Thermophilic hydrogen fermentation using Thermotoga neapolitana DSM 4359 by fed-batch culture

Abstract

Biohydrogen fermentation by the hyperthermophile Thermotoga neapolitana was conducted in a continuously stirred anaerobic bioreactor (CSABR). The production level of H 2 from fermentation in a batch culture with pH control was much higher than without pH control from pentose (xylose) and hexose (glucose and sucrose) substrates. The respective H 2 yield in the batch culture with pH control from xylose and glucose was 2.22 ± 0.11 mol-H 2 mol −1 xylose consumed and 3.2 ± 0.16 mol-H 2 mol −1 glucose consumed, which was nearly 1.2-fold greater for xylose and 1.6-fold greater for glucose than without pH control. In the case of sucrose, the H 2 yield from fermentation increased by 40.63%, compared with fermentation in batch cultures without pH control, from 3.52 ± 0.171 to 4.95 ± 0.25 mol-H 2 mol −1 sucrose consumed. The effects of stirring speed and different pH levels on growth and H 2 production were studied in the CSABR for highly efficient H 2 production. Growth and H 2 production of this bacterial strain in a batch culture with pH control or without pH control using a 3 L bioreactor was limited within 24 h due to substrate exhaustion and a decrease in the culture’s pH. The pH-controlled fed-batch culture with a xylose substrate added in doses was studied for the prevention of substrate-associated growth inhibition by controlling the nutrient supply. The highest H 2 production rates were approximately 4.6, 4.1, 3.9, and 4.3 mmol-H 2 L −1 h −1 at 32, 52, 67, and 86 h, respectively.