title: Hydrogen production under salt stress conditions by a freshwater Rhodopseudomonas palustris strain.
abstract: Hydrogen represents a possible alternative energy carrier to face the growing request for energy and the shortage of fossil fuels. Photofermentation for the production of H2 constitutes a promising way for integrating the production of energy with waste treatments. Many wastes are characterized by high salinity, and polluted seawater can as well be considered as a substrate. Moreover, the application of seawater for bacterial culturing is considered cost-effective. The aims of this study were to assess the capability of the metabolically versatile freshwater Rhodopseudomonas palustris 42OL of producing hydrogen on salt-containing substrates and to investigate its salt stress response strategy, never described before. R. palustris 42OL was able to produce hydrogen in media containing up to 3 % added salt concentration and to grow in media containing up to 4.5 % salinity without the addition of exogenous osmoprotectants. While the hydrogen production performances in absence of sea salts were higher than in their presence, there was no significant difference in performances between 1 and 2 % of added sea salts. Nitrogenase expression levels indicated that the enzyme was not directly inhibited during salt stress, but a regulation of its expression may have occurred in response to salt concentration increase. During cell growth and hydrogen production in the presence of salts, trehalose was accumulated as a compatible solute; it protected the enzymatic functionality against salt stress, thus allowing hydrogen production. The possibility of producing hydrogen on salt-containing substrates widens the range of wastes that can be efficiently used in production processes.
authors.affiliation: Department of Agrifood Production and Environmental Sciences, University of Florence, Piazzale delle Cascine 24, 50144, Florence, Italy.|Institute of Chemistry of Organometallic Compounds (ICCOM), CNR, via Madonna del Piano 10, 50019, Sesto Fiorentino, Florence, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Adessi
authors.affiliation: Department of Agrifood Production and Environmental Sciences, University of Florence, Piazzale delle Cascine 24, 50144, Florence, Italy.
authors.forename: Margherita
authors.initials: M
authors.lastname: Concato
authors.affiliation: Department of Agrifood Production and Environmental Sciences, University of Florence, Piazzale delle Cascine 24, 50144, Florence, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Sanchini
authors.affiliation: Department of Agrifood Production and Environmental Sciences, University of Florence, Piazzale delle Cascine 24, 50144, Florence, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Rossi
authors.affiliation: Department of Agrifood Production and Environmental Sciences, University of Florence, Piazzale delle Cascine 24, 50144, Florence, Italy. roberto.dephilippis@unifi.it.|Institute of Chemistry of Organometallic Compounds (ICCOM), CNR, via Madonna del Piano 10, 50019, Sesto Fiorentino, Florence, Italy. roberto.dephilippis@unifi.it.
authors.forename: Roberto
authors.initials: R
authors.lastname: De Philippis
mesh_terms: D003470:Culture Media / Q000737:chemistry; D005618:Fresh Water / Q000382:microbiology; D006859:Hydrogen / Q000378:metabolism*; D009591:Nitrogenase / Q000032:analysis; D009997:Osmotic Pressure; D012241:Rhodopseudomonas / Q000737:chemistry / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*; D054712:Salinity; D012492:Salts / Q000378:metabolism*; D014199:Trehalose / Q000032:analysis
chemical_list: D003470:Culture Media; D012492:Salts; D006859:Hydrogen; D014199:Trehalose; D009591:Nitrogenase
keywords: Biological hydrogen production; Photofermentation; Rhodopseudomonas palustris; Salt stress; Trehalose