Effects of mass transfer and light intensity on substrate biological degradation by immobilized photosynthetic bacteria within an annular fiber-illuminating biofilm reactor

• Annular fiber-illuminating bioreactor for continuous substrate biodegradation.
• Photosynthetic bacteria are immobilized on surface of side-glowing optical fiber.
• Coupled processes of substrate transfer and biodegradation within bioreactor.
• Substrate concentration, flow rate and light intensity were associated with model.
• Operational parameters for biodegradation can be determined by model analysis.

In this work, effects of mass transfer and light intensity on performance of substrate biodegradation by cell-immobilized photosynthetic bacteria were investigated within an annular fiber-illuminating bioreactor (AFIBR). In AFIBR, stable biofilm of photosynthetic bacteria was generated on the surface of side-glowing optical fiber to provide sufficient light supply and uniform light distribution in cell-immobilized zone for continuous substrate biodegradation during hydrogen production process. To optimize operation parameters for substrate degradation, a two-dimensional mass transfer model based on experimental data to describe coupled processes of substrate transfer and biodegradation in biofilm with substrate diffusion and convection in bulk flow region was proposed. Investigations on influences of substrate concentration, flow rate and light intensity were carried out. It was showed that the optimum operational parameters for the substrate degradation in the AFIBR are: 10 g/l substrate concentration, 100 ml/h flow rate and 3.1 W/m2 light intensity.