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Quantification of microbial load in diesel storage tanks using culture- and qPCR-based approaches
(2016)
Microbial contamination of fuels, associated with a wide variety of bacteria and fungi, leads to decreased product quality and can compromise equipment performance by biofouling and microbiologically influenced corrosion of pipelines and storage tanks. Detection and quantification of biomass are critical in monitoring fuel systems for an early detection of microbial outbreaks. The aims of this study are (i) to quantify bacterial and fungal contamination in samples from diesel storage tanks of petrol stations, using both culture dependent- and culture independent (qPCR) approaches, and (ii) to analyse the diversity of cultivable diesel-contaminating microorganisms with the purpose to create a strain collection for further use in biodeterioration experiments. Both methodological approaches revealed a high microbial contamination in all studied samples, with the bacterial load being much higher than the fungal load. The diversity of cultivable microorganisms was rather low. Based on criteria of abundance and fuel degradation potential, the most relevant microorganisms were identified as bacteria of genera Bacillus, Citrobacter, Burkholderia and Acetobacter, the filamentous fungi Paecilomyces variotii and Pseudallescheria boydii, and a Dipodascaceae yeast. Furthermore the validity and utility of qPCR-based methods are discussed.
Soiling of photovoltaic (PV) systems compromises their performance causing a significant power loss and demanding periodical cleaning actions. This phenomenon raises great concerns in the solar energy field, thus leading to notable research efforts over the last decades. Soiling is caused by a dual action of dust deposition and biofouling. However, surprisingly, the microbiological contribution to PV soiling is often overlooked or underestimated. In this study, a variety of qPCR-based methods have been developed to quantify the microbial load of fungi, bacteria and phototrophs on PV panels. These protocols were evaluated by comparison with culturedependent methods, and were implemented with real solar plants for two years. The results show that the developed molecular methods are highly sensitive and reliable to monitor the microbial component of the soiling. Fungal biomass was clearly dominant in all analysed PV modules, while bacteria and phototrophs showed much lower abundance. Light microscopy and qPCR results revealed that melanised microcolonial fungi and phototrophs are the main biofilm-forming microorganisms on the studied solar panels. In particular, the fungal qPCR protocol is proposed as a useful tool for monitoring of PV soiling, and investigating the microbial contribution to specific soiling cases.
A wide variety of fungi and bacteria are known to contaminate fuels and fuel systems. These microbial contaminants have been linked to fuel system fouling and corrosion. The fungus Hormoconis resinae, a common jet fuel contaminant, is used in this study as a model for developing innovative risk assessment methods. A novel qPCR protocol to detect and quantify H. resinae in, and together with, total fungal contamination of fuel systems is reported. Two primer sets, targeting the markers RPB2 and ITS, were selected for their remarkable specificity and sensitivity. These primers were successfully applied on fungal cultures and diesel samples demonstrating the validity and reliability of the established qPCR protocol. This novel tool allows clarification of the current role of H. resinae in fuel contamination cases, as well as providing a technique to detect fungal outbreaks in fuel systems. This tool can be expanded to other well-known fuel-deteriorating microorganisms.