Rapid enrichment of (homo)acetogenic consortia from animal feces using a high mass-transfer gas-lift reactor fed with syngas

A gas-lift reactor having a high mass transfer coefficient (k _L a = 80.28 h^-1) for a relatively insoluble gas (carbon monoxide; CO) was used to enrich (homo)acetogens from animal feces. Samples of fecal matter from cow, rabbit, chicken, and goat were used as sources of inoculum for the enrichment of CO and H₂ utilizing microbial consortia. To confirm the successful enrichment, the Hungate roll tube technique was employed to count and then isolate putative CO utilizers. The results of this work showed that CO and H₂ utilizing consortia were established for each inoculum source after 8 days. The number of colony-forming units in cow, rabbit, chicken, and goat fecal samples were 3.83 × 10⁹, 1.03 × 10 ⁹, 8.3 × 10⁸, and 3.25 × 10⁸ cells/ml, respectively. Forty-two colonies from the animal fecal samples were screened for the ability to utilize CO/H₂. Ten of these 42 colonies were capable of utilizing CO/H₂. Five isolates from cow feces (samples 5, 6, 8, 16, and 22) were highly similar to previously unknown (homo)acetogen, while cow-7 has shown 99 % similarity with Acetobacterium sp. as acetogens. On the other hand, four isolates from chicken feces (samples 3, 8, 10, and 11) have also shown high CO/H₂ utilizing activity. Hence, it is expected that this research could be used as the basis for the rapid enrichment of (homo)acetogenic consortia from various environmental sources.