Caracterização das comunidades de bactérias responsáveis pela biodegradação de resíduos orgânicos no processo de compostagem

Abstract

Brazil is one of the largest exporters of food in the world, and agriculture is one of the main bases of its economy. Still, the major bottlenecks that are presented are the rate of waste, the volume of organic waste generated, and its proper treatment. Considering the great problem in question, we realized the importance of reducing waste generation as a first alternative, and, if it is not possible, seek alternatives, such as composting, to achieve sustainability. The degradation of this material is usually carried out by biological processes and, because of that, the studies for microbiota presented in the composting process is important, as well as the physical-chemical influence present over time. The objective of this work is to characterize the composting process in terms of microbiological and physico-chemical parameters for the production of a quality compound that can be reused, and that can soften the undue accumulation of residues problem; to know and study its biodiversity in the different treatments: commercial and non commercial, as well as to isolate, characterize and locate these microorganisms, and to verify the optimization of the composting process among treatments. In a first moment, we will approach the subject with a theoretical reference, measuring the main points and the most relevant information about the technique, in what mainly concerns the reality of Minas Gerais, as well as the composting plants, and then we will present the experiment conducted in the Biodiesel Department of the Federal University of Lavras in a greenhouse, under controlled conditions of temperature, irrigation and aeration, and the subsequent physical-chemical and microbiological analyzes carried out in the Department of Agricultural Microbiology. As raw material, it was used food waste from the university restaurant and the garden waste, from the campus landscaping. The samples were collected in triplicate at 0, 5, 10, 20, 40, 60, 90 and 120 days, according to the phase changes for counting, isolation and identification of microorganisms, by 10 -8 serial dilution. The isolates were morphologically characterized, purified and submitted to biochemical tests in order to be grouped and tested for the eight enzymatic activities: lignolytic, cellulolytic, amylolytic, pectinolytic, proteolytic, lipolytic, ammonification and phosphate solubilization. 83 mesophilic microorganisms were gotten and they presented Index Enzymatic Index - IE> 2 for pectinolytic, proteolytic and mainly cellulite activities. These microorganisms, in ideal conditions, settle in the field and play an important role in the decomposition of the raw material. The results showed no significant difference between non-commercial, commercial and control treatments, with small variations in relation to physical-chemical and microbiological parameters. Persistent inoculums of isolates were observed throughout the composting process, which were thermotolerant at the beginning of the process. In parallel, the treatments were also tested for phytotoxicity, following the germinative test protocol, with lettuce (Lactuca sativa) and eggplant (Solanum melongena). The Germination Index was higher for lettuce, when 50% commercial treatment was used. When using the environmental treatment, the index for eggplant was higher. In relation to the highest concentrations of the inoculated treatments, the induction index was decreasing in eggplant seeds; the same did not occur with the control.