Hydrogen is now considered one of the alternatives to fossil fuels. It is preferred to biogas or methane
because hydrogen is not chemically bound to carbon and therefore, combustion does not contribute to
green house gases or acid rain . One alternative to sustainable H2 energy production from
renewable energy sources is through microbiological fermentation. There have been many studies
examining the effect of pH in fermentative hydrogen production from glucose and sucrose using mixed
microflora [2,3,4,5,6]. However, fermentative hydrogen production from arabinose, one of the most
common pentoses and a component of various biopolymers such as hemicellulose and plant
polysaccharides using mixed microflora has not been previously examined. Understanding the
influence of pH on biohydrogen production is necessary to develop arabinose-based hydrogen
fermentation applications, such as the use of agricultural wastes.
Biohydrogen production from arabinose was examined using three different anaerobic sludges with
different pHs ranging from 4.5 to 8.0. Arabinose (30 g/L) was used as the substrate for all experiments.
Individual cumulative hydrogen production data were used to estimate the three parameters of the
modified Gompertz equation. This model has been used for describing the progress of cumulative gas
production obtained from the batch experiments. Higher hydrogen production potentials (more than 35
mL) were observed with pH values greater than 6.0 for Unicer (granular sludge) and Choupal (disperse
anaerobic digester sludge supplemented with fat) and greater than 6.5 for Freixo (disperse anaerobic
digester sludge). Choupal biomass had the largest hydrogen production rate (4.8±1.4 mL/h) at pH 7.5,
compared with the other two sludges. Unicer biomass had the shortest lag time (10.6±2.4 h) at pH 8.0.
The highest hydrogen yield was observed with Choupal biomass (2.5 mol H2/mol arabinose
consumed), with pH 6.0. The granular biomass showed different behaviour than the suspended
biomasses. The differences may be explained by smaller lag phases, the percentage of acetate
produced, the higher percentage of ethanol produced, and the amount of arabinose consumed. The
percentage of n-butyrate was highly correlated with the percentage of acetate (R2 = 0.980) in Freixo
biomass. A high correlation (R2 = 0.973) was observed between the percentage of n-butyrate and the
percentage of ethanol in Unicer biomass, suggesting that the fermentation is following the
butyrate/ethanol pathways which correspond to the lower yields of hydrogen obtained.
Bio-hydrogen, L-arabinose, pH, Microbiological fermentation, Granular biomass, Disperse biomass
Publication Type: Abstracts in Conference Proceedings