COMPARED PERFORMANCE OF HYPERTHERMOPHILIC HOLLOW FIBER MEMBRANE AND GAS LIFT BIOREACTORS USING A PURE CARBOXYDOTHERMUS HYDROGENOFORMANS CULTURE FOR SYNGAS UPGRADING INTO HYDROGEN

(pCO) (from 1 to 2.5 atm), CO loading rate (from 1.3 to 16.5 mol CO per liter of reactor (rxr) and per day), gas recirculation rates (0.3 and 1.5 L·min –1 ), CO feeding rates (from 0.05 to 0.46 mol·L – 1 rxr·d –1 ), and bacto-peptone addition to the medium. Overall, HFMBR results indicated a relatively constant H2 yield of 92±4% (mol H2·mol –1 CO), regardless of the operational condition tested. Permeation across the colonized membrane was improved by three orders of magnitude as compared to the abiotic membrane. Once the biofilm was sufficiently developed, a maximum CO conversion activity of 0.44 mol CO·g –1 volatile suspended solid (VSS)·d –1 was achieved at a pCO of 2 atm or above and a liquid velocity of 65 m·h –1 . In GLR the H2 yields were approximately constant at 100±6% (mol H2·mol–1 CO) with unsupported growth, at any operational conditions tested. At the highest biomass density, a maximum CO conversion activity of 0.22 molCO·L -1 rxr·d -1 was achieved. Overall, a low cell density, typical of C. hydrogenoformans growth, limited the CO conversion performance. This limitation was found to be the most restrictive factor for higher CO loading rates for GLR systems.