Effect of conductive material for overcoming inhibitory conditions derived from red algae-based substrate on biohydrogen production

Marine biomass contains sugars that can generate high value-added energy; however, it inevitably produces various by-products such as formic and levulinic acids and 5-hydroxylmethyl furfural (5-HMF) during the extraction process. Thus, the aim of this study was to evaluate the efficacy of conductive carriers as a means to overcome hydrogen production inhibition with various byproducts. As a result, under a mixed sugar condition in which metabolic delay may occur via diauxic growth, a magnetite (Fe₃O₄) supplement resulted in a 64% increase in total hydrogen production. The hydrogen production yield and maximum production rate were 1.7 mol-H₂/mol-consumed sugar and 15.5 mL/h, respectively. 5-HMF had an inhibitory effect at all concentration, whereas formic acid and levulinic acid caused hormesis at concentration below 1.1 and 3.0 g/L, respectively. However, regardless of the type of toxic substance, the magnetite supplement resulted in a greater than 20% increase in hydrogen production at each concentration less than 2, 3, and 2 g/L of formic acid, levulinic acid, and 5-HMF, respectively.