Improvement of acetate production from lactose by growing Clostridium thermolacticum in mixed batch culture

Aims: The objective of this study was to increase the acetate production by Clostridium thermolacticum growing on lactose, available as a renewable resource in the milk and whey permeate from the cheese industry. Methods and Results: Experiments for increased acetate productivity by thermophilic anaerobes grown on lactose were carried out in batch cultures. Lactose at concentration of 30 mmol l(-1) (10 g l(-1)) was completely degraded by Cl. thermolacticum and growth rate was maximal. High concentrations of by-products, ethanol, lactate, hydrogen and carbon dioxide were generated. By using an efficient hydrogenotroph, Methanothermobacter thermoautotrophicus, in a defined thermophilic anaerobic consortium (58degreesC) with Cl. thermolacticum and the acetogenic Moorella thermoautotrophica, the hydrogen partial pressure was dramatically lowered. As a consequence, by-products concentrations were significantly reduced and acetate production was increased. Conclusion: Through efficient in situ hydrogen scavenging in the consortium, the metabolic pattern was modified in favour of acetate production, at the expense of reduced by-products like ethanol. Significance and Impact of the Study: The use of this thermophilic anaerobic consortium opens new opportunities for the efficient valorization of lactose, the main waste from the cheese industry, and production of calcium-magnesium acetate, an environmentally friendly road de-icer

Conjugation of atrazine in vetiver (Chrysopogon zizanioides Nash) grown in hydroponics

International audienceThe resistance mechanism of vetiver (Chrysopogon zizanioides Nash) to atrazine was investigated to evaluate its potential for phytoremediation of environment contaminated with the herbicide. Plants known to metabolise atrazine rely on hydroxylation mediated by benzoxazinones, conjugation catalyzed by glutathione-S-transferases (GST) and dealkylation probably mediated by cytochromes P450. All three possibilities were explored in mature vetiver grown in hydroponics during this research project. Here we report on the role of glutathione-S-transferase in the detoxification of atrazine, as determined in vetiver leaf and root of 5-week- and 8-month-old plants grown in hydroponics. Fresh vetiver roots and leaves were cut to extract and study their GST activities toward 1-chloro-2,4-dinitrobenzene (CDNB) and atrazine, using HPLC to quantify the biosynthesis of atrazine conjugates. The global GST activity was three orders of magnitude higher than that of GST isoform able to conjugate atrazine. In vitro activities of conjugation of CDNB were similar in all root and leaf vetiver extracts, whereas activities on atrazine were only detected in leaf extracts. Entire vetiver plants exposed to C-14-atrazine were found to accumulate radioactivity at the tip of leaves under moderate transpiring conditions (75% humidity). Vetiver transformed atrazine mainly into polar compounds, identified as conjugates by TLC analyses. After 20 days of exposure, the proportion of atrazine and metabolites compared to the total penetrated radioactivity into plants was: 50% of conjugates, 28% of atrazine plus possible dealkylates and 22% of unidentified products. The maximum conjugates production was observed at the tip of leaves (29 nmol g(-1) fresh biomass), as compared to roots (6 nmol g(-1) fresh biomass). Altogether, these metabolic features indicate that conjugation to glutathione was a major metabolic pathway to detoxify atrazine in vetiver. (c) 2005 Elsevier B.V. All rights reserved

Acetate production from lactose by Clostridium thermolacticum and hydrogen-scavenging microorganisms in continuous culture - Effect of hydrogen partial pressure

The effect of the addition of hydrogen-consuming microorganisms on the metabolism of Clostridium thermolacticum was studied. By growing this bacterium in continuous culture at 58 degrees C, on 29 mmol lactose l(-1) (10 g l(-1)) in the feed, with the H-2-consuming microorganisms Methanothermobacter thermoautotrophicus and Moorella thermoautotrophica, the volumetric productivity of acetate was increased up to 3.9 mmol l(-1) h(-1) at a dilution rate of 0.058 h(-1). This was about three times higher than the maximal acetate volumetric productivity quiantified when C. thermolacticum was cultivated alone. In the consortium, C. thermolacticum was the only species able to metabolize lactose; it produced not only acetate, but also hydrogen, carbon dioxide and lactate. The other species of the consortium were growing on these by-products. Meth. thermoautotrophicus played an important role as a very efficient hydrogen scavenger and decreased the hydrogen partial pressure drastically: hydrogen was converted to methane. Moor. thermoautotrophica converted lactate as well as hydrogen and carbon dioxide into acetate. As a consequence, lactose was efficiently consumed and the only organic product in the liquid phase was acetate. (C) 2005 Elsevier B.V. All rights reserved

Hydrogen production by Clostridium thermolacticum during continuous fermentation of lactose

In the production of acetate by Clostridium thermolacticum growing on lactose, considerable amounts of hydrogen were generated. Lactose available in large amounts from milk permeate, a wastestream of the dairy industry, appears to be a valuable substrate for cheap production of biohydrogen. In this study, continuous cultivation of C thermolacticum was carried out in a bioreactor, under anaerobic thermophilic conditions, on minimal medium containing 10 g l(-1) lactose. Different dilution rates and pH were tested. C thermolacticum growing on lactose produced acetate, ethanol and lactate in the liquid phase. For all conditions tested, hydrogen was the main product in the gas phase. Hydrogen specific production higher than 5 mmol H-2 (g cell)(-1) h(-1) was obtained. By operating this fermentation at high-dilution rate and alkaline pH, the hydrogen content in the gas phase was maximized. (C) 2004 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved

