RESUMO

Conversion of organic matter to biohydrogen possesses promising application potential. In this study, low-cost ferrihydrite nanorods were used to enhance hydrogen production by Clostridium pasteurianum. The maximum cumulative hydrogen production and the hydrogen yield were 1.03 mmol and 3.55 mol H2/mol glucose, respectively, which were 68.9% and 15.6% higher than those of the batch groups without ferrihydrite addition. Moreover, in comparison with magnetite and hematite nanoparticles, ferrihydrite presented the best stimulation for hydrogen evolution. The enhancement mechanisms were explored based on metabolic distribution, gene expression, enzymatic activity, and metabolite determination, such as Fe(II) concentration and pH value. The potential stimulation mechanisms are summarized as follows: ferrihydrite improves glucose conversion efficiency and promotes cell growth; ferrihydrite elevates the transcripts and activity of hydrogenase; and ferrihydrite reduction via its buffer function could ease acidification. This study demonstrates that ferrihydrite addition is an effective and green strategy to enhance fermentative hydrogen production.

Assuntos

RESUMO

In this study, the biohydrogen (bioH2) production of a microbial consortium was optimized by adjusting the type and configuration of two impellers, the mixing regimen and the mass transfer process (KLa coefficients). A continuous stirred-tank reactor (CSTR) system, with a nonstandard geometry, was characterized. Two different mixing configurations with either predominant axial (PB4 impeller) or radial pumping (Rushton impeller) were assessed and four different impeller configurations to produce bioH2. The best configuration for an adequate mixing time was determined by an ANOVA analysis. A response surface methodology was also used to fully elucidate the optimal configuration. When the PB4 impellers were placed in best configuration, c/Dt = 0.5, s/Di = 1, the maximum bioH2 productivity obtained was 440 mL L-1 hr-1, with a bioH2 molar yield of 1.8. The second best configuration obtained with the PB4 impellers presented a bioH2 productivity of 407.94 mL L-1 hr-1. The configurations based on Rushton impellers showed a lower bioH2 productivity and bioH2 molar yield of 177.065 mL L-1 hr-1 and 0.71, respectively. The experiments with axial impellers (PB4) showed the lowest KLa coefficient and the highest bioH2 production, suggesting that mixing is more important than KLa for the enhanced production of bioH2.

Assuntos

RESUMO

This research assessed the viability to use disposable diapers as a substrate for the production of biohydrogen, a valuable clean-energy source. The important content of cellulose of disposable diapers indicates that this waste could be an attractive substrate for biofuel production. Two incubation temperatures (35 °C and 55 °C) and three diaper conditioning methods (whole diapers with faeces, urine, and plastics, WD; diapers without plastic components, with urine and faeces, DWP; diapers with urine but without faeces and plastic, MSD) were tested in batch bioreactors. The bioreactors were operated in the solid substrate anaerobic hydrogenogenic fermentation with intermittent venting mode (SSAHF-IV). The batch reactors were loaded with the substrate at ca. 25% of total solids and 10% w/w inoculum. The average cumulative bioH2 production followed the order WD > MSD > DWP. The bio-H2 production using MSD was unexpectedly higher than DWP; the presence of plastics in the first was expected to be associated to lower degradability and H2 yield. BioH2 production at 55 °C was superior to that of 35 °C, probably owing to a more rapid microbial metabolism in the thermophilic regime. The results of this work showed low yields in the production of H2 at both temperatures compared with those reported in the literature for municipal and agricultural organic waste. The studied process could improve the ability to dispose of this residue with H2 generation as the value-added product. Research is ongoing to increase the yield of biohydrogen production from waste disposable diapers.

Assuntos

RESUMO

ABSTRACT Biohydrogen production from starch processing wastewater in this study resulted the highest yield of 61.75 mL H2/g COD at initial pH 7.0, thermophilic temperature, and iron concentration 800 mg Fe/L. The yield was 2-folded higher than the operation at mesophilic temperature or without iron addition. Cell immobilization by addition of biomaterials (BM) could improve the hydrogen yield by 2-folded comparing to the non-addition. BM from plants (loofa sponge) was found producing higher yield than that from animals (silk cocoon), and optimal concentration of BM was 5% (V/V). Furthermore, it was revealed further inside its ecosystem using SEM, 16S rDNA sequencing and FISH. There was found rod-shaped microorganisms of Bacillus cereus, which reported as efficient starch-utilizing hydrogen producers, was dominant in the system with population of 47% of all specie identified.

RESUMO

Biohydrogen production was studied from the vermicelli processing wastewater using synthetic and biological materials as immobilizing substrate employing a mixed culture in a batch reactor operated at the initial pH 6.0 and thermophilic condition (55 ± 1ºC). Maximum cumulative hydrogen production (1,210 mL H2/L wastewater) was observed at 5% (v/v) addition of ring-shaped synthetic material, which was the ring-shaped hydrophobic acrylic. Regarding 5% (v/v) addition of synthetic and biological materials, the maximum cumulative hydrogen production using immobilizing synthetic material of ball-shaped hydrophobic polyethylene (HBPE) (1,256.5 mL H2/L wastewater) was a two-fold increase of cumulative hydrogen production when compared to its production using immobilizing biological material of rope-shaped hydrophilic ramie (609.8 mL H2/L wastewater). SEM observation of immobilized biofilm on a ball-shaped HBPE or a rope-shaped hydrophilic ramie was the rod shape and gathered into group.