Bioethanol Production via Syngas Fermentation

Abstract

Abstract. Bioconversion of C-1 carbon in syngas through microbial fermentation presents a huge potential to be further explored for ethanol production. Syngas can be obtained from the gasification of lignocellulosic biomass, by which most of carbon content of the biomass was converted into CO and CO2. These gases could be further utilized by carbon-fixing microorganism such as Clostridium sp. to produce ethanol as the end product. In order to obtain an optimum process, a robust and high performance strain is required and thus high ethanol yield as the main product can be expected. In this study, series of batch fermentation was carried out to select high performance strains for ethanol production. Bottle serum fermentations were performed using CO-gas as the sole carbon source to evaluate the potential of some Clostridia species such as Clostridium ljungdahlii, C. ragsdalei, and C. carboxidovorans in producing ethanol at various concentration of yeast extract as the organic nitrogen source, salt concentration, and buffer composition. Strain with the highest ethanol production in the optimum media will be further utilized in the upscale fermentation.

Bioethanol Production via Syngas Fermentation of Clostridium Ljungdahlii in a Hollow Fiber Membrane Supported Bioreactor

“…As suggested in a previous study, it is possible for the high availability of electrons from CO and H2 oxidation to induce ethanol production as a mixed growth-associated product, which was also observed in our study (Hurst & Lewis, 2010). (Anggraini et al, 2018) b values were calculated at 7 days' fermentation c lower specific growth rate in HFM-supported bioreactor due to biofilm formation on the membrane surface from bioreactor-to-membrane shells liquid recirculation d not determined…”

“…A comparison between the HFM-supported bioreactor and other fermentation systems examined in our study revealed the potential of the membrane to provide high CO mass transfer efficiency. By employing the same strain of C. ljungdahlii as a previous study on serum bottle fermentation, Anggraini et al (2018) observed a lower ethanol titer despite the presence of a high ethanol-to-acetate ratio, which corresponded to the low density of cells. This may have been caused by a limited CO gas supply ( Table 1).…”

“…Fermentation was carried out in an STR with no HFM as a gas-liquid contactor. The composition of the fermentation medium was prepared based on that used in a previous study by Anggraini et al (2018), to obtain an optimum condition for acclimatization with a higher concentration of Ni, Se, and W in the trace elements solution and a lower yeast extract concentration (0.05% w/v). The bioreactor containing 1.5 L medium was sterilized at 121 o C for 15 minutes.…”

Enhance the Growth of <i>Clostridium ljungdahlii</i> Microbial Cells by Modifying the Medium Composition and Trace Metals

“…In the fermentation process, the pH of the fermenter is controlled so that it is not lower than 4.5 to avoid cell death, and pH control is carried out with 2M HCl and 2M NaOH solutions. Details configuration of the bioreactor used was described in Anggraini [25].…”