Article

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.

0 Bookmarks
 · 
171 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Combined biohydrogen and bioethanol (CHE) production from monosugars, polymetric carbohydrates and hydrolysates made from various lignocellulosic biomasses was investigated by strain AK 54 , a saccharolytic, thermophilic ethanol and hydrogen producing bacteria isolated from a hot spring in Iceland. Optimum growth conditions for the strain were at pH between 5.0 -6.0 and at 65°C. As determined by full 16S rRNA analysis, strain AK 54 belongs to the genus Thermoanaerobacterium, affiliated with T. aciditolerans (99.0%). Effect of increased initial glucose concentration on growth and end product formation was investigated and good correlation observed between increased substrate loadings and end product formation of up to 50 mM where clear inhibition was shown. The ability to utilize various carbon substrates was tested with positive growth on xylose, glucose, fructose, mannose, galactose, sucrose and lactose. The major end products in all cases were ethanol, acetate, lactate, hydrogen and carbon dioxide. By lowering the partial pressure of hydrogen during glucose degradation, the end product formation was directed towards hydrogen, acetate and ethanol but away from lactate. Hydrogen and ethanol production from hydrolysates from biomass (7.5 g L -1 (dw)); cellulose, newspaper, grass (Phleum pratense), barley straw (Hordeum vulgare), and hemp (Cannabis sativa L), was investigated. The biomass was chemically (acid/base) and enzymatically pretreated. The highest ethanol production was observed from cellulose hydrolysates (24.2 mM) but less was produced from lignocellulosic biomasses. Chemical pretreatment of biomass hydrolysates increased hydrogen and ethanol yields substantially from barley straw, hemp and grass but not from cellulose or newspaper. The highest hydrogen was also produced from cellulose hydrolysates (13.2 mol H 2 /g VS cellulose pretreated with base) but of the lignocellulosic biomass, highest yields were from grass pretreated with base (9.1 mol H 2 /g VS).
  • [Show abstract] [Hide abstract]
    ABSTRACT: An integrated bio-hydrogen production system involving fermentative hydrogen production and product separation is proposed. In this process, microorganisms conduct ethanol-type fermentation and generate H2 gas in anaerobic bioreactor, and acetate is removed from fermentation broth by using a two chamber bipolar membrane electrodialysis as separation unit. A comparative study of fermentative hydrogen production of Ethanoligenens harbinese B49 in the integrated system with traditional fermentation process was carried out. Compared to traditional process, accumulated H2 elevated 23%, glucose utilization ratio increased by 135% and cell growth increased by 27% in the integrated system. The specific hydrogen production rate reached 2.2 mol H2/mol glucose, indicating that separation of acetate from fermentation system has a great role in promoting hydrogen producing capacity. Bipolar membrane electrodialysis showed high acetate separation efficiency and low glucose loss rate. In the integrated system, pH could be used to direct electrodialysis operation, since it has an exponential correlation with acetate concentration in fermentation broth. These results provide a new method for achieving efficient and stable H2 production with simultaneous glucose recovery and acetate inhibition release.
    International Journal of Hydrogen Energy 08/2014; 39(25):13375–13380. · 2.93 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This study performed to extract operation factors of major organic wastes, which were food wastes and waste activated sludge generated in industries in order to use them as a substrate for bio-H2 production. According to the results of experimental analysis for hydrogen production capacity by various organic concentrations, the hydrogen production yield was the highest at 80 g/L, and the efficiency was improved by the pretreatment of waste activated sludge (acid treatment, alkali treatment). Hydrogen production efficiency was improved by mixing food wastes and waste activated sludge if waste activated sludge was below than 30%, however, it was decreased when it was more than 50%. The impacts of heavy metals on the hydrogen production shows that the inhibition level depends on the concentration of Cr, Zn, and Cu, Fe was able to enhance the hydrogen production.
    Journal of Korean Society of Water and Wastewater. 01/2010; 24(6).

Full-text (2 Sources)

Download
26 Downloads
Available from
Aug 25, 2014