Demonstration of a two-stage aerobic/anaerobic chemostat for the enhanced production of hydrogen and biomass from unicellular nitrogen-fixing cyanobacterium

Dynamic modelling of high biomass density cultivation and biohydrogen production in different scales of flat plate photobioreactors

“…The formulation of the present model is presented in Equations (5a–j). In the current experiment, cells continue growing for a while after the consumption of nitrate because of the accumulation of intracellular nitrogen when nitrate is present in the culture (Dechatiwongse et al, ). Therefore, the cell growth rate is a function of intracellular nitrogen concentration which is always represented by the nitrogen quota, the latter being defined as the ratio of intracellular nitrogen element mass to cell mass.…”

“…In fact, as hydrogen is mainly generated in the cyanobacterial stationary and decay phases (Dechatiwongse et al, ), biomass concentration usually keeps decreasing when the gas is produced. In order to guarantee that the entire volume of the photobioreactor is viable for gas production, the maximum biomass concentration should be controlled around 1.0 g L −1 in the current PBR.…”

“…A cell decay term is also not included in Equation (5f) since it is assumed that glycerol consumption is independent of cell decay; otherwise an increase on glycerol concentration will be estimated based on Equation (5f) when cells start to decay, which is not physically correct. Two switch functions (Zhang et al, ), given in Equations (5i) and (5j), are applied to mediate the start and termination of hydrogen production as nitrogenase (the enzyme catalyzing the reduction of protons) is only activated when the culture is anaerobic and nitrate concentration is lower than 100 mg L −1 (Dechatiwongse et al, ; Min and Sherman, ).…”

“…The current experimental data are used to estimate the parameters in this model. The detailed of the current experimental work and reactor used can be found in (Dechatiwongse et al, ; Tamburic et al, ).…”

“…In laboratory scale studies, biohydrogen productivity is determined to be 1.30 – 1.50 mL H 2 L −1 (culture) h −1 from green alga Chlamydomonas reinhardtii , and 2.33 mL L −1 h −1 for cyanobacterium Cyanothece sp. in a 1 L flat plate PBR with a width of 0.025 m (Dechatiwongse et al, ; Tamburic et al, , ). However, once the width increases up to 0.040 m, biohydrogen productivity from green algae C. reinhardtii and C. noctigama reduces to 0.97 mL L −1 h −1 and 0.56 mL L −1 h −1 , respectively (Skjanes, ).…”