial Cell Factories for the Biotechnological Production of Melanin.

Melanins are complex, polymeric pigments with interesting properties like UV-light absorbance ability, metal ion chelation capacity, antimicrobial action, redox behaviors, and scavenging properties. Based on these characteristics, melanins might be applied in different industrial fields like food packaging, environmental bioremediation, and bioelectronic fields. The actual melanin manufacturing process is not environmentally friendly as it is based on extraction and purification from cuttlefish. Synthetic melanin is available on the market, but it is more expensive than animal-sourced pigment and it requires long chemical procedures. The biotechnological production of microbial melanin, instead, might be a valid alternative. Streptomycetes synthesize melanins as pigments and as extracellular products. In this review, the melanin biotechnological production processes by different Streptomyces strains have been revised according to papers in the literature. The different fermentation strategies to increase melanin production such as the optimization of growth conditions and medium composition or the use of raw sources as growth substrates are here described. Diverse downstream purification processes are also reported as well as all the different analytical methods used to characterize the melanin produced by Streptomyces strains before its application in different fields.

Biotechnological Production and Characterization of Extracellular Melanin by Streptomyces nashvillensis.

Melanins are pigments employed in food, cosmetic, and textile industries, manufactured by extraction from cuttlefishes. Their biotechnological production by Streptomycetes, instead, has been poorly investigated so far. In this paper, for the first time, the strain Streptomyces nashvillensis DSM 40314 was tested as an extracellular melanin producer by investigating the influence of diverse temperatures (26, 28, and 30 °C) and pH values (6.0 and 7.0) on bacterial growth, melanin production, and on the activity of the secreted tyrosinase, the first enzyme of the pigment biosynthetic pathway. In physiological 96-h shake flask experiments, the optimal growth parameters resulted to be 28 °C and pH 7.0, at which a maximum biomass of 8.4 ± 0.5 gcdw/L, a melanin concentration of 0.74 ± 0.01 g/L (yield on biomass of 0.09 ± 0.01 g/gcdw and productivity of 0.008 ± 0.001 g/L/h), and a final tyrosinase activity of 10.1 ± 0.1 U/mL were reached. The produced pigment was purified from the broth supernatant with a two-step purification process (75.0 ± 2.0% of purity with 65.0 ± 5.0% of recovery) and tested for its chemical, antioxidant, and photoprotective properties. Finally, characterization by UV-visible and FT-IR spectroscopy, elemental analyses, and mono- and bi-dimensional NMR suggested the eumelanin-like nature of the pigment.

Physicochemical Characterization of Chitosan/Poly-γ-Glutamic Acid Glass-like Materials.

This paper sets up a new route for producing non-covalently crosslinked bio-composites by blending poly-γ-glutamic acid (γ-PGA) of microbial origin and chitosan (CH) through poly-electrolyte complexation under specific experimental conditions. CH and two different molecular weight γ-PGA fractions have been blended at different mass ratios (1/9, 2/8 and 3/7) under acidic pH. The developed materials seemed to behave like moldable hydrogels with a soft rubbery consistency. However, after dehydration, they became exceedingly hard, glass-like materials completely insoluble in water and organic solvents. The native biopolymers and their blends underwent comprehensive structural, physicochemical, and thermal analyses. The study confirmed strong physical interactions between polysaccharide and polyamide chains, facilitated by electrostatic attraction and hydrogen bonding. The materials exhibited both crystalline and amorphous structures and demonstrated good thermal stability and degradability. Described as thermoplastic and saloplastic, these bio-composites offer vast opportunities in the realm of polyelectrolyte complexes (PECs). This unique combination of properties allowed the bio-composites to function as glass-like materials, making them highly versatile for potential applications in various fields. They hold potential for use in regenerative medicine, biomedical devices, food packaging, and 3D printing. Their environmentally friendly properties make them attractive candidates for sustainable material development in various industries.

Advanced Biomaterials for Food Edible Coatings.

The aim of this Special Issue is to highlight recent investigations on different biopolymers obtained from renewable sources for use as edible coatings [...].

Sustainable Exploitation of Posidonia oceanica Sea Balls (Egagropili): A Review.

Posidonia oceanica (L.) Delile is the main seagrass plant in the Mediterranean basin that forms huge underwater meadows. Its leaves, when decomposed, are transported to the coasts, where they create huge banquettes that protect the beaches from sea erosion. Its roots and rhizome fragments, instead, aggregate into fibrous sea balls, called egagropili, that are shaped and accumulated by the waves along the shoreline. Their presence on the beach is generally disliked by tourists, and, thus, local communities commonly treat them as waste to remove and discard. Posidonia oceanica egagropili might represent a vegetable lignocellulose biomass to be valorized as a renewable substrate to produce added value molecules in biotechnological processes, as bio-absorbents in environmental decontamination, to prepare new bioplastics and biocomposites, or as insulating and reinforcement materials for construction and building. In this review, the structural characteristics, and the biological role of Posidonia oceanica egagropili are described, as well as their applications in different fields as reported in scientific papers published in recent years.

