Illumination and fluid flow effects on bioplastic production and biohydrogen generation in microbioreactors with different geometries

The utilization of photofermentative processes to create biohydrogen and bioplastic has significant environmental and economic benefits. In this study, a mechanistic model of photo fermentation of acetic acid to investigate simultaneous bioplastic and biohydrogen production was developed. Two distinct bioreactors: one with a porous structure generated by X-ray CT and another one with an array of solid blocks were simulated to examine the effects of varied velocities and light intensities on biohydrogen and bioplastic production. The results revealed that biohydrogen production depends on not only bioplastic accumulation in biofilms but also illumination intensities and fluid velocities. Illumination intensity affected the bioplastic generation and decreased the time to reach the highest normalized bioplastic concentration. Higher bioplastic productions were achieved at lower illumination intensity. The base illumination (6000lx) had the lowest bioplastic formation while the lowest illumination intensity (3000lx) could increase it by 30%. Changing velocity could increase +48.1% of the bioplastic normalized concentration at the highest velocity and decrease −38.1% at the lowest. Biofilm growth could significantly reduce biohydrogen extraction at low velocities due to bioclogging. The CT-bioreactor outperformed the block-bioreactor in terms of bioplastic concentration, while the block-bioreactor exceeded the CT-bioreactor in terms of biohydrogen generation.