Primary Bioreceptivity Research Articles

From Biodeterioration to Creativity: Bioreceptivity of Spruce Pine 87 Glass Batch by Fungi

The bioreceptivity, and the consequent biodeterioration of contemporary glass, used by artists worldwide, was studied. The two main objectives were: first, to verify if fungi with some culture media would produce more damages than the same fungi without a nutritional source, and to verify if the two genera of fungi produce the same damage on the same glass. Colourless glass samples with Spruce Pine 87 Batch (SPB-87) composition were inoculated with two distinct fungal species, Penicillium chrysogenum and Aspergillus niger, separately: (i) half with fungal spores (simulating primary bioreceptivity), and (ii) half with fungi in a small portion of culture media (simulating organic matter that can be deposited on exposed glassworks, i.e., secondary bioreceptivity). The alteration of glass surfaces were analysed by Optical Microscopy, SEM-EDS and µ-Raman. The mycelium of Penicillium chrysogenum generated a higher amount of fingerprints, stains and iridescence, whereas Aspergillus niger produced more biopitting and crystals on the glass surface. However, both species damaged the glass to different degrees in 4 and 6 months after the inoculation, producing physico-chemical damage (e.g., iridescence, biopitting), and chemical alterations (e.g., depletion and deposition of elements and crystals). The primary bioreceptivity experiment of glass samples inoculated with Aspergillus niger results in less damage than in the case of secondary bioreceptivity, being almost similar for Penicillium chrysogenum. The new and in-depth understanding of the bioreceptivity and deterioration of post-modern glass art and cultural heritage provided here is of paramount importance for the scientific, conservation and artistic communities—to protect glass cultural materials, or seen by artists as innovative and inspirational ways of creating glass art in the future.

A laboratory approach on the combined effects of granite bioreceptivity and parameters modified by climate change on the development of subaerial biofilms on cultural heritage

Conservation of cultural heritage buildings and monuments may be negatively affected by the impact of climate change on substrates and colonizing microorganisms. In this study, four types of commercial granite, in which the bioreceptivity ranged from very low to very high, were inoculated with a multispecies microbial culture and exposed to different temperatures (18 and 24 °C) and levels of water availability (1 day, 3 days and 7 days of water availability/week) to simulate different climatic conditions. The effects on biofilm formation of the interactions between the substrate bioreceptivity and the environmental parameters were investigated. Biofilm growth and photosynthetic efficiency were monitored over 42 days by pulse-amplitude modulated (PAM) fluorometry and spectrophotometric colour measurement. The primary bioreceptivity of the granite was a determining factor in the organisms' capacity to attach to the substrate and interacted through the experiment with the climatic conditions by modifying the development of the microorganisms. Water availability was a limiting factor for the colonizing microorganisms, in terms of both growth and photosynthetic efficiency. At the higher temperature, metabolic reactions were enhanced under water restriction (but not under maximum water availability) and the microbial ecology was altered, leading to a higher proportion of cyanobacteria relative to algae.

Impact of colour on the bioreceptivity of granite to the green alga Apatococcus lobatus: Laboratory and field testing

Recent work has demonstrated that surface colour affects the formation of cyanobacterial subaerial biofilms on polycarbonate coupons and, in turn, influences their bioreceptivity. To explore whether colour is important on other substrates, the influence of colour on the primary bioreceptivity of granite to the terrestrial green alga Apatococcus lobatus (Trebouxiophyceae, Chlorophyta) has been assessed. Two granitoids (Grissal and Rosa Porriño) with the same texture, and very similar chemical composition, open porosity and surface roughness, but different coloration related to feldspars (i.e. greyish and reddish) were used to conduct bioreceptivity studies in parallel field and laboratory tests. Light microscopy, colour spectrophotometry, PAM fluorometry, and optical profilometry were used to evaluate colonisation and its impacts. Short-term results (after 7 and 10 weeks of colonisation by a mono-species biofilm) from both lab and field trials, showed significantly more algae growth on reddish granite (Rosa Porriño) than on greyish granite (Grissal). Also, optical profilometry and light microscopy demonstrated that on both granites algal aggregates developed in hollows. We attribute the roughly double levels of A. lobatus growth on reddish vs greyish granite to differences in the amount of radiant energy absorbed and the higher levels of red wavelength light (known to encourage algal growth) reflected from the reddish surface.

