Definitions

Dark_fermentation

Dark fermentation

Dark fermentation is the fermentative conversion of organic substrate to biohydrogen, it is a complex process manifested by diverse group of bacteria by a series of biochemical reactions involving three steps similar to anaerobic conversion. Dark fermentation differs from photofermentation because it proceeds without the presence of light.

Fermentative/hydrolytic microorganisms hydrolyze complex organic polymers to monomers which further converted to a mixture of lower molecular weight organic acids and alcohols by obligatory H2 producing acidogenic bacteria.

Utilization of wastewater as a potential substrate for biohydrogen production has been drawing considerable interest in recent years especially in dark fermentation process. Industrial wastewater as fermentative substrate for H2 production addresses most of the criteria required for substrate selection viz., availability, cost and biodegradability (Angenent, et al., 2004; Kapdan and Kargi, 2006). Chemical wastewater (Venkata Mohan, et al., 2007a,b), cattle wastewater (Tang, et al., 2008), diary process wastewater (Venkata Mohan, et al. 2007c), starch hydrolysate wastewater (Chen, et al., 2008) and designed synthetic wastewater (Venkata Mohan, et al., 2007a,2008b) have been reported to produce biohydrogen apart from wastewater treatment from dark fermentation process using selectively enriched mixed culture under acidophilic conditions. Various wastewaters viz., paper mill wastewater (Idania, et al., 2005), starch effluent (Zhang, et al., 2003), food processing wastewater (Shin et al., 2004, van Ginkel, et al., 2005), domestic wastewater (Shin, et al., 2004, 2008e), rice winery wastewater (Yu et al., 2002), distillery and molasses based wastewater (Ren, et al., 2007, Venkata Mohan, et al., 2008a), wheat straw wastes (Fan, et al., 2006) and palm oil mill wastewater (Vijayaraghavan and Ahmed, 2006) were also studied as fermentable substrates for H2 production along with wastewater treatment. Using wastewater as a fermentable substrate facilitates both wastewater treatment apart from H2 production. The efficiency of dark fermentative H2 production process was found to depend on the pre-treatment of the mixed consortia used as biocatalyst, operating pH, organic loading rate apart from wastewater characteristics (Venkata Mohan, et al., 2007d,2008c,d, Vijaya Bhaskar, et al., 2008d).

Employing mixed culture is extremely important and well-suited to the non-sterile, ever-changing, complex environment of wastewater treatment (Angenent, et al., 2004, Das, 2008). Typical anaerobic mixed cultures can not produce H2 as it is rapidly consumed by the methane-producing bacteria (Sparling, et al., 1997). Successful biological H2 production requires inhibition of H2 consuming microorganisms, such as methanogens and pre-treatment of parent culture is one of the strategies used for selecting the requisite microflora. The physiological differences between H2 producing bacteria (also referred to as acidogenic bacteria) and H2 consuming bacteria (methanogenic bacteria) form the fundamental basis behind the development of various methods used for the preparation of H2 producing seeds (Zhu and Beland, 2006). When parent inoculum was exposed to extreme environments such as high temperature, extreme acidity and alkalinity, spore forming H2 producing bacteria such as Clostridium survived, but methanogens had no such capability. Pre-treatment helps to accelerate the hydrolysis step, thus, reducing the impact of rate limiting step and augment the anaerobic digestion to enhance the H2 generation (Kim, et al., 2003, Venkata Mohan, et al. 2007d, 2008c). Several pre-treatment procedures viz., heat-shock, chemical, acid, alkaline, oxygen-shock, load-shock, infrared, freezing, etc., were employed on a variety of mixed cultures (Sparling, et al., 1997; Logan et al., 2002; Ferchichi et al., 2005; Kim, et al., 2003, Valdez-Vazquez, et al., 2006; Kraemer and Bagley, 2007; Venkata Mohan et al., 2007c,d,2008a,e) for selective enrichment of acidogenic H2 producing inoculum. pH also plays a critical role in governing the metabolic pathways of the organism where the activity of acidogenic group of bacteria is considered to be crucial (Fan, et al., 2006). Optimum pH range for the methanogenic bacteria is reported to be between 6.0 and 7.5, while acidogenic bacteria functions well below 6 pH (van Ginkel, et al., 2005). The pH range of 5.5-6.0 is considered to be ideal to avoid both methanogenesis and solventogenesis (Fan, et al., 2006, Venkata Mohan, et al., 2007d,2008c,d) which is the key for effective H2 generation.

