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Cancer is a leading cause of death worldwide with a huge societal and economic impact. Clinically effective and less expensive anticancer agents derived from natural sources can help to overcome limitations and negative side effects of chemotherapy and radiotherapy. Previously, we showed that the extracellular carbohydrate polymer of a Synechocystis ΔsigF overproducing mutant displayed a strong antitumor activity towards several human tumor cell lines, by inducing high levels of apoptosis through p53 and caspase-3 activation. Here, the ΔsigF polymer was manipulated to obtain variants that were tested in a human melanoma (Mewo) cell line. Our results demonstrated that high molecular mass fractions were important for the polymer bioactivity, and that the reduction of the peptide content generated a variant with enhanced in vitro antitumor activity. This variant, and the original ΔsigF polymer, were further tested in vivo using the chick chorioallantoic membrane (CAM) assay. Both polymers significantly decreased xenografted CAM tumor growth and affected tumor morphology, by promoting less compact tumors, validating their antitumor potential in vivo. This work contributes with strategies for the design and testing tailored cyanobacterial extracellular polymers and further strengths the relevance of evaluating this type of polymers for biotechnological/biomedical applications.

Biocrusts provide numerous ecological functions in drylands. Recovering biocrusts via cyanobacterial inoculation recently gathered interest for ecological restoration, yet it still lacks long-term experiments to unravel biocrust community dynamics. To examine how cyanobacterial inoculants influenced local microbial community and biocrust development, we observed a 2 km2 (Qubqi Desert, China) inoculation experiment after 10 and 15 years, following biocrust formation. Our results revealed that biocrust development was in line with ecological regime shift, providing evidence for biocrust community succession, from cyanobacteria- to moss-dominated types. Associated with biocrust development, microbial communities differed significantly with less specialists compared to shifting sands. Cyanobacterial community analysis showed that Microcoleus vaginatus and Scytonema javanicum are an ideal inoculating model, as they were still dominating the community after 15 years since inoculation, while other nitrogen-fixing cyanobacteria occurred profusely with biocrust development. Biocrust community composition combined with thickness, Chl-a and exopolysaccharide measurements revealed the large variation of cyanobacterial ecological functions along biocrust development, suggesting a main function shift: from carbon fixation associated with exopolysaccharide secretion in bare sandy soils to nitrogen fixation in developed biocrusts. This large-scale field study verifies that cyanobacterial inoculation accelerates biocrust development and forwards succession, shaping the biocrust community composition over a long time.

A novel method was developed for virus-like particle (VLP) extraction and characterization from biological soil crust (BSC) after microbial community reactivation. The method consisted of a single cell analysis by flow cytometry to monitor viable cells in BSC reactivated under controlled hydration, temperature, and light/dark exposure. Then, VLPs were extracted from reactivated BSCs, followed by viral DNA extraction and shotgun metagenomic analysis. The hydrated BSC under light/dark conditions showed the highest number of viable cells, and this condition was optimal for VLPs isolation. Taxonomic composition showed that families of the order of Caudovirales (Podoviridae, Myoviridae and Syphoviridiae) were the most abundant double strand DNA phages while Microviridiae were the most abundant single strand DNA phages. The isolated VLPs also carried sequences of relevant bacterial inhabiting soil. The functional categories of “phages, prophages, transposable elements, plasmids” and “clustering-base subsystem” were abundant (38 and 12%, respectively). All these data suggest viral predation as a key factor in shaping and maintaining bacterial diversity in the BSCs.

BACKGROUND: Purple Queen® is an early ripening pomegranate cultivar growing well in soilless cultivation. Substrates have direct effects on plant development and, due to progressive peatland exhaustion, the request for new materials for plant growth is high. OBJECTIVE: The objective of this work was to verify the effects of a new potential substrate obtained from the remediation of marine port sediments on the nutraceutical profile of Purple Queen® fruits, using 50% and 100% of reclaimed sediment. METHODS: The study was carried out determining ellagitannins and polysaccharides obtained from peel after decoction, and anthocyanins in aril juice on fruits from two agronomic seasons. RESULTS: The presence of 100% of the sediment had a partial detrimental effect on fruits size and weight. Compared to a peat-based commercial substrate (control), remediated sediment preserved ellagitannin content and increased the anthocyanin amount (up to 40% higher) and polysaccharide content up to 34% on dry fruit. High molecular weight polysaccharides (>2000 kDa) were identified in all the fruits with glucose and galacturonic acid as the major sugars. CONCLUSIONS: Fruits from plants cultivated only on sediment or in a mixture with 50% of peat showed significant increases of bioactive compounds as stress response in two consecutive seasons.

In the scenario of alarming increase in greenhouse and toxic gas emissions from the burning of conventional fuels, it is high time that the population drifts towards alternative fuel usage to obviate pollution. Hydrogen is an environment-friendly biofuel with high energy content. Several production methods exist to produce hydrogen, but the least energy intensive processes are the fermentative biohydrogen techniques. Dark fermentative biohydrogen production (DFBHP) is a value-added, less energy-consuming process to generate biohydrogen. In this process, biohydrogen can be produced from sugars as well as complex substrates that are generally considered as organic waste. Yet, the process is constrained by many factors such as low hydrogen yield, incomplete conversion of substrates, accumulation of volatile fatty acids which lead to the drop of the system pH resulting in hindered growth and hydrogen production by the bacteria. To circumvent these drawbacks, researchers have come up with several strategies that improve the yield of DFBHP process. These strategies can be classified as preliminary methodologies concerned with the process optimization and the latter that deals with pretreatment of substrate and seed sludge, bioaugmentation, co-culture of bacteria, supplementation of additives, bioreactor design considerations, metabolic engineering, nanotechnology, immobilization of bacteria, etc. This review sums up some of the improvement techniques that profoundly enhance the biohydrogen productivity in a DFBHP process.

