Anaerobic co-metabolic biodegradation of pharmaceuticals and personal care products driven by glycerol fermentation.

Anaerobic digestion in two sequential phases, acidogenesis and methanogenesis, has been shown to be beneficial for enhancing the biomethane generation from wastewater. In this work, the application of glycerol (GOH) as a fermentation co-substrate during the wastewater treatment was evaluated on the biodegradation of different pharmaceuticals and personal care products (PPCPs). GOH co-digestion during acidogenesis led to a significant increase in the biodegradation of acetaminophen (from 78 to 89%), ciprofloxacin (from 25 to 46%), naproxen (from 73 to 86%), diclofenac (from 36 to 48%), ibuprofen (from 65 to 88%), metoprolol (from 45 to 59%), methylparaben (from 64 to 78%) and propylparaben (from 68 to 74%). The heterotrophic co-metabolism of PPCPs driven by glycerol was confirmed by the biodegradation kinetics, in which kbio (biodegradation kinetics constant) values increased from 0.18 to 2.11 to 0.27-3.60 L g-1-VSS d-1, for the operational phases without and with GOH, respectively. The assessment of metabolic pathways in each phase revealed that the prevalence of aromatic compounds degradation, metabolism of xenobiotics by cytochrome P450, and benzoate degradation routes during acidogenesis are key factors for the enzymatic mechanisms linked to the PPCPs co-metabolism. The phase separation of anaerobic digestion was effective in the PPCPs biodegradation, and the co-fermentation of glycerol provided an increase in the generation potential of biomethane in the system (energetic potential of 5.0 and 6.3 kJ g-1-CODremoved, without and with GOH, respectively). This study showed evidence that glycerol co-fermentation can exert a synergistic effect on the PPCPs removal during anaerobic digestion mediated by heterotrophic co-metabolism.

Bio-CH4 yield of swine manure and food waste optimized by co-substrate proportions diluted in domestic sewage and pH interactions using the response surface approach.

This research aimed at evaluating optimal conditions to obtain value-added metabolites, such as bio-CH4, by co-digesting swine manure and food waste diluted in domestic sewage. The assays were carried out in batches using the statistical methods of Rotational Central Composite Design (RCCD) and Surface Response to evaluate the ranges of food waste (1.30-9.70 gTS.L-1), pH (6.16-7.84) and granular Upflow Anaerobic Sludge Blanket sludge as inoculum (2.32-5.68 gTS.L-1), besides about 250 mL of swine manure in 500 mL Duran flasks. According to the RCCD matrix, bio-CH4 yields among 600.6 ± 60.1 and 2790.0 ± 112.0 mL CH4 gTS.L-1 were observed, besides the maximum CH4 production rate between 0.4 ± 0.5 and 49.7 ± 2.0 mL CH4 h-1 and λ between ≤0.0 and 299.3 ± 4.5 h. In the validation assay, the optimal conditions of 9.98 gTS.L-1 of food waste, pH adjusted to 8.0 and 2.20 gTS.L-1 of inoculum were considered, and the bio-CH4 yield obtained (5640.79 ± 242.98 mL CH4 gTS.L-1 or also 5201.83 ± 224.07 mL CH4 gTVS.L-1) was 11.3 times higher than in assays before optimization (499.3 ± 16.0 mL CH4 gTS.L-1) with 5 gTS.L-1 of food waste, 3 gTS.L-1 of inoculum and pH 7.0. Besides, the results observed about the energetic balance of the control and validation assays highlight the importance of process optimization, as this condition was the only one with energy supply higher than the energy required for its operation, exceeding max consumption sevenfold. Based on the most dominant microorganisms (Methanosaeta, 31.06%) and the metabolic inference of the validation assay, it could be inferred that the acetoclastic methanogenesis was the predominant pathway to CH4 production.

Metataxonomic characterization of an autochthonous and allochthonous microbial consortium involved in a two-stage anaerobic batch reactor applied to hydrogen and methane production from sugarcane bagasse.

Enzymatically pre-treated sugarcane bagasse (SCB) was used as substrate for sequential production of hydrogen (H2) and methane (CH4). In stage I, SCB was used by autochthonous bacteria, such as Enterococcus (42.4 % relative abundance) and Paraclostridium (16.8 %) for H2 production (166.8 mL H2/L), while the metabolites accumulated at the end of this stage (9140.5 mg HAc/L) were used by allochthonous inoculum for CH4 production (870.8 mL CH4/L) in stage II. In stage II, hydrogenotrophic (Methanoculleus, 49.1 %) and acetoclastic (Methanosaeta, 15.5 %) archaeal genera were identified and considered important to maintain low H2 pressure in the system. According to gene inference, the hydrolysis of the SCB fiber was performed in both stages, as potential ß-glucosidase and 1,4-ß-xylosidase encoding genes were predicted. However, the energy metabolism of microbial populations differed, as potential genes involved in CH4 metabolism were predominant in phase II (39.0 %).