Paper sludge hydrolysate

Yields from Glucose, Xylose, and Paper Sludge Hydrolysate During Hydrogen Production by the Extreme Thermophile Caldicellulosiruptor saccharolyticus... 

Index Entries Hydrogen production paper sludge hydrolysate extreme thermophile Caldicellulosiruptor saccharolyticus, glucose xylose carbon balances. 

In this article, we present our findings on hydrogen production by the extreme thermophilic C. saccharolyticus using paper sludge hydrolysate in a controlled laboratory fermentor, which allowed accurate determinations of hydrogen yields and production rates. 

Fermentation experiments utilizing sugars present in paper sludge hydrolysate were first carried out on complete medium as presented in Materials and Methods. Results on carbohydrate consumption and hydrogen production of two typical fermentations are shown in Table 2 (conditions D1 and D2). Acetate and lactate were the main byproducts. 

Fig. 2. Hydrogen production by C. saccharolyticus using paper sludge hydrolysate. (—<>—), Hydrogen (— —), acetate (—x—), lactate (— —), glucose (— —), xylose (—O—), OD580nm.

Lactic acid formation occurred