José-Julio Ortega-Calvo

Biodeterioration of building materials by cyanobacteria and algae

Abstract A study of the presence of cyanobacteria and algae in different building materials from Spain (Salamanca, Seville and Toledo Cathedrals) and Sweden (Lund Cathedral) and their possible relation to the stone decay was accomplished. Colonization of stone with the cyanobacterium Microcoleus vaginatus and the chlorophyte Klebsormidium flaccidum was also induced in the laboratory. In both field and laboratory samples, the microbial film, spontaneously detached, showed on its reverse side the presence of grains removed from the stone surface, thus causing mechanical deterioration on the colonized materials.

Factors affecting the weathering and colonization of monuments by phototrophic microorganisms

Phototrophic microorganisms are common inhabitants of monuments. This paper reviews different aspects of their culture, ecology and deterioration mechanisms. Opportunistic species of cyanobacteria and chlorophytes, present in soils and in the air, are commonly found on the surfaces of monuments. Their growth represents a significant input of organic matter to the stone, as estimated through chlorophyll a quantification. Monuments provide unusual niches for the growth of algal communities, as in the case of black sulfated crusts, or endolithic and hypogeal niches, where more specific processes and/or communities occur.

Lichen colonization of the Roman pavement at Baelo Claudia (Cadiz, Spain): biodeterioration vs. bioprotection

This paper describes the effect of lichen colonization on the first century A.D. pavement of the forum at Baelo Claudia, a Roman city located in southern Spain. Lichen colonization is scarce, covering only 13% of the total surface. The rest of the flagstones are mostly uncovered but show strong physico-chemical weathering. The flagstones colonized by lichens do not show weathering. The distribution of the species is influenced by environmental factors, confirming the role of lichens as bioindicators of different habitats. The lichen/sandstone interface shows some weathering, but nevertheless, the protective role of lichens in an aggressive environment is noticeable.

Is it possible to increase bioavailability but not environmental risk of PAHs in bioremediation

The current poor predictability of end points associated with the bioremediation of polycyclic aromatic hydrocarbons (PAHs) is a large limitation when evaluating its viability for treating contaminated soils and sediments. However, we have seen a wide range of innovations in recent years, such as an the improved use of surfactants, the chemotactic mobilization of bacterial inoculants, the selective biostimulation at pollutant interfaces, rhizoremediation and electrobioremediation, which increase the bioavailability of PAHs but do not necessarily increase the risk to the environment. The integration of these strategies into practical remediation protocols would be beneficial to the bioremediation industry, as well as improve the quality of the environment.

Endolithic cyanobacteria in Maastricht limestone

Abstract The Maastricht limestone used for the construction of the 14th century O.L. Basilica in Tongeren, Belgium, is a light yellowish, porous, soft rock of the Late Cretaceous age. The limestone has a high carbonate content (> 95%); quartz and glauconite occur rarely. On the north side of the building, there is extensive growth of epilithic algae. On the south side, an assemblage of organisms was observed beneath the abiotic surface. This community, developed as a green layer 1 mm below the surface, is dominated by cyanobacteria. A moss was also present. The organisms were studied by transmitted light, phase contrast and scanning electron microscopy, and isolated in cultures. The cyanobacteria belong to the genera Synechococcus and Chroococcidiopsis, and the moss was identified as Tortula muralis Hedw. The organic matter present in the green layer was characterized in terms of molecular components using analytical pyrolysis. Pyrolysis products from polysaccharides and proteins, and evaporation/pyrolysis products from lipids, comprise the vast majority of identified compounds. The identification of specific biomarkers such as 7-methylheptadecane is further evidence of the presence of cyanobacteria. Phytenes and phytadienes are indicative of phototrophic organisms, as they are pyrolysis products from chlorophylls.

Enhanced kinetics of solid-phase microextraction and biodegradation of polycyclic aromatic hydrocarbons in the presence of dissolved organic matter†

