Percorrer por autor "Zaiat, Marcelo"
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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.
- Modulating microalgal metabolism and its integration into dark fermentation: Challenges and opportunities with wastewater-grown biomassPublication . Ferreira, Jessica; Silva, Thiago; Saleme Aona de Paula Pereira, Alexia; Reis, Alberto; Zaiat, Marcelo; ; Calijuri, Maria LuciaABSTRACT: Microalgae represent a promising feedstock for the sustainable production of bioproducts and bioenergy, due to their versatile biochemical composition and environmental adaptability. Given the wide range of bioproducts that can be derived from their biomass, its biochemical composition suggests more favorable conversion routes and can be enhanced through cultivation conditions focused on the synthesis of one (or more) metabolites of interest to the biotechnology market. Accordingly, this review focuses on approaches for modulating microalgal metabolism, such as nutrient depletion and reactor configuration characteristics, among others, as well as on key outcomes obtained through two-stage cultivation, which combine phases of high biomass and metabolite productivity. From a resource recovery perspective, emphasis was placed on approaches that are more readily applicable to wastewater treatment plants. Furthermore, as energy-oriented routes are more suitable for valorizing of biomass grown in wastewater and considering that biohydrogen has been shown to be an emerging product of scientific relevance, this review also analyzes the limitations and strategies for integrating its production via dark fermentation. Pretreatment techniques and co-fermentation approaches were discussed as strategies to overcome the challenges associated with the anaerobic fermentation/digestion of microalgae due to their characteristics and biochemical composition. Finally, biorefinery configurations that integrate these processes were discussed from a scale-up perspective.