Microalgae show great potential for wastewater treatment and nutrient recovery. However, microalgae cultivation and harvesting are affected by the low biomass concentrations which are inherent to the ...photoautotrophic growth process. Mixotrophic growth can be a solution as it increases microalgae biomass concentration independently from the incident light intensity. In this work, a combined respirometric-titrimetric unit was used to assess the microalgae kinetics during such mixotrophic growth conditions for Chlorella vulgaris. Based on the experimental results, a microalgae model was extended in order to gain more insight in the delicate balance between photoautotrophic and heterotrophic growth. The results suggest that during heterotrophic growth with light in absence of external inorganic carbon sources (i.e. photoheterotrophic growth), all CO2 produced by the heterotrophic pathway is internally recycled for photoautotrophic growth. Moreover, it was shown that photoautotrophic growth is the preferential growth mechanism under mixotrophic cultivation conditions (i.e. light + inorganic carbon + organic carbon), but that high oxygen concentrations activate the heterotrophic growth pathway to avoid photorespiration. The extended microalgae model supports these findings, with good model performance for all conducted experiments.
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•Combined respirometry-titrimetry was used to quantify growth modes of C. vulgaris.•All CO2 produced during photoheterotrophic growth seems to be internally recycled.•Mixotrophic growth did not occur at oxygen concentrations lower than 15–20 mg.L−1.•The mixotrophic growth pathway was activated to avoid photorespiration.•A microalgae model was developed to describe the mixotrophic growth kinetics.
There is increasing industrial interest in the use of the milkfat globule membrane as a food ingredient. The objective of this research was to determine whether the aerosol whipping performance of ...cream separated into butter and buttermilk, and then recombined, would perform in a manner similar to untreated cream. Churning of cream tempered to different solid fat contents was used to separate butter from buttermilk, which were then recombined at the same ratios as the initial extraction yield, or with 25% extra buttermilk. Differences in milkfat globule size distributions among the recombined creams were apparent; however, their whipping behavior and overrun were similar. Importantly, all recombined creams did not yield properties similar to the original cream, indicating that the unique native milkfat globule membrane structure plays a role in cream performance well beyond its simple presence.
► Sulfide concentration governs the location of metal precipitates in sulfate reducing bioreactors. ► High dissolved sulfide induces metal precipitation in the bulk liquid as fines. ► Low dissolved ...sulfide concentrations yield local supersaturation and thus metal precipitation in the biofilm.
The effect of the sulfide concentration on the location of the metal precipitates within sulfate-reducing inversed fluidized bed (IFB) reactors was evaluated. Two mesophilic IFB reactors were operated for over 100 days at the same operational conditions, but with different chemical oxygen demand (COD) to SO
4
2− ratio (5 and 1, respectively). After a start up phase, 10
mg/L of Cu, Pb, Cd and Zn each were added to the influent. The sulfide concentration in one IFB reactor reached 648
mg/L, while it reached only 59
mg/L in the other one. In the high sulfide IFB reactor, the precipitated metals were mainly located in the bulk liquid (as fines), whereas in the low sulfide IFB reactor the metal preciptiates were mainly present in the biofilm. The latter can be explained by local supersaturation due to sulfide production in the biofilm. This paper demonstrates that the sulfide concentration needs to be controlled in sulfate reducing IFB reactors to steer the location of the metal precipitates for recovery.
The incidence of chronic liver disease is constantly increasing, owing to the obesity epidemic. However, the causes and mechanisms of inflammation-mediated liver damage remain poorly understood. ...Endoplasmic reticulum (ER) stress is an initiator of cell death and inflammatory mechanisms. Although obesity induces ER stress, the interplay between hepatic ER stress, NLRP3 inflammasome activation and hepatocyte death signaling has not yet been explored during the etiology of chronic liver diseases. Steatosis is a common disorder affecting obese patients; moreover, 25% of these patients develop steatohepatitis with an inherent risk for progression to hepatocarcinoma. Increased plasma LPS levels have been detected in the serum of patients with steatohepatitis. We hypothesized that, as a consequence of increased plasma LPS, ER stress could be induced and lead to NLRP3 inflammasome activation and hepatocyte death associated with steatohepatitis progression. In livers from obese mice, administration of LPS or tunicamycin results in IRE1α and PERK activation, leading to the overexpression of CHOP. This, in turn, activates the NLRP3 inflammasome, subsequently initiating hepatocyte pyroptosis (caspase-1, -11, interleukin-1β secretion) and apoptosis (caspase-3, BH3-only proteins). In contrast, the LPS challenge is blocked by the ER stress inhibitor TUDCA, resulting in: CHOP downregulation, reduced caspase-1, caspase-11, caspase-3 activities, lowered interleukin-1β secretion and rescue from cell death. The central role of CHOP in mediating the activation of proinflammatory caspases and cell death was characterized by performing knockdown experiments in primary mouse hepatocytes. Finally, the analysis of human steatohepatitis liver biopsies showed a correlation between the upregulation of inflammasome and ER stress markers, as well as liver injury. We demonstrate here that ER stress leads to hepatic NLRP3 inflammasome pyroptotic death, thus contributing as a novel mechanism of inflammation-mediated liver injury in chronic liver diseases. Inhibition of ER-dependent inflammasome activation and cell death pathways may represent a potential therapeutic approach in chronic liver diseases.