Therapeutic thermal mud produced by spas of the Euganean Thermal District (Italy) is used as a treatment for arthro-rheumatic diseases. Its production involves the growth of a specific microbiota embedded in a polysaccharidic matrix. Polysaccharides (Microbial-PolySaccharides, M-PS) released in the mud by the resident microorganisms were extracted and analyzed. The monosaccharidic composition analysis showed the presence of galacturonic acid, mannose, xylose, ribose and glucose and a high percentage of sulfated groups in the polymers. To assess their involvement in the therapeutic efficacy of the mud, the M-PS were tested using the model organism zebrafish (Danio rerio). The anti-inflammatory and antioxidant activities were evaluated after confirming the lack of toxic effects during development. Inflammatory state was induced chemically with copper sulfate, or through tail fin amputation procedure and UVB exposure. Recovery from inflammatory condition after exposure to M-PS was always observed with specific morphometric analyses, and further supported by qPCR. Genes linked with the inflammatory and oxidative stress response were investigated confirming the M-PS treatment's efficacy.

Cyanobacteria can cope with various environmental stressors, due to the excretion of exopolysaccharides (EPS). However, little is known about how the composition of these polymers may change according to water availability. This work aimed at characterizing the EPS of Phormidium ambiguum (Oscillatoriales; Oscillatoriaceae) and Leptolyngbya ohadii (Pseudanabaenales; Leptolyngbyaceae), when grown as biocrusts and biofilms, subject to water deprivation. The following EPS fractions were quantified and characterized: soluble (loosely bound, LB) and condensed (tightly bound, TB) for biocrusts, released (RPS), and sheathed in P. ambiguum and glycocalyx (G-EPS) in L. ohadii for biofilms. For both cyanobacteria upon water deprivation, glucose was the main monosaccharide present and the amount of TB-EPS resulted was significantly higher, confirming its importance in these soil-based formations. Different profiles of monosaccharides composing the EPSs were observed, as for example the higher concentration of deoxysugars observed in biocrusts compared to biofilms, demonstrating the plasticity of the cells to modify EPS composition as a response to different stresses. For both cyanobacteria, both in biofilms and biocrusts, water deprivation induced the production of simpler carbohydrates, with an increased dominance index of the composing monosaccharides. The results obtained are useful in understanding how these very relevant cyanobacterial species are sensitively modifying the EPS secreted when subject to water deprivation and could lead to consider them as suitable inoculants in degraded soils.

Arthrospira platensis is a cyanobacterium known for its widespread use as nutraceutical and food additive. Besides a high protein content, this microorganism is also endowed with several bioactivities related to health benefits in humans that make it a candidate for functional foods. These properties are strain and culture condition dependent. We compared, in terms of biomass productivity and protein, C-phycocyanin, and polysaccharide content, two A. platensis strains, A. platensis F&M-C256 and A. platensis F&M-C260, characterized by morphological differences. The organisms were grown in annular photobioreactors with light-emitting diodes (LED) as light source in fed-batch and semi-continuous regimes. No significant differences in biomass productivity were found between the two strains. Both strains showed a protein content >55% in all culture conditions. C-phycocyanin content was higher in A. platensis F&M-C260 in semi-continuous regime. Cellular polysaccharide (PS) content, which included intracellular polysaccharide and those bound to the cell wall, was higher in A. platensis F&M-C256 during semi-continuous cultivation. In both strains, a higher release of polysaccharide was observed at the end of the fed-batch regime. A. platensis F&M-C256 showed the advantage to form clumps which facilitate harvesting, behavior not observed in A. platensis F&M-C260 and probably related to the different predominant monosaccharide found in the PS of the two strains (i.e., rhamnose in A. platensis F&M-C256 and glucose in A. platensis F&M-C260). The results show that the two strains are suitable for commercial production of high-value products, such as protein and C-phycocyanin, while for polysaccharide production, A. platensis F&M-C256 is preferable.

The study analysed polysaccharides and phenolic compounds in widely consumed but little studied date fruits varieties such as Sukkari, Ajwa, Segae, Barrny and Khalas harvested at Tamr stage. The total phenols were in similar amount in the five varieties and ranged from 20 to 50 mg/100 g DW. The decoction and successive centrifugation made it possible to collect two main polysaccharide fractions for all the selected fruits. For each variety the first fraction was more abundant, with a lower swelling capacity and a higher amount of galacturonic acid (28.3% to 40.1%). The second fraction was only soluble in alkaline solution, with an average galacturonic acid content of only 17%. The different structure of the two polysaccharide fractions was also confirmed by the composition in neutral sugars and the degrees of methylation and acetylation. The proposed extraction procedure could be applied for larger scale extraction of the date fruit polysaccharides.

