Análise da produção de compostos orgânicos voláteis por leveduras da microbiota de besouros e abelhas

Abstract

Ethanol production through microbial fermentation has been a consolidated practice for decades, representing a sustainable and renewable alternative. In nature, yeasts consume carbohydrates such as sucrose, which is present in sugarcane and flower nectar, and convert them into ethanol and other Volatile Organic Compounds (VOCs). Although Saccharomyces cerevisae is the most widely used yeast in various biotechnological processes, it has some limitations in producing specific metabolites, requiring genetic modifications to meet demands. However, wild yeasts present in different environments can be explored as an alternative. For example, yeasts that inhabit floral nectaries consume nectar nutrients and produce VOCs crucial in attracting or repelling insects. This directly impacts pollination and can serve as a biocontrol method against pests, protecting certain plants. In this context, this study isolated 26 yeast strains, 7 from stingless bees and 19 from beetles. Among them, seven were randomly selected for testing in rich media or media simulating flower nectar to observe their growth profiles and volatile compound production. Among these yeasts, three strains (CHAP-242, CHAP-245, and CHAP-248) stood out and were subjected to a Central Composite Design (CCD) with four variables: pH and concentration of sucrose, casein peptone, and yeast extract. Sucrose consumption and ethanol production were analyzed by HPLC in these samples after 34 and 96 hours of incubation. In the DCC, CHAP-248 obtained the best results in all analyzed responses, reaching, in some conditions, 100% sucrose consumption, fermentative yield of up to 472.66 mgethanol/gsucrose and productivity of 1595.96 mg/L*h. In addition to ethanol production, VOCs production was evaluated by liquid-liquid extraction and GC-MS at the end of all cultures. Five compounds were more prevalent. 2-Phenylethanol was identified in all samples, while tryptophol was identified in CHAP 245 in the initial screening media and some DCC conditions. Methionol was only found in cultures in rich mediums during screening, with strains CHAP-245 and CHAP-248. Triethyl phosphate was only identified in the rich screening medium in 70% of the strains analyzed, while 2-cyclohexen-1,3,5,5-trimethyl was only found in the synthetic nectar in 60% of the strains analyzed.