Combined gasification and fermentation technologies can potentially produce biofuels from renewable biomass. Gasification generates synthesis gas consisting primarily of CO, CO(2), H(2), N(2), with smaller amounts of CH(4), NO(x), O(2), C(2) compounds, ash and tars. Several anaerobic bacteria species can ferment bottled mixtures of pure synthesis gas constituents. However, there are challenges to maintaining culture viability of synthesis gas exposed cells. This study was designed to enhance culture stability and improve ethanol-to-acetate ratios using resting (non-growing) cells in synthesis gas fermentation. Resting cell states were induced in autotrophic Clostridium ljungdahlii cultures with minimal ethanol and acetate production due to low metabolic activity compared to growing cell production levels of 5.2 and 40.1 mM of ethanol and acetate. Clostridium autoethanogenum cultures were not induced into true resting states but did show improvement in total ethanol production (from 5.1 mM in growing cultures to 9.4 in one nitrogen-limited medium) as well as increased shifts in ethanol-to-acetate production ratios.

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The chemical parameters, antimicrobial activity, and tissue toxicity of two sodium hypochlorite (NaOCl) solutions buffered to a physiologic pH were studied. Initially, a 0.5% NaOCI solution buffered with 3 g of NaH2PO4 per liter was examined. The solution had a pH of 7.49 and an osmolality of 352 mOsmol/liter. When compared with unbuffered and NaHCO3-buffered 0.5% NaOCl solutions, the NaH2PO4-buffered solution was significantly more effective in killing Staphylococcus aureus in vitro. However, the pH of the NaH2PO4-buffered solution decreased over time with a concomitant decrease in antibacterial activity. A freshly prepared solution decontaminated human cadaveric skin colonized by S. aureus, Pseudomonas aeruginosa, or Candida albicans in vitro within 10 min of exposure, whereas a 24-h-old solution cleared the skin of organisms within 15 min. When gauze soaked with 0.5% NaOCI was applied to guinea pig skin for 2 weeks, a 15% decrease in basal cell viabilities was noted. Because of the pH instability and basal cell toxicity, a 0.1% NaOCl solution buffered with NaH2PO4-Na2HPO4 was evaluated. This solution had an osmolality of 386 mOsmol/liter and a pH of 7.4 that was stable over 1 week. A freshly prepared 0.1% NaOCl solution decontaminated skin colonized with S.

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Syngas fermentation is considered an alternate processing method for biofuel and biochemical production as part of thermochemical biomass conversion. Exposure of syngas fermenting microorganisms to sugars, either in the primary syngas fermentation or through pre-adaptation in the seed culture, has the potential to enhance overall fermentation performance and stress tolerance. In this rapid communication, Clostridium ljungdahlii was grown on different carbon sources including syngas only, syngas-fructose and fructose only to identify ideal pre-adaptation conditions for ethanol and acetate production from subsequent cultures grown in reactors containing syngas only or fructose-syngas substrates. In syngas only reactors, cultures pre-adapted to fructose had faster cell production rates (2X) and at least 83% higher ethanol and 16% higher acetate formation than cells pre-adapted on syngas or syngas-fructose. In syngasfructose reactors, cultures did not show significant growth or acetate production differences under pre-adaptation treatments. Nevertheless, in these syngas-fructose reactors, cultures pre-adapted on syngas and syngas-fructose had nearly 20% higher ethanol production than those pre-adapted on fructose. Among pre-adaptation treatments, fructose had better results in syngas only reactors than syngas-fructose reactors. However, the presence of syngas in preadaptation cultures was better overall for ethanol production.