Based on the derived function a maximum VHP value

Based on the derived function, a maximum VHP value of 3197.5 mL-H2 d−1 L−1reactor was predicted for a sOLR of 0.97 g-Total carbohydrates g-VS−1 h−1. The maximum value for VHP, as measured using analytical methods (2283.8 mL-H2 d−1 L−1reactor for a sOLR of 1.3 g-Total carbohydrates g-VS−1 h−1), was 71.4% of the maximum value estimated by the model, indicating close agreement between the values for hydrogen produced based on variations in sOLR that GDC0199 occur during APBR operation. Hafez et al. (2010) suggested sOLR values between 0.17 and 0.24 g-Carbohydrate g-VS−1 h−1 in continuous stirred reactors applied to produce hydrogen using a glucose-based lab-made wastewater as a substrate at 37 °C. The authors also reported inhibition by excess substrate under a wide range of sOLR (0.33 and 1.17 g-Carbohydrate g-VS−1 h−1). Such range includes the experimental and optimum sOLR values obtained in this work. However, it is important to highlight that in packed-bed reactors, biomass growth rates and HRT are independent of each other, which facilitate maintaining long solids retention time (SRT), and thus, higher substrate saturation constant and inhibition by excess substrate constant may be achieved in this type of reactor in comparison to the CSTR. Furthermore, the temperature is another factor to be accounted. In accordance to Pan et al. (2008), thermophilic fermentation responds more stably to the increase of substrate concentration to a fixed microorganism concentration than the mesophilic one, i.e., higher sOLR can be applied in packed-bed reactors operating with higher temperatures.