Cyanobacteria are photoautotrophic prokaryotes which include a large variety of species of widespread occurrence and with diverse morphological, physiological and biochemical properties. Many cyanobacteria are known to be able to synthesise outermost slimy investments and to release polysaccharidic material into the culture medium during cell growth. These released polysaccharides (RPSs), being easily recoverable from the culture medium, are attracting much interest in view of their possible uses in several industrial applications. In this paper, an overview of the current knowledge on both RPS‐producing cyanobacterial strains (including the possible roles of the exopolysaccharides) and chemical characteristics of the cyanobacterial RPSs is given, with particular emphasis on RPS properties and possible industrial applications. On the whole, cyanobacterial RPSs are characterised by a great variety in both number (from two to 10) and type of constitutive monosaccharides (various arrangements of acidic and neutral sugars). Most polymers show an anionic nature due to the presence of uronic acids and/or other charged groups such as pyruvyl or sulfate. Polypeptide moieties as well as acetyl substituents have also sometimes been found, causing additional structural complexity. All the cyanobacterial RPSs so far tested showed a pseudoplastic behaviour, but with marked differences in both viscosity values and shear thinning. In terms of RPS production, the responses of cyanobacteria to changes of culture conditions appear strain‐dependent. RPS productivities shown by some cyanobacteria are well comparable with those reported for other photosynthetic microorganisms proposed for polysaccharide production, but very low in comparison with those of heterotrophic microorganisms. Nevertheless, cyanobacteria may be regarded as a very abundant source of structurally diverse polysaccharides, some of which may possess unique properties for special applications, not fulfilled by the polymers currently available. However, much work has still to be done to bridge the wide gap existing between data on the biology of the RPS‐producer strains and information concerning technological and other useful properties of the cyanobacterial RPS.

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Osteocyte apoptosis due to microdamage and/or oxidative stress is related to increased local bone turnover and resorption observed in various bone diseases. Previous data on osteoblasts and osteoclasts have linked reactive oxygen species and antioxidants to bone remodelling. This study performs a comprehensive analysis on the effect of antioxidants such as glutathione (GSH), N-acetylcysteine and lipoic acid (LA) on starvation-induced osteocyte apoptosis and on cytokines involved in bone remodelling such as the receptor activator kB ligand (RANKL), osteoprotegerin (OPG) and sclerostin. For this study, apoptosis was induced by serum starvation in a murine osteocyte-like cell line MLO-Y4; this condition mimics in part osteocyte apoptosis due to microdamage. The results show that starvation-induced apoptosis and expression of RANKL, OPG and sclerostin are redox regulated processes. All antioxidants are able to inhibit the apoptosis due to starvation. They down-regulate the expression and the release of RANKL, the expression of sclerostin and RANKL/OPG ratio, whereas they only in part up-regulate OPG expression. Antioxidants mediate their effect on starvation-induced apoptosis by JNK signalling and on cytokine expression by both JNK and ERK1/2 activities. This study shows the possible involvement of biological antioxidants such as GSH and LA on redox regulated mechanisms related to apoptosis and expression of cytokines involved in bone remodelling. Moreover, it suggests that both JNK and ERK1/2 may be useful biological targets for drugs affecting bone diseases associated with increased oxidative stress.

L. GRANCHI, M. BOSCO, A. MESSINI and M. VINCENZINI.1999.PCR–RFLP analysis of the rDNA–ITS (internal transcribed spacer) region was applied to 174 yeast strains belonging to 30 species of oenological significance and including 27 type strains in order to define a rapid identification protocol for yeast colonies. DraI‐or HaeIII‐PCR–RFLP patterns were species‐specific with the exception of teleomorphic and anamorphic forms. An improved protocol taking about 30 h was used for the detection and quantification of yeast species occurring in the course of a spontaneous wine fermentation at industrial level. Wine samples were taken and plated daily on an agar medium and the developed colonies were analysed by PCR–RFLP after 24 h of incubation. A representative sample of these colonies was also identified by traditional methods. Both procedures gave identical results. However, PCR–RFLP analysis allowed a more precise enumeration of the yeast populations, proving to be a reliable and simple method for monitoring the development of the yeast community throughout wine fermentation.

The biogenic amine-producing capability of several Oenococcus oeni strains, originally isolated from different Italian wines, was determined. The amine-producing capability was quali-quantitatively variable among the strains: out of the 44 strains investigated under optimal growth conditions, more than 60% were able to produce histamine, at concentrations ranging from 1.0 to 33 mg/L, and about 16% showed the additional capability to form both putrescine and cadaverine, to different extents and variable relative proportions. The amine-producing behavior of the strains was confirmed under stress culture conditions, while performing malolactic fermentation. In wine, one randomly chosen strain was very effective in forming putrescine from ornithine. The formation of putrescine from arginine by some strains has been also demonstrated. Consequently, O. oeni can really and significantly contribute to the overall biogenic amine content of wines. Practical consequences of these findings are discussed.

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This study comprised a comprehensive analysis of the glutathione (GSH) redox system during osteogenic differentiation in human osteoblast-like SaOS-2 cells. For the first time, a clear relationship between expression of specific factors involved in bone remodeling and the changes in the GSH/ oxidized GSH (GSSG) redox couple induced during the early phases of the differentiation and mineralization process is shown. The findings show that the time course of differentiation is characterized by a decrease in the GSH/GSSG ratio, and this behavior is also related to the expression of osteoclastogenic markers. Maintenance of a high GSH/GSSG ratio due to GSH exposure in the early phase of this process increases mRNA levels of osteogenic differentiation markers and mineralization. Conversely, these events are decreased by a low GSH/GSSG ratio in a reversible manner. Redox regulation of runt-related transcription factor-2 (RUNX-2) activation through phosphorylation is shown. An inverse relationship between RUNX-2 activation and extracellular signal-regulated kinases related to GSH redox potential is observed. The GSH/GSSG redox couple also affects osteoclastogenesis, mainly through osteoprotegerin down-regulation with an increase in the ratio of receptor activator of NF-jB ligand to osteoprotegerin and vice versa. No redox regulation of receptor activator of NF-jB ligand expression was found. These results indicate that the GSH/GSSG redox couple may have a pivotal role in bone remodeling and bone redox-dysregulated diseases. They suggest therapeutic use of compounds that are able to modulate not just the GSH level but the intracellular redox system through the GSH/GSSG redox couple.

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