Enhanced Production of Bioethanol by Fermentation of Autohydrolyzed and C4mimOAc-Treated Sugarcane Bagasse Employing Various Yeast Strains

Journal Article · Tue Aug 01 04:00:00 UTC 2017 · Energies

DOI: https://doi.org/10.3390/en10081207 · OSTI ID:1376645

Hashmi, Muzna ^[1]; Shah, Aamer ^[2]; Hameed, Abdul ^[3]; Ragauskas, Arthur ^[4]

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1. Quaid-i-Azam Univ., Islamabad (Pakistan); Univ. of Tennessee, Knoxville, TN (United States)
2. Quaid-i-Azam Univ., Islamabad (Pakistan)
3. Quaid-i-Azam Univ. and International Islamic Univ., Islamabad (Pakistan)
4. Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Natural dissolved organic matter (DOM) affects mercury (Hg) redox reactions and anaerobic microbial Hg methylation in the environment. Several studies have shown that DOM can enhance Hg methylation, especially under sulfidic conditions, whereas others show that DOM inhibits Hg methylation due to strong Hg-DOM complexation. Here, we investigated and compared the effects of DOM on Hg methylation by an iron-reducing bacterium Geobacter sulfurreducens PCA and a sulfate-reducing bacterium Desulfovibrio desulfuricans ND132 under non-sulfidic conditions. The methylation experiment was performed with washed cells either in the absence or presence of DOM or glutathione, both of which form strong complexes with Hg via thiol-functional groups. DOM was found to greatly inhibit Hg methylation by G. Sulfurreducens PCA but enhance Hg methylation by D. desulfuricans ND132 cells with increasing DOM concentration. These strain-dependent opposing effects of DOM were also observed with glutathione, suggesting that thiols in DOM likely played an essential role in affecting cell Hg uptake and methylation. Additionally, DOM and glutathione decreased Hg sorption by G. sulfurreducens PCA, but not by D. desulfuricans ND132 cells, demonstrating that ND132 has a higher affinity to sorb or take up Hg than the PCA strain. Our observations indicate that DOM effects on Hg methylation are bacterial strain specific, depend on the DOM:Hg ratio or site-specific conditions, and may thus offer new insights into the role of DOM in methylmercury production in the environment.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1376645
• Journal Information: Energies, Journal Name: Energies Journal Issue: 8 Vol. 10; ISSN 1996-1073; ISSN ENERGA
• Publisher: MDPI AGCopyright Statement
• Country of Publication: United States
• Language: English