CO₂ Dissolution and Design Aspects of a Multiorifice Oscillatory Baffled Column

Dissolution of CO₂ in water was studied for a batch vertical multiorifice baffled column (MOBC) with varying orifice diameters (<i>d</i>₀) of 6.4–30 mm and baffle open area (α) of 15–42%. Bubble size distributions (BSDs) and the overall volumetric CO₂ mass transfer coefficient (<i>K</i>_L<i>a</i>) were experimentally evaluated for very low superficial gas velocities, <i>U</i>_G of 0.12–0.81 mm s^–1, using 5% v/v CO₂ in the inlet gas stream at a range of fluid oscillations (<i>f</i> = 0–10 Hz and <i>x</i>₀ = 0–10 mm). Remarkably, baffles presenting large <i>d</i>_o = 30 mm and α = 36%, therefore in the range typically found for single-orifice oscillatory baffled columns, were outperformed with respect to BSD control and CO₂ dissolution by the other baffle designs or the same aerated column operating without baffles or fluid oscillations. Flow visualization and bubble tracking experiments also presented in this study established that a small <i>d</i>_o of 10.5 mm combined with a small value of α = 15% generates sufficient, strong eddy mixing capable of generating and trapping an extremely large fraction of microbubbles in the MOBC. This resulted in increased interfacial area yielding <i>K</i>_L<i>a</i> values up to 65 ± 12 h^–1 in the range of the <i>U</i>_G tested, representing up to 3-fold increase in the rate of CO₂ dissolution when compared to the unbaffled, steady column. In addition, a modified oscillatory Reynolds number, <i>Re</i>_o^′ and Strouhal number, <i>St</i>′ were presented to assist on the design and scale-up of gas–liquid systems based on multiorifice oscillatory baffled columns. This work is relevant to gas–liquid or multiphase chemical and biological systems relying on efficient dissolution of gaseous compounds into a liquid medium

Conversion of C_n‑Unsaturated into C_n‑2-Saturated LCFA Can Occur Uncoupled from Methanogenesis in Anaerobic Bioreactors

Fat, oils, and grease present in complex wastewater can be readily converted to methane, but the energy potential of these compounds is not always recyclable, due to incomplete degradation of long chain fatty acids (LCFA) released during lipids hydrolysis. Oleate (C18:1) is generally the dominant LCFA in lipid-containing wastewater, and its conversion in anaerobic bioreactors results in palmitate (C16:0) accumulation. The reason why oleate is continuously converted to palmitate without further degradation via β-oxidation is still unknown. In this work, the influence of methanogenic activity in the initial conversion steps of unsaturated LCFA was studied in 10 bioreactors continuously operated with saturated or unsaturated C16- and C18-LCFA, in the presence or absence of the methanogenic inhibitor bromoethanesulfonate (BrES). Saturated C_n‑2-LCFA accumulated both in the presence and absence of BrES during the degradation of unsaturated C_n-LCFA, and represented more than 50% of total LCFA. In the presence of BrES further conversion of saturated intermediates did not proceed, not even when prolonged batch incubation was applied. As the initial steps of unsaturated LCFA degradation proceed uncoupled from methanogenesis, accumulation of saturated LCFA can be expected. Analysis of the active microbial communities suggests a role for facultative anaerobic bacteria in the initial steps of unsaturated LCFA biodegradation. Understanding this role is now imperative to optimize methane production from LCFA

Additional file 1 of Metabolic engineering of Clostridium autoethanogenum for ethyl acetate production from CO

Additional file 1: Table S1. List of primers used in this study. Table S2. Sequences of genes expressed in this study. Figure S1. Image of Sanger sequencing results showed the nature of the in-frame deletion in the pta gene (CAETHG_3358). Figure S2. Image of Sanger sequencing results showed the nature of the in-frame deletion in the Ald subunit of the adhE1 gene (CAETHG_3747). Figure S3. Change in CO headspace pressure for C. autoethanogenum strains carrying plasmids for AAT expression on CO as main carbon source. Figure S4. Screening of ethyl acetate production by C. autoethanogenum strains carrying plasmids for AAT expression on 40 mM fructose. Figure S4. Investigating growth of C. autoethanogenum on CO and ethyl acetate. Figure S5. Investigating ethyl acetate degradation by C. autoethanogenum grown on CO. Figure S6. Eat1 in vivo alcoholysis assay for C. autoethanogenum and E. coli. Figure S7. Investigating the effects of ethanol supplementation on growth of C. autoethanogenum [PThl-Atf1] grown on CO. Figure S8. Investigating the effects of ethanol supplementation on ethyl acetate production by C. autoethanogenum [PThl-Atf1] grown on C