In spite of advantages, the main challenge observed with fermentative H2 production process is relatively low energy conversion efficiency from the organic source. Typical H2 yields range from 1 to 2 mol of H2/mol of glucose, which results in 80-90% of the initial COD remaining in the wastewater in the form of various volatile organic acids (VFAs) and solvents, such as acetic, propionic, butyric acids and ethanol (Logan, 2004). Even under optimal conditions about 60-70% of the original organic matter remains in solution (Das and Veziroglu, 2001, Venkata Mohan et al., 2007a,2008f). Bioaugmentation with selectively enriched acidogenic consortia to enhance H2 production was also reported (Venkata Mohan, et al., 2007b). Generation and accumulation of soluble acid metabolites causes sharp drop in the system pH and inhibit the H2 production process. Usage of unutilized carbon sources present in acidogenic process for additional biogas production sustains the practical applicability of the process. One way to utilize/recover the remaining organic matter in a useable form are to produce additional H2 by terminal integration of photo-fermentative process H2 production (Venkata Mohan, et al., 2008e) and methane by integrating acidogenic process to terminal methanogenic process (Venkata Mohan, et al., 2008b).

See also

References

  • Angenent, L.T., Karim, K., Al-Dahhan, M.H., Wrenn, B.A., Domíguez-Espinosa, R., 2004. Production of bioenergy and biochemicals from industrial and agricultural wastewater. “Trends in Biotechnology” 22, 477-85.
  • Chen, S.-D., Lee, K.-S., Lo, Y.-C., Chen, W.-M., Wu, J.-F., Lin, C.-Y., Chang, J.-S.,2008, Batch and continuous biohydrogen production from starch hydrolysate by Clostridium species. “Int J Hydrogen Energy” 33, 1803-1812.
  • Dabrock, B., Bahl, H., Gottschalk, G., 1992. Parameters affecting solvent production by Clostridium pasteurianum, “Appl Environ Microbiol”, 58, 1233-1239.
  • Das, D., Veziroglu, T.N., 2001. Hydrogen production by biological process: a survey of literature. “Int J Hydrogen Energy” 26, 13-28.
  • Das, D., 2008, International workshop on biohydrogen production technology (IWBT 2008),7–9 February 2008, IIT Kharapgur. “Int J Hydrogen Energy” 33, 2627-2628.
  • Fan, Y.T, Zhang, Y.H., Zhang, S.F., Hou, H-W., Ren, B-Z., 2006. Efficient conversion of wheat straw wastes into biohydrogen gas by cow dung compost. “Biores Technol” 97, 500-505.
  • Ferchichi, M., Crabbe, E., Gwang-Hoon, G., Hintz, W., Almadidy, A., 2005. Influence of initial pH on hydrogen production from cheese whey. “J Biotechnol” 120, 402-409.
  • Idania, V.V., Richard, S., Derek, R., Noemi, R.S., Hector, M.P.V., 2005. Hydrogen generation via anaerobic fermentation of paper mill wastes. “Biores Technol” 96, 1907-1913.
  • Kapdan, I. K., Kargi, F., 2006. Bio-hydrogen production from waste materials, “Enzyme Microb Technol” 38, 569–582.
  • Kim, J., Park, C., Kim, T-H., Lee, M., Kim, S., Kim, S., Seung-Wook., Lee, J., 2003. Effects of various pretreatments for enhanced anaerobic digestion with waste activated sludge. “J. Biosci. Bioeng” 95, 271-275.
  • Kraemer, J.T., Bagley, D.M., 2007. Improving the yield from fermentative hydrogen production. “Biotechnol Let” 29, 685–695.
  • Logan, B.E., 2004. Feature article: biologically extracting energy from wastewater: Biohydrogen production and microbial fuel cells. “Environ Sci Technol” 38,160A-167A.
  • Logan, B.E., Oh, S.E., van Ginkel, S., Kim, I.S., 2002. Biological hydrogen production measured in batch anaerobic respirometers. “Environ Sci Technol” 36, 2530-2535.
  • Ren, N.Q., Chua, H., Chan, S.Y., Tsang, Y.F., Wang, Y.J., Sin, N., 2007. Assessing optimal fermentation type for bio-hydrogen production in continuous flow acidogenic reactors, “Biores Technol” 98, 1774-1780.
  • Roy Chowdhury, S., Cox, D., Levandowsky, M., 1988. Production of hydrogen by microbial fermentation. “Int J Hydrogen Energy” 13, 407-410.
  • Shin, H.S., Youn, J.H., Kim, S.H., 2004. Hydrogen production from food waste in anaerobic mesophilic and thermophilic acidogenesis. “Int J Hydrogen Energy” 29, 1355-1363.
  • Sparling, R., Risbey, D., Poggi-Varaldo, H.M., 1997. Hydrogen production from inhibited anaerobic composters. “Int J Hydrogen Energy” 22, 563–566.
