This study was devoted to investigate production of hydrogen gas from acid hydrolyzed
molasses by Escherichia coli HD701 and to explore the possible use of the waste bacterial
biomass in biosorption technology. In variable substrate concentration experiments (1, 2.5,
5, 10 and 15 g L1), the highest cumulative hydrogen gas (570 ml H2 L1) and formation rate
(19 ml H2 h1 L1) were obtained from 10 g L1 reducing sugars. However, the highest yield
(132 ml H2 g1 reducing sugars) was obtained at a moderate hydrogen formation rate (11 ml
H2 h1 L1) from 2.5 g L1 reducing sugars. Subsequent to H2 production, the waste E. coli
biomass was collected and its biosorption efficiency for Cd2þ and Zn2þ was investigated.
The biosorption kinetics of both heavy metals fitted well with the pseudo second-order
kinetic model. Based on the Langmuir biosorption isotherm, the maximum biosorption
capacities (qmax) of E. coli waste biomass for Cd2þ and Zn2þ were 162.1 and 137.9 (mg/g),
respectively. These qmax values are higher than those of many other previously studied
biosorbents and were around three times more than that of aerobically grown E. coli. The
FTIR spectra showed an appearance of strong peaks for the amine groups and an increase
in the intensity of many other functional groups in the waste biomass of E. coli after
hydrogen production in comparison to that of aerobically grown E. coli which explain the
higher biosorption capacity for Cd2þ or Zn2þ by the waste biomass of E. coli after hydrogen
production. These results indicate that E. coli waste biomass after hydrogen production can
be efficiently used in biosorption technology. Interlinking such biotechnologies is potentially
possible in future applications to reduce the cost of the biosorption technology and
duplicate the benefits of biological H2 production technology.