The kinetic characterization of photofermentative bacterium Rhodopseudomonas faecalis RLD-53 and its application for enhancing continuous hydrogen production

In this work, the kinetic characterization of hydrogen production by the photofermentative bacteria Rhodopseudomonas faecalis RLD-53 was investigated at different growth phase. During entire fermentation, 89.30% of total biomass was accumulated in exponential growth phase, while hydrogen yield was only 1.82 mol H2/mol acetate at the expense of 51.25% substrate. In the stationary phase, biomass synthesis was minimal (7.51%), and 38.17% of the substrate was directly converted into hydrogen. As a result, hydrogen (59.19%) was mainly produced in stationary phase with highest hydrogen yield of 3.67 mol H2/mol acetate. Consequently, bacteria in stationary phase were most effective for hydrogen production. Based on these findings, a novel membrane photobioreactor was developed to retain bacteria during stationary phase in reactor through membrane separation. Maximum rate (32.82 ml/l/h) and yield (3.27 mol H2/mol acetate) of hydrogen production were achieved using membrane photobioreactor under the continuous operation. Therefore, using bacteria in stationary phase as hydrogen producer can offer considerable benefits for enhancing photo-hydrogen production.

► Hydrogen production rate had a linear relationship with nitrogenase activity. ► Bacteria in stationary phase were most effective for photo-hydrogen production. ► Membrane photobioreactor was developed in line with characteristics of bacteria. ► Bacteria in stationary phase were retained in reactor through membrane separation. ► Using bacteria in stationary phase can offer considerable benefits for H2 production.