This study assessed the accumulation of Cd (II), Hg (II), Cr (VI) and Pb (II) in Gynerium sagittatum (Gs), Colocasia esculenta (Ce) and Heliconia psittacorum (He) planted in constructed wetlands ...treating synthetic landfill leachate. Sixteen bioreactors were operated in two experimental blocks. Metal concentrations in the influent and effluent; root, stem, branch and leaves of plants were analysed, as well as COD, N-NH ₄⁺, TKN, T, pH, ORP, DO, and EC. Average removal efficiencies of COD, TKN and NH ₄⁺-N were 66, 67 and 72%, respectively and heavy metal removal ranged from 92 to 98% in all units. Cr (VI) was not detected in any effluent sample. The bioconcentration factors (BCF) were 10 ⁰ -10 ². The BCF of Cr (VI) was the lowest: 0.59 and 2.5 (L kg ⁻¹) for Gs and He respectively; whilst Cd (II) had the highest (130–135 L kg ⁻¹) for Gs. Roots showed a higher metal content than shoots. Translocation factors (TF) were lower, He was the plant exhibiting TFs >1 for Pb (II), Cr (T) and Hg (II) and 0.4–0.9 for Cd (II) and Cr (VI). The evaluated plants demonstrate their suitability for phytoremediation of landfill leachate and all of them can be categorized as metals accumulators.
The freeze/thaw stability of water-in-oil emulsions is strongly influenced by the sequence of crystallization events (i.e., dispersed
vs. continuous phase or
vice versa) and the solid–liquid behavior ...of interfacially-bound surfactants.
Factors influencing water-in-oil emulsion stability during freeze/thaw-cycling, namely interfacial crystallization
vs. network crystallization and the sequence of crystallization events (i.e., dispersed
vs. continuous phase or
vice versa), are assessed. We show that destabilization is most apparent with a liquid-state emulsifier and a continuous oil phase that solidifies prior to the dispersed phase. Emulsions stable to F/T-cycling are obtained when the emulsifier crystallizes at the oil–water interface or in emulsions where the continuous phase crystallizes after the dispersed aqueous phase. The materials used are two food-grade oil-soluble emulsifiers – polyglycerol polyricinoleate (PGPR) and glycerol monostearin (GMS) and two continuous oil phases with differing crystallization temperatures – canola oil and coconut oil. Emulsion stability is assessed with pulsed field gradient NMR droplet size analysis, sedimentation, microscopy and differential scanning calorimetry. This study demonstrates the sequence of crystallization events and the physical state of the surfactant at the oil–water interface strongly impact the freeze–thaw stability of water-in-oil emulsions.
This study assessed the accumulation of metals in a horizontal subsurface flow constructed wetland treating domestic wastewater of 350 PE after three years of operation. Metal concentrations in the ...influent wastewater, effluent, sediment, leaves, stems, and belowground biomass of
Phragmites australis were analysed. Spatial variations were assessed by sampling at increasing distance from the inlet and at different positions across the width of the reed bed. All metals except Fe and Mn were efficiently removed in the CW, total metal concentrations in the effluent complied with basic environmental quality standards for surface water, and dissolved metal concentrations were often lower than analytical detection limits. Removal efficiencies varied between 49% for Ni and 93% for Al. Export of dissolved Mn and particulate Fe occurred, probably related to redox conditions in the sediment. After 3 years of operation, the sediment in the inlet area was significantly contaminated with Zn, Cu, and Cd, whereas Pb could form a contamination problem within the near future. The Cr and Ni levels in the sediment were low throughout the entire reed bed. At this stage of operation, the contamination problem was still situated within the inlet area and metal concentrations in the sediment decreased towards background values further along the treatment path. An exponential decrease of the metal mass in the sediment and belowground biomass was seen for all metals except Mn. Contrary to the other metals, Mn concentrations in the sediment increased with distance. For all metals, less than 2% of the mass removed from the wastewater after passage through the reed bed is accumulated in the aboveground reed biomass. The sediment acts as the primary sink for metals.
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