Annarita Poli

Bacterial Exopolysaccharides from Extreme Marine Habitats: Production, Characterization and Biological Activities

Many marine bacteria produce exopolysaccharides (EPS) as a strategy for growth, adhering to solid surfaces, and to survive adverse conditions. There is growing interest in isolating new EPS producing bacteria from marine environments, particularly from extreme marine environments such as deep-sea hydrothermal vents characterized by high pressure and temperature and heavy metal presence. Marine EPS-producing microorganisms have been also isolated from several extreme niches such as the cold marine environments typically of Arctic and Antarctic sea ice, characterized by low temperature and low nutrient concentration, and the hypersaline marine environment found in a wide variety of aquatic and terrestrial ecosystems such as salt lakes and salterns. Most of their EPSs are heteropolysaccharides containing three or four different monosaccharides arranged in groups of 10 or less to form the repeating units. These polymers are often linear with an average molecular weight ranging from 1 × 105 to 3 × 105 Da. Some EPS are neutral macromolecules, but the majority of them are polyanionic for the presence of uronic acids or ketal-linked pyruvate or inorganic residues such as phosphate or sulfate. EPSs, forming a layer surrounding the cell, provide an effective protection against high or low temperature and salinity, or against possible predators. By examining their structure and chemical-physical characteristics it is possible to gain insight into their commercial application, and they are employed in several industries. Indeed EPSs produced by microorganisms from extreme habitats show biotechnological promise ranging from pharmaceutical industries, for their immunomodulatory and antiviral effects, bone regeneration and cicatrizing capacity, to food-processing industries for their peculiar gelling and thickening properties. Moreover, some EPSs are employed as biosurfactants and in detoxification mechanisms of petrochemical oil-polluted areas. The aim of this paper is to give an overview of current knowledge on EPSs produced by marine bacteria including symbiotic marine EPS-producing bacteria isolated from some marine annelid worms that live in extreme niches.

Synthesis, Production, and Biotechnological Applications of Exopolysaccharides and Polyhydroxyalkanoates by Archaea

Extreme environments, generally characterized by atypical temperatures, pH, pressure, salinity, toxicity, and radiation levels, are inhabited by various microorganisms specifically adapted to these particular conditions, called extremophiles. Among these, the microorganisms belonging to the Archaea domain are of significant biotechnological importance as their biopolymers possess unique properties that offer insights into their biology and evolution. Particular attention has been devoted to two main types of biopolymers produced by such peculiar microorganisms, that is, the extracellular polysaccharides (EPSs), considered as a protection against desiccation and predation, and the endocellular polyhydroxyalkanoates (PHAs) that provide an internal reserve of carbon and energy. Here, we report the composition, biosynthesis, and production of EPSs and PHAs by different archaeal species.

The prebiotic source influences the growth, biochemical features and survival under simulated gastrointestinal conditions of the probiotic Lactobacillus acidophilus

The viability of the probiotic strain Lactobacillus acidophilus DSM 20079, after its passage through the simulated gastric and pancreatic juices, was evaluated as function of its pre-growth in a medium containing the known prebiotics pectin or inulin, and was compared to glucose used as control. The presence of pectin or inulin did not affect the growth (12.11(log10) colony forming units/mL and 12.08(log10) colony forming units/mL for pectin and inulin respectively versus 12.22(log10) colony forming units/mL obtained for glucose). Pectin and inulin, in contrast to glucose, induced cell stress resistance against gastrointestinal juices (Δ(log10) 1 and 2 colony forming units/mL respectively, versus Δ(log10) 4.5 for glucose). The data were confirmed by the analysis of the protein pattern following stress treatments which, in the case of microbial cells grown with glucose, revealed a relevant protein degradation after the double passage through simulated gastric and intestinal juices. An impressive metabolic change, as function of the growth conditions, was demonstrated by analyzing the proteomic profile with a μ-2DE system, used herein for the first time as evaluation tool of prebiotic-probiotic interactions. The analysis revealed a different pH protein distribution that was mostly acidic in the presence of pectin and neutral-alkaline in the presence of inulin. Both prebiotics stimulated the production of butyrate, a relevant healthy bio-molecule not detectable in the presence of glucose, that was measured by HPLC analysis to be 14.5 fold higher after growth in the presence of inulin, as compared to pectin. Three specific proteins were detected at pH 6 after growth in the presence of pectin or inulin. They could be correlated to the stress resistance and/or to the production of butyrate, the common phenotypic characteristics induced in the bacterial strain by the two prebiotics.

