Polyhydroxyalkanoates production from cheese whey under near-seawater salinity conditions.

Treating saline streams presents considerable challenges due to their adverse effects on conventional biological processes, thereby leading to increased expenses in managing those side streams. With this in consideration, this study explores into the potential for valorizing fermented cheese whey (CW), a by-product of the dairy industry, into polyhydroxyalkanoates (PHA) using mixed microbial cultures (MMC) under conditions of near-seawater salinity (30 g/L). The selection of a PHA-accumulating MMC was successfully achieved using a sequential batch reactor operated under a feast and famine regime, with a hydraulic retention time of 14.

Donnan Dialysis for Recovering Ammonium from Fermentation Solutions Rich in Volatile Fatty Acids.

For the production of polyhydroxyalkanoates (PHA) using nitrogen-rich feedstocks (e.g., protein-rich resources), the typical strategy of restricting cell growth as a means to enhance overall PHA productivity by nitrogen limitation is not applicable.

Taxonomic distribution, structure/function relationship and metabolic context of the two families of sulfide dehydrogenases: SQR and FCSD.

Hydrogen sulfide (HS) is a versatile molecule with different functions in living organisms: it can work as a metabolite of sulfur and energetic metabolism or as a signaling molecule in higher Eukaryotes. HS is also highly toxic since it is able to inhibit heme cooper oxygen reductases, preventing oxidative phosphorylation. Due to the fact that it can both inhibit and feed the respiratory chain, the immediate role of HS on energy metabolism crucially relies on its bioavailability, meaning that studying the central players involved in the HS homeostasis is key for understanding sulfide metabolism.

Structural and Functional insights into the catalytic mechanism of the Type II NADH:quinone oxidoreductase family.

Type II NADH:quinone oxidoreductases (NDH-2s) are membrane proteins involved in respiratory chains. These proteins contribute indirectly to the establishment of the transmembrane difference of electrochemical potential by catalyzing the reduction of quinone by oxidation of NAD(P)H. NDH-2s are widespread enzymes being present in the three domains of life.

Type II NADH:quinone oxidoreductase family: phylogenetic distribution, structural diversity and evolutionary divergences.

Type II NADH:quinone oxidoreductases (NDH-2s) are membrane proteins, crucial for the catabolic metabolism, because they contribute to the maintenance of the NADH/NAD balance. In several pathogenic bacteria and protists, NDH-2s are the only enzymes performing respiratory NADH:quinone oxidoreductase activity. For this reason and for being considered absent in mammals, NDH-2s were proposed as suitable targets for novel antimicrobial therapies.

Exploring membrane respiratory chains.

Acquisition of energy is central to life. In addition to the synthesis of ATP, organisms need energy for the establishment and maintenance of a transmembrane difference in electrochemical potential, in order to import and export metabolites or to their motility. The membrane potential is established by a variety of membrane bound respiratory complexes.

Respiratory complex I: A dual relation with H(+) and Na(+)?

Respiratory complex I couples NADH:quinone oxidoreduction to ion translocation across the membrane, contributing to the buildup of the transmembrane difference of electrochemical potential. H(+) is well recognized to be the coupling ion of this system but some studies suggested that this role could be also performed by Na(+). We have previously observed NADH-driven Na(+) transport opposite to H(+) translocation by menaquinone-reducing complexes I, which indicated a Na(+)/H(+) antiporter activity in these systems.

Respiratory complex I from Escherichia coli does not transport Na(+) in the absence of its NuoL subunit.

We investigated H(+) and Na(+) transport by complex I from Escherichia coli devoid of the NuoL subunit, which is probably part of the ion translocating machinery. We observed that complex I devoid of the NuoL subunit still translocates H(+), although to a smaller extension than the complete version of complex I, but does not transport Na(+). Our results unequivocally reinforce the observation that E.

The antiporter-like subunit constituent of the universal adaptor of complex I, group 4 membrane-bound [NiFe]-hydrogenases and related complexes.

We have recently investigated the long-recognized relationship between complex I and group 4 [NiFe] hydrogenases and we have established the so-called Energy-converting hydrogenase related (Ehr) complex as a new member of the family. We have also observed that four subunits, homologues to NuoB, D, H and L, are common to the members of the family. We have designated this common group of subunits the universal adaptor.

A missing link between complex I and group 4 membrane-bound [NiFe] hydrogenases.

Complex I of respiratory chains is an energy transducing enzyme present in most bacteria, mitochondria and chloroplasts. It catalyzes the oxidation of NADH and the reduction of quinones, coupled to cation translocation across the membrane. The complex has a modular structure composed of several proteins most of which are identified in other complexes.

The role of proton and sodium ions in energy transduction by respiratory complex I.

Respiratory complex I plays a central role in energy transduction. It catalyzes the oxidation of NADH and the reduction of quinone, coupled to cation translocation across the membrane, thereby establishing an electrochemical potential. For more than half a century, data on complex I has been gathered, including recently determined crystal structures, yet complex I is the least understood complex of the respiratory chain.

Study of ion translocation by respiratory complex I. A new insight using (23)Na NMR spectroscopy.

The research on complex I has gained recently a new enthusiasm, especially after the resolution of the crystallographic structures of bacterial and mitochondrial complexes. Most attention is now dedicated to the investigation of the energy coupling mechanism(s). The proton has been identified as the coupling ion, although in the case of some bacterial complexes I Na(+) has been proposed to have that role.

Decoupling of the catalytic and transport activities of complex I from Rhodothermus marinus by sodium/proton antiporter inhibitor.

The energy transduction by complex I from Rhodothermusmarinus was addressed by studying the influence of 5-(N-ethyl-N-isopropyl)-amiloride (EIPA) on the activities of this enzyme. EIPA is an inhibitor of both Na(+)/H(+) antiporter and complex I NADH:quinone oxidoreductase activity. We performed studies of NADH:quinone oxidoreductase and H(+) and Na(+) translocation activities of complex I from R.