Leveduras associadas a frutos da macaúba (Acrocomia aculeata (Jaq.) Lodd. ex Mart): diversidade e caracterização quanto à produção de exoenzimas e fatores de crescimento

Abstract

The study of the diversity of microorganisms associated with plants and the various organic compounds produced in this interaction is important to determine the beneficial or harmful effects on the host. This work aimed to study the diversity of yeasts isolated from macaw palm fruit, a promising plant for biodiesel production in Brazil, and to characterize those microorganisms regarding the potential production of extracellular enzymes and growth promoting factors. A total of 529 yeast isolates was obtained from the surface and internal tissues of fruits with different times of deposition in the soil. The isolates were grouped according to their macro-morphology and banding pattern by PCR fingerprinting using primer (GTG)5, and identified by sequencing the D1/D2 regions of the 26S rRNA gene and ITS1 5.8S - ITS2 rDNA using the primers NL1/NL4 and ITS1/ITS4. A total of 39 species belonging to 19 genera was identified. The most frequent taxa identified were Meyerozyma guilliermondii, Candida sorboxylosa, Hanseniaspora opuntiae, Hanseniaspora uvarum, Pichia membranifaciens and Fellomyces polyborus. Epiphytic communities presented higher values of richness, abundance and colonization rate than the endophytic communities. Among the communities collected at different times, the increase in abundance as a function of the time of deposition of the fruits in the soil (only for epiphytic) was observed as well as a high rate of species substitution. The dominance of M. guilliermondii was observed during the experimental period. In the qualitative assays on solid medium, 6.6% of the isolates were positive for amylase production; 12 % for cellulose; 7.9% for pectinase; 1.2% for xylanase; 6.6% for lipase; 5.4% for proteinases; 88.8% were able to solubilize calcium phosphate; and 48.5% were able to hydrolyze phytate calcium. A total of 98% of the isolates was able to produce indole-3-acetic acid on liquid medium supplemented with L- tryptophan, at concentrations ranging from 1.63 to 238.65 g* mL-1*OD600-1 . AIA concentrations were obtained using the photocolorimetric method of Salkoviski reagent. Enzyme activities and the production of phytase by isolates displayed distinct distribution when considering different times of macaw palm fruit deposition in the soil.