Polysaccharides from pomegranate peel (Wonderful and Purple Queen® varieties) were extracted by hot water and fractionated using ethanol. Three fractions (F1-F2-F3) were obtained for each sample. Polysaccharides' yield was higher for Purple Queen®: 13% dw. Polysaccharides of the three fractions were characterized by size exclusion chromatography (SEC), dynamic light scattering (DLS)

An intricate set of interactions characterizes marine ecosystems. One of the most important is represented by the so-called microbial loop, which includes the exchange of dissolved organic matter (DOM) from phototrophic organisms to heterotrophic bacteria. Here, it can be used as the major carbon and energy source. Arguably, this interaction is one of the foundations of the entire ocean food-web. Carbon fixed by phytoplankton can be redirected to bacterial cells in two main ways; either i) bacteria feed on dead (eventually lysed) phytoplankton cells or ii) DOM is actively released by phytoplankton cells (a widespread process that may result in up to 50% of the fixed carbon leaving the cell). In this work, we have set up a co-culture of the model diatom Phaeodactylum tricornutum and the model chemoheterotrophic bacterium Pseudoalteromonas haloplanktis TAC125 and used this system to study the interactions between these two representatives of the microbial loop. We show that the bacterium can indeed thrive on diatom-derived carbon and that this growth can be sustained by both diatom dead cells and diatom-released compounds. These observations were formalized in a network of putative interactions between P. tricornutum and P. haloplanktis and implemented in a mathematical model that reproduces the observed co-culture dynamics, suggesting that our hypotheses on the interactions occurring in this two-player system can accurately explain the experimental data.

Interactions amongst marine microalgae and heterotrophic bacteria drive processes underlying major biogeochemical cycles and are important for many artificial systems. These dynamic and complex interactions span the range from cooperative to competitive, and it is the diverse and intricate networks of metabolites and chemical mediators that are predicted to principally dictate the nature of the relationship at any point in time. Recent advances in technologies to identify, analyze, and quantify metabolites have allowed for a comprehensive view of the molecules available for exchange and/or reflective of organismal interactions, setting the stage for development of mechanistic understanding of these systems. Here, we (i) review the current knowledge landscape of microalgal–bacterial interactions by focusing on metabolomic studies of selected, simplified model systems; (ii) describe the state of the field of metabolomics, with specific focus on techniques and approaches developed for microalga–bacterial interaction studies; and (iii) outline the main approaches for development of mathematical models of these interacting systems, which collectively have the power to enhance interpretation of experimental data and generate novel testable hypotheses. We share the viewpoint that a comprehensive and integrated series of -omics approaches that include theoretical formulations are necessary to develop predictive and mechanistic understanding of these biological entities.

The induction of biocrusts through inoculation-based techniques has gained increasing scientific attention in the last 2 decades due to its potential to address issues related to soil degradation and desertification. The technology has shown the most rapid advances in the use of biocrust organisms, particularly cyanobacteria and mosses, as inoculants and biocrust initiators. Cyanobacteria and mosses are poikilohydric organisms – i.e., desiccation-tolerant organisms capable of reactivating their metabolism upon rehydration – that can settle on bare soils in abiotically stressing habitats, provided that selected species are used and an appropriate and customized protocol is applied. The success of inoculation of cyanobacteria and mosses depends on the inoculant's physiology, but also on the ability of the practitioner to identify and control, with appropriate technical approaches in each case study, those environmental factors that most influence the inoculant settlement and its ability to develop biocrusts. This review illustrates the current knowledge and results of biocrust induction biotechnologies that use cyanobacteria or mosses as inoculants. At the same time, this review's purpose is to highlight the current technological gaps that hinder an efficient application of the technology in the field.

The Euganean Thermal District (Italy) represents the oldest and largest thermal center in Europe, and its therapeutic mud is considered a unique product whose beneficial effects have been documented since Ancient Roman times. Mud properties depend on the heat and electrolytes of the thermal water, as well as on the bioactive molecules produced by its biotic component, mainly represented by cyanobacteria. The investigation of the healing effects of compounds produced by the Euganean cyanobacteria represents an important goal for scientific validation of Euganean mud therapies and for the discovering of new health beneficial biomolecules. In this work, we evaluated the therapeutic potential of exopolysaccharides (EPS) produced by Phormidium sp. ETS05, the most abundant cyanobacterium of the Euganean mud. Specifically, Phormidium EPS resulted in exerting anti-inflammatory and pro-resolution activities in chemical and injury-induced zebrafish inflammation models as demonstrated using specific transgenic zebrafish lines and morphometric and expression analyses. Moreover, in vivo and in vitro tests showed no toxicity at all for the EPS concentrations tested. The results suggest that these EPS, with their combined anti-inflammatory and pro-resolution activities, could be one of the most important therapeutic molecules present in the Euganean mud and confirm the potential of these treatments for chronic inflammatory disease recovery.

The extracellular polysaccharides produced by cyanobacteria have distinctive characteristics that make them promising for applications ranging from bioremediation to biomedicine. In this study, a sulfated polysaccharide produced by a marine cyanobacterial strain and named cyanoflan was characterized in terms of morphology, chemical composition, and rheological and emulsifying properties. Cyanoflan has a 71 % carbohydrate content, with 11 % of sulfated residues, while the protein account for 4 % of dry weight. The glycosidic-substitution analysis revealed a highly branched complex chemical structure with a large number of sugar residues. The cyanoflan high molecular mass fractions (above 1 MDa) and entangled structure is consistent with its high apparent viscosity in aqueous solutions and high emulsifying activity. It showed to be a typical non-Newtonian fluid with pseudoplastic behavior. Altogether, these results confirm that cyanoflan is a versatile carbohydrate polymer that can be used in different biotechnological applications, such as emulsifying/thickening agent in food or cosmetic industries. published

One third of the World's entire food production is lost or wasted every year. Biohydrogen production offers a possibility to re-use this resource; in particular, bread and bakery products wastes, due to their composition (up to 70% of carbohydrates, mostly starch), represent an appropriate source of nutrients for microorganisms. The aim of this work was to convert bread wastes into hydrogen with a sequential system composed of lactic fermentation and photofermentation, with a minimum number of treatments to the substrate. The best results were provided by Lactobacillus amylovorus DSM 20532, followed by photofermentation by Rhodopseudomonas palustris 42OL, supplemented with ferric citrate and magnesium sulfate. The process led to 3.1 mol H2 mol−1 glucose, among the highest yields obtained on starch containing substrates, with an energy recovery of 54 MJ t−1 dry waste. This study promotes the re-use of energy-containing food wastes for improving circular economy.