Bioaugmentation of Sewage Sludge with <i>Trametes versicolor</i> in Solid-Phase Biopiles Produces Degradation of Pharmaceuticals and Affects Microbial Communities

The use of sludge (biosolids) in land application may contribute to the spread of organic micropollutants as wastewater treatments do not completely remove these compounds. Therefore, the development of alternative strategies for sludge treatment is a matter of recent concern. The elimination of pharmaceuticals at pre-existent concentrations from sewage sludge was assessed, for the first time, in nonsterile biopiles by means of fungal bioaugmentation with <i>Trametes versicolor</i> (BTV-systems) and compared with the effect of autochthonous microbiota (NB-systems). The competition between the autochthonous fungal/bacterial communities and <i>T. versicolor</i> was studied using denaturing gradient gel electrophoresis (DGGE) and the cloning/sequencing approach. An inhibitory effect exerted by <i>T. versicolor</i> over bacterial populations was suggested. However, after 21 days, <i>T. versicolor</i> was no longer the main taxon in the fungal communities. The elimination profiles revealed an enhanced removal of atorvastatin-diclofenac-hydrochlorothiazide (during the whole treatment) and ranitidine-fenofibrate (at short periods) in the BTV biopiles in respect to NB biopiles, coincident with the presence of the fungus. For ibuprofen-clarithromycin-furosemide, the elimination profiles were similar irrespective of the system, and with carbamazepine no significant degradation was obtained. The results suggest that a fungal treatment with <i>T. versicolor</i> could be a promising process for the remediation of some pharmaceuticals in complex matrices such as biosolids

Other cellulosomal proteins with significantly different levels when comparing Tissue and Whatman Paper incubations.

<p>Other cellulosomal proteins with significantly different levels when comparing Tissue and Whatman Paper incubations.</p

ABC transporter proteins with significantly different levels when comparing Tissue and Whatman Paper incubations.

<p>ABC transporter proteins with significantly different levels when comparing Tissue and Whatman Paper incubations.</p

Cellulosomal endoglucanases with significantly different levels when comparing Tissue and Whatman Paper incubations.

<p>Cellulosomal endoglucanases with significantly different levels when comparing Tissue and Whatman Paper incubations.</p

Growth and fermentation dynamics of <i>R</i>. <i>cellulolyticum</i> on Tissue (black symbols), Whatman Paper (grey symbols) and Cotton (light grey symbols).

<p>Acetate (A), ethanol (B) and lactate (C) are the three most abundant fermentation products and their concentration ratios are shown in (D-E). Genome copy numbers estimated from the amount of total extracted DNA are shown in (F). Error bars indicate standard deviations calculated from triplicate samples, except in F (duplicate samples). Light grey areas indicate the time points selected for subsequent proteomic analyses.</p

Non-cellulosomal CAZymes with at least one statistically significant effect when comparing incubations on Tissue and Whatman Paper.

<p>Non-cellulosomal CAZymes with at least one statistically significant effect when comparing incubations on Tissue and Whatman Paper.</p

Proteins with significant effects when comparing growth on Tissue and Whatman Paper mapped over <i>R</i>. <i>cellulolyticum</i> glucose and xylose catabolic pathways.

<p>Statistically significant substrate and substrate-by-time interaction effects were considered. The green color indicates positive effects while the red color indicates negative effects. Positive effects correspond to quantified protein levels higher in Tissue incubations than in Whatman Paper incubations (substrate effect) and to quantified protein levels increasing more or decreasing less in Tissue incubations than in Whatman Paper incubations (substrate-by-time interaction effect). The statistical models (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170524#sec002" target="_blank">Materials and Methods</a>) take into account the replicates and their variability. Protein names and EC numbers are indicated in grey. * indicate effects not significant when adjusting for multiple comparisons (Q-values > 0.01) but still supporting the overall trend (p-values < = 0.05). ** indicate a significant negative substrate effect (q-value ≤ 0.01) and a positive interaction effect (q-value > 0.01 but p-value ≤ 0.05). Pathways were adapted from the Biocyc website (<a href="http://biocyc.org/" target="_blank">http://biocyc.org/</a>).</p