Biorrefinaria aplicada à cadeia de soja: um estudo de caso de extração verde e sustentável de isoflavonas

Abstract

SOY BIOREFINERY: GREEN AND SUSTAINABLE EXTRACTION OF ISOFLAVONES. Brazil has the potential to be the world's largest producer of soybeans (Glycine max), being, in 2020, responsible for the production of 124 Mt of oilseeds. However, about 70% of the mass produced ends up being transformed into waste during the countless processing steps to generate oil, bran and grains. These agro-industrial residues have high added-value substances that can be extracted and reintegrated into the production chain using green techniques. Considering new practices aligned with sustainable development to face global challenges, such as the circular economy and the use of green and sustainable chemical processes, the concept of biorefinery presents itself as an economically viable way to achieve such objectives. This concept seeks creative processes for the extraction and transformation of this residual material that are sustainable in their core. Therefore, the investigation of by-products from soy processing is the first step to reinsert them in the production chain through the concepts of biorefinery and green and sustainable chemistry, establishing initial steps towards a non-linear economy. Thus, the extraction of two bioactive compounds from soy agro-industrial residues, the isoflavones of commercial interest daidzein and genistein, was investigated. For the extraction of these substances, two industrially scalable techniques were used: Extraction Assisted by High-Speed Homogenizer and Extraction Assisted by Ultrasound. For the optimization of procedures, the following chemometric treatments were performed: Full Factorial Design and Fractional Factorial Design, for the selection of the most relevant variables for higher extraction yields, and the Central Composite Design, for the creation of mathematical models capable of describing the best parameters for extraction. In order to make the procedure more sustainable, the extractions were performed only with mixtures of water and ethanol as the extraction solvent and, also, a chromatographic method was developed for quantification in an Ultra High Performance Liquid Chromatograph coupled to a diode array detector in the ultraviolet-visible range. In order to analyze the efficiency of resources use of the experiments, the metric "sustainable factors" was employed, considering sample mass, solvent volume, energy and time. The chromatographic method developed proved to be selective, linear and with adequate limits of detection and quantification for the extracts obtained. Among the variables studied, the sample-to-solvent ratio and the composition of the extraction solvent are the most significant for both techniques. The highest extraction yield obtained (in mg g-1) for extraction using homogenizer was 0.11 for daidzein and 0.071 for genistein; and for extraction using the ultrasonic bath it was 0.14 for daidzein and 0.082 for genistein. When analyzing the results, some experiments with slightly lower extraction yields showed greater efficiency in the use of resources considering the mass of the extracted analytes. In general, it was shown that it is possible to adopt agro-industrial residues as sources of commercially important molecules. These compounds extraction from processing residues can be carried out in an efficient and sustainable manner.