Cyanobacteria are widespread prokaryotic organisms that represent feasible biotechnological tools to set up valid approaches to counteract desertification. Their peculiar physiological traits, and their resilience to abiotic stresses, allow their application on abiotically constrained soils to trigger their stabilization. A successful cyanobacteria inoculation results in the formation of cyanobacterial biocrusts, complex microbial communities characterized by tangled filament meshes imbued in a matrix of self-secreted extracellular polysaccharides (EPS) that keep loose sediments and aggregates firmly in place. However, the capability to form stable cyanobacterial biocrusts is not common to all the species, and a mix of factors can hamper the process, notably inoculum amount, and substrate characteristics. The aim of this work was to assess the influence of inoculum quantity and substrate granulometry on the physical stability of cyanobacterial biocrusts induced by inoculating the strain Leptolyngbya ohadii in a microcosm experiment, under laboratory conditions. After applying three different initial inoculum amounts on two different sand granulometries (medium and coarse sand), we assayed aggregate stability, physical stability and surface hydrophobicity on the resulting biocrusts during a 30-day incubation. Also, the features and the role of the EPS synthesized by L. ohadii were studied following their isolation, characterization, and direct application on the sand. The two EPS fractions produced by the strain, one more soluble and easily released in the surrounding medium (released polysaccharides, RPS) and one solidly attached to the filaments (glycocalyx EPS, G-EPS), were separately tested. Cyanobacterial biocrusts visibly formed in all the microcosms after 15 days. However, we observed a strong effect of sand granulometry in affecting aggregate stability and tensile strength, both of which appeared weaker on coarse sand. A higher amount of initial inoculum was necessary to produce stable biocrusts on coarse sand compared to medium sand. Also, we observed how the inoculation of EPS alone did not sort most of the significant effects that we detected by inoculating the whole culture, pointing at the importance of the action of the cyanobacterial filaments in soil conglomeration. However, a significant increase in physical stability was achieved by inoculating G-EPS on medium sand, suggesting the involvement of this fraction in biocrusts structuration. This work analyzes for the first time the effects of the variable grain size and inoculum amount in the achievement of physically stable biocrusts by cyanobacteria inoculation. The results that we obtained are useful in improving and optimizing the process of biomass preparation and dispersion for future indoor and outdoor studies.

Cyanobacterial extracellular carbohydrate polymers are particularly attractive for biotechnological applications. Previously, we determined the monosaccharidic composition of the polymer of a Synechocystis ΔsigF overproducing mutant. Here, we further characterized this polymer, demonstrated that it is possible to recover it in high yields, and successfully use it for biomedical research. This amorphous polymer is formed by a mesh of fibrils/lamellar structures with high porosity, is constituted by high molecular mass fractions, is highly sulfated and displays low viscosity, even in highly concentrated aqueous solutions. FTIR analysis confirmed the presence of several functional groups. We demonstrated that the ΔsigF polymer has strong biological activity, decreasing the viability of melanoma, thyroid and ovary carcinoma cells by inducing high levels of apoptosis, through p53 and caspase-3 activation. Therefore, the ΔsigF Synechocystis mutant is a promising platform for the sustainable production of biological active carbohydrate polymer(s) with the desired characteristics for biomedical applications.

Cyanobacteria inoculation to promote biocrust formation and improve soil properties has shown positive results in indoor studies, but limited success when applied under field conditions. Successful results of application of this technology in the field have been only found in desert sand dunes in China. Therefore, further development of this technique is necessary to extend its applicability to other soil types and regions. In this study, we inoculated a consortium of three N-fixing native cyanobacteria (Nostoc commune, Scytonema hyalinum and Tolypothrix distorta) on degraded soils from three semiarid study sites in south-eastern Spain with differing soil properties and soil development. After two years, chlorophyll a spectral absorption and albedo in inoculated and control plots were similar. Consequently, a second experiment was conducted to test the effectiveness of progressive cyanobacterial preacclimation before inoculation as well as the use of habitat amelioration techniques, consisting of covering the inoculated soils with a vegetal fiber mesh or a plastic grid, to improve cyanobacteria performance. Our results showed that: 1) hardening these cyanobacterial strains did not enhance their colonization capability, and 2) covering inoculated soils with a vegetal mesh did promote soil colonization by cyanobacteria, as shown by higher chlorophyll a soil content and Chla spectral absorption and lower albedo than in the uncovered plots. Moreover, it promoted the presence of more condensed, tightly-bound exopolysaccharides (EPS) and higher molecular weight molecules in the more soluble loosely-bound EPS fraction, both of which could be involved in the improvement of soil aggregation. Finally, higher abundance of xylose and galactose was also found in this treatment, likely indicating a greater development of the induced biocrusts. The results of this study show that direct soil inoculation with cyanobacteria, whether subjected to desiccation hardening or not, did not promote the artificial formation of biocrusts in the field. However, more positive results were found when the inoculated soils were covered with a vegetal mesh to help cyanobacteria cope with abiotic stress and soil erosion. Therefore, developing diversified efficient habitat amelioration strategies might be key in the successful application of this restoration technique in the field.

