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- Member of: ASU Regents' Professors Open Access Works
- Member of: Glen Canyon Dam Adaptive Management Program Administrative History
Grand Canyon and the Colorado River are important places on the landscape for many Native American Tribes. The Glen Canyon Dam Adaptive Management Program (GCDAMP) is designed to employ science as a means for gathering, analyzing, and disseminating information on the condition of resources. A Western science perspective dominates this program with recognition of Native American traditional perspectives as a valued component. Analogous to a confluence of rivers, Native American traditional perspec-tives were initially envisioned as enhancing the Western science approach by creating a more holistic understanding of this valued ecosystem; however, this integration has not been realized. Identified barriers to effective participation by Native American stakeholders are vast cultural differences that express themselves in complex sociocultural scenarios such as conflict resolution discourse and a lack of insight on how to incorporate Native American values into the program. Also explored is the use of “science” as a sociopolitical tool to validate authoritative roles that have had the unintended effect of further disenfranchising Native Americans through the promotion of colonialist attitudes. Solutions to these barriers are offered to advance a more effective and inclusive participation of Native American stakeholders in this program. Finally, drawing from the social sciences, a reflexive approach to the entire GCDAMP is advocated.
Syngas fermentation, the bioconversion of CO, CO[subscript 2], and H[subscript 2] to biofuels and chemicals, has undergone considerable optimization for industrial applications. Even more, full-scale plants for ethanol production from syngas fermentation by pure cultures are being built worldwide. The composition of syngas depends on the feedstock gasified and the gasification conditions. However, it remains unclear how different syngas mixtures affect the metabolism of carboxidotrophs, including the ethanol/acetate ratios. In addition, the potential application of mixed cultures in syngas fermentation and their advantages over pure cultures have not been deeply explored. In this work, the effects of CO[subscript 2] and H[subscript 2] on the CO metabolism by pure and mixed cultures were studied and compared. For this, a CO-enriched mixed culture and two isolated carboxidotrophs were grown with different combinations of syngas components (CO, CO:H[subscript 2], CO:CO[subscript 2], or CO:CO[subscript 2]:H[subscript 2]).
Results
The CO metabolism of the mixed culture was somehow affected by the addition of CO[subscript 2] and/or H[subscript 2], but the pure cultures were more sensitive to changes in gas composition than the mixed culture. CO[subscript 2] inhibited CO oxidation by the Pleomorphomonas-like isolate and decreased the ethanol/acetate ratio by the Acetobacterium-like isolate. H[subscript 2] did not inhibit ethanol or H[subscript 2] production by the Acetobacterium and Pleomorphomonas isolates, respectively, but decreased their CO consumption rates. As part of the mixed culture, these isolates, together with other microorganisms, consumed H[subscript 2] and CO[subscript 2] (along with CO) for all conditions tested and at similar CO consumption rates (2.6 ± 0.6 mmol CO L[superscript −1] day[superscript −1]), while maintaining overall function (acetate production). Providing a continuous supply of CO by membrane diffusion caused the mixed culture to switch from acetate to ethanol production, presumably due to the increased supply of electron donor. In parallel with this change in metabolic function, the structure of the microbial community became dominated by Geosporobacter phylotypes, instead of Acetobacterium and Pleomorphomonas phylotypes.
Conclusions
These results provide evidence for the potential of mixed-culture syngas fermentation, since the CO-enriched mixed culture showed high functional redundancy, was resilient to changes in syngas composition, and was capable of producing acetate or ethanol as main products of CO metabolism.