Abstract The emergence of bacterial resistance to antimicrobials poses a significant health threat. To address this issue, exploring the fungal diversity in freshwater environments in the Amazon Forest has potential in the search for new antimicrobials. This study aimed to investigate the production of antibacterial metabolites by aquatic fungi from Amazon lakes, specifically Lake Juá and Lake Maicá (Brazil-PA). The fungal isolates were obtained from wood fragments submerged in these lakes, and the ethyl acetate extracts were evaluated for antibacterial activity against Staphylococcus aureus ATCC 25923, S. aureus (MRSA), ATCC 43300, Escherichia coli ATCC 25922, and E. coli (ESBL) NCTC 13353. Additionally, toxicity of the extracts (EtOAc with antimicrobial activity) against human fibroblasts MRC-5 was investigated. The study identified 40 fungal strains with antimicrobial screening, and the ethyl acetate extracts of Fluviatispora C34, Helicascus C18, Monodictys C15, and Fusarium solani LM6281 exhibited antibacterial activity. F. solani LM6281 showed the lowest minimum inhibitory concentration (MIC) of 50 µg/mL against S. aureus strains and MIC of 100 µg/mL against E. coli strains including ESBL. The cytotoxicity (IC50) of the extract (EtOAc) of F. solani LM6281 was 34.5 µg/mL. Preliminary studies of the TLC culture and RNM-H from the extract (EtOAc) of F. solani suggested the presence of substances from the class of terpenes, quinones, phenolics, and flavonoids. This study highlights the potential of submerged wood fungi in the Amazon region to produce antibacterial substances, thus identifying them as sources of novel bioactive compounds with potential use in the pharmaceutical industry and regional bioeconomy.

Resumo O surgimento de resistência bacteriana a antimicrobianos representa uma ameaça significativa à saúde. Para abordar esta questão, explorar a diversidade fúngica em ambientes de água doce na Floresta Amazônica tem potencial na busca de novos antimicrobianos. Este estudo teve como objetivo investigar a produção de metabólitos antibacterianos por fungos aquáticos de lagos amazônicos, especificamente os lagos Juá e Maicá (Brasil-PA). Os isolados fúngicos foram obtidos de fragmentos de madeira submersos nesses lagos, e os extratos de acetato de etila foram avaliados quanto à atividade antibacteriana contra Staphylococcus aureus ATCC 25923, S. aureus (MRSA), ATCC 43300, Escherichia coli ATCC 25922 e E. coli (ESBL) NCTC 13353. Além disso, a toxicidade dos extratos (EtOAc com atividade antimicrobiana) contra fibroblastos humanos MRC-5 foi investigada. O estudo identificou 40 cepas de fungos com triagem antimicrobiana, e os extratos de acetato de etila de Fluviatispora C34, Helicascus C18, Monodictys C15 e Fusarium solani LM6281 exibiram atividade antibacteriana. F. solani LM6281 apresentou a menor concentração inibitória mínima (CIM) de 50 µg/mL contra cepas de S. aureus e CIM de 100 µg/mL contra cepas de E. coli incluindo ESBL. A citotoxicidade (IC50) do extrato (EtOAc) de F. solani LM6281 foi de 34,5 µg/mL. Estudos preliminares da cultura TLC e RNM-H do extrato (EtOAc) de F. solani sugeriram a presença de substâncias da classe dos terpenos, quinonas, fenólicos e flavonoides. Este estudo destaca o potencial de fungos de madeira submersos na região amazônica para produzir substâncias antibacterianas, identificando-os como fontes de novos compostos bioativos com potencial de uso na indústria farmacêutica e na bioeconomia regional.

This work investigates the synergistic use of Theobroma cacao (Cocoa), and Elaeis guineensis (Palm oil) as corrosion inhibitors for carbon steel in 0.5 mol.L-1 hydrochloric acid solution, in the absence and presence of different mixture concentrations of the studied compounds. The efficiency of corrosion inhibitors was studied by gravimetric tests and the corrosion resistance by electrochemical tests, such as electrochemical impedance spectroscopy (EIS) and polarization curves. The chemical composition of the cocoa bark powder and palm kernel cake powder was evaluated by Fourier transform infrared spectroscopy (FTIR). The results of the gravimetric tests showed an inhibition efficiency of 79% for the cocoa bark powder and 76% for palm kernel cake powder, however, the mixture of the compounds presented an inhibition superior to 94%, showing the great synergism between the studied species. These results corroborate the values obtained from EIS.

The performance of an electrocoagulation (EC) system with aluminium and iron electrodes for removing heavy metal ions (Cd2+, Cu2+, Cr3+, Sr2+ and Zn2+) present in synthetic produced water on laboratory scale was studied systematically. Experimental parameters such as applied current, flow effluent and sacrificial electrodes were investigated in order to understand their influence on the EC process. Increasing the current density accelerated the electrocoagulation process, but made it less efficient. Cd2+, Cu2+, Sr2+ and Zn2+ showed similar removal rates, under similar conditions, indicating a uniform electrochemical behavior. The study gave indications on the removal mechanisms of the investigated metals. Cd2+, Cu2+ and Zn2+ ions are hydrolyzed and co-precipitated as hydroxides. Cr4+, was proposed to be reduced first to Cr3+ at the cathode before precipitating as hydroxide. The process expenditure was estimated and reported showing the viability of this process as a green alternative, obtaining modest costs using Fe electrodes.