DETECTION OF BIOACTIVE COMPOUNDS IN WASTES OF CERRADO FRUITS BY ARTEMIA SALINA BIOASSAY AND PARA-MAGNETIC RESSONANCE. STUDY OF THEIR INFLUENCE ON BIOETHANOL PRODUCTION

The study of biotechnological potential of fruit wastes such as seeds and peels involves not only their nutritional content to sustain a fermentation process, but also the presence of bioactive compounds that could prevent or disrupt cell growth and product formation. The aim of this work was to study the influence of antioxidant compounds and toxic acetogenins on yeast growth and ethanol production using shells of Caryocar brasiliensis (pequi), Dypterix alata (baru), and seeds of Annona muricata (graviola), Annona squamosa (ata) and Annona crassiflora (araticum) as substrates. Toxins were detected using bioassay with Artemia salina while paramagnetic resonance analysis was used to detect antioxidant compounds. Samples were treated with amyloglucosidase for starch hydrolysis and added to yeast broth as carbohydrate substitutes. Fermentations were run in triplicates, in 100 mL Erlenmeyer flasks during 48 hours, using Saccharomyces cerevisiae, strain S-05. Cell growth was evaluated by counting in Neubauer chamber, while ethanol production was calculated from the amount of carbon dioxide released (weight loss). Antioxidant compounds were found only in baru shells while toxic acetogenins were present in all annonaceous seeds. Cell concentration increased from 1.23x10⁷ cells/mL to 3.07x10⁷ cells/mL. Ethanol yield ranged from 1.35 to 9.14 g/100 mL. Phenolic compounds found in baru shells did not affect fermentation process. Acetogenins inhibit the electron transport chain and cell respiration. Some yeast species can find alternate routes when exposed to inhibitors and this could explain the cell growth observed in all cultures containing annonaceous seeds. Since ethanol production is an anaerobic process, it was not apparently affected by acetogenins. These results evidence the potential of such wastes for ethanolic fermentation, with no need to previously remove or inactivate bioactive compounds and moreover, a possibility to reduce high volumes of residues generated from fruit consumption, both in natura or from manufactured industrial derivatives.