Hydrogen is recognized as a clean, renewable and promising
future fuel. Production of hydrogen through a biological route utilizing
waste biomass represents an important area of bio-energy
production. Biological hydrogen production is a microbial conversion
process, carried out by bacteria capable of synthesizing
hydrogen producing enzymes, such as hydrogenase and nitrogenase,
in dark and photo-fermentation, respectively. Biological
hydrogen production is classified into four categories, namely (1)
biophotolysis of water using solar energy and algae/cyanobacteria,
(2) photodecomposition of organic compounds using light energy
and photosynthetic bacteria, (3) fermentative hydrogen evolution
to breakdown carbohydrate-rich substrates to hydrogen and other
products such as acids and alcohols using anaerobic bacteria and
(4) hybrid systems combining dark and photofermentation either
directly or in a series-type (Kothari et al., 2012).
Among all these processes, the dark fermentation route is the
most feasible technology with commercial values as it does not
require any external energy as well as light source and can be run at
low cost (Sreela et al., 2011a). Upon dark fermentative transformation,
hydration of glucose molecule elucidates a concurrent
generation of acetic acid and hydrogen in the ratio of 1:2 (Eq. (1)). It
also offers an excellent potential for practical application and
integration with emerging hydrogen and fuel cell technologies