Volume No. 8 Issue No.: 4 Page No.: 946-954 April-June 2014




Bhagat Anirudh P.,1 Shindikar Mahesh2 and Pethkar A.V.*3

1. Department of Biotechnology, KTHM College, Nashik, Maharashtra (INDIA)
2. Department of Applied Science, College of Engineering, Pune (INDIA)
3. Department of Microbiology, Govt. Institute of Science, Aurangabad, Maharashtra (INDIA)


Received on : January 15, 2014




Hydrogen gas with the highest gravimetric energy density of all known fuels produces energy without giving rise to the notorious carbon emissions that damage the environment. A promising nextgeneration non-conventional resource, hydrogen yields energy to the tune of about 122kJ/g. Biological processes for hydrogen production proffer distinct advantages such as clean and green energy that may be economically attractive. Among several known processes, two processes viz. direct and indirect biohydrogen production are reported in algae and cyanobacteria, respectively. In the direct process, photosystem II (PSII) dependent and PSII independent reaction cascades operate, out of which the PSII independent process appears to be more efficient and economical. Here, under anoxic conditions (induced by blockage of PSII) electrons derived from endogenous substrates such as proteins and carbohydrates are channelized via cytochrome b6f to PSI. The absorbance of light by reactive center of PSI subsequently allows transfer of the electrons to ferrodoxin and then to an active hydrogenase enzyme on the outer face of the thylakoid membrane. Under oxygen limiting conditions the hydrogenase is active and utilizes the electrons to reduce protons that are released out of the thylakoid membrane during ATP (Adenosine Triphosphate Synthesis). Attractive as it may seem, recent breakthroughs in H2 photoproduction have been able to tap only about 15% of the theoretical maximum, suggesting room for substantial improvement in the energy yield. Urgent steps need to be taken in order to develop the technology for commercial scale production of biohydrogen. Certain approaches appear to be promising in this regard, viz. (i) reducing antenna size to minimize shading effect and to avoid loss of energy during transfer of photons from antenna to the reaction center with the overall effect of increasing conversion efficiency, (ii) enriching the quality of endogenous substrate that would enhance generation of electrons, (iii) enhancing the release of hydrogen ions entrapped in thylakoid membrane by using protonophores. Additionally in a fourth approach, efforts need to be taken for designing photobioreactors that will minimize loss of photons and ensure availability of specific wavelengths of light for hydrogen production. Experimental data pertaining to some of these approaches will be discussed in the presentation.


Keywords : Biohydrogen, Photosystem II, Protonophores, Photobioreactor, Hydrogenase, Adenosine Triphosphate Synthesis (ATP)