Aim of this study was to evaluate the suitability of ensiled giant reed, ensiled maize, ensiled olive pomace, wheat bran for combined systems (CS: dark fermentation + anaerobic digestion (AD)) producing hydrogen-rich biogas (biohythane), tested in batch under basic operational conditions (mesophilic temperatures, no pH control). Substrates were also analyzed under a single stage AD batch test, in order to investigate the effects of DF on estimated energy recovery (ER) in combined systems. In CS, maize and wheat bran exhibited the highest hydrogen potential (13.8 and 18.9 NL kgVS (1)) and wheat bran the highest methane potential (243.5 NL kgVS (1)). In one-stage AD, giant reed, maize and wheat bran showed the highest methane production (239.5, 267.3 and 260.0 NL kgVS (1)). Butyrate/acetate ratio properly described the dark fermentation, correlating with hydrogen production (r = 0.92). Wheat bran proved to be a promising residue for CS in terms of hydrogen/methane potential and ER. (C) 2016 Elsevier Ltd. All rights reserved.

Biological Soil Crusts (BSCs) represent an important part of the living cover in drylands worldwide. BCSs change soil hydrology due to extracellular polymeric substances (EPS)-excreting species of cyanobacteria, dominant members of dryland-BSCs. The presence of EPS allowed matric potential (Ψm) to remain unchanged down to 20% water content, whereas, without EPS, Ψm started decreasing at 80% water content. The EPS matrix improved the water retaining capacity of soil, suggesting that BSCs would delay onset of restrictive matric potential values due to its larger water holding capacity.

Hydrogen represents a possible alternative energy carrier to face the growing request for energy and the shortage of fossil fuels. Photofermentation for the production of H2 constitutes a promising way for integrating the production of energy with waste treatments. Many wastes are characterized by high salinity, and polluted seawater can as well be considered as a substrate. Moreover, the application of seawater for bacterial culturing is considered cost-effective. The aims of this study were to assess the capability of the metabolically versatile freshwater Rhodopseudomonas palustris 42OL of producing hydrogen on salt-containing substrates and to investigate its salt stress response strategy, never described before. R. palustris 42OL was able to produce hydrogen in media containing up to 3 % added salt concentration and to grow in media containing up to 4.5 % salinity without the addition of exogenous osmoprotectants. While the hydrogen production performances in absence of sea salts were higher than in their presence, there was no significant difference in performances between 1 and 2 % of added sea salts. Nitrogenase expression levels indicated that the enzyme was not directly inhibited during salt stress, but a regulation of its expression may have occurred in response to salt concentration increase. During cell growth and hydrogen production in the presence of salts, trehalose was accumulated as a compatible solute; it protected the enzymatic functionality against salt stress, thus allowing hydrogen production. The possibility of producing hydrogen on salt-containing substrates widens the range of wastes that can be efficiently used in production processes.

Aims Aim of the paper was to assess the feasibility of producing hydrogen as a biofuel by photofermentation of fermented water lettuce (Pistia stratiotes L.) waste biomass, after a nitrogen-stripping treatment. Methods and Results A natural (42OL) and an engineered strain (CGA676, with low-ammonium sensitivity) of Rhodopseudomonas palustris were used for producing hydrogen. The stripping procedure was highly effective for ammonium removal, with an acceptable selectivity (91% of ammonium was removed; only 14% of total organic acids were lost). Both strains were able to produce hydrogen only in the nitrogen-stripped substrate. The natural strain R.palustris 42OL showed a higher Biochemical Hydrogen Potential (1224 mL L−1 vs 720 mL L−1; 50.0 mol m−3 vs 29.4 mol m−3), but at a lower rate (5.6 mL L−1 h−1 vs 7.3 mL L−1 h−1; 0.23 mol m−3 h−1 vs 0.29 mol m−3 h−1) than strain CGA676. Conclusions Water lettuce waste biomass can be used for biofuel production, after hydrolization, fermentation and nitrogen stripping. Impact of the study The investigation on novel, low cost and sustainable biomasses as feedstocks for biofuel production is a priority. Aquatic plants do not compete for arable land. Moreover, water lettuce is a floating and invasive weed, thus its biomass must be harvested when detrimental, and can now be biotransformed in clean hydrogen. This article is protected by copyright. All rights reserved.

H 2 is a clean, renewable and energy-efficient fuel. However, in order for it to be a fuel effectively utilizable at an industrial level, key issues about its economically and environmentally sustainable production have still to be solved. Microbial hydrogen production is a process with a low environmental impact and, among microbial processes, photofermentation is considered a promising and sustainable solution. However, the energy input for the biological processes is still higher than the energy output in the form of H 2 gas. One possibility for improving this ratio is to increase the efficiency of the process while at the same time reducing electricity consumption, both of which relate to the issue of an optimal photobioreactor design. This review focuses on recent advances made in photobioreactor design towards higher light conversion efficiency, a greater hydrogen production rate and substrate conversion in hydrogen production processes carried out with purple non sulfur bacteria, giving particular attention to the light source and to illumination protocols. Recent achievements in outdoor hydrogen production in large scale photobioreactors are also reviewed.

