Identificação e aplicações biotecnológicas de leveduras isoladas de larvas, intestino de besouros, galerias e madeira em decomposição em áreas de floresta amazônica brasileira

Abstract

The Amazon rainforest may harbor the greatest biodiversity on the planet. However, few studies have been carried out aiming to characterize the diversity of yeasts in the environments of the Brazilian Amazon. The study of yeast interaction with beetles has revealed the presence of unknown species of these microorganisms, many with properties of biotechnological interest. The benefits accrued by both microorganisms and insects during these interactions are still poorly understood. The beetles of the family Passalidae live and feed on decaying wood, having intestines richly colonized by yeasts. Furthermore, some species of yeast associated with decaying wood could ferment D-xylose, the main pentose found in lignocellulosic residues. These microorganisms have potential for use in the production of second-generation ethanol, produced from agricultural, agro-industrial and forest residues. Thus, the objective of this work was to isolate and identify yeasts present in decomposing wood, larvae, and intestinal tract of beetles of the Passalidae family and their habitat (galleries) in areas of the Amazon rainforest in Itacoatiara - Amazonas state. For this purpose, 35 specimens of adult beetles and 11 larvae of the Passalidae family were collected, 29 samples from the interior of galleries inhabited by these insects and 60 samples of decomposing wood from three points in the Amazon forest. In these samples, 143 yeast isolates were obtained from the intestine of beetles, 71 from beetle galleries, 34 from beetle larvae and 82 from samples of decaying wood. The molecular identification of yeast isolates obtained in this work from the four substrates studied, showed the occurrence of 71 species distributed in 24 genera, 37 of which are probable new species. Among the isolated species, Spathaspora passalidarum (n=12) stands out, considered the best producer of ethanol from D- xylose, with great potential to produce 2G bioethanol, in addition to two possible new species of the genus Spathaspora. Overall, the most frequent species were: Apiotrichum siamense (8.6%), Scheffersomyces amazonensis (9.9%), Sugiyamaella sp. 4 (6.6%), Sugiyamaella sp. 5 (5.6%), Sugiyamaella sp. 6 (8.6) and Sugiyamaella sp. 11 (6.3%). The 12 S. passalidarum isolates were submitted to fermentation tests using D-xylose culture medium (30 g/L). These isolates showed ethanol yields (0.16 g/g to 0.41 g/g) and productivities (0.07 g/L/h to 0.24 g/L/h). The new species of Spathaspora sp. 1 produced xylitol as the main fermentation product, showing a yield of 0.54 g/g and productivity of 0.27 g/L/h, with a concentration of 16.1 g/L of xylitol. Spathaspora sp. 2 produced 5.4 g/L of xylitol and 3.19 g/L of ethanol and was able to consume approximately 77% of the D-xylose in 72 h. In trials with hemicellulose hydrolysate of sugarcane bagasse, the tested strains of S. passalidarum showed ethanol yields ranging from 0.28 g/g to 0.32 g/g, productivity from 0.28 g/L/h to 0.32 g/L/h, and ethanol concentrations between 16.4 g/L to 19.4 g/L. The genus Sugiyamaella had 23 possible new species distributed among the four substrates and in the three locations studied. Species of this genus are known for their ability to produce extracellular xylanases, which would help in the degradation of decaying wood. These results show the importance of bioprospecting studies of Amazonian biomes to obtain wild lineages for possible biotechnological applications.