Polysaccharides from extremophilic microorganisms.

Several marine thermophilic strains were analyzed for exopolysaccharide production. The screening process revealed that a significant number of thermophilic microorganisms were able to produce biopolymers, and some of them also revealed interesting chemical compositions. We have identified four new polysaccharides from thermophilic marine bacteria, with complex primary structures and with different repetitive units: a galacto-mannane type from strain number 4004 and mannane type for the other strains.The thermophilic Bacillus thermantarcticus produces two exocellular polysaccharides (EPS 1, EPS 2) that give the colonies a typical mucous character. The exopolysaccharide fraction was produced with all substrates assayed, although a higher yield 400 mg liter-1 was obtained with mannose as carbon and energy source. NMR spectra confirmed that EPS 1 was a heteropolysaccharide of which the repeating unit was constituted by four different α-D-mannoses and three different β-D-glucoses. It seems to be close to some xantan polymers. EPS 2 was a mannan. Four different α-D-mannoses were found as the repeating unit.Production and chemical studies of biopolymers produced by halophilic archaea, Haloarcula species were also reported.

Fermentation technologies for the optimization of marine microbial exopolysaccharide production.

In the last decades, research has focused on the capabilities of microbes to secrete exopolysaccharides (EPS), because these polymers differ from the commercial ones derived essentially from plants or algae in their numerous valuable qualities. These biopolymers have emerged as new polymeric materials with novel and unique physical characteristics that have found extensive applications. In marine microorganisms the produced EPS provide an instrument to survive in adverse conditions: They are found to envelope the cells by allowing the entrapment of nutrients or the adhesion to solid substrates. Even if the processes of synthesis and release of exopolysaccharides request high-energy investments for the bacterium, these biopolymers permit resistance under extreme environmental conditions. Marine bacteria like Bacillus, Halomonas, Planococcus, Enterobacter, Alteromonas, Pseudoalteromonas, Vibrio, Rhodococcus, Zoogloea but also Archaea as Haloferax and Thermococcus are here described as EPS producers underlining biopolymer hyperproduction, related fermentation strategies including the effects of the chemical composition of the media, the physical parameters of the growth conditions and the genetic and predicted experimental design tools.

Halomonas smyrnensis sp. nov., a moderately halophilic, exopolysaccharide-producing bacterium.

Four Gram-negative, moderately halophilic, exopolysaccharide-producing strains, designated AAD6(T), AAD4, AAD17 and AAD21, were isolated from Çamaltı Saltern Area, a wildlife reserve in Sasalı, İzmir province located in the Aegean Region of Turkey. The isolates grew at an optimum NaCl concentration of 10% (w/v). The major cellular fatty acids were C(16:0), C(18:1)ω7c, C(16:1)ω7c and C(12:0) 3OH, respectively and the predominant lipoquinone was ubiquinone Q-9. The G+C content of the genomic DNA of strains AAD6(T), AAD4, AAD17 and AAD21 was 63.0, 63.3, 62.8 and 62.6 mol %, respectively. Comparative 16S rRNA gene sequence studies showed that the isolates belonged to the genus Halomonas. The DNA-DNA hybridization mean values between the representative strain AAD6(T) and the closely related species Halomonas salina DSM 5928(T), Halomonas halophila DSM 4770(T), Halomonas maura DSM 13445(T), Halomonas organivorans DSM 16226(T), Halomonas elongata DSM 2581(T), Halomonas koreensis JCM 12237(T) and Halomonas nitroreducens LMG 24185, were 40.8, 39.6, 24.2, 23.3, 12.6, 14.5 and 12.2%, respectively. Based on these data the strains represent a novel species of the genus Halomonas for which the name Halomonas smyrnensis sp. nov. is proposed. The type strain is AAD6(T) (= DSM 21644(T) = JCM 15723(T)).