Secondary bioreceptivity of granite: effect of salt weathering on subaerial biofilm growth

Salt crystallisation is a very common and powerful weathering agent that can modify the petrophysical properties of building stone such as granite. In addition, the weathering can affect the susceptibility of the stone to biological colonisation. The aims of the present study were to examine the properties of a granite weathered by sodium chloride crystallisation and to evaluate the effects of the weathering on the secondary bioreceptivity of the stone to subaerial phototrophic biofilms. For this purpose, granite samples were subjected to a laboratory-based accelerated salt weathering test, and changes in weight, open porosity, bulk density, capillary water content, abrasion pH and surface roughness of the samples were determined. Samples of both weathered and non-weathered granite were then inoculated with a multi-species phototrophic culture derived from a natural subaerial biofilm and incubated under standardised laboratory conditions for 3 months. The weight loss produced by the weathering process was consistent with significant changes in abrasion pH and surface roughness. The bioreceptivity of the stone was also altered. According to the bioreceptivity index, the granite under study was characterised by ‘mild primary bioreceptivity’, but ‘high secondary bioreceptivity’ after the salt weathering process. Study of the secondary bioreceptivity of stone materials can provide very useful information about response to weathering effects, and the findings can be used to improve the selection of materials for building purposes.

Bioreceptivity index for granitic rocks used as construction material

Bioreceptivity is a fundamental concept in the ornamental stone industry and in the fields of cultural heritage and civil engineering to understand the susceptibility of stone constructions to biological colonisation and subsequent biodeterioration. However, a bioreceptivity index (BI) has not yet been established for any construction material. The aim of the present study is developing a simple, robust and well-founded BI for granitic rocks. For this purpose, a standardised laboratory protocol was used to grow phototrophic biofilms on several varieties of granite. The colonisation was then assessed by chlorophyll fluorescence and colour measurements. Based on the results thus obtained, a BI including two components (BIgrowth and BIcolour) is proposed. BIgrowth quantifies the extent of the biological growth and BIcolour quantifies the colour change undergone by the stone due to the colonisation, which can be considered the bioreceptivity perceptible to the human eye. The values of BI, BIgrowth and BIcolour were fitted to a scale of 0–10, thus enabling qualitative classification of the lithotypes according to their primary bioreceptivity. Eleven varieties of granite commonly used as construction material and with a honed surface finish (one variety with three additional surface finishes: polished, sawn and sanded) were thus assigned the corresponding BI, which represents a new quality factor for the stone industry. The index can therefore be used by end-users as a decision-making tool in the selection of appropriate lithotypes for building and/or ornamental purposes.

Influence of the properties of granitic rocks on their bioreceptivity to subaerial phototrophic biofilms

As any stone substrate is susceptible to biological colonisation, the choice of lithotype used for construction is a key strategy for preventing biodeterioration. For this purpose, a comprehensive evaluation of the primary bioreceptivity to phototrophic biofilms of eleven varieties of granitic rocks, commonly used as building material, was carried out. Blocks were inoculated with a multi-species phototrophic culture and subjected to standardised growth conditions for three months. Biofilm formation was assessed by chlorophyll (chl) fluorescence, colour measurements and extracellular polymeric substances (EPS) quantification. Relationships between the biofilm growth indicators and the properties of the different rocks studied were then analysed. Results showed that the bioreceptivity of the granites is more strongly affected by the physical characteristics of the stones than by their chemical and mineralogical properties, possibly because of the similar composition of the rocks studied. Growth of phototrophic biofilms was enhanced by high open porosity, capillary water content and surface roughness, and the bioreceptivity of weathered granites was higher than that of sound granites. The results obtained can therefore help in the selection of appropriate lithotypes for building purposes. The amounts of EPS produced by subaerial biofilms primarily depended on the requirements and/or characteristics of the biofilm-forming microorganisms, rather than on the bioreceptivity of the substratum, and microorganisms produce the amounts of EPS required at the initial stage of establishment on the stone surface, independently of the subsequent biomass development. These findings are especially important from the point of view of biodeterioration, in which the EPS matrix plays a central role.

Optimising the bioreceptivity of porous glass tiles based on colonization by the alga Chlorella vulgaris

Green façades on buildings can mitigate greenhouse gas emissions. An option to obtain green facades is through the natural colonisation of construction materials. This can be achieved by engineering bioreceptive materials. Bioreceptivity is the susceptibility of a material to be colonised by living organisms. The aim of this research was to develop tiles made by sintering granular waste glass that were optimised for bioreceptivity of organisms capable of photosynthesis. Tiles were produced by pressing recycled soda-lime glass with a controlled particle size distribution and sintering compacted samples at temperatures between 680 and 740°C. The primary bioreceptivity of the tiles was evaluated by quantifying colonisation by the algae Chlorella vulgaris (C. vulgaris), which was selected as a model photosynthetic micro-organism. Concentrations of C. vulgaris were measured using chlorophyll-a extraction. Relationships between bioreceptivity and the properties of the porous glass tile, including porosity, sorptivity, translucency and pH are reported. Capillary porosity and water sorptivity were the key factors influencing the bioreceptivity of porous glass. Maximum C. vulgaris growth and colonisation was obtained for tiles sintered at 700°C, with chlorophyll-a concentrations reaching up to 11.1±0.4μg/cm2 of tile. Bioreceptivity was positively correlated with sorptivity and porosity and negatively correlated with light transmittance. The research demonstrates that the microstructure of porous glass, determined by the processing conditions, significantly influences bioreceptivity. Porous glass tiles with high bioreceptivity that are colonised by photosynthetic algae have the potential to form carbon-negative façades for buildings and green infrastructure.