Polylactic acid (PLA), a bioplastic synthesized from lactic acid, has a broad range of applications owing to its excellent proprieties such as a high melting point, good mechanical strength, transparency, and ease of fabrication. However, the safe disposal of PLA is an emerging environmental problem: it resists microbial attack in environmental conditions, and the frequency of PLA-degrading microorganisms in soil is very low. To date, a limited number of PLA-degrading bacteria have been isolated, and most are actinomycetes. In this work, a method for the selection of rare actinomycetes with extracellular proteolytic activity was established, and the technique was used to isolate four mesophilic actinomycetes with the ability to degrade emulsified PLA in agar plates. All four strains&mdash, designated SO1.1, SO1.2, SNC, and SST&mdash, belong to the genus Amycolatopsis. The PLA-degrading capability of the four strains was investigated by testing their ability to assimilate lactic acid, fragment PLA polymers, and deteriorate PLA films. The strain SNC was the best PLA degrader&mdash, it was able to assimilate lactic acid, constitutively cleave PLA, and form a thick and widespread biofilm on PLA film. The activity of this strain extensively eroded the polymer, leading to a weight loss of 36% in one month in mesophilic conditions.

During the last few years, progress has been made in developing cleaner and more efficient bioenergy producing systems. Innovative processes and novel substrates were assessed at lab scale, in order to investigate and promote a sustainable development of photobiological hydrogen production. Recent and innovative processes and the use of novel substrates are discussed in this chapter. The main focus is on photofermentation systems conducted on biomass derived substrates, as these are considered to be the applicative goal of hydrogen production. Indeed, it is also present a short excursus on some synthetic media, investigated as interesting opportunities for enlarging applicability of the hydrogen technology. The number of new findings here reported demonstrates that it is worth continuing the efforts for increasing the knowledge on the photofermentation process for H2 production, in particular owing to the need of reducing the use of fossil fuels for mitigating the emissions of GHG in the atmosphere.

The ability of Rhodopseudomonas palustris cells to rapidly acclimate to high light irradiance is an essential issue when cells are grown under sunlight. The aim of this study was to investigate the photo-acclimation process in Rhodopseudomonas palustris 42OL under different culturing conditions: (i) anaerobic (AnG), (ii) aerobic (AG), and (iii) under H2-producing (HP) conditions both at low (LL) and high light (HL) irradiances. The results obtained clearly showed that the photosynthetic unit was significantly affected by the light irradiance at which Rp. palustris 42OL was grown. The synthesis of carotenoids was affected by both illumination and culturing conditions. At LL, lycopene was the main carotenoid synthetized under all conditions tested, while at HL under HP conditions, it resulted the predominant carotenoid. Oppositely, under AnG and AG at HL, rhodovibrin was the major carotenoid detected. The increase in light intensity produced a deeper variation in light-harvesting complexes (LHC) ratio. These findings are important for understanding the ecological distribution of PNSB in natural environments, mostly characterized by high light intensities, and for its growth outdoors.

The main crude polysaccharides (CPS), extracted from two widely cultivated pomegranate varieties, Laffan and Wonderful, were studied and characterized. We obtained the highest CPS extraction yield (approximatively 10% w/w on dried matter) by 1h of decoction (ratio 1/40w/v). The predominant polymers (75–80%) of the CPS samples showed a hydrodynamic volume close to 2000kDa by size exclusion chromatography and the exocarp and mesocarp profiles were very similar. The proton spectra (1H NMR), according to sugar composition and gelling ability, confirmed the main polysaccharide fractions were pectin with different acylation and methylation degree. The CPS from Laffan and Wonderful mesocarp showed prebiotic properties in vitro with Lactobacillus and Bifidobacterium strains. The composition of the decoction (12% ellagitannins and 10% of CPS) obtained by a green extraction process of pomegranate by-products, makes it a suitable component of functional food formulations.

The present study was aimed at assessing the biotransformation of dark fermented agroindustrial residues and energy crops for the production of hydrogen and poly-β-hydroxybutyrate (PHB), in lab-scale photofermentation. The investigation on novel substrates for photofermentation is needed in order to enlarge the range of sustainable feedstocks. Dark fermentation effluents of ensiled maize, ensiled giant reed, ensiled olive pomace, and wheat bran were inoculated with Rhodopseudomonas palustris CGA676, a mutant strain suitable for hydrogen production in ammonium-rich media. The highest hydrogen producing performances were observed in wheat bran and maize effluents (648.6 and 320.3mLL(-1), respectively), both characterized by high initial volatile fatty acids (VFAs) concentrations. Giant reed and olive pomace effluents led to poor hydrogen production due to low initial VFAs concentrations, as the original substrates are rich in fiber. The highest PHB content was accumulated in olive pomace effluent (11.53%TS), ascribable to magnesium deficiency.

Research on photobiological H2 production processes is pointing towards the use of low cost substrates as sources of reduced carbon for H2 generation. Those substrates (either wastewaters or effluents derived from other fermentation processes) are often rich not only in carbon, but also in fixed nitrogen. NH 4 + is an inhibitor of nitrogenase-mediated H2 production in purple non sulfur bacteria. A Rhodopseudomonas palustris mutant strain (NifA*), which constitutively expresses nitrogenase genes, was utilized in order to test the use of NH 4 + containing fermentation products for photobiological production of H2. The strain was grown on both synthetic and waste-derived NH 4 + containing media. The nifA* mutant produced H2 in the presence of high concentrations of NH 4 + , both in a synthetic medium and in a real vegetable waste-derived medium resulting in higher H2 levels than the wild-type strain. Thus, this study demonstrates that the NifA* strain is well suited to overcome the effects of inhibitory naturally occurring NH 4 + as it converts agricultural waste into biofuel.

