Enhancement of ethanol production using CO2and CO gases in a continuous fixed-film bioreactor

Abstract

Ethanol-producing bacteria play an essential role in enhancing bioethanol production efficiency. This study aimed to develop an application of Petrobacter sp. SUTSP5, an ethanol-producing bacterium, from carbon-rich gas by using a fixed-film ethanol bioreactor called FEthaRex to enhance ethanol production efficiency. The fixed-film consortium was initially grown in a combination nutrient with a carbon-rich gas composed of 15:25:40 (by volume) CO2:CO:H2 and supplied to the FEthaRex column at an average flow rate of 100 mL/min. Nutritional liquid medium was circulated at a flow rate of 20 mL/min. The system achieved an ethanol production rate of approximately 0.1305 g/L/h within 24 h, which increased significantly to 0.1780 g/L/h after a 48-h operation period; the ethanol production rate increased from 0.1585-0.2132 g/L/h as the gas composition increased to 30:50:20 (by volume); continuous operation of the FEthaRex system was achieved after mixed gas feeding was stopped; and the maximum ethanol concentration observed after 48 h was 1.9860 g/L/h, or 6.0411 % by volume, with the ethanol-producing cells reaching a count of approximately 107 CFU/mL and average biofilm cell attached to packing media roughly 0.0058 g. At these optimum conditions, which achieved an ethanol yield higher than that of a free suspended cell reactor (EthaRex) with the same gas feed conditions. The FEthaRex system was demonstrated as a promising approach to achieving cell density and stability in the microbial community. This technology could be an efficient tool for enhancing sustainable bioethanol production.