Free-radical scavenging properties and antioxidant activities of botryosphaeran and some other ß-D-glucans.

ß-D-Glucans are known to present antitumor, anticancer, and anti-inflammatory activities that are influenced by their own antioxidant capacity. The antioxidant activity of botryosphaeran, an exopolysaccharide of the (1 → 3;1 → 6)-ß-D-glucan type produced by the Botryosphaeria rhodina MAMB-05 was evaluated and compared to some other ß-D-glucans (lasiodiplodan an exocellular (1 → 6)-ß-D-glucan from Lasiodiplodia theobromae, laminarin and curdlan), and oligosaccharides, disaccharides, and monosaccharides in a study of scavenging activities of free radicals in-vitro. Botryosphaeran displayed high total antioxidant activity (80%) as well as good scavenging activity against hydroxyl radical (90.6%), superoxide anion (37%), hydrogen peroxide (38%), and nitric oxide radical (90%). No reducing power, metal-chelating capacity or inhibition of lipid peroxidation was observed for these ß-D-glucans. The results demonstrated that botryosphaeran exhibited effective antioxidant activity as supported by many different assays, suggesting that this ß-D-glucan may serve as a source of a new bioactive compound with effective antioxidant activity.

Degradative actions of microbial xylanolytic activities on hemicelluloses from rhizome of Arundo donax.

Polysaccharidases from extremophiles are remarkable for specific action, resistance to different reaction conditions and other biotechnologically interesting features. In this article the action of crude extracts of thermophilic microorganisms (Thermotoga neapolitana, Geobacillus thermantarcticus and Thermoanaerobacterium thermostercoris) is studied using as substrate hemicellulose from one of the most interesting biomass crops, the giant reed (Arundo donax L.). This biomass can be cultivated without competition and a huge amount of rhizomes remains in the soil at the end of cropping cycle (10-15 years) representing a further source of useful molecules. Optimization of the procedure for preparation of the hemicellulose fraction from rhizomes of Arundo donax, is studied. Polysaccharidases from crude extracts of thermophilic microorganisms revealed to be suitable for total degradative action and/or production of small useful oligosaccharides from hemicelluloses from A. donax. Xylobiose and interesting tetra- and pentasaccharide are obtained by enzymatic action in different conditions. Convenient amount of raw material was processed per mg of crude enzymes. Raw hemicelluloses and pretreated material show antioxidant activity unlike isolated tetra- and pentasaccharide. The body of results suggest that rhizomes represent a useful raw material for the production of valuable industrial products, thus allowing to increase the economic efficiency of A. donax cultivation.

Production and properties of two novel exopolysaccharides synthesized by a thermophilic bacterium Aeribacillus pallidus 418.

Synthesis of innovative exocellular polysaccharides (EPSs) was reported for few thermophilic microorganisms as one of the mechanisms for surviving at high temperature. Thermophilic aerobic spore-forming bacteria able to produce exopolysaccharides were isolated from hydrothermal springs in Bulgaria. They were referred to four species, such as Aeribacillus pallidus, Geobacillus toebii, Brevibacillus thermoruber, and Anoxybacillus kestanbolensis. The highest production was established for the strain 418, whose phylogenetic and phenotypic properties referred it to the species A. pallidus. Maltose and NH4Cl were observed to be correspondingly the best carbon and nitrogen sources and production yield was increased more than twofold in the process of culture condition optimization. After purification of the polymer fraction, a presence of two different EPSs, electroneutral EPS 1 and negatively charged EPS 2, in a relative weight ratio 3:2.2 was established. They were heteropolysaccharides consisting of unusual high variety of sugars (six for EPS 1 and seven for EPS 2). Six of the sugars were common for both EPSs. The main sugar in EPS 1 was mannose (69.3 %); smaller quantities of glucose (11.2 %), galactosamine (6.3 %), glucosamine (5.4 %), galactose (4.7 %), and ribose (2.9 %) were also identified. The main sugar in EPS 2 was also mannose (33.9 %), followed by galactose (17.9 %), glucose (15.5 %), galactosamine (11.7 %), glucosamine (8.1 %), ribose (5.3 %), and arabinose (4.9 %). Both polymers showed high molecular weight and high thermostability.

A novel EPS-producing strain of Bacillus licheniformis isolated from a shallow vent off Panarea Island (Italy).

A haloalkaliphilic, thermophilic Bacillus strain (T14), isolated from a shallow hydrothermal vent of Panarea Island (Italy), produced a new exopolysaccharide (EPS). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain T14 was highly related (99 % similarity) to Bacillus licheniformis DSM 13(T) and Bacillus sonorensis DSM 13779(T). Further DNA-DNA hybridization analysis revealed 79.40 % similarity with B. licheniformis DSM 13(T) and 39.12 % with B. sonorensis DSM 13779(T). Sucrose (5 %) was the most efficient carbon source for growth and EPS production. The highest EPS production (366 mg l(-1)) was yielded in fermenter culture at 300 rpm after 48 h of incubation. The purified fraction EPS1 contained fructose/fucose/glucose/galactosamine/mannose in a relative proportion of 1.0:0.75:0.28:tr:tr and possessed a molecular weight of 1,000 kDa displaying a trisaccharide unit constituted by sugars with a ß-manno-pyranosidic configuration. Screening for biological activity showed anti-cytotoxic effect of EPS1 against Avarol in brine shrimp test, indicating a potential use in the development of novel drugs.

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 x 10(5) to 3 x 10(5) 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.