Photo-fermentative hydrogen production from organic acids mixtures evaluated through predictive models for Rhodobacter capsulatus strains

This research aimed to evaluate growth and hydrogen production from Rhodobacter capsulatus DSM155 and B10 strains in function of volatile fatty acids (VFA) media composition, as well as to assess the light intensity effect on hydrogen production. The growth of DSM155 and B10 was verified in media containing either acetic acid, butyric acid, or sodium lactate, or a mixture of them (ABL medium), being the ABL medium that produced the maximum cell dry weight, 2.15 and 1.67 g/L for DSM155 and B10, respectively. Biohydrogen production was evaluated in media containing acetic and butyric acids (AB medium), and ABL medium. Both strains presented the highest hydrogen production using ABL medium, being the highest 239.2 mL H2 for DSM155. Finally, light intensity (10, 20, and 30 klux) effect on biohydrogen production was studied using the best strain and medium, i.e., DSM155 and ABL medium. DSM155 produced hydrogen increasingly in the order 10, 20, and 30 klx (2753.5, 2850.5, and 2946.3 mL H2/Lop, respectively); however, the light conversion efficiency into hydrogen showed an inverse trend, 7.47, 4.16, and 2.67 %. In conclusion, R. capsulatus DSM155 is advisable for biohydrogen production using ABL medium in the range 10-30 klux. Moreover, further work is recommended on DSM 155 using organic acid-rich real effluents from dark fermentation.