Publications by authors named "Anna Podmaniczki"

4 Publications

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Thin cell layer cultures of Chlamydomonas reinhardtii L159I-N230Y, pgrl1 and pgr5 mutants perform enhanced hydrogen production at sunlight intensity.

Bioresour Technol 2021 Aug 27;333:125217. Epub 2021 Apr 27.

Institute of Plant Biology, Biological Research Centre, Szeged, Temesvári krt. 62, H-6726 Szeged, Hungary. Electronic address:

Photobiological hydrogen (H) production is a promising renewable energy source. HydA hydrogenases of green algae are efficient but O-sensitive and compete for electrons with CO-fixation. Recently, we established a photoautotrophic H production system based on anaerobic induction, where the Calvin-Benson cycle is inactive and O scavenged by an absorbent. Here, we employed thin layer cultures, resulting in a three-fold increase in H production relative to bulk CC-124 cultures (50 µg chlorophyll/ml, 350 µmol photons m s). Productivity was maintained when increasing the light intensity to 1000 µmol photons ms and the cell density to 150 µg chlorophyll/ml. Remarkably, the L159I-N230Y photosystem II mutant and the pgrl1 photosystem I cyclic electron transport mutant produced 50% more H than CC-124, while the pgr5 mutant generated 250% more (1.2 ml H/ml culture in six days). The photosynthetic apparatus of the pgr5 mutant and its in vitro HydA activity remained remarkably stable.
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http://dx.doi.org/10.1016/j.biortech.2021.125217DOI Listing
August 2021

Ascorbate inactivates the oxygen-evolving complex in prolonged darkness.

Physiol Plant 2021 Feb 6;171(2):232-245. Epub 2020 Dec 6.

Institute of Plant Biology, Biological Research Centre, Szeged, Hungary.

Ascorbate (Asc, vitamin C) is an essential metabolite participating in multiple physiological processes of plants, including environmental stress management and development. In this study, we acquired knowledge on the role of Asc in dark-induced leaf senescence using Arabidopsis thaliana as a model organism. One of the earliest effects of prolonged darkness is the inactivation of oxygen-evolving complexes (OEC) as demonstrated here by fast chlorophyll a fluorescence and thermoluminescence measurements. We found that inactivation of OEC due to prolonged darkness was attenuated in the Asc-deficient vtc2-4 mutant. On the other hand, the severe photosynthetic phenotype of a psbo1 knockout mutant, lacking the major extrinsic OEC subunit PSBO1, was further aggravated upon a 24-h dark treatment. The psbr mutant, devoid of the PSBR subunit of OEC, performed only slightly disturbed photosynthetic activity under normal growth conditions, whereas it showed a strongly diminished B thermoluminescence band upon dark treatment. We have also generated a double psbo1 vtc2 mutant, and it showed a slightly milder photosynthetic phenotype than the single psbo1 mutant. Our results, therefore, suggest that Asc leads to the inactivation of OEC in prolonged darkness by over-reducing the Mn-complex that is probably enabled by a dark-induced dissociation of the extrinsic OEC subunits. Our study is an example that Asc may negatively affect certain cellular processes and thus its concentration and localization need to be highly controlled.
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http://dx.doi.org/10.1111/ppl.13278DOI Listing
February 2021

Water-splitting-based, sustainable and efficient H production in green algae as achieved by substrate limitation of the Calvin-Benson-Bassham cycle.

Biotechnol Biofuels 2018 19;11:69. Epub 2018 Mar 19.

1Institute of Plant Biology, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Temesvári krt. 62, 6726 Szeged, Hungary.

Background: Photobiological H production has the potential of becoming a carbon-free renewable energy source, because upon the combustion of H, only water is produced. The [Fe-Fe]-type hydrogenases of green algae are highly active, although extremely O-sensitive. Sulphur deprivation is a common way to induce H production, which, however, relies substantially on organic substrates and imposes a severe stress effect resulting in the degradation of the photosynthetic apparatus.

Results: We report on the establishment of an alternative H production method by green algae that is based on a short anaerobic induction, keeping the Calvin-Benson-Bassham cycle inactive by substrate limitation and preserving hydrogenase activity by applying a simple catalyst to remove the evolved O. Cultures remain photosynthetically active for several days, with the electrons feeding the hydrogenases mostly derived from water. The amount of H produced is higher as compared to the sulphur-deprivation procedure and the process is photoautotrophic.

Conclusion: Our protocol demonstrates that it is possible to sustainably use algal cells as whole-cell catalysts for H production, which enables industrial application of algal biohydrogen production.
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http://dx.doi.org/10.1186/s13068-018-1069-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5858145PMC
March 2018

The mechanism of photosystem-II inactivation during sulphur deprivation-induced H production in Chlamydomonas reinhardtii.

Plant J 2018 05 31;94(3):548-561. Epub 2018 Mar 31.

Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary.

Sulphur limitation may restrain cell growth and viability. In the green alga Chlamydomonas reinhardtii, sulphur limitation may induce H production lasting for several days, which can be exploited as a renewable energy source. Sulphur limitation causes a large number of physiological changes, including the inactivation of photosystem II (PSII), leading to the establishment of hypoxia, essential for the increase in hydrogenase expression and activity. The inactivation of PSII has long been assumed to be caused by the sulphur-limited turnover of its reaction center protein PsbA. Here we reinvestigated this issue in detail and show that: (i) upon transferring Chlamydomonas cells to sulphur-free media, the cellular sulphur content decreases only by about 25%; (ii) as demonstrated by lincomycin treatments, PsbA has a significant turnover, and other photosynthetic subunits, namely RbcL and CP43, are degraded more rapidly than PsbA. On the other hand, sulphur limitation imposes oxidative stress early on, most probably involving the formation of singlet oxygen in PSII, which leads to an increase in the expression of GDP-L-galactose phosphorylase, playing an essential role in ascorbate biosynthesis. When accumulated to the millimolar concentration range, ascorbate may inactivate the oxygen-evolving complex and provide electrons to PSII, albeit at a low rate. In the absence of a functional donor side and sufficient electron transport, PSII reaction centers are inactivated and degraded. We therefore demonstrate that the inactivation of PSII is a complex and multistep process, which may serve to mitigate the damaging effects of sulphur limitation.
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http://dx.doi.org/10.1111/tpj.13878DOI Listing
May 2018