Seventeen purple non-sulfur bacterial strains, isolated from the trophic lake Averno, Naples, Italy, were phylogenetically classified and their H2-producing performances were tested utilizing various synthetic substrates and the fermentation broth derived from the spontaneous fermentation of vegetable residues. All the strains showed the capability to produce hydrogen on at least one of the four carbon substrates tested (malic, lactic, acetic and succinic acid). On lactate, Rhodopseudomonas palustris strain AV33 showed the best maximum production rate (50.7 ± 2.6 mL (H2) L−1 h−1), with a mean rate, calculated on the whole period of production, of 17.9 mL ± 0.7 (H2) L−1 h−1. In the presence of acetate, AV33 produced only few mL of H2, but intracellularly accumulated poly-β-hydroxybutyrate up to a concentration of 21.4 ± 3.4% (w/w) of cell dry weight. Rp. palustris AV33 also produced H2 on the fermentation broth supplemented with Fe, with a maximum production rate of 16.4 ± 2.3 mL (H2) L−1 h−1 and a conversion yield of 44.2%.

The ability of coping with the damaging effects of high light intensity represents an essential issue when purple non-sulfur bacteria (PNSB) are grown under direct sunlight for photobiological hydrogen production. This study was aimed at investigating whether H2 photo-evolution could represent, for Rhodopseudomonas palustris 42OL, a safety valve to dissipate an excess of reducing power generated under high light intensities. The physiological status of this strain was assessed under anaerobic (AnG) and aerobic (AG) growing conditions and under H2-producing (HP) conditions at low and high light intensities. The results obtained clearly showed that Fv/Fm ratio was significantly affected by the light intensity under which R. palustris 42OL cells were grown, under either AnG or AG conditions, while, under HP, it constantly remained at its highest value. The increase in light intensity significantly increased the H2 production rate, which showed a positive correlation with the maximum electron transfer rate (rETRmax). These findings are important for optimization of hydrogen production by PNSB under solar light.

Access to publishers version: http://dx.doi.org/10.1016/j.ejpb.2015.06.013 To date the effectiveness of antibiotics is undermined by microbial resistance, threatening public health worldwide. Enhancing the efficacy of the current antibiotic arsenal is an alternative strategy. The administration of antimicrobials encapsulated in nanocarriers, such as liposomes, is considered a viable option, though with some drawbacks related to limited affinity between conventional liposomes and bacterial membranes. Here we propose a novel ‘‘top-down’’ procedure to prepare unconventional liposomes from the membranes of prokaryotes (PD-liposomes). These vectors, being obtained from bacteria with limited growth requirements, also represent low-cost systems for scalable biotechnology production. In depth physico-chemical characterization, carried out with dynamic light scattering (DLS) and Small Angle X-ray Scattering (SAXS), indicated that PD-liposomes can be suitable for the employment as antibiotic vectors. Specifically, DLS showed that the mean diameter of loaded liposomes was 200–300 nm, while SAXS showed that the structure was similar to conventional liposomes, thus allowing a direct comparison with more standard liposomal formulations. Compared to free penicillin G, PD-liposomes loaded with penicillin G showed minimal inhibitory concentrations against E. coli that were up to 16-times lower. Noteworthy, the extent of the bacterial growth inhibition was found to depend on the microorganisms from which liposomes were derived.

Two-stage process based on photofermentation of dark fermentation effluents is widely recognized as the most effective method for biological production of hydrogen from organic substrates. Recently, it was described an alternative mechanism, named capnophilic lactic fermentation, for sugar fermentation by the hyperthermophilic bacterium Thermotoga neapolitana in CO2-rich atmosphere. Here, we report the first application of this novel process to two-stage biological production of hydrogen. The microbial system based on T. neapolitana DSM 4359(T) and Rhodopseudomonas palustris 42OL gave 9.4 mol of hydrogen per mole of glucose consumed during the anaerobic process, which is the best production yield so far reported for conventional two-stage batch cultivations. The improvement of hydrogen yield correlates with the increase in lactic production during capnophilic lactic fermentation and takes also advantage of the introduction of original conditions for culturing both microorganisms in minimal media based on diluted sea water. The use of CO2 during the first step of the combined process establishes a novel strategy for biohydrogen technology. Moreover, this study opens the way to cost reduction and use of salt-rich waste as feedstock.

Light-dependent hydrogen production by purple non sulfur bacteria (PNSB) has been studied for several decades. However the exact route that energy takes from the moment a photon is absorbed to the formation of a molecule of hydrogen is quite complex. The aim of this chapter is to review the researches carried out on the metabolic processes related to hydrogen production in PNSB, in particular stressing the issues related with the efficiency in the conversion of the energy deriving from the light in the energy-rich H2 molecule produced. The metabolic processes that bring form the light capturing to hydrogen production are described, with the relative bottlenecks and hurdles.

The aim of this thesis was to verify the feasibility of the hydrogen production process with purple non sulfur bacteria both under sunlight irradiation in an up-scaled system and with the use of low cost substrates. Among the products offermentations tested the best results were obtained with a medium derived from vegetable wastes. The use of a genetically modified strain of Rhodopseudomonas palustris insensitive to ammonium opened the way towards the use of wastes with attainment of high hydrogen yields also in inhibiting conditions. The experimentation carried out under natural irradiation demonstrated the full feasibility of the process using sunlight instead of artificial light in a semi-pilot reactor: the production rates were the highest so far reported for comparable outdoor systems.

