Inhibition of Bio-Hydrogen Production by Un-Dissociated Acetic and Butyric Acids

Department of Civil and Environmental Engineering, Penn State University, University Park, PA 16802, USA.
Environmental Science and Technology (Impact Factor: 5.33). 12/2005; 39(23):9351-6. DOI: 10.1021/es0510515
Source: PubMed


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.

Download full-text


Available from: Bruce E Logan, Aug 25, 2014
45 Reads
  • Source
    • "Therefore, both ethanol and propionic acid can explain the decrease of the hydrogen/gaseous product ratio. Microorganisms involved in the production of ethanol and propionic acid are known to be more resistant to environmental stress than hydrogen-producing bacteria [18,31]. The decrease of substrate conversion yield of 30% between groups W and D (1,300 down to 900 mmol.kgTS-1 of fermentative product) was likely caused by the decrease of substrate accessibility due to the reduction of water content. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In solid-state anaerobic digestion (AD) bioprocesses, hydrolytic and acidogenic microbial metabolisms have not yet been clarified. Since these stages are particularly important for the establishment of the biological reaction, better knowledge could optimize the process performances by process parameters adjustment. This study demonstrated the effect of total solids (TS) content on microbial fermentation of wheat straw with six different TS contents ranging from wet to dry conditions (10 to 33% TS). Three groups of metabolic behaviors were distinguished based on wheat straw conversion rates with 2,200, 1,600, and 1,400 mmol.kgVS-1 of fermentative products under wet (10 and 14% TS), dry (19 to 28% TS), and highly dry (28 to 33% TS) conditions, respectively. Furthermore, both wet and dry fermentations showed acetic and butyric acid metabolisms, whereas a mainly butyric acid metabolism occurred in highly dry fermentation. Substrate conversion was reduced with no changes of the metabolic pathways until a clear limit at 28% TS content, which corresponded to the threshold value of free water content of wheat straw. This study suggested that metabolic pathways present a limit of TS content for high-solid AD.
    Biotechnology for Biofuels 11/2013; 6(1):164. DOI:10.1186/1754-6834-6-164 · 6.04 Impact Factor
  • Source
    • "It can penetrate the cell membrane in undissociated form and inhibits products production through chemical interference, causing pH imbalances at high concentration and eventually cell growth inhibition or death (24,25). However, acetic acid does not necessarily play the decisive role in causing the difference in fermentability, since some strains can directly utilize acetic acid as substrate for bioconversion such as H2 production (26,27). In addition, formic acid and levulinic acid may be evolved in hydrolysates and even cause the particularly poor fermentability of the hydrolysates. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Lignocellulosic materials are commonly used in bio-H2 production for the sustainable energy resource development as they are abundant, cheap, renewable and highly biodegradable. In the process of the bio-H2 production, the pretreated lignocellulosic materials are firstly converted to monosaccharides by enzymolysis and then to H2 by fermentation. Since the structures of lignocellulosic materials are rather complex, the hydrolysates vary with the used materials. Even using the same lignocellulosic materials, the hydrolysates also change with different pretreatment methods. It has been shown that the appropriate hydrolysate compositions can dramatically improve the biological activities and bio-H2 production performances. Over the past decades, hydrolysis with respect to different lignocellulosic materials and pretreatments has been widely investigated. Besides, effects of the hydrolysates on the biohydrogen yields have also been examined. In this review, recent studies on hydrolysis as well as their effects on the biohydrogen production performance are summarized. [BMB Reports 2013; 46(5): 244-251].
    BMB reports 05/2013; 46(5):244-251. DOI:10.5483/BMBRep.2013.46.5.038 · 2.60 Impact Factor
  • Source
    • "The presence of acetic acid within the range of 4e10 g/L could inhibit the microbial growth in subsequent fermentation process. It suppresses the fermentation by entering the cell membrane and decreasing the intracellular pH, thus affecting the metabolism of the microorganism [1] [29] [32] [40] [41]. This study revealed that the highest amount of acetic acid (4.33 g/L) was obtained at 8% sulfuric acid concentration and this concentration of acetic acid was sufficient to restrain the fermentation efficiency. "
    [Show abstract] [Hide abstract]
    ABSTRACT: a b s t r a c t Carbohydrates from hydrolyzed biomass has been a potential feedstock for fermentative hydrogen production. In this study, oil palm empty fruit bunch (OPEFB) was treated by sulfuric acid in different concentrations at 120 C for 15 min in the autoclave. The optimal condition for pretreatment was obtained when OPEFB was hydrolyzing at 6% (w/v) sulfuric acid concentration, which gave the highest total sugar of 26.89 g/L and 78.51% of sugar production yield. However, the best conversion efficiency of OPEFB pretreatment was 39.47 at sulfuric acid concentration of 4%. A series of batch fermentation were performed to determine the effect of pH in fermentation media and the potential of this prehydrolysate was used as a substrate for fermentative hydrogen production under optimum pretreat-ment conditions. The prehydrolysate of OPEFB was efficiently converted to hydrogen via fermentation by acclimatized mixed consortia. The maximum hydrogen production was 690 mL H 2 L À1 medium, which corresponded to the yield of 1.98 molH 2 /mol xylose achieved at pH 5.5 with initial total sugar concentration of 5 g/L. Therefore, the results implied that OPEFB prehydrolysate is prospective substrate for efficient fermentative hydrogen con-ducted at low controlled pH. No methane gas was detected throughout the fermentation.
Show more