Bioreactors Metagenome. Bioreactors

Total pressure (TP) affects the level of dissolved hydrogen gas in the fermentationmedium leading to metabolic shifts in mixed microbial-culture-based systems. In thisstudy, the effect on hydrogen production rate and yield a was investigated at differentTP of a hydrogen-producing system using a microbial open culture previously heat-treated. Four continuous stirred-tank reactors (CSTR) were operated in parallel on amineral salts-molasses medium (21 g-COD. L −1 ) at 35°C, pH 5.5 and hydraulic retentiontime (HRT) of 6 h. The TP was set at 80 kPa (R1), 100 kPa (R2), 120 (R3) and 140 kPa(R4) and reactor performances were estimated at steady-state. As the increase of TPconsequently increased the partial pressure of hydrogen (), the hydrogen production rate(HPR) and yield (HY) were consistently negatively influenced. The highest HPR andHY (406.1 ± 36.8 mL-H 2 h −1 ; 4.51 molH 2 mol -1 suc eq. ) were achieved at close-to-vacuumconditions (80 kPa). The composition of the microbial community mainly representedby species from Sporolactobacillus and Clostridium genera, did not change with theincrease and /or decrease of the TP, indicating a -regulation at cellular but notpopulation level.