Resumo

Biological treatment by activated sludge process has been widely used to industrial effluents. The microbiota capacity to degrade different organic compounds suggests that biological system could consume the blend and polymers formulation. Many synthetic materials like poly (ε-caprolactone) (PCL) are partial degraded by microorganism in the environment which contributes to their long life-time. One viable alternative to accelerate the biological attack to PCL is the addition of natural polymers like starch, to guarantee potential biodegradation. Starch is an abundant and low cost raw material in the market. Fluorescent in situ hybridization (FISH) is a molecular technique that is often used to identify and enumerate specific microbial groups. This technique can be used to detect specific genetic elements in a sample using a fluorescent labeled probe and fluorescent microscopy. The aim of this study is identify, by FISH, the activated sludge microbiota responsible to biodegradation of PCL and their blend with starch. The material used in this study was PCL P-787 (Union Carbide, Brazil) and maize starch SNOW-FLAKE® 064051 (Corn Products, Brazil). The blend proportion was 35% (w/w) starch, 15% (w/w) plasticizer and the 50% (w/w) PCL. The blend and plasticized PCL were prepared as films with 0.90 mm of thickness and 2 x 6 cm sizes. Aerobic biodegradation was performed in a batch reactor (capacity of 2, 5 L), containing PCL and PCL/starch blend films and inoculums, at room temperature under constant aeration for until 120 days. The biodegradation process was observed by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The FISH analysis was carried out using different probes specific for Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Actinobacteria, Archaea, Firmicutes, Chloroflexi, Mycobacterium and Eukaria. PCL presented low degradation by this biological system, however, the blend degradation increased as verified by SEM and AFM. This behaviour was expected since starch is recognized by many microorganisms in nature, facilitating the PCL biodegradation. It was observed a low mass reduction in 84 % to the blend PCL/starch and 41% to PCL film. FISH results show that the microbiota suffered variation under PCL biodegradation process and it was observed positive fluorescent signal for Gammaproteobacteria, Firmicutes, and Mycobacterium. To PCL/starch blend biodegradation the positive results were for Alphaproteobacteria and Betaproteobacteria. The activated sludge was a very promising process to study the biodegradation of PCL/starch blend and PCL film as observed in this work.