Only the most adapted organisms can survive an environment exposed to the sun daily and the temperature variations that occur throughout the day. Where water, when it appears, does not stay for long.
Researchers supported FAPESP found a set of bacteria and yeast adapted to these conditions in photovoltaic panels, those that transform solar energy into electricity, installed in the cities of Sorocaba and Itatiba, in the interior of São Paulo.
The study was published in the magazine Microbiology Letters, from the Federation of European Societies for Microbiology, and was chosen by the journal’s editors as one of the highlights of the issue.
Due to their characteristics, the microorganisms found have great potential for the development of products that can be exposed for long periods to solar radiation, such as sunscreens, pigments for the food, chemical, textile, pharmaceutical and cosmetic industries, in addition to more efficient detergents for cleaning the panels themselves, with antimicrobial action.
“We observed that the composition of this microbiota is very similar to that found in photovoltaic panels in Valencia [Espanha], Berkeley [Estados Unidos] and even in the Arctic and Antarctica”, says Juliane Moura, who carried out the study during her master’s degree in the Postgraduate Program in Biotechnology and Environmental Monitoring (PPGBMA) at the Federal University of São Carlos (UFSCar), in Sorocaba, with a grant from Coordination for the Improvement of Higher Education Personnel (Capes).
“Although the climatic conditions are different between the panels in the countries studied, the surface of the equipment houses a community of microorganisms adapted to solar radiation, temperature fluctuations, scarcity of water and the material the plates are made of”, he explains Ioland Duarte, professor at the Department of Biology at the Center for Human and Biological Sciences (CCHB) at UFSCar and coordinator of the study.
To collect the samples, the researchers passed a cotton cloth soaked in a sterile solution over photovoltaic modules in Sorocaba and Itatiba. The material was then packaged and taken to the UFSCar Applied Microbiology Laboratory, where the DNA was extracted.
Using partial gene sequencing 16S rRNA, the researchers found a similar microbial composition among the analyzed samples, although the one from Sorocaba, collected in the rural area, presented a slightly greater diversity.
The results were similar to those of works carried out in Spain, the United States and the poles, despite the geographic distance and climatic differences. Bacterial genera Methylobacterium-methylorubrum and Hymenobacter accounted for more than 90% of the diversity observed in the study.
Understanding how the microorganism community in photovoltaic panels works can even help to maintain the efficiency of this equipment over time. In Brazil, studies have already shown that the dust accumulated on the plates can reduce energy capture by 11% after 18 months of installation. In deserts, the reduction can reach 39%, going from 50% when there are extreme events, such as sandstorms, for example.
In addition to sand and other particles, the dust found in these equipment is rich in microorganisms. As a survival strategy, some bacteria are grouped in so-called biofilms, films that end up covering the panels and helping to reduce the capture of solar radiation.
For the next phase of the work, which is not included in the article published now, the researchers isolated a pigmented yeast, also found in solar panels in cold climate regions, which can produce biodetergents.
These molecules are considered versatile in terms of their applications, since they have surface-active characteristics, that is, they reduce the surface tension of water and, thus, help to mix water and insoluble substances.
Furthermore, they can be used as antimicrobials, antitumours and in bioremediation, as the use of biological processes to degrade, transform or remove contaminants from the environment is called.
“Biofilm removal is a difficult problem to be solved in many economic activities. Thus, the study is fundamental for the development of new management strategies for these panels. Future research with biodetergent-producing yeast may offer an alternative in the formulation of more effective cleaning products for these and other equipment”, says Duarte.
Organisms that withstand conditions such as those found in photovoltaic panels are known as extremophiles. Some of the groups of bacteria found in Sorocaba and Itatiba, for example, have already been found in soil samples from the deserts of Taklamaken, China, Gobi, Mongolia, and Atacama, Chile.
Some of the isolates caught the researchers’ attention because they are pigmented and grow in different temperature ranges (3 oC to 50 oC). The presence of pigment may be associated with the potential to overcome the so-called oxidative stress, when there is an excessive production of free radicals and reactive oxygen species, which start to cause damage to the body.
Solar radiation and water loss are some of the causes of oxidative stress. With a smooth and sloping surface, the photovoltaic panels are designed so as not to retain water from rain or occasional washing.
The researchers isolated 63 microorganisms with the potential to resist ultraviolet rays. In the laboratory, they will be evaluated regarding their resistance to this radiation and the possibilities of biotechnological application.
The article Extremophilic taxa predominate in a microbial community of photovoltaic panels in a tropical region, by Juliane B. Moura, Tiago P. Delforno, Pierre F. do Prado and Iolanda C. Duarte, can be read in: https://academic.oup.com/femsle/article/368/16/fnab105/6350555.