Enhanced Streptomyces roseochromogenes melanin production by using the marine renewable source Posidonia oceanica egagropili.

Since the possibility to biotechnologically produce melanin by Streptomycetes using plant biomass has been so far poorly investigated, Posidonia oceanica egagropili, a marine waste accumulating along the Mediterranean Sea coasts, was explored as a renewable source to enhance extracellular melanin production by Streptomyces roseochromogenes ATCC 13400. Therefore, different amounts of egagropili powder were added to a culture medium containing glucose, malt extract, and yeast extract, and their effect on the melanin biosynthesis was evaluated. A 2.5 g·L-1 supplementation in 120-h shake flask growths at 26 °C, at pH 6.0 and 250 rpm, was found to enhance the melanin production up to 3.94 ± 0.12 g·L-1, a value 7.4-fold higher than the control. Moreover, 2-L batches allowed to reach a concentration of 9.20 ± 0.12 g·L-1 in 96 h with a productivity of 0.098 g·L-1·h-1. Further studies also demonstrated that the melanin production enhancement was due to the synergistic effect of both the lignin carbohydrate complex and the holocellulose components of the egagropili. Finally, the pigment was purified from the broth supernatant by acidic precipitation and reversed-phase chromatography, characterized by UV absorbance and one- and two-dimensional NMR, and also tested for its chemical, antioxidant, and photo-protective properties. KEY POINTS: • S. roseochromogenes ATCC 13400 produces extracellular soluble melanin. • Egagropili added to the growth medium enhances melanin production and productivity. • Both the lignin carbohydrate complex and the holocellulose egagropili components influence the melanin biosynthesis.

Argan (Argania spinosa L.) Seed Oil Cake as a Potential Source of Protein-Based Film Matrix for Pharmaco-Cosmetic Applications.

Various different agri-food biomasses might be turned into renewable sources for producing biodegradable and edible plastics, potentially attractive for food, agricultural and cosmeceutical sectors. In this regard, different seeds utilized for edible and non-edible oil extraction give rise to high amounts of organic by-products, known as seed oil cakes (SOCs), potentially able to become protein-rich resources useful for the manufacturing of biodegradable films. This study reports the potential of SOC derived from Argania spinosa (argan), a well-known plant containing valuable non-refined oil suitable for food or cosmetic use, to be a promising valuable source for production of a protein-based matrix of biomaterials to be used in the pharmaco-cosmetic sector. Thus, glycerol-plasticized films were prepared by casting and drying using different amounts of argan seed protein concentrate, in the presence of increasing glycerol concentrations, and characterized for their morphological, mechanical, barrier, and hydrophilicity properties. In addition, their antioxidant activity and effects on cell viability and wound healing were investigated. The hydrophobic nature of the argan protein-based films, and their satisfying physicochemical and biological properties, suggest a biorefinery approach for the recycling of argan SOC as valuable raw material for manufacturing new products to be used in the cosmeceutical and food industries.

Pandemic COVID-19, an update of current status and new therapeutic strategies.

The global COVID-19 pandemic is underway. In recent weeks, several countries throughout the globe, and particularly in Europe, have experienced an exponential increase in the number of individuals infected with COVID-19, probably induced by a new variant of SARS-CoV-2, called the "Omicron variant." Mass vaccination against COVID-19 continues worldwide. Are authorized mRNA vaccines effective against the new Omicron variant? Recently, several pharmaceutical companies have developed oral antiviral pills against SARS-CoV-2, i.e., molnupiravir and paxlovid, that inhibit SARS-CoV-2 viral replication by acting on the RNA polymerase of SARS-CoV. In pre-registration clinical trials, molnupiravir and paxlovid have shown excellent clinical efficacy results, but what impact will these new oral antiviral agents have against pandemic COVID-19? In what specific clinical situations are they preferred over other antivirals such as remdesivir? In this brief review, we explore these important aspects.

Bio-Based Materials for Packaging.

Plastic pollution is currently one of the most pressing environmental problems, especially in countries with a low recycling rate that is mainly due to the insufficient collection of plastic waste [...].

Exploiting Potential Biotechnological Applications of Poly-γ-glutamic Acid Low Molecular Weight Fractions Obtained by Membrane-Based Ultra-Filtration.

