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Percorrer ENERGIA por Objetivos de Desenvolvimento Sustentável (ODS) "06:Água Potável e Saneamento"
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- Enhancing microalgal biohydrogen production: Unlocking higher yields with hydrothermal pretreatment with niobium phosphatePublication . Silva, Thiago; Jesus Junior, Maurino Magno; Neves de Araujo, Matheus; Castro, Laressa Santos; Fuess, Lucas Tadeu; Rodrigues, Fábio de Ávila; Zaiat, Marcelo; Reis, Alberto; Calijuri, Maria LuciaABSTRACT: Microalgae cultivated in wastewater hold promise as a substrate for biohydrogen (bioH2) production. However, their rigid cell walls pose a challenge to fermentability. In this context, this study evaluated hydrothermal pretreatment with niobium phosphate (NbP) at 100-180 degrees C for 0-70 min, using up to 75 % NbP (relative to the dry weight of microalgal biomass). The hydrothermal pretreatment at 180 degrees C for 10 min with 75 % NbP released 7431 mg total carbohydrates (CHt) L-1, increasing the availability of fermentable substrates in subsequent dark fermentation (DF). When this pretreated biomass was subsequently fermented at pH 5.0 (sample PB5), bioH2 production reached 1.03 mmol H2 mol-1 CHt, with a maximum cumulative output of 0.17 mmol H2 and a CHt conversion efficiency of 83.6 %. In contrast, pH 5.5 and 6.0 reduced bioH2 yields and promoted methanogenic activity, while no pH control resulted in negligible bioH2 evolution. In conclusion, hydrothermal pretreatment with niobium phosphate and pH improvement synergize to enhance hydrogenogenesis, integrating wastewater treatment and renewable biohydrogen production.
- Inter-equipment ongoing validation of microplastic identification by micro-FTIR using optimal resourcesPublication . Fernandes, Rafaela; Miclea, Paul-Tiberiu; ROSSI, Andrea Mario; Giovannozzi, Andrea M.; Putzu, Mara; Morgado, Vanessa; Palma, Carla; Almeida, José Miguel; Pedro, Matilde São; Drago, Claudia; Quendera, Raquel Maria Pina Amaral; Pellegrino, Olivier; Bettencourt da Silva, RicardoABSTRACT: FTIR is widely used for identifying microplastics due to its performance and affordable equipment. However, there is a need for a universal method for the automatic identification of microplastics by FTIR, robust to different spectra collection conditions, and capable of adapting to the diversity of particle spectra. This research presents a method for developing a reliable and simple algorithm for inter-instrumental microplastic identification using micro-FTIR. Spectra collected from different equipments and settings across various laboratories, from microparticles previously confirmed as PET (positive cases) and non-PET (negative cases), were compared with a PET reference using multiple algorithms (match methods) based on six weighted and unweighted correlation coefficients. After excluding low signal-to-noise spectra with a newly developed universal algorithm, the 5th percentile of the match values for positive cases, estimated using a robust bootstrap method, was used as a minimum match (P5 & raquo;P) to ensure a 95% true positive rate (TP). Assuming a normal distribution of the match values for negative cases, the false positive rate (FP) was calculated. The best method identified uses an unweighted correlation of differentiated signals, resulting in a P5 & raquo;P = 0.4140 and FP = 0.0005% for spectra with a minimum signal-to-noise ratio of three. This identification performance, estimated from 117 spectra, is statistically equivalent to that observed from the identification of 405 additional particles using the validated method, at a 99% confidence level set by the Clopper-Pearson method, thereby extending the method's applicability to 522 particles. The developed method for PET identification by FTIR is robust across various acquisition conditions and instruments, was implemented in a user-friendly MS Excel spreadsheet, and can be easily tested with more particles and different instrumental settings. The validity of the identification algorithm and the defined criteria cannot be extrapolated to a different reality with respect to spectral collection conditions and the diversity of negative cases without a prior performance assessment.
- Reducing nutrient requirement using nitrogen-fixing bacteria for microalgae cultivationPublication . Melkonyan, Lusine; Ferreira, Alice; Bastos, Carolina R. V.; Figueiredo, Daniel; Lopes da Silva, Teresa; Avetisova, Gayane; Karapetyan, Zh.; Toplaghaltsyan, A.; Gouveia, LuisaABSTRACT: In environments, microalgae have been observed to coexist with bacteria. Different nitrogen-fixing bacteria (NFB) were isolated from Armenian soils and their growth was evaluated in co-cultivation with the microalga Tetradesmus obliquus and cyanobacteria Synechocystis sp. PCC 6803. The most effective mutualistic consortium was T. obliquus-NFB5 (Sphingobacterium sp. L13G8). This resulted an increase in both populations, chlorophyll fluorescence, biomass protein, carbohydrate content, an effect on lipid metabolism, without the need for external nitrogen. The findings demonstrated the significance of employing NFB for microalga growth, as they facilitate the essential nitrogen provision in N-free Bristol medium. Moreover, in mutualistic consortia, microalgae facilitate the exudation of dissolved organic carbon and O2 to bacteria, which, in turn, become available for bacteria, thereby reducing the necessity for energy-consuming aeration processes in co-cultivation. In return, the bacteria provide the microalgae with CO2, B vitamins and demineralize N2, P, S, thereby further supporting the growth of microalgae.