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Hydrogen is a renewable fuel that can be biologically produced by green algae in closed anaerobic photobioreactors with light and organic carbon as energy sources. This research aimed to investigate the influence of sulfur concentration and light intensity on hydrogen and ethanol production, as well as on nutrient removal by Chlamydomonas reinhardtii (CC425) in batch cultures. The strain was cultivated in two phases: in the first step, the cultures were maintained under aerobic conditions to obtain biomass; in the second step, the biomass was transferred to closed anaerobic photobioreactors for gas generation under continuous illumination. A factorial design was accomplished to improve the biomass production in the first step, with light variation, pH, and glucose addition. Afterward, light intensity and sulfur concentration were varied to test hydrogen production in the second step. The best hydrogen production occurred in photobioreactors without sulfur addition (average increase of 7 times in the production) and under higher light intensity the productivity was 37% higher than lower light intensity (39.64 ± 2.44 µmol H2 L−1 h−1). There was an effect of sulfur concentration in the ethanol production and under higher light intensity the production was higher (203.20 ± 31.49 mg L−1). Furthermore, under conditions with the presence of sulfur, there was greater removal of ammoniacal nitrogen (5.3%), phosphate (85.0%), COD (9.1%) and acetic acid (97.2%). This research demonstrates the efficient production of hydrogen by C. reinhardtii and it shows that the process can be associated with ethanol production and nutrient removal. [ABSTRACT FROM AUTHOR]

To provide new insight into the dark fermentation process, a multi-lateral study was performed to study the microbiology of 20 different lab-scale bioreactors operated in four different countries (Brazil, Chile, Mexico, and Uruguay). Samples (29) were collected from bioreactors with different configurations, operation conditions, and performances. The microbial communities were analyzed using 16S rRNA genes 454 pyrosequencing. The results showed notably uneven communities with a high predominance of a particular genus. The phylum Firmicutes predominated in most of the samples, but the phyla Thermotogae or Proteobacteria dominated in a few samples. Genera from three physiological groups were detected: high-yield hydrogen producers ( Clostridium, Kosmotoga, Enterobacter), fermenters with low-hydrogen yield (mostly from Veillonelaceae), and competitors ( Lactobacillus). Inocula, reactor configurations, and substrates influence the microbial communities. This is the first joint effort that evaluates hydrogen-producing reactors and operational conditions from different countries and contributes to understand the dark fermentation process. [ABSTRACT FROM AUTHOR]

This study presents a column-switching solid-phase extraction online-coupled to a liquid chromatography/tandem mass spectrometry (SPE-LC-MS/MS) method for simultaneous analysis of 12 antibiotics (7 sulfonamides and 5 fluoroquinolones) and caffeine detected in the sewage and effluent of a pilot anaerobic reactor used in sewage treatment. After acidification and filtration, the samples were directly injected into a simple and conventional LC system. Backflush and foreflush modes were compared based on the theoretical plates and peak asymmetry observed. The method was tested in terms of detection (MDL) and quantification limit (MQL), linearity, relative recovery, and precision intra- and inter-day in lab-made sewage samples. The method presented suitable figures of merit in terms of detection, varying from 8.00 × 10 to 6.00 × 10 ng (0.800 up to 600 ng L; caffeine) with direct injection volume of only 100 μL and 13 min of total analysis time (sample preparation and chromatographic run). When the method was applied in the analysis of sewage and effluent of the anaerobic reactor ( n = 15), six antibiotics and caffeine were detected in concentrations ranging from 0.018 to 1097 μg L. To guarantee a reliable quantification, standard addition was used to overcome the matrix effect. [ABSTRACT FROM AUTHOR]