Since the potentialities of applications of low molecular weight poly-γ-glutamic acid (γ-PGA) chains have been so far only partially explored, the separation of diverse molecular families of them, as well as their characterization for potential bioactivity and ability to form films, were investigated. Two different approaches based on organic solvent precipitation or on ultra- and nano-filtration membrane-based purification of inexpensive commercial material were employed to obtain size-specific γ-PGA fractions, further characterized by size exclusion chromatography equipped with a triple detector array and by ultra-high-performance liquid chromatography to assess their average molecular weight and their concentration. The γ-PGA low molecular weight fractions, purified by ultra-filtration, have been shown both to counteract the desiccation and the oxidative stress of keratinocyte monolayers. In addition, they were exploited to prepare novel hydrocolloid films by both solvent casting and thermal compression, in the presence of different concentrations of glycerol used as plasticizer. These biomaterials were characterized for their hydrophilicity, thermal and mechanical properties. The hot compression led to the attainment of less resistant but more extensible films. However, in all cases, an increase in elongation at break as a function of the glycerol content was observed. Besides, the thermal analyses of hot compressed materials demonstrated that thermal stability was increased with higher γ-PGA distribution po-lymer fractions. The obtained biomaterials might be potentially useful for applications in cosmetics and as vehicle of active molecules in the pharmaceutical field.

Pleiotropic effects of AT-1 receptor antagonists in hypoxia induced by cardiac ischaemia.

The renin-angiotensin system (RAS) plays a crucial role and coordinates multiple body functions through its hormonal mechanism. The RAS is supported in its function by numerous peptides such as angiotensin II (Ang II), Ang IV, Ang III, angiotensin (1-7) and (1-9). The system formed by ACE2/Ang(1-7)/MASr is a regulatory pathway within the RAS system and its functions are different from those of the ACE/Ang II/AT-1r system. Recently, it has been discovered that a key role of the RAS and the ACE2/Ang(1-7)/MASr system is in inflammatory processes such as cardiac hypertrophy and heart failure. Studies are ongoing to better understand and comprehend the function of the RAS in inflammation. Recent evidence associates AT-1r antagonists with a cardioprotective, anti-inflammatory, and anti-hypertrophic role. In this in vitro study, we demonstrate the protective role of treatment (50 and 200 µM) of an AT-1r antagonist, irbesartan, on hypoxia and inflammation-induced damage in cardiomyocytes.

The risks of liver injury in COVID-19 patients and pharmacological management to reduce or prevent the damage induced.

BACKGROUND: The global pandemic COVID-19 caused by the new coronavirus SARS-CoV-2 has already caused about 1.4 million deaths, and to date, there are no effective or direct antiviral vaccines. Some vaccines are in the last stages of testing. Overall mortality rates vary between countries, for example, from a minimum of 0.05% in Singapore to a maximum of 9.75 in Mexico; however, mortality and severity of COVID-19 are higher in the elderly and in those with comorbidities already present such as diabetes, hypertension, and heart disease. MAIN TEXT: Recent evidence has shown that an underlying liver disease can also be a risk factor, and SARS-CoV-2 itself can cause direct or indirect damage to liver tissue through multisystem inflammation generated especially in the more severe stages. In the current pandemic, liver dysfunction has been observed in 14-53% of patients with severe COVID-19. In addition, drugs administered during infection may be an additional factor of liver damage. The mechanism of cellular penetration of the virus that occurs by viral entry is through the receptors of the angiotensin 2 conversion enzyme (ACE-2) host that are abundantly present in type II pneumocytes, heart cells, but also liver cholangiocytes. CONCLUSION: In this manuscript, we describe the clinical management aimed at preserving the liver or reducing the damage caused by COVID-19 and anti-COVID-19 drug treatments.

Lignin/Carbohydrate Complex Isolated from Posidonia oceanica Sea Balls (Egagropili): Characterization and Antioxidant Reinforcement of Protein-Based Films.