Biological Soil Crusts (BSCs) are complex microbial associations widely distributed in arid and semiarid environments. These microbial associations have recently been acknowledged as important in restoration ecology (Bowker 2007). The primary colonization of cyanobacteria and other crust organisms after events such as fire or cessation of plowing is considered critical for later vascular plant establishment, due to the control of seed germination and due to the complex pathways that BSCs are capable to establish between plants and crust organisms and exudates (Rossi et al. 2013). In a ten year study carried out in the hyper-arid region of Inner Mongolia (China), introduction of man - made BSCs (induced BSCs, IBSCs) proved to be effective in producing a shift of the ecosystem state from high abiotic to low abiotic stress, evidenced by an increase in photothrophic abundance and subshrub cover. The prerequisite for an efficient exploitation of crust organisms as soil colonizers is their capability to secrete large amount of exopolysaccharides (EPS) which are important, among the reasons, as they lead to soil and BSC stabilization and represent a noticeable source of C that can be respired by the crustal community. By these means, a deep chemical and physiological knowledge concerning these exudates is required. Notwithstanding the large amount of literature available, recently thoroughly reviewed by Mager and Thomas (2011), the chemical characteristics of EPS from BSCs, and in particular from IBSCs, have not been investigated yet. We analyzed the monosaccharidic composition and the molecular weight distribution of two EPS fractions, the more soluble fraction and the fraction more tightly bound to cells, extracted from IBSCs collected in the Inner Mongolian desert, inoculated in different years (namely 4, 6 and 8 years before the sampling), thus characterized by different developmental stages. We thereafter investigated the degradation processes involving EPS, assessing the activity of two key enzymes for sugar degradation: dehydrogenase and sucrase. The results obtained demonstrated a high complexity in terms of monosaccharidic composition and molecular weight, the latter resulting differently distributed between the two fractions. Enzymatic activity resulted mainly directed to the more soluble, low - molecular weight carbohydrates. The data presented represent a first study of the biochemical processes involving carbon from EPS released by IBSCs on bare substrates after the colonization of soils by the inoculated cyanobacteria.

The development of biological soil crusts (BSCs) is widely recognized as beneficial to soil fertility due to their contribution to the stabilization of soils and to the increase in their carbon and moisture content. An important role in these processes is played by the extracellular polysaccharidic (EPS) matrix embedding microbial cells and soil particles in BSCs. The present study was aimed at investigating the molecular and chemical features of the EPSs and the degradation processes of the polysaccharidic matrix (i.e. dehy-drogenase and sucrase activities) in induced biological soil crusts (IBSCs) of different ages displayed within an investigation area in Hobq Desert (Dalatequi County, Inner Mongolia, China). Two operationally defined EPS fractions, the colloidal (C-EPS) and the EDTA extractable (tightly bound, TB-EPS) fractions, were analyzed. In BSCs, C-EPSs are loosely bound to cells and sediments while TB-EPSsare tightly bound to the crustal biotic and abiotic constituents of the crusts. In this study, the C-EPSand TB-EPS fractions extracted from the IBSCs of different age (4-, 6- and 8-years old IBSCs) were foundpresent in comparable amounts but showed marked differences in terms of their molecular size distribution and monosaccharidic composition. C-EPS showed to be mostly constituted by sugar fractions with molecular weight (MW) distributed in the range 2000 e 76 kDa and in the range 64 E 0.34 kDa. Conversely, the TB-EPSs showed to be prominently constituted by one fraction having a MW in the range 2000 e 76 kDa. While the chemical and macromolecular characteristics of TB-EPSs did not show significant changes with the age of the crusts, the older IBSCs showed a lower content of low MW C-EPSs, as well a higher number of different types of monosaccharides constituting the C-EPS. Moving from these results, it can be hypothesized that C-EPSs, which are dispersed in the soil and thus more accessible, have been rather easily degraded by the heterotrophic microorganisms dwelling in mature IBSCs and reduced to low MW carbohydrates that are easily metabolized by chemoheterotrophs. This hypothesis is supported by the higher activity observed in older IBSCs of the two enzymes associated with sugar degradation in the soil, dehydrogenases and sucrases, that is consistent with an increased release of low MW carbohydrates in the crusts. The results obtained suggest that the colloidal fraction of the EPSs, which is more dispersed in the soil, is more easily degradable by the microflora, while the EPS fraction tightly bound to the soil particles, which is characterized by a high MW, plays a key role in giving a structural stability to the crusts and in affecting the hydrological behavior of the soil covered by IBSCs.

Purple bacteria form a heterogeneous group of microorganisms capable of growing under anoxic conditions by anoxygenic photosynthesis. They can be divided into purple nonsulfur bacteria, which are able to grow both phototrophically and in darkness, and purple sulfur bacteria, all of them capable to grow in the light but only few of them in the dark. They are characterized by a remarkable complexity in the metabolism, most of them being able to grow switching from chemotrophy to phototrophy, from organotrophy to litotrophy, and from heterotrophy to autotrophy. In this article, the main electron acceptors and donors involved in the photosynthetic and in the respiratory electron transport chains are described, pointing out the crucial role of the quinone pool for the energetic processes in the cell.