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.

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.

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.

This study evaluated both the possible fungal metabolites involved in the degradation of the commercial consolidant known as Paraloid^® B72 and the national artisanal consolidant named transparent dispersion of casein and the deteriorative potential of melanised fungi. Fungi were found to have the capacity to produce organic acids, proteases and esterases when they grow on consolidants, which can be used as nutrients. Mycelia produced by melanised fungi affected the appearance, as well as the integrity, of consolidants applied on painted experimental models and fragments of frescoes. In treatment trials with biocides (Biotin R^®, Biotin T^® and Preventol^® RI 80), the morphology of the consolidants, as well as the vitality of the fungi, were assessed 30 days after the inoculation with melanic fungi. Direct observation, optical microscopy, colourimetry and microbiological analysis highlighted the degradation of the consolidants by fungi and their acquired resistance after biocidal treatments. Biotin R^® applied by brushing on the surface of the consolidants proved to be the most effective treatment, followed by Biotin T^®. Considering the overall results for both Paraloid^® B72 and transparent dispersion of casein, use of Biotin R^® applied by brushing is recommended for preventive conservation.

This study highlights the decomposing role through the hydrolytic activities of fungi isolated from natural environments represented by brackish and hypersaline lakes in Romania. Novel strains belonging to the Penicillium, Aspergillus, and Emericellopsis genera were isolated and screened for the ability to produce extracellular hydrolytic enzymes, i.e., proteases, lipases, amylases, cellulases, xylanases, and pectinases. According to salt requirements, they were classified as moderate halophilic and halotolerant strains. Agar plate-based assays with Tween 80, slide cultures with organic deposits, and quantitative evaluation allowed the selection of Aspergillus sp. BSL 2-2, Penicillium sp. BSL 3-2, and Emericellopsis sp. MM2 as potentially good decomposers of organic matter not only in lakes but also on deposits covering the mural paintings. Experiments performed on painted experimental models revealed that only Penicillium sp. BSL 3-2 decomposed Paraloid B72, transparent dispersion of casein, beeswax, sunflower oil, and soot. Moreover, using microscopic, spectroscopic, and imaging methods, it was proved the efficiency of Penicillium sp. BSL 3-2 for decomposition of organic deposits artificially applied on frescoes fragments.