Halobacillus alkaliphilus sp. nov., a halophilic bacterium isolated from a salt lake in Fuente de Piedra, southern Spain

A Gram-positive, spore-forming, halophilic bacterial strain, FP5T, was isolated from a salt lake in southern Spain and subjected to a polyphasic taxonomic study. Strain FP5T was strictly aerobic. Cells were coccoidal, occurring singly or in clusters. The cell-wall peptidoglycan type of strain FP5T was A4 beta based on l-Orn-d-Asp. Strain FP5T was characterized chemotaxonomically by having MK-7 as the major menaquinone and anteiso-C15 : 0, anteiso-C17 : 0, iso-C15 : 0 and iso-C16 : 0 as the main fatty acids. The isolate grew optimally at 37 degrees C and in presence of 10 % NaCl; no growth was observed in the absence of NaCl. The DNA G+C content was 43.5 mol%. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain FP5T falls within the evolutionary radiation of species of the genus Halobacillus. Levels of 16S rRNA gene sequence similarity between strain FP5T and the type strains of nine recognized Halobacillus species were in the range 97.0-99.0 %. Levels of DNA-DNA relatedness indicated that strain FP5T represents a genomic species that is distinct from recognized Halobacillus species. Strain FP5T could be differentiated from recognized Halobacillus species based on several phenotypic characteristics. On the basis of phenotypic, phylogenetic and genomic data, strain FP5T is considered to represent a novel species of the genus Halobacillus, for which the name Halobacillus alkaliphilus sp. nov. is proposed. The type strain is FP5T (=DSM 18525T =ATCC BAA-1361T).

Exopolysaccharide production by a new Halomonas strain CRSS isolated from saline lake Cape Russell in Antarctica growing on complex and defined media

A haloalkalophilic Halomonas strain CRSS, isolated from salt sediments in Antarctica, produced exocellular polysaccharides (EPS) up to 2.9gg-1 dry cells. Acetate was the most efficient carbon source for EPS production. The composition of media strongly affected the nature of the polymers; a mannan and a xylo-mannan, were obtained when cells were grown on complex media. Acetate was the most efficient carbon source for EPS production and in presence of this substrate, a new polysaccharide, a fructo-glucan, was produced. The EPS fraction was composed by glucose, fructose, glucosamine and galactosamine in relative proportions of 1:0.7:0.3:trace.

Antioxidative Activity and Lycopene and β-Carotene Contents in Different Cultivars of Tomato (Lycopersicon Esculentum)

Nine different Lycopersicon esculentum varieties were analysed in order to determine differences in the antioxidant activity, both hydrophilic and lipophilic. To assess the nutritional value of all varieties, the total content of principal carotenoids, lycopene, and β-carotene was also analysed. On the basis of analyses performed on all lipophilic fractions, we can affirm that the total antioxidant activity of tomato is due to the integrated action of different compounds instead of that of any single compound such as lycopene and β-carotene. Anticytotoxic activities by brine shrimps assay were also tested on all lipophilic fractions to evaluate potential antitumoral activity.

Biosorption of Heavy Metals (Cd2+, Cu2+, Co2+, and Mn2+) by Thermophilic Bacteria, Geobacillus thermantarcticus and Anoxybacillus amylolyticus: Equilibrium and Kinetic Studies

ABSTRACT Two strains of thermophilic bacteria, Geobacillus thermantarcticus and Anoxybacillus amylolyticus, were employed to investigate the biosorption of heavy metals including Cd2+, Cu2+, Co2+, and Mn2+ ions. The effects of different biosorption parameters such as pH (2.0–10.0), initial metal concentrations (10.0–300.0 mg L−1), amount of biomass (0.25–10 g L−1), temperature (30–80°C), and contact time (15–120 min) were investigated. Concentrations of metal ions were determined by using an inductively coupled plasma optical emission spectrometry (ICP-OES). Optimum pHs for Cd2+, Cu2+, Co2+, and Mn2+ biosorption by Geobacillus thermantarcticus were found to be 4.0, 4.0, 5.0, and 6.0, respectively. For Anoxybacillus amylolyticus, the optimum pHs for Cd2+, Cu2+, Co2+, and Mn2+ biosorption were found to be 5.0, 4.0, 5.0, and 6.0, respectively. The Cd2+, Cu2+, Co2+, and Mn2+ removals at 50 mg L−1 in 60 min by 50 mg dried cells of Geobacillus thermantarcticus were 85.4%, 46.3%, 43.6%, and 65.1%, respectively, whereas 74.1%, 39.8%, 35.1%, and 36.6%, respectively, for Anoxybacillus amylolyticus. The optimum temperatures for heavy metal biosorption were near the optimum growth temperatures for both strains. Scatchard plot analysis was employed to obtain more compact information about the interaction between metal ions and biosorbents. The plot results were further studied to determine if they fit Langmuir and Freundlich models.