Biohydrogen Production Using Suspended and Immobilized Mixed Microflora

Abstract

Suspended and immobilized anaerobic sludge were utilized to produce hydrogen gas in batch reactors using sucrose as the sole carbon substrate. A variety of immobilization matrices and methods were examined for their suitability to make immobilized H2 producers. The results show that cells immobilized by calcium alginate matrix supplemented with chitosan and titanium oxide carriers (CA+CH+TiO2) were the most effective in H2 production, giving a H2 production rate of 21.3 mmol·L -1 ·h -1 (at 35 o C and 20 g COD·L -1 of sucrose), which was over three-fold of that obtained from suspended cells (6.8 mmol·L -1 ·h -1 ). The sucrose conversion was essentially 85% or higher in all runs, and the biogas consisted of only H2 and CO2. The major soluble metabolites were butyric acid, acetic acid, and propionic acid, while a small amount of ethanol was also produced. Addition of trace metal salts (Ca 2+ and Ni 2+ ) appeared to enhance the H2 producing performance for the suspended culture, elevating H2 production rate from 6.8 to 9.3 and 8.7 mmol·L -1 ·h -1 , respectively. Moreover, the immobilization matrix containing TiO2 seemed to result in better H2 production in general.