{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,26]],"date-time":"2026-06-26T05:49:48Z","timestamp":1782452988738,"version":"3.54.5"},"reference-count":86,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,6,26]],"date-time":"2026-06-26T00:00:00Z","timestamp":1782432000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100004955","name":"\u00d6sterreichische Forschungsf\u00f6rderungsgesellschaft","doi-asserted-by":"publisher","award":["FO999910834"],"award-info":[{"award-number":["FO999910834"]}],"id":[{"id":"10.13039\/501100004955","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Microbiol."],"abstract":"<jats:p>\n                    Biological hydrogen (H\n                    <jats:sub>2<\/jats:sub>\n                    ) production\n                    <jats:italic>via<\/jats:italic>\n                    dark fermentation (DF) offers a renewable pathway for energy recovery from biomass, but process performance is highly strain dependent and often limited by suboptimal operating conditions. The present study characterizes fermentation physiology and optimizes small-scale H\n                    <jats:sub>2<\/jats:sub>\n                    production by the recently discovered thermophilic anaerobe\n                    <jats:italic>Thermoactinomyces mirandus<\/jats:italic>\n                    . Batch cultivations at 52 \u00b0C in anoxic serum bottles were used to screen carbon sources (glucose, fructose, xylose, arabinose, and lactose), nitrogen sources (yeast extract, casein peptone, casamino acids, and ammonium chloride), carbon to nitrogen (C\/N) ratios, and a targeted set of potential inhibitory factors. Yeast extract supported the highest H\n                    <jats:sub>2<\/jats:sub>\n                    yields, while fructose, xylose, and lactose were the most effective carbon sources. Baseline lactose fermentation without pH control yielded 118.31 \u00b1 19.91 mmol H\n                    <jats:sub>2<\/jats:sub>\n                    mol hexose equivalent\n                    <jats:sup>\u22121<\/jats:sup>\n                    after 11 days, with incomplete lactose conversion. Implementing a small-scale, closed-flask pH control at setpoint 7.2 increased the yield 4.2-fold to 466.6 \u00b1 10.2 mmol H\n                    <jats:sub>2<\/jats:sub>\n                    mol hexose equivalent\n                    <jats:sup>\u22121<\/jats:sup>\n                    and achieved 99.4 \u00b1 0.2% lactose consumption. Daily nitrogen (N\n                    <jats:sub>2<\/jats:sub>\n                    ) gas sparging modestly improved conversion, while 10-fold supplementation of trace elements, ferrous iron, or formate had no effect. Under controlled pH, an optimum pH range of 7.5\u20138.0 for maximum H\n                    <jats:sub>2<\/jats:sub>\n                    production rate (VHPR) was identified. Higher lactose loads increased the VHPR by 147% from 5.6 to 13.9 mmol lactose L\n                    <jats:sup>\u22121<\/jats:sup>\n                    , with a trade-off in yield (26% decrease). Fermentation product profiles shifted under pH control, with ethanol and acetate increasing relative to lactate, consistent with enzyme pH optima and upregulation of\n                    <jats:italic>pflB<\/jats:italic>\n                    (pyruvate formate lyase) after 4 days cultivation. These results demonstrate that pH control is a key factor for enhancing H\n                    <jats:sub>2<\/jats:sub>\n                    yield by\n                    <jats:italic>T. mirandus<\/jats:italic>\n                    , define quantitative operating windows, and deliver a transferable workflow to identify and mitigate inhibitory factors in DF processes.\n                  <\/jats:p>","DOI":"10.3389\/fmicb.2026.1827551","type":"journal-article","created":{"date-parts":[[2026,6,26]],"date-time":"2026-06-26T05:44:54Z","timestamp":1782452694000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Optimizing dark fermentation for hydrogen production: lessons from Thermoactinomyces mirandus"],"prefix":"10.3389","volume":"17","author":[{"given":"Selina V.","family":"Haller","sequence":"first","affiliation":[{"name":"Department Microbiology, Universit\u00e4t Innsbruck","place":["Innsbruck, Austria"]},{"name":"Department Biotechnology, MCI Internationale Hochschule GmbH","place":["Innsbruck, Austria"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Luise","family":"Ebert","sequence":"additional","affiliation":[{"name":"Department Biotechnology, MCI Internationale Hochschule GmbH","place":["Innsbruck, Austria"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mira","family":"Mutschlechner","sequence":"additional","affiliation":[{"name":"Department Biotechnology, MCI Internationale Hochschule GmbH","place":["Innsbruck, Austria"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Harald","family":"Sch\u00f6bel","sequence":"additional","affiliation":[{"name":"Department Biotechnology, MCI Internationale Hochschule GmbH","place":["Innsbruck, Austria"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andreas O.","family":"Wagner","sequence":"additional","affiliation":[{"name":"Department Microbiology, Universit\u00e4t Innsbruck","place":["Innsbruck, Austria"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,6,26]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"335","DOI":"10.1016\/j.ijhydene.2023.05.161","article-title":"Biohydrogen production through dark fermentation: recent trends and advances in transition to a circular bioeconomy","volume":"52","author":"Ahmad","year":"2024","journal-title":"Int. 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