Diversidade de fungos presentes em lagos da Antártica e detecção de enzimas e biossurfactantes de interesse industrial

Abstract

Antarctica is known for its extreme environmental characteristics with low temperatures, high salinity, high exposure to UV radiation, desiccation, nutrient scarcity, pH variations and freeze-thaw cycles. Faced with these life-limiting conditions, microorganisms represent the dominant forms of life in this environment.. The microorganisms residing in Antarctica are known as extremophiles, as they have adaptive strategies to ensure their survival in the face of extreme conditions in the region. Among the Antarctic microorganisms, fungal communities present in lakes stand out, as they are responsible for biogeochemical cycles and mineralization of organic matter present in these habitats and, consequently, are potential producers of enzymes active at low temperatures of great industrial interest, which can be up to 10 times more active at low temperatures compared to mesophilics. Considering the capacity of Antarctic fungi to produce several enzymes with biotechnological potential, the objective of the present work was to characterize the resident fungi in lakes of the Antarctic Peninsula and evaluate them regarding the production of enzymes and biosurfactants of industrial interest. The fungi were obtained from two Antarctic lakes, the first located at the Hennequin Point, on King George Island, using submerged string baits for two years and the second from biofilms formed at Kroner Lake, on Deception Island. In the evaluated substrates, 154 cultivable fungal isolates were obtained, of which 89 (58%) were represented by filamentous fungi and 65 (42%) by yeasts. Of these isolates, 94 (61%) were obtained from string baits collected on King George Island, 45 (48%) of which were filamentous fungi and 49 (52%) yeasts. The other 60 (39%) isolates were obtained from the biofilm collected on Deception Island, being 44 (73%) filamentous fungi and 16 (27%) yeasts. The phylum Ascomycota was the most abundant and represented by 89 (58%) isolates, followed by Basidiomycota with 58 (38%) isolates and, finally, Mortierellomycota with seven (4%) isolates. Of the 94 isolates from string baits, Thelebolus globosus with 24 (26%) isolates and Goffeauzyma sp. with 19 (20%) isolated were the filamentous fungus and yeast, respectively, more abundant. Regarding the 60 isolates from the biofilm, Pseudogymnoascus verrucosus, with 27 (45%) isolates, was the most abundant taxon among the filamentous fungi and Metschnikowia australis the most abundant yeast, with five (8%) isolates. In enzymatic tests with cultivable fungi, 133 isolates from string and biofilm were evaluated for the production of cellulase, protease, lipase, agarase, carrageenase, invertase, amylase, esterase, pectinase, inulinase and gelatinase enzymes. The most commonly detected enzyme was protease (77%), followed by lipase (63%); the least produced were cellulase (32%) and pectinase (12%). The same 133 isolates were submitted to the drop-collapse test to evaluate the production of biosurfactants and all isolates were negative. Regarding the uncultivable fungi, characterized in the string baits obtained from the lakes of Hennequin Point on King George Island and Soto on Deception Island, 258.326 DNA reads were detected distributed in 34 amplicon sequence variants (ASVs) belonging to the phyla Ascomycota, Basidiomycota, Mortierellomycota, Chytridiomycota and Rozellomycota. The majority of ASVs (27) were detected in Lake Hennequin and 13 ASVs detected in Lake Soto. Tetracladium marchlianum, Tetracladium sp., Rozellomycota sp., Fungal sp. 1 and Fungal sp. 2 were the most common taxa within the lake fungus communities. Tetracladium marchlianum (142.805) and Tetracladium sp. (99.392) had the highest numbers of DNA reads. The data obtained in this work contribute to broaden the knowledge of fungal communities present in oligotrophic lacustrine environments in Antarctica with the presence of endemic and cosmopolitan taxa adapted to cold, as well as possible new species. These fungi residing in Antarctic lakes proved to be potential sources of different enzymes, which can have their activity at low temperatures and, therefore, represent great potential for biotechnological use in the industrial sector.