일산화탄소를 이용한 초고온성 고세균, Thermococcus onnurineus NA1의 바이오수소 생산

Abstract

The hyperthermophilic archaeon, Thermococcus onnurineus NA1 has been reported to be able to grow on carbon monoxide (CO) producing hydrogen (H2) through the water-gas shift reaction. In gas fermentation, mass transfer of gaseous substrate to liquid medium is typically known as a rate-limiting factor. Therefore, in this study, we investigated the effect of volumetric gas-liquid mass transfer coefficient (kLa) on the CO-dependent H2 production by T. onnurineus NA1. For this, a series of batch cultures of T. onnurineus NA1 were conducted under various kLa by changing CO supply and agitation rates in 2.5 L bioreactor with working volume of 1.6 L. At fixed CO rate of 76 mL/min, kLa increased from 10 to 40 h-1 by increasing agitation speed from 400 to 900 rpm, resulting in 2.5-fold enhancement of H2 production rate from 40 to 102 mmol/L/h. In addition, the increase in CO supply rate was also effective in enhancing H2 production. At fixed agitation speed of 900 rpm, H2 production rate was linearly enhanced depending on CO supply rate mainly due to an increase of gas-liquid mass transfer. By applying CO rate of 280 mL/min at 900 rpm, which is corresponded to the value of kLa of 113 h-1, the H2 production rate could be reached up to 245 mmol/L/h, which is the highest value to date.o liquid medium is typically known as a rate-limiting factor. Therefore, in this study, we investigated the effect of volumetric gas-liquid mass transfer coefficient (kLa) on the CO-dependent H2 production by T. onnurineus NA1. For this, a series of batch cultures of T. onnurineus NA1 were conducted under various kLa by changing CO supply and agitation rates in 2.5 L bioreactor with working volume of 1.6 L. At fixed CO rate of 76 mL/min, kLa increased from 10 to 40 h-1 by increasing agitation speed from 400 to 900 rpm, resulting in 2.5-fold enhancement of H2 production rate from 40 to 102 mmol/L/h. In addition, the increase in CO supply rate was also effective in enhancing H2 production. At fixed agitation speed of 900 rpm, H2 production rate was linearly enhanced depending on CO supply rate mainly due to an increase of gas-liquid mass transfer. By applying CO rate of 280 mL/min at 900 rpm, which is corresponded to the value of kLa of 113 h-1, the H2 production rate could be reached up to 245 mmol/L/h, which is the highest value to date.