Accelerated weathering of cementitious matrix for the development of an accelerated laboratory test of biodeterioration

Cement based materials are porous, may contain organic adjuvants, and thus possesses an important primary bioreceptivity. To preserve constructions from fungal colonization and to act efficiently against fungal biodeterioration, it is necessary to have a better understanding of biodeterioration mechanisms and its effects on materials properties. An accelerated laboratory test which allows us to compare the growth of three fungal strains and the aesthetic biodeterioration of a cementitious matrix was developed. As the surface pH of the fresh cement specimen is too high to allow fungal growth (pH ~12), accelerating weathering of the matrix, consisting of the combination of carbonation and leaching, was performed to reduce the matrix alkalinity. XRD analyses and SEM observations pointed out that the matrix surface is progressively covered by a calcium carbonate layer as the weathering increases. Results point out that the microbial growth occurs on matrix with a surface composition more like a limestone than a cementitious one.

Primary bioreceptivity of limestones used in southern European monuments

Abstract Different Mediterranean Basin limestones, like Calcário Ançã (Portugal), Calcário Lioz (Portugal), Piedra San Cristobal (Spain), Piedra Escúzar (Spain) and Pietra di Lecce (Italy), have been widely used as building materials in the European architecture. The aim of this study was focused on biodeterioration, mainly on evaluation of the primary bioreceptivity of those materials. A set of samples was inoculated with a cultured photosynthetic biofilm under laboratory conditions. Several assessment tools were applied to monitor the colonization overtime of the different lithotypes. After 3 months of incubation the colonization occurred endolithically in some lithotypes, namely Piedra San Cristobal and Piedra Escúzar . Spectrophotometric determination of chlorophyll a was a useful analytical technique to achieve the total amount of photosynthetic biomass on rock substrates, demonstrating that Piedra Escúzar and Calcário Lioz were the highest and lowest bioreceptive lithotypes, respectively. Microscopic and image analyses were essential to understand the stone colonization process and its pattern of distribution. Physical stone parameters and exposure conditions were shown to play an important role in the establishment and development of photosynthetic colonization.

Evaluation of the efficiency of water-repellent and biocide compounds against microbial colonization of mortars

Abstract Mortars are building material with a high primary bioreceptivity and thus, they are easily colonized by different microorganisms. To reduce this problem, especially if it concerns restoration and conservation of works of art, water repellents and biocides can be applied alone or in combination. This paper describes experimental data carried out in laboratory conditions as well as outdoors with artificially infected mortars to reproduce natural colonization. The effects of three hydrophobic compounds (RHODORSIL RC80, HYDROPHASE SUPERFICI and HYDROPHASE MALTE) applied alone or in combination with the biocide ALGOPHASE and with the new water miscible formulation (ALGOPHASE PH025/d) were studied. Effectiveness was compared with the behavior of untreated mortars. In both types of experiments, it was clearly shown that water repellents alone do not stop microbial colonization, while water repellents plus biocides prevent microbial growth. In addition, it was shown under indoor and outdoor conditions that fungi are able to colonize untreated mortars as well as those treated only with hydrophobic compounds before phototrophic microorganisms. No significant differences were observed among the compounds tested in their efficacy in preventing colonization.

Primary bioreceptivity: A comparative study of different Portuguese lithotypes

The current condition of many historical monuments clearly reveals that they are not immune to “weathering” factors such as biological decay or biodeterioration. In the present study, Portuguese lithotype samples were inoculated in the laboratory with the microalga Stichococcus bacillaris and the cyanobacterium Gloeocapsa alpina in order to study their primary bioreceptivity and to establish an index of bioreceptivity. The types of building stones used were Ançã and Lioz limestone, Portalegre granite and Vila Viçosa white marble, which are materials renowned in Portuguese architecture. Microbial growth, including the area of the stone surface covered, was evaluated by visual examination and measurement of in vivo chlorophyll a fluorescence using a spectrofluorometer fitted with a fibre-optic accessory. It was possible to verify that 4 months after inoculation, colonization had led to development of biofilms similar to those occurring on stone monuments located outdoors. The results showed that Ançã limestone had the highest primary bioreceptivity, followed by Lioz limestone, with Portalegre granite being weakly colonized or not colonized at all. White marble was not taken into account for the bioreceptivity index, since ANOVA results of microbial growth showed greater internal variance among replicates than between these and the other lithotypes.