Produção de bio-hidrogênio por co-cultura de Enterobacter cloacae e Rhodopseudomonas palustris utilizando lactose do soro de leite como fonte de carbono

Abstract

Hydrogen (H 2 ) production through biotechnology pathway can be achieved through microbial fermentation by converting organic waste into biohydrogen (BioH 2 ). This approach has excellent sustainable performance and aims to contribute to establish of this biofuel in the energy matrix. This conversion can be performed using pure cultures of fermentative or photosynthetic bacteria, or through co-culture, which aims to maximize H 2 yield in a simple, single-stage bioprocess. For this purpose, numerous organic wastes can be used as substrates, including cheese whey, an important agroindustrial residue. Therefore, the objective of this study was to evaluate the production of BioH 2 , using pure cultures of the bacteria Enterobacter cloacae and Rhodopseudomonas palustris and a co-culture of both microorganisms. The experiments were conducted with lactose concentrations of 9, 18, 35, or 50 g/L, derived from cheese whey as the carbon source, at 32 °C, 100 rpm agitation, and light exposure (2000 lux). In the bioprocess using E. cloacae, the highest H₂ production was 60.1 ± 9.1 mmol/L, with a yield of 1.8 ± 0.2 mol H₂/mol lactose consumed, observed at 35 g/L of lactose. Regarding R. palustris, H₂ production reached 3.5 ± 0.7 mmol/L, with a yield of 0.3 ± 0.1 mol H₂/mol lactose consumed. In co-cultures with 9 g/L lactose, supplementation of FeSO 4 with 60 µmol/L did not result in a statistically significant impact on H₂ production, yielding a maximum of 10.3 ± 0.8 mmol/L. The highest yield among co-cultures was observed in the bioprocess using 35 g/L lactose without supplementation, producing 58.9 ± 10.4 mmol H₂/L and a yield of 2.5 ± 0.3 mol H₂/mol lactose consumed. A total viable count analysis confirmed the ability of E. cloacae to grow both in the presence and absence of light. In addition to H₂ production, other value-added byproducts were generated in the co-culture bioprocesses, including ethanol (2.6 ± 0.4 g/L), lactic acid (2.2 ± 0.1 g/L), and 2,3- butanediol (1.5 ± 0.2 g/L). The results confirm the potential of the biotechnological route for BioH₂ production using both pure cultures and co-cultures. Cheese whey demonstrated significant potential as a substrate for H₂ generation, representing a

promising approach for the valorization of this agroindustrial byproduct. This process aligns with the United Nations (UN) Sustainable Development Goals (SDGs), promoting actions against climate change and fostering sustainable urban development.