A lignin fraction (LF) was extracted from the sea balls of Posidonia oceanica (egagropili) and extensively dialyzed and characterized by FT-IR and NMR analyses. LF resulted water soluble and exhibited a brownish-to-black color with the highest absorbance in the range of 250-400 nm, attributed to the chromophore functional groups present in the phenylpropane-based polymer. LF high-performance size exclusion chromatography analysis showed a highly represented (98.77%) species of 34.75 kDa molecular weight with a polydispersity index of 1.10 and an intrinsic viscosity of 0.15. Quantitative analysis of carbohydrates indicated that they represented 28.3% of the dry weight of the untreated egagropili fibers and 72.5% of that of LF. In particular, eight different monosaccharides were detected (fucose, arabinose, rhamnose, galactose, glucose, xylose, glucosamine and glucuronic acid), glucuronic acid (46.6%) and rhamnose (29.6%) being the most present monosaccharides in the LF. Almost all the phenol content of LF (113.85 ± 5.87 mg gallic acid eq/g of extract) was water soluble, whereas around 22% of it consisted of flavonoids and only 10% of the flavonoids consisted of anthocyanins. Therefore, LF isolated from egagropili lignocellulosic material could be defined as a water-soluble lignin/carbohydrate complex (LCC) formed by a phenol polymeric chain covalently bound to hemicellulose fragments. LCC exhibited a remarkable antioxidant activity that remained quite stable during 6 months and could be easily incorporated into a protein-based film and released from the latter overtime. These findings suggest egagropili LCC as a suitable candidate as an antioxidant additive for the reinforcement of packaging of foods with high susceptibility to be deteriorated in aerobic conditions.

Host defense peptides identified in human apolipoprotein B as novel food biopreservatives and active coating components.

The effectiveness of three novel "host defence peptides" identified in human Apolipoprotein B (ApoB) as novel antimicrobial and antibiofilm agents to be employed in food industry is reported. ApoB-derived peptides have been found to exert significant antimicrobial effects towards Salmonella typhimurium ATCC® 14028 and Salmonella enteritidis 706 RIVM strains. Furthermore, they have been found to retain antimicrobial activity under experimental conditions selected to simulate those occurring during food storage, transportation and heat treatment, and have been found to be endowed with antibiofilm properties. Based on these findings, to evaluate the applicability of ApoB-derived peptides as food biopreservatives, coating solutions composed by chitosan (CH) and an ApoB-derived peptide have been prepared and found to be able to prevent Salmonella cells attachment to different kinds of surfaces employed in food industry. Finally, obtained coating solution has been demonstrated to hinder microbial proliferation in chicken meat samples. Altogether, obtained findings indicate that ApoB-derived peptides are promising candidates as novel biopreservatives for food packaging.

Functional Properties of Rye Prolamin (Secalin) and Their Improvement by Protein Lipophilization through Capric Acid Covalent Binding.

Secalin (SCL), the prolamin fraction of rye protein, was chemically lipophilized using acylation reaction by treatment with different amounts of capric acid chloride (0, 2, 4, and 6 mmol/g) to enhance its functional properties. It was shown that SCL lipophilization increased the surface hydrophobicity and the hydrophobic interactions, leading to a reduction in protein solubility and water absorption capacity and to a greater oil absorption. In addition, SCL both emulsifying capacity and stability were improved when the protein was treated with low amount of capric acid chloride. Finally, the foaming capacity of SCL markedly increased after its treatment with increasing concentrations of the acylating agent, even though the foam of the modified protein was found to be more stable at the lower level of protein acylation. Technological application of lipophilized SCL as a protein additive in food preparations is suggested.

Anthropocene, the plastic age and future perspectives.

The issue of plastic waste is one of the main topics on the international societal and political agenda since ever-increasing growth in the quantity of plastic materials produced has gone beyond the ability to manage them effectively at their end-of-life. Mostly pushed by social campaigns, an ever-increasing number of initiatives have been taken by different institutions to reduce the huge amount of plastic waste: first of all, specific legal regulations have been introduced, both to realize effective systems of plastic collection, reuse and recycling, and to outlaw the use of unnecessary disposable one-use items. However, due to the indisputable advantages derived from the use of such a material, every action of decision makers to limit the production or use of plastics is unavoidably affected by economic evaluations, as well as by the deficiency or drawbacks of alternative materials, rather than by environmental reasons. In the three reviews in this Special 'In the Limelight' section, Oliver Bajt, Paola Fabbri et al. and Frederic Debeaufort - invited speakers at the Special Session on Science & Society, entitled 'Plastics: revolution, pollution and substitution', of the 45th FEBS Congress to be held in Ljubljana, Slovenia, on 3-8 July 2021 - describe in detail the consequences of plastic pollution (Bajt, 2021, FEBS Open Bio 11, 954-966), the complex transition to bioplastics (Degli Esposti et al., 2021, FEBS Open Bio 11, 967-983) and the possibility to obtain these innovative biodegradable materials from food and marine waste (Debeaufort 2021, FEBS Open Bio 11, 984-998), respectively. This introductory commentary highlights that, in the frame of the bioeconomy paradigm, not only multidisciplinary but also inter- and transdisciplinary research with integrated and multifaceted approaches are needed to produce novel eco-friendly materials with features similar to those of traditional plastics, as well as with acceptable economic and environmental impact.