Identificação de fungos filamentosos contaminantes em sistema aberto de tratamento de soro do leite por microalgas

Abstract

Inadequate disposal of effluents from dairy manufacturing units can degrade the environment due to the high level of pollutants present in whey. Therefore, it is necessary to pre-treat this effluent before releasing it into water bodies, however, the physical-chemical treatments generally applied to this type of effluent are highly expensive, making it unfeasible for small and medium-sized industries. In this context, biological processes gain prominence due to the simplicity of their application and economic viability. Compared to traditional biological treatment strategies, the use of microalgae has advantages such as greater nutrient consumption capacity, mainly nitrogen and phosphorus, and they are generally cultivated in an open system, which has a high risk of contamination by other microbiological groups. In view of this, the symbiotic relationship between algae and fungi is highlighted as this association facilitates the harvesting of algae by copelletizing them into fungus pellets, which can increase the efficiency of the treatment. Therefore, the present work aims to characterize filamentous fungi isolated during the tertiary treatment process of whey by microalgae of the species Tetradesmus obliquus LCE-01 in an open system. The treatment system for T. obliquus LCE01 was composed of open reactors using residual effluent with organic loads (Chemical Oxygen Demand) between 1000-4000 mg L-1, magnetically stirred, during 15 days of process, maintained at 30-35ºC and pH 7.5-8.0 with lateral illumination of 100 µmol m-2 s-1. The reactor samples were collected after vigorous microbial growth in the reactor (log CFU mL-1 between 9-10) and inoculated by spreading in Petri dishes with PDA medium (potato dextrose agar) in dilutions 10-2, 10-4 and 10-6, in order to favor the growth of isolated colonies. It was possible to isolate 9 fungal strains, of which, after a few generations of breeding, only 5 remained viable for cultivation in the laboratory (F2, F4, F5, F6 and F10), which were used for the characterization steps at the macro and micromolecular level, being It is possible to find the genus of the strains specifically, Cladosporium, Epidermophyton, Trichophyton, Chrysosporium and Penicillium, respectively. Preliminary molecular characterization was carried out following the steps of DNA extraction and amplification of fungal DNA using the primers ITS (Internal Transcript Spacer) (1 and 4) and beta-tubulin (β-tub or BT) (2a, 2b, T1 and T2), which was effective, and can be sequenced for inferring phylogenetic trees and depositing them in databases.