Seleção de leveduras potencialmente aromática isoladas da compostagem de serragem enriquecida com farelos

Abstract

Pure sawdust compost has low nitrogen content, hindering the development of microorganisms. However, when enriched with bran, sawdust can be used in composting for mushroom cultivation. During this process, volatile aromatic compounds are produced, indicating the presence of aroma-producing microorganisms. This research aimed to isolate and select yeasts with aromatic potential. The volatile organic compound (VOC) profiles of composts prepared from combinations of different brands (T1 - Sawdust + 20% wheat bran; T2 - Sawdust + 20% rice bran; T3 - Sawdust + 20% cornmeal; T4 - Sawdust + 7% wheat bran + 7% rice bran + 7% cornmeal) were evaluated by gas chromatography-mass spectrometry (GC-MS). After selecting the best compost, yeasts were isolated in DRBC and YEPG media, identified by MALDI-TOF and ITS region sequencing, and subjected to physiological tests. Organic acids produced in BD broth (potato, dextrose) were evaluated by high-performance liquid chromatography (HPLC). Compost T2 was selected because it showed a higher concentration of volatile aromatic compounds, including aldehydes (74.9%), alcohol (44.5%), and esters (38.6%). Before composting, the strains with the highest population were Hanseniaspora valbyensis (8.34 log CFU/g) and Nakazawaea holstii (8.06 log CFU/g). After 48, 96, and 144 hours of composting, Nakazawaea holstii (7.53 log CFU/g), Hanseniaspora valbyensis (6.81 CFU/g), and Pichia manshurica (7.38 log CFU/g) were the species with the highest populations, respectively. Eleven yeasts were selected from the physiological tests and evaluated for the production of VOCs and organic acids in BD medium. Succinic and citric acids were the most abundant organic acids. 2-phenylethyl ester with fruity notes (apple and pear) and phenylethyl alcohol (sweet floral with rose aromas) stood out in the highest area concentration. Although they are not the strains with the largest population, strains 8 (esters - 41% and aldehydes 25.91%), 81 (esters - 53.10%), and P35 (alcohols 42.71%), identified as Wickerhamomyces anomalus, were good producers of VOCs of interest and have potential for use in the natural production of flavors.