Título: Insights of Light Spectra on Biohydrogen Production by Photo-Fermentation
Autores: SANTOS, G. A.; BORTOLI, L. D.; SANTOS, D. A.; LOBATO, F. S.; CARDOSO, V. L.; BATISTA, F. R. X.
Revista: International Journal of Hydrogen Energy, 149, 150088 (1-12), 2025.
Resumo: Biohydrogen production by purple non-sulfur bacteria typically relies on infrared light to excite bacteriochlorophyll. However, the roles of visible wavelengths, especially red and blue, and the contribution of carotenoids remain poorly defined. In the current study, it was performed the first unified comparison of four LED spectra in a co-culture of Rhodobacter capsulatus and Rhodospirillum rubrum using lactose from milk whey permeate. Small-scale tests (50 mL) under Cool White, Infrared, and Targeted-Spectrum LEDs revealed that Cool White LEDs achieved the highest H2 productivity (8.23 mmol H2 (L.day)). Remarkably, the Targeted Spectrum LED alone yielded significant H2 (5.76 mol H2/mol lactose), demonstrating that pronounced carotenoid excitation can drive production with minimal emission for BChl alpha excitation. The visible wavelengths can scatter more uniformly, benefiting non-stirred systems, while Infrared alone underperforms when cells settle. Scaling to a 2.1 L stirred flat-plate reactor increased productivity to 18.64 mmol H2 (L.day) (3.26 % LCE), applying the Cool white LED as light source. Raising light intensity to 5,000 lx and renewing half the medium further boosted productivity to 26.93 mmol H2 (L.day) (4.49 % LCE) while maintaining an optimal SOLR (∼4.8 g lactose/ gVS.h). Finally, bi-logistic and modified Gompertz models accurately described multiphasic H2 accumulation, offering a robust framework for optimizing complex photofermentative systems. This work highlights the need to tailor light spectra, reactor design, and process control to maximize biohydrogen yields.

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