The uptake kinetics of fluorene, phenanthrene, fluoranthene, pyrene, and benzo[e]pyrene by solid-phase microextraction fibers was studied in the presence of dissolved organic matter (DOM) obtained from sediment pore water and resulted in increased fiber absorption and desorption rate coefficients. Compared to the control without DOM, these rate coefficients were increased at a DOM concentration of 36.62 mg/L by a factor of 1.27 to 2.21 and 1.31 to 2.10 for fluorene and benzo[e]pyrene, respectively. The calculated values for the fiber absorption and desorption rate coefficients show that diffusion through an unstirred boundary layer (UBL) surrounding the fiber probably forms the rate-limiting step of the process. The mineralization of aqueous-phase phenanthrene and pyrene by a representative polycyclic aromatic hydrocarbon (PAH)-degrading bacterium (Mycobacterium gilvum VM552) also was found to be enhanced by DOM. The initial degradation rates of phenanthrene (9.03 μg/L) and pyrene (1.96 μg/L) were significantly higher compared to the control values and were enhanced by a factor of 1.32 and 1.26 at a DOM concentration of 43.14 and 42.15 mg/L, respectively. We suggest that such an enhancement results from the combination of faster uptake kinetics of the water-dissolved compounds in the UBL surrounding microbial cells and direct access of the bacteria to DOM-associated PAHs. These enhanced kinetic effects of DOM may have strong implications in sediment processes like desorption, nonequilibrium exposure, and biodegradation.

Microbial communities in weathered sandstones: the case of Carrascosa del Campo church, Spain

An integrated study of the microorganisms growing on the weathered sandstone of the church of Carrascosa del Campo (Spain) was carried out. Whilst lichens played only a minor role in colonization, algae and bryophytes were abundant in the sandstone and mortars on the north facade. Although the contribution of algae to deterioration is considered less important, they supported the colonization and development of an allied heterotrophic population of bacteria and fungi, and ultimately, after organic matter decomposition and humification, led to mosses and plants which could have a higher deterioration potential.

Effect of organic matter and clays on the biodegradation of Phenanthrene in soils

Abstract Soil organic matter and clays represent an important hinderance for bioremediation technologies, as they may cause a retardation in the biological removal of hydrophobic pollutants. To overcome this limitation it is necessary to understand how these two soil constituents influence biodegradation. The results herein reported suggest that the bioavailability of phenanthrene in soils is affected not only by sorption to the organic matter or clays, but also by the interaction of phenanthrene with humic fractions-clay complexes.

Effect of a nonionic surfactant on biodegradation of slowly desorbing PAHs in contaminated soils.

The influence of the nonionic surfactant Brij 35 on biodegradation of slowly desorbing polycyclic aromatic hydrocarbons (PAHs) was determined in contaminated soils. We employed a soil originated from a creosote-polluted site, and a manufactured gas plant soil that had been treated by bioremediation. The two soils differed in their total content in five indicator 3-, 4-, and 5-ring PAHs (2923 mg kg(-1) and 183 mg kg(-1) in the creosote-polluted and bioremediated soils, respectively) but had a similar content (140 mg kg(-1) vs 156 mg kg(-1)) of slowly desorbing PAHs. The PAHs present in the bioremediated soil were highly recalcitrant. The surfactant at a concentration above its critical micelle concentration enhanced the biodegradation of slowly desorbing PAHs in suspensions of both soils, but it was especially efficient with bioremediated soil, causing a 62% loss of the total PAH content. An inhibition of biodegradation was observed with the high-molecular-weight PAHs pyrene and benzo[a]pyrene in the untreated soil, possibly due to competition effects with other solubilized PAHs present at relatively high concentrations. We suggest that nonionic surfactants may improve bioremediation performance with soils that have previously undergone extensive bioremediation to enrich for a slowly desorbing profile.

Role of Desorption Kinetics in the Rhamnolipid-Enhanced Biodegradation of Polycyclic Aromatic Hydrocarbons

The main aim of this study was to investigate the effect of a rhamnolipid biosurfactant on biodegradation of (14)C-labeled phenanthrene and pyrene under desorption-limiting conditions. The rhamnolipid caused a significant solubilization and enhanced biodegradation of PAHs sorbed to soils. The enhancement was, however, negatively influenced by experimental conditions that caused an enrichment of slow desorption fractions. These conditions included aging, a higher organic matter content in soil, and previous extraction with Tenax to remove the labile-desorbing chemical. The decline in bioavailability caused by aging on sorbed (14)C-pyrene was partially reversed by rhamnolipids, which enhanced mineralization of the aged compound, although not so efficiently like with the unaged chemical. This loss in biosurfactant efficiency in promoting biodegradation can be explained by intra-aggregate diffusion of the pollutant during aging. We suggest that rhamnolipid can enhance biodegradation of soil-sorbed PAHs by micellar solubilization, which increase the cell exposure to the chemicals in the aqueous phase, and partitioning into soil organic matter, thus enhancing the kinetics of slow desorption. Our study show that rhamnolipid can constitute a valid alternative to chemical surfactants in promoting the biodegradation of slow desorption PAHs, which constitutes a major bottleneck in bioremediation.