  • Tang, G., Huang, J., Sun, Z., Tang, Q., Yan, C., Liu, G., 2008. Biohydrogen production from cattle wastewater by enriched anaerobic mixed consortia: Influence of fermentation temperature and pH. “J Biosci Bioengng.”, 106, 80-7
  • Valdez-Vazquez, I., Rıos-Leal, E., Munoz-Paez, K.M., Carmona-Martınez, A., Poggi-Varaldo, H.M., 2006. Effect of inhibition treatment, type of Inocula, and incubation temperature on batch H2 production from organic solid waste. “Biotechnol Bioeng” 95, 342-349.
  • van Ginkel, S.W., Oh, S.E., Logan. B. E., 2005. Biohydrogen gas production from food processing and domestic wastewaters. “Int. J. Hydrogen Energy” 30, 1535-1542.
  • Venkata Mohan, S., Vijaya Bhaskar, Y., Sarm, P.N., 2007a. Biohydrogen production from chemical wastewater treatment by selectively enriched anaerobic mixed consortia in biofilm configured reactor operated in periodic discontinuous batch mode. “Water Res” 41, 2652-2664.
  • Venkata Mohan, S., Mohanakrishna G., Veer Raghuvulu S., Sarma, P.N., 2007b. Enhancing biohydrogen production from chemical wastewater treatment in anaerobic sequencing batch biofilm reactor (AnSBBR) by bioaugmenting with selectively enriched kanamycin resistant anaerobic mixed consortia. “Int J Hydrogen Energy” 32, 3284–3292.
  • Venkata Mohan, S., Lalit Babu, V., Sarma, P.N., 2007c. Anaerobic biohydrogen production from dairy wastewater treatment in sequencing batch reactor (AnSBR): Effect of organic loading rate. “Enzyme and Microbial Technology” 41(4), 506-515.
  • Venkata Mohan, S., Bhaskar, Y.B., Krishna, T.M., Chandrasekhara Rao N., Lalit Babu V., Sarma, P.N., 2007d. Biohydrogen production from chemical wastewater as substrate by selectively enriched anaerobic mixed consortia: Influence of fermentation pH and substrate composition. “Int J Hydrogen Energy”, 32, 2286– 2295.
  • Venkata Mohan, S., Mohanakrishna, G., Ramanaiah, S.V, Sarma, P.N., 2008a. Simultaneous biohydrogen production and wastewater treatment in biofilm configured anaerobic periodic discontinuous batch reactor using distillery wastewater. “Int J Hydrogen Energy”33(2), 550-558.
  • Venkata Mohan, S., Mohanakrishna, G., Ramanaiah, S.V, Sarma, P.N., 2008b. Integration of acidogenic and methanogenic processes for simultaneous production of biohydrogen and methane from wastewater treatment. “Int J Hydrogen Energy” 33, 2156–2166.
  • Venkata Mohan ,S., Lalit Babu, V., Sarma, P.N., 2008c. Effect of various pre-treatment methods on anaerobic mixed microflora to enhance biohydrogen production utilizing dairy wastewater as substrate. “Biores Technol” 99, 59-67.
  • Venkata Mohan, S., Lalit Babu, V., Srikanth, S., Sarma, P.N., 2008d. Bio-electrochemical behavior of fermentative hydrogen production process with the function of feeding pH. “Int J Hydrogen Energy” doi:10.1016/j.ijhydene.2008.05.073.
  • Venkata Mohan, S., Srikanth, S., Dinakar, P., Sarma, P.N., 2008e. Photo-biological hydrogen production by the adopted mixed culture: Data enveloping analysis. “Int J Hydrogen Energy” 33(2), 559-569.
  • Venkata Mohan, S., Mohanakrishna,G., Reddy, S.S., Raju, B.D., Rama Rao, K.S., Sarma, P,N., 2008f.Self-immobilization of acidogenic mixed consortia on mesoporous material (SBA-15) and activated carbon to enhance fermentative hydrogen production. “Int J Hydrogen Energy” doi:10.1016/j.ijhydene.2008.07.096.
  • Vijaya Bhaskar, Y., Venkata Mohan S, Sarma, P.N., 2008. Effect of substrate loading rate of chemical wastewater on fermentative biohydrogen production in biofilm configured sequencing batch reactor. “Biores Technol” 99, 6941–6948.
  • Vijayaraghavan, K., Ahmad, D., Biohydrogen generation from palm oil mill effluent using anaerobic contact filter. “Int J Hydrogen Energy” 31, 1284-1291.
  • Yu, H., Zhu, Z., Hu, W., Zhang, H., 2002. Hydrogen production from rice winery wastewater in an upflow anaerobic reactor by using mixed anaerobic cultures, “Int J Hydrogen Energy” 27, 1359-1365.
  • Zhang, T., Liu, H., Fang, H.H.P., 2003. Biohydrogen production from starch in wastewater under thermophilic condition. “J Environ Manag” 69, 149-156.
  • Zhu, H., Beland, M., 2006, Evaluation of alternative methods of preparing hydrogen producing seeds from digested wastewater sludge. “Int J Hydrogen Energy” 31, 1980-1988.

External links

Search another word or see Dark_fermentationon Dictionary | Thesaurus |Spanish
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature