The associated use of biocides and biopolymer membranes is a viable alternative to the microbiological control of systems involving water distribution, replacing more aggressive products, which can cause damage to the environment and compromise sustainability. The conclusion is a doctoral thesis by biochemical pharmacist Raquel Vannucci Capelletti, defended at the Faculty of Chemical Engineering (FEQ) at Unicamp, under the guidance of professor Ângela Maria Moraes. According to the author, the study opens up a wide range of applications for this strategy, mainly from the combination of biocides with chitosan membranes.

According to Raquel, microorganisms have been present on Earth long before the emergence of the human species. And it is very likely that they will survive it. These microscopic beings can be found on the most varied surfaces in nature, as well as in industrial processes designed by man. Their colonies can concentrate on moist interfaces in the form of films, forming what experts call biofilms. These can be found, for example, on the surface of teeth or in water pipes in industries, homes and hospitals.

The presence of biofilms in these places, observes Raquel, can lead to the spread of pathogenic agents throughout the environment, eventually causing the contamination of people. “The presence of biofilms in hospital water pipes, for example, can be decisive for the spread of infectious diseases, especially among people with weakened immune systems, such as patients admitted to ICUs. Hypothetically, this contamination can even occur when bathing, through shower water”, he warns.

In the case of a food industry, continues the author of the thesis, biofilms can develop on the surface of tanks and pipes responsible for processing or transporting food, causing serious risks of contamination or damage to equipment. One of the ways to promote microbiological control is to carry out constant cleaning and sanitation procedures. One of the most used strategies is the application of biocides, substances with germicidal action. “It turns out that the indiscriminate use of these products to combat microbial activity can generate resistant cultures and cause corrosion in pipes”, observes Raquel.

The researcher highlights that eliminating biofilms from industrial, hospital and residential environments is not a trivial task. Although this type of procedure can be carried out with 100% effectiveness, it is not always recommended that the eradication of microorganisms be complete, both because of the costs involved and technical issues. “Some industrial processes can coexist with small clusters of biofilms. However, it is worth emphasizing that patients with poor health or who use prostheses or catheters are at greater risk from biofilms.”

Water, remembers Raquel, is an essential compound for the development of living beings, including microorganisms. “In other words, wherever there is water there will be microbial activity. Depending on the conditions of this aqueous medium, we may have a greater or lesser amount of dispersed or associated microorganisms,” she explains. In her research, Raquel promoted the combined use of commercial biocides with biopolymer membranes with the aim of preventing contamination by biofilms. “We use reference biocides with [long-lasting] preservative and [ephemeral] sanitizing action”, she informs.

As for biopolymer membranes, the researcher used materials developed at FEQ's Bioreaction and Colloid Engineering Laboratory. Membranes produced with chitosan [a substance obtained from chitin, present in the carapace of crustaceans, notably crabs and shrimps] and alginate [whose main sources are some species of algae], both of low toxicity to humans, were tested. Chitosan, by itself, has appreciable antimicrobial properties under certain conditions of use.

Alginate, on the other hand, has more limited activity. “During the tests, several steps were completed. Firstly, we checked whether it was technically feasible to use membranes produced with different types of chitosan and alginate, alone or in combination with biocides, replacing more aggressive chemical agents in microbial control”, details the researcher.

Afterwards, Raquel evaluated the antimicrobial activity of the devices against microorganisms usually applied for laboratory validation of these systems and also against resistant cultures originating from water systems in industrial environments. Next, she sought to determine how the membrane selected as the most promising works, in this case the one produced from chitosan, and its level of effectiveness. “What we were able to verify was that the use of chitosan and alginate as materials for the production of membranes that incorporate agents with antimicrobial activities proved to be suitable for the purpose of controlling the development of biofilms formed by common contaminants”, she states.

Based on the steps completed throughout the research, the author of the thesis proposed a set of recommendations on the care that should be adopted by the industrial segment. The suggestions also indicate guidelines for other environments susceptible to contamination, such as the food processing segment, articles for human use and health care. According to Raquel, the tests that made up the study were carried out in a changing room located in an industrial unit that processes chemical products for school production, in which important sources of contamination were identified and, consequently, a high potential for compromising human health. .

Raquel considers that the research uncovered a wide range of applications for the use of this type of microbiological control strategy, particularly the use of chitosan membrane associated with biocides. “We are considering continuing the study, this time analyzing the feasibility of using membranes to cover material surfaces in water distribution facilities, similar to what is done with reverse osmosis membranes. This would allow, for example, the incorporation of new contaminant detection technologies through real-time computerized monitoring, for a more accurate assessment of system performance,” she infers.

The biochemical pharmaceutical company did not receive a scholarship from funding agencies, but had the support of the company she works for, Thor Brasil Ltda, which provided its laboratories to carry out the analyses, as well as releasing it on certain days of the week. to participate in theoretical studies and experiments at Unicamp. “This type of partnership between the private sector and renowned research institutions such as Unicamp, which results in the training of qualified personnel and the development of new technologies, is very important for the production chain and the advancement of our country”, he considers Raquel.

Publication
Thesis: “Analysis of the association of antimicrobial agents with biopolymers for the control of biofilms in environments susceptible to the development of contaminants from water”
Author: Raquel Vannucci Capelletti
Advisor: Angela Maria Moraes
Unity: Faculty of Chemical Engineering (FEQ)