Improvement of biohydrogen production from date wastes by Thermotoga maritima using a continuous anaerobic membrane bioreactor

Abstract Hydrogen (H 2 ) is a promising energy carrier owing to its environmentally friendly properties and high energy content. The aim of this work is to achieve a continuous H 2 production from a simplified culture medium composed of date wastes (DW) and natural seawater using the marine bacterium, Thermotoga maritima . Increasing the dilution rate ( D ) from 0.02 to 0.25 h -1 in the continuous stirred tank reactor (CSTR) improved the volumetric H 2 production rate ( Q H2 ) from 2 to 17 mmol/L.h. At a D above 0.25 h -1 , a washout of the bacterium cells was observed, resulting in a significant decrease of biomass concentration (BC) and then the drop in Q H2 . The production of H 2 was improved by using a membrane bioreactor (MBR) due to the cell retention in the reactor. At a high D of 0.6 h -1 , the maximum Q H2 was increased from 0.6 to 61.75 mmol/L.h, which is higher than those previously reported on continuous H 2 production from different substrates. Moreover, increasing the hexose concentration in the date juice (DJ) from 30 to 60 mmol/L further enhanced the H 2 production. It allowed a Q H2 . of 70.2 mmol/L.h which is interesting for a large scale production of H 2 from date wastes.