Dark fermentation: isolation and characterization of hydrogen-producing strains from sludges Authors Haifa Rajhi Mónica Conthe Daniel Puyol Emiliano Díaz José Luis Sanz Abstract To improve bacterial hydrogen production, ten hydrogen-producing strains belonging to Clostridium spp.were isolated from various sludges under low vacuum. Hydrogenogenesis by dark fermentation in batch cultures of thesestrains was optimal at about 35 ºC and an initial pH of 6.5, which for all strains gradually dropped to ca. pH 4 during thefermentation. Clostridium roseum H5 and C. diolis RT2 had the highest hydrogen yields per total substrate (120 ml H2/ginitial COD). Substrate consumption alone by C. beijerinckii UAM and C. diolis RT2 reached 573 and 475 ml H2/gconsumed COD, respectively. Butyric acid fermentation was predominant, with butyrate and acetate as the majorby-products and propionate, ethanol, and lactate as secondary metabolites. The acetate:butyrate ratios and fermentationpathways varied depending on the strains and environmental conditions. Hydrogenogenesis was studied in greater detailin C. saccharobutylicum H1. In butyric acid fermentation by this representative strain, acetoacetate was detected as anintermediate metabolite. Hydrogenogenesis was also analyzed in an enrichment culture, which behaved similarly to theaxenic cultures. [Int Microbiol 2013; 16(1):53-62] Downloads PDF Issue Vol. 16 No. 1 (2013) Section Research Articles License Submission of a manuscript to International Microbiology implies: that the work described has not been published before, including publication in the World Wide Web (except in the form of an Abstract or as part of a published lecture, review, or thesis); that it is not under consideration for publication elsewhere; that all the coauthors have agreed to its publication. The corresponding author signs for and accepts responsability for releasing this material and will act on behalf of any and all coauthors regarding the editorial review and publication process.If an article is accepted for publication in International Microbiology, the authors (or other copyright holder) must transfer to the journal the right–not exclusive–to reproduce and distribute the article including reprints, translations, photographic reproductions, microform, electronic form (offline, online) or any other reproductions of similar nature. Nevertheless, all article in International Microbiology will be available on the Internet to any reader at no cost. The journal allows users to freely download, copy, print, distribute, search, and link to the full text of any article, provided the authorship and source of the published article is cited. The copyright owner's consent does not include copying for new works, or resale. In these cases, the specific written permission of International Microbiology must first be obtained.Authors are requested to create a link to the published article on the journal's website. The link must be accompanied by the following text: "The original publication is available on LINK at <http://www.im.microbios.org>. Please use the appropiate URL for the article in LINK. Articles disseminated via LINK are indexed, abstracted, and referenced by many abstracting and information services, bibliographic networks, subscription agencies, library networks, and consortia.
