Inhibition of biohydrogen production by undissociated acetic and butyric acids

Department of Civil and Environmental Engineering, Penn State University, University Park, PA 16802, USA.
Environmental Science and Technology (Impact Factor: 5.48). 12/2005; 39(23):9351-6. DOI: 10.1021/es0510515
Source: PubMed

ABSTRACT Glucose fermentation to hydrogen results in the production of acetic and butyric acids. The inhibitory effect of these acids on hydrogen yield was examined by either adding these acids into the feed of continuous flow reactors (external acids), or by increasing glucose concentrations to increase the concentrations of acids produced by the bacteria (self-produced). Acids added to the feed at a concentration of 25 mM decreased H2 yields by 13% (acetic) and 22% (butyric), and 60 mM (pH 5.0) of either acid decreased H2 production by >93% (undissociated acid concentrations). H2 yields were constant at 2.0 +/- 0.2 mol H2/mol glucose for an influent glucose concentration of 10-30 g/L. At 40 g glucose/L, H2 yields decreased to 1.6 +/- 0.1 mol H2/mol glucose, and a switch to solventogenesis occurred. A total undissociated acid concentration of 19 mM (self-produced acids) was found to be a threshold concentration for significantly decreasing H2 yields and initiating solventogenesis. Hydrogen yields were inhibited more by self-produced acids (produced at high glucose feed concentrations) than by similar concentrations of externally added acids (lower glucose feed concentrations). These results show the reason hydrogen yields can be maximized by using lower glucose feed concentrations is that the concentrations of self-produced volatile acids (particularly butyric acid) are minimized.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Dark fermentation of organic biomass, i.e. agricultural residues, agro-industrial wastes and organic municipal waste is a promising technology for producing renewable biohydrogen. In spite of its potential, this technology needs further research and development to improve the biohydrogen yield by optimizing substrate utilization, microbial community enrichment and bioreactor operational parameters such as pH, temperature and H2 partial pressure. On the other hand, the technical and economic viability of the processes need to be enhanced by the use of valuable by-products from dark fermentation, which mostly includes volatile fatty acids. This paper reviews a range of different organic biomasses and their biohydrogen potential from laboratory to pilot-scale systems. A review of the advances in H2 yield and production rates through different seed inocula enrichment methods, bioreactor design modifications and operational conditions optimization inside the dark fermentation bioreactor is presented. The prospects of valorizing the co-produced volatile fatty acids in photofermentation and bioelectrochemical systems for further H2 production, methane generation and other useful applications have been highlighted. A brief review on the simulation and modeling of the dark fermentation processes and their energy balance has been provided. Future prospects of solid state dark fermentation are discussed.
    Applied Energy 04/2015; 144:73-95. DOI:10.1016/j.apenergy.2015.01.045 · 5.26 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Treated activated carbon (T-AC) was found to be highly effective for fermentative hydrogen production due to its highly porous structure. The addition of T-AC at 8.3-33.3 g/L in batch experiments increased the hydrogen production rate and yield from 0.8 to 1.8 mL of H2/h and from 1.24 ± 0.13 to 2.60 ± 0.21 mol of H2/mol of sucrose, respectively. The high activity of T-AC was attributed to a greater porosity and active sites as compared to commercial activated carbon. The use of T-AC reduced the inhibitory effect of butyric acid with selective adsorption of butyric acid over metabolite products. Moreover, T-AC showed a highly durable performance for three repeated cycles for hydrogen production. The hydrogen production increased by 73% as compared to the control for the first cycle and dropped by 32% after three consecutive cultivation cycles. It is postulated that a highly porous surface and affinity of T-AC may provide sites for volatile fatty acids adsorption, thereby reducing the inhibitory effect on hydrogen-producing bacteria.
    Energy & Fuels 07/2014; 28(7):4554-4559. DOI:10.1021/ef500530v · 2.73 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The main objective of this work was to examine the feasibility of coupling electrochemical and biological processes to destroy nitrate ions (NO3−) while producing biohydrogen. In this integrated process NO3− was firstly converted to ammonium using an electrochemical flow cell. After only one pass of concentrated nitrate solutions (3 g NO3− L−1) through the flow cell, ammonium ions selectivity of 98.8%, corresponding to 0.86 g NH4+ L−1 was recorded. The obtained ammonium solution was then tested as a nitrogen source to produce H2 in a batch system involving heat-treated aerobic activated sludge.
    Biochemical Engineering Journal 02/2015; 94. DOI:10.1016/j.bej.2014.11.019 · 2.37 Impact Factor

Full-text (2 Sources)

Available from
Aug 25, 2014