Unprecedented process can mitigate effects
harmful by-product generated by the orange juice industry

Microorganisms
degrade industrial pollutant

MANUEL ALVES FILHO

O Control of industrial pollutants through biological processes is one of the objectives of a line of research coordinated by professor Lucia Regina Durrant, from the Faculty of Food Engineering (FEA) at Unicamp. Recently, the effort gained a new contribution, thanks to the study developed for the doctoral thesis of one of his supervisees, pharmacist Fabiana André Falconi. She isolated and subsequently selected microorganisms capable of degrading high concentrations of D-limonene, a byproduct generated by the orange juice industry and which can cause damage to the environment if discarded together with effluents. The degradation rates obtained from laboratory tests were 80% and 50%, in a synthetic medium with D-limonene and in citrus industry effluents, respectively.

Countries already manufacture packages of microorganisms

Fabiana's research, which has unprecedented contours, started from a practical problem, as explained by professor Lucia Durrant. The FEA professor was called by an orange juice industry located in the region of São José do Rio Preto, in the interior of São Paulo, to verify a problem related to its effluent treatment line, which emitted a strong and unpleasant odor. On that occasion, the company interrupted its activities for more than a week. “Based on data from the literature, I imagined that the problem was related to the high concentration of D-limonene. This gave me the idea of ​​proposing the development of a study focused on the biodegradation of this compound, a challenge that was readily embraced by Fabiana”.

Simply put, D-limonene is the main component of orange peel oil. It is that substance that, when in contact with the eyes, causes burning. Although it has applications in the chemical, pharmaceutical, and cosmetics industries, D-limonene also has a strong antimicrobial action. Its release into the industrial effluent treatment line is harmful, as it can destroy the microbial flora present there. The work of the thesis author consisted, firstly, of isolating the microorganisms present in the effluent generated by the citrus industry. Initially, it reached 570 fungi, bacteria and yeasts. To these were added another 58 microorganisms belonging to the collection of the FEA Microbial Systematics and Physiology Laboratory, making a total of 628.

The next step was to select those that had the capacity to degrade high concentrations of D-limonene. Of the total, only five microorganisms were considered. Of these, three were identified and effectively used in laboratory tests: the bacteria Pseudomonas sp and Enterobacter sp and the fungus Fusarium sp. The degradation rates obtained, as already mentioned, were 80% and 50% in synthetic media with D-limonene and in effluents from the citrus industry, respectively. The concentration of D-limonene in which the microorganisms showed better growth, percentage of degradation and enzymatic activities was 3%.

The results achieved by the study are encouraging, according to professor Lucia Durrant. “We have a good indication that the microorganisms that Fabiana worked with can be returned to the effluents and, thus, act on the degradation of D-limonene. This proof, however, will depend on new studies”, she explains. Fabiana highlights that she worked with microorganisms in isolation. “The sequence to be taken in new research is to promote a consortium of microorganisms, to check whether it is possible to further improve degradation rates,” she says. The pharmaceutical company adds that the objective to be achieved in the future is the total degradation of D-limonene in effluents. In the area of ​​fine chemistry, the goal is to use microorganisms to transform the substance into compounds that can be used in the manufacture of medicines, perfumes, etc.

According to professor Lucia Durrant, the development of this type of technology is very important for Brazil. She points out that some countries already manufacture “packages” of microorganisms that fulfill the function of degrading pollutants, a concept known as bioremediation. However, these products, normally priced in dollars, are very expensive. Furthermore, there is always the risk that bacteria, fungi or yeasts that are not native to Brazil could have harmful effects on our environment.

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