loadings, however, increased chemical addition is required for
effective pretreatment and subsequent neutralization. This
results in greater salts concentration which could inhibit
hydrogen-producing microorganisms. Sodium is an ion that is
introduced in a significant amount during the pretreatment or
neutralization of duckweed. Since it is one of the key inhibitors
to hydrogen-producing microorganisms [28,29], efforts
were made to establish a correlation between sodium
levels and biohydrogen production. All these fermentation
experiments were carried out in 250 mL glass bottles incubated
at the desired temperature, initial pH, and biomass
loading for two to three weeks. The experimental procedures
were the same as those used in the study on pretreatment,
except that 0.05 M phosphate buffer was added instead of DI
water for pH control.