Dinâmica microbiana sob ação de inoculantes em compostagem de resíduos orgânicos

Abstract

Knowledge of the composition and microbial structure of compost is necessary to control the process and determine the quality of the compost. The objective of this work was to evaluate the physicochemical and microbial dynamics of the composting process of the organic residues of the Federal University of Lavras - UFLA, compare the use of two inoculants for the process, isolate, characterize and identify strains of yeasts and filamentous fungi in different treatments throughout the composting process. Composting was performed in the Biodiesel - UFLA sector. Samples were collected during the process according to temperature changes for physical, chemical, counting, isolation and identification of microorganisms, followed by clustering of the isolates by MALDI-TOF MS and sequencing of the rDNA region. The isolated microorganisms were tested for the expression of eight activities of biotechnological interest and the enzymatic potential of these microorganisms was evaluated. The HPLC technique was used to identify metabolites. The profile of the microbial community during the composting process was evaluated through the PCR-DGGE technique. The identified yeasts belonged to the species Issatchenkia orientalis, Myllerozyma farinosa, Pichia kudriavzevii, Candida tropicalis, Blastobotrys raffinosifermentans, Blastobotrys adeninivorans, Wickerhamomyces anomalus, Hanseniaspora opuntiae, Bipolaris sorokiniana. The species Blastobotrys adeninivorans, Blastobotrys raffinosifermentans and Bipolaris sorokiniana had not yet been reported in the composting process. Some genera and species of fungi in common were observed in all treatments: Aspergillus niger, Aspergillus parasiticus, Aspergillus ochraceus, Aspergillus oryzae, Aspergillus caepitosus, Penicillium solitum, Rhizopus and Cladosporium. The results obtained allow to highlight the isolates of the species Issatchenkia orientalis, Candida tropicalis, Millerozyma farinosa and Aspergillus spp. as promising enzymes producers. The analysis of organic matter transformation during composting of organic wastes shows complex physical, chemical and microbiological interactions. The thermophilic phase is crucial to determine the evolution of the process and the temperature was considered one of the most important factors that impacted the composting process due to its critical role in the selection of several microorganisms that degrade organic compounds and promote the maturation of the compound. The detection and quantification of the present metabolites justifies the pH values and characterizes the activities of the microorganisms throughout the composting process. Several isolates of yeasts and fungi exhibited metabolic capacities that may find many biotechnological applications, especially the isolates of the species Issachenkia orientalis, Candida tropicalis, Millerozyma farinosa and Aspergillus spp. as promising enzymes producers. This study contributes to the cataloging of specific microorganisms in the composting ecosystem and reaffirms the potential of composting as a source of biotechnologically relevant microorganisms.