Characterization of Some Salt-Tolerant Bacterial Hydrolases with Potential Utility in Cultural Heritage Bio-Cleaning.

Salt-tolerant enzymes produced by halophilic and halotolerant microorganisms have been proposed to be used in various applications that involve high saline conditions. Considering their biotechnological significance and the current need for more efficient producers of such catalysts, the present study aimed to evaluate the extracellular proteolytic, esterolytic, cellulolytic and xylanolytic activities of some halotolerant strains, and to characterize their functional parameters. A total of 21 bacterial and fungal strains belonging to the genera Bacillus, Virgibacillus, Salinivibrio, Salinicoccus, Psychrobacter, Nocardiopsis, Penicillium, Aspergillus, and Emericellopsis were assayed by quantitative methods. Among them, the members of the Bacillus genus exhibited the highest catalytic activities. The exoenzymes produced by three selected Bacillus strains were active over wide ranges of salinity, temperature and pH. Proteases were active at 20-80 °C, pH 6-10, and 0-1 M NaCl, while esterases showed good catalytic activities at 20-80 °C, pH 7.5-10, and 0-4 M NaCl. Cellulases and xylanases were active at 20-80 °C, pH 5-10, and 0-5 M NaCl. Due to such properties, these hydrolases could be used in a newly proposed application, namely to clean aged consolidants and organic deposits accumulated over time from the surfaces of salt-loaded wall paintings.

Bioprospecting for Novel Halophilic and Halotolerant Sources of Hydrolytic Enzymes in Brackish, Saline and Hypersaline Lakes of Romania.

Halophilic and halotolerant microorganisms represent promising sources of salt-tolerant enzymes that could be used in various biotechnological processes where high salt concentrations would otherwise inhibit enzymatic transformations. Considering the current need for more efficient biocatalysts, the present study aimed to explore the microbial diversity of five under- or uninvestigated salty lakes in Romania for novel sources of hydrolytic enzymes. Bacteria, archaea and fungi were obtained by culture-based approaches and screened for the production of six hydrolases (protease, lipase, amylase, cellulase, xylanase and pectinase) using agar plate-based assays. Moreover, the phylogeny of bacterial and archaeal isolates was studied through molecular methods. From a total of 244 microbial isolates, 182 (74.6%) were represented by bacteria, 22 (9%) by archaea, and 40 (16.4%) by fungi. While most bacteria synthesized protease and lipase, the most frequent hydrolase produced by fungi was pectinase. The archaeal isolates had limited hydrolytic activity, being able to produce only amylase and cellulase. Among the taxonomically identified isolates, the best hydrolytic activities were observed in halotolerant bacteria belonging to the genus Bacillus and in extremely halophilic archaea of the genera Haloterrigena and Halostagnicola. Therefore, the present study highlights that the investigated lakes harbor various promising species of microorganisms able to produce industrially valuable enzymes.

The effect of spaceflight on growth of Ulocladium chartarum colonies on the international space station.

The objectives of this 14 days experiment were to investigate the effect of spaceflight on the growth of Ulocladium chartarum, to study the viability of the aerial and submerged mycelium and to put in evidence changes at the cellular level. U. chartarum was chosen for the spaceflight experiment because it is well known to be involved in biodeterioration of organic and inorganic substrates covered with organic deposits and expected to be a possible contaminant in Spaceships. Colonies grown on the International Space Station (ISS) and on Earth were analysed post-flight. This study clearly indicates that U. chartarum is able to grow under spaceflight conditions developing, as a response, a complex colony morphotype never mentioned previously. We observed that spaceflight reduced the rate of growth of aerial mycelium, but stimulated the growth of submerged mycelium and of new microcolonies. In Spaceships and Space Stations U. chartarum and other fungal species could find a favourable environment to grow invasively unnoticed in the depth of surfaces containing very small amount of substrate, posing a risk factor for biodegradation of structural components, as well as a direct threat for crew health. The colony growth cycle of U. chartarum provides a useful eukaryotic system for the study of fungal growth under spaceflight conditions.