Increased tolerance of sunflower mutant seedlings to Cd and Zn in hydroponic culture

Cadmium and zinc show similarities in their chemistry, geochemistry and environmental properties. Whereas Cd is a phytotoxic non-essential element, Zn is an essential trace element for plant growth and development. Zinc plays a fundamental role in several key cellular functions, such as protein metabolism, gene expression, chromatin structure, photosynthetic carbon metabolism and indole acetic acid metabolism (Vallee and Falchuk, 1993; Marschner, 1995; Bonnet et al., 2000; Cakmak and Braun, 2001). Zinc is also an important component of many enzymes and proteins (Broadley et al., 2007). Cadmium can readily inhibit most of the Zn-dependent processes by binding to the membrane and to enzyme active sites, thus inactivating their functions (Aravind and Prasad, 2005). However, increasing Zn concentrations can replace such wrongly bound Cd (Van Assche and Clijsters, 1990; Shaw et al., 2004). Cadmium has been shown to cause many morphological, physiological, biochemical and structural changes in plants, such as growth inhibition, reduction in photosynthesis, transpiration or water imbalance (Sanità di Toppi and Gabbrielli, 1999; Schützendübel et al., 2001; Benavides et al., 2005; Mishra et al., 2006). Cadmium and high zinc concentration affect plant growth and metabolism, but the intensity of their toxic effects depends on plant species and the way and duration of metal exposure. Plants called hyperaccumulators are able to tolerate and accumulate extraordinary levels of trace elements in their above-ground tissue without developing any toxicity symptoms (Baker and Brooks, 1989; Reeves and Baker, 2000). Their high metal accumulation capability makes them interesting for the decontamination technique called phytoextraction, which uses plants for environmental clean-up (Salt et al., 1998). However, their low biomass production strongly limits the real application of this soil decontamination strategy. The ideal plant for phytoextraction should provide both a high biomass and a high tolerance and metal accumulation (Schwitzguébel et al., 2002). High biomass producing plants with improved tolerance to trace elements and with an enhanced metal accumulation capacity should be good candidates for metal removal from contaminated area. Previous studies have shown enhanced tolerance and metal accumulation properties in transgenic tobacco plants (Pomponi et al., 2006; Gorinova et al., 2007; Wojas et al., 2008). However, the main disadvantage of genetic engineering is still public acceptance and free-land application. In vitro breeding techniques have also been successfully used to obtain tobacco lines with a considerably enhanced Cd, Zn and Cu tolerance and metal accumulation (Herzig et al., 1997; Guadagnini et al., 1999; Herzig et al., 2003). In addition, the chemical mutagen ethyl methane sulphonate has been used to develop new sunflower lines with a significantly enhanced biomass and metal uptake on a metal contaminated field (Nehnevajova et al., 2007, 2009). Although these field experiments have revealed the potential of sunflower mutants for metal phytoextraction, their tolerance to trace elements and the effect of Cd and Zn on growth and photosynthetic pigments were not studied within previous free-land experimentation. The aim of the present work was thus to assess the tolerance to Cd and excess Zn of selected sunflower mutant lines with improved biomass and metal uptake capacity, by measuring different physiological parameters. For such a purpose, sunflower seedlings of eight selected mutant lines were cultivated under hydroponic conditions in the presence and in the absence of Cd and Zn to study the effect of these trace elements on (1) growth parameters, such as root elongation, root and shoot dry mass; (2) chlorophyll content; (3) carotenoid content; (4) Cd and Zn accumulation capacity of sunflower mutants; and (5) a possible correlation between Cd and Zn accumulation in sunflower shoots and roots

Glenoid loosening and migration in reverse shoulder arthroplasty

AIMS The aim of this study was to report the outcomes of different treatment options for glenoid loosening following reverse shoulder arthroplasty (RSA) at a minimum follow-up of two years. PATIENTS AND METHODS We retrospectively studied the records of 79 patients (19 men, 60 women; 84 shoulders) aged 70.4 years (21 to 87) treated for aseptic loosening of the glenosphere following RSA. Clinical evaluation included pre- and post-treatment active anterior elevation (AAE), external rotation, and Constant score. RESULTS From the original cohort, 29 shoulders (35%) were treated conservatively, 27 shoulders (32%) were revised by revision of the glenosphere, and 28 shoulders (33%) were converted to hemiarthroplasty. At last follow-up, conservative treatment and glenoid revision significantly improved AAE, total Constant score, and pain, while hemiarthroplasty did not improve range of movement or clinical scores. Multivariable analysis confirmed that conservative treatment and glenoid revision achieved similar improvements in pain (glenoid revision vs conservative, beta 0.44; p = 0.834) but that outcomes were significantly worse following hemiarthroplasty (beta -5.00; p = 0.029). CONCLUSION When possible, glenoid loosening after RSA should first be treated conservatively, then by glenosphere revision if necessary, and last by salvage hemiarthroplasty Cite this article: Bone Joint J 2019;101-B:461-469