Pamela Principi

Feasibility of Removing Surface Deposits on Stone Using Biological and Chemical Remediation Methods

The study was conducted on alterations found on stone artwork and integrates microbial control and a biotechnological method for the removal of undesirable chemical substances. The Demetra and Cronos sculptures are two of 12 stone statues decorating the courtyard of the Buonconsiglio Castle in Trento (Italy). An initial inspection of the statues revealed putative black crusts and highlighted the microbial contamination causing discoloration. In 2006, the Cultural Heritage Superintendence of Trento commissioned us to study and remove these chemical and biological stains. Stereomicroscopy characterised the stone of the sculptures as oolitic limestone, and infrared analyses confirmed the presence of black crusts. To remove the black crusts, we applied a remediation treatment of sulphate-reducing bacteria, which removes the chemical alteration but preserves the original stone and the patina noble. Using traditional and biomolecular methods, we studied the putative microbial contamination and confirmed the presence of biodeteriogens and chose biocide Biotin N for the removal of the agents causing the discolouration. Denaturing gradient gel electrophoresis fluorescent in situ hybridisation established that Cyanobacteria and green algae genera were responsible for the green staining whereas the black microbial contamination was due to dematiaceous fungi. After the biocide Biotin N treatment, we applied molecular methods and demonstrated that the Cyanobacteria, and most of the green algae and dematiaceous fungi, had been efficiently removed. The reported case study reveals that conservators can benefit from an integrated biotechnological approach aimed at the biocleaning of chemical alterations and the abatement of biodeteriogens.

Synthetic Consolidants Attacked by Melanin-Producing Fungi: Case Study of the Biodeterioration of Milan (Italy) Cathedral Marble Treated with Acrylics

ABSTRACT Monuments and artistic stone surfaces are often consolidated and protected with synthetic polymers, in particular, acrylics. Although it is generally thought that acrylic polymers are resistant to biodeterioration, we report for the first time the systematic occurrence of dematiaceous meristematic fungi on many marble samples of the cathedral in Milan (Italy) previously treated with this material. Fourier transform infrared spectroscopy applied to the Milan cathedral stone samples revealed characteristic features of biodeteriorated synthetic resins that differentiated them from the aged but nonbiodeteriorated samples. Samples showing biological colonization were analyzed for the presence of fungi. Cultivation and morphological characterization and methods independent from cultivation, such as denaturing gradient gel electrophoresis coupled with partial 18S rRNA gene sequencing and immunofluorescence staining with melanin-binding antibodies, showed that melanin-producing species are heavily present on stone surfaces protected with acrylic resins. This observation raises the question of the effectiveness of acrylics in protecting stone artworks.

Bacterial aerosol emission from wastewater treatment plants:Culture methods and bio-molecular tools

In this report we describe the results of a studyconducted in order to better estimate airbornemicroorganisms. A method based on a bio-moleculartechnique, Polymerase Chain Reaction (PCR) wascompared with the culture methods based on the viablecounts of total and fecal bacteria. Microbial aerosolemission from the surfaces of aeration tanks of anindustrial and municipal wastewater treatment plant(Como, Italy), at different seasons, was determined.This study was accomplished by conducting test runs inwhich SAS (Surface Air Systems, PBI) viable sampler,Sartorius MD8 with membrane gelatine filter andgravity method with Petri dishes were used to collectbacterial aerosol samples in situ. Total aerobicheterothropic bacteria, Mycetes, total and fecalcoliforms were determined. The preliminary resultsshow that: no correlation was found between the twodifferent passive and active culture techniques, dueto the different mechanisms of capture of bioaerosolagents on the media; optimal values for the recoveryof E. coli viable bacteria by MD8 samplerwith gelatine membrane, time and temperature ofstorage, were recognised. For the PCR technique, acouple of primers (URL 301–URR 432) to detect E. coli, on definite air samples, was used, operativeconditions were defined, and then, applied inmonitoring on in situ bioaerosol samples. At thewastewater plant, the highest total aerobic bacteriaemission rate during the preliminary mechanicaltreatments and in correspondence of the enclosedactivated sludge phase, as a consequence of theremarkable aeration of the tanks, were registered. Thesensitivity (82 CFU/m3) and rapidity (less than 8hours) of the biomolecular methods to determine thepresence and the fecal coliforms (E. coli) ratein bioaerosols was considered satisfactory.

A simple and reliable methodology to detect egg white in art samples

A protocol for a simple and reliable dot-blot immunoassay was developed and optimized to test work of art samples for the presence of specific proteinaceus material (i.e. ovalbumin-based). The analytical protocol has been extensively set up with respect, among the other, to protein extraction conditions, to densitometric analysis and to the colorimetric reaction conditions. Feasibility evaluation demonstrated that a commercial scanner and a free image analysis software can be used for the data acquisition and elaboration, thus facilitating the application of the proposed protocol to commonly equipped laboratories and to laboratories of museums and conservation centres. The introduction of method of standard additions in the analysis of fresh and artificially aged laboratory-prepared samples, containing egg white and various pigments, allowed us to evaluate the matrix effect and the effect of sample aging and to generate threshold density values useful for the detection of ovalbumin in samples from ancient works of art. The efficacy of the developed dot-blot immunoassay was proved testing microsamples from 13th–16th century mural paintings of Saint Francesco Church in Lodi (Italy). Despite the aging, the altered conditions of conservation, the complex matrix, and the micro-size of samples, the presence of ovalbumin was detected in all those mural painting samples where mass-spectrometry-based proteomic analysis unambiguously detected ovalbumin peptides.

The effect of copper on the structure of the ammonia-oxidizing microbial community in an activated sludge wastewater treatment plant.

Molecular approaches based on both whole-cell and extracted DNA were applied to assess chronic and acute effects of copper on the ammonia oxidizing bacteria (AOB) community in an activated sludge system. The ammonia monooxygenase amoA gene was chosen as the functional marker to evaluate changes in the AOB community. Using in situ polymerase chain reaction, we were able to visualize the peripheric distribution of the amoA gene-possessing bacteria in activated sludge flocs. The AOB biomass content was constant in both chronic and acute toxicity experiments, but the ammonia oxidizing activity, measured as ammonia uptake rate, was different. The AOB community structural changes due to the copper presence were evaluated by multivariate analysis of the DGGE bands profiles. The chronic contamination caused a change in the AOB community compared to the control. In contrast, acute inputs led to a temporary change in the AOB community, after which the community was similar to the control. Recovery after acute intoxication was achieved after 72 h. The present study reports on the effects of chronic and acute copper contamination on the ammonia uptake ability of the AO microorganisms and the structure of the AOB community in a wastewater system and, as a consequence, gives indications on the response of wastewater plants under similar conditions.

Microbiological aspects of humid husk composting.

The feasibility of composting as disposal practice of husk mixed with olive mill wastewaters (OMW) was studied in the present research. The process was investigated with regards to some reliable and easy to be determined microbial activity parameters such as the ATP content, the activity of a pool of enzymes and the viable counts, keeping in mind the well known bias of this last technique. Two different composting technologies were compared: static pile and reactor by studying the cured composts obtained. Among the bioindicators tested, the composting process trend was described better by the ATP content and the activity of some enzymes. In fact, the ATP content showed an increase during the thermophilic phase in both the pile and the reactor, and decreased at the end of the process, it was also higher in the bioreactor‐pile technology than in the pile. With regard to the enzymatic activity, with the reactor technology experiment, two peaks were evidenced in the thermophilic phase and during the curing phase in pile, and a drop during the transfer of material from the reactor to the pile. The quality of the cured product obtained using the reactor technology has been evaluated considering phytoxicity and hygienic features: the stabilised compost resulted to have neither phytoxical effect, nor faecal indicator contaminants.

Pile Composting of Two-phase Centrifuged Olive Husks: Bioindicators of the Process

Composting is a process largely used to solve the organic material disposal problem, but composting of the olive husks produced by two-phase technology remains largely unknown. Because of their high content of salts, polyphenols, fatty acids and tannins, husk utilisation as fertiliser is not possible. Composting of the husks could permit the reduction of salt content and conversion of phenolic compounds into humic substances, but the knowledge about conditions of starting up, running the plant, degradation and microbiological characteristics of the cured compost has to be improved. Trials were carried out with uninoculated (A), and inoculated (B) piles and the process was monitored by ATP content and a pool of enzyme activities. The results showed that the performance of the process improved from pile A to pile B and ATP and mainly a pool of enzyme activities (alkaline phosphatase, esterase, esterase-lipase, phosphoamidase, β-galactosidase, β-gluco-sidase) showed effectiveness in the description of process. Finally, the molecular methods used to detect faecal contaminants in the cured compost resulted to be reliable.

Permeabilization method for in‐situ investigation of fungal conidia on surfaces

Aims:  4′,6‐diamidino‐2‐phenylindole (DAPI) staining and fluorescent in‐situ hybridization (FISH) show great potential for the detection of fungal conidia, also conserving the spatial architecture of their colonization. These investigations are often greatly hampered by the complicated wall structure of many fungal taxa. The aim of the present study was to develop an efficient permeabilization strategy for both DAPI staining and the FISH technique, applicable to various fungal species and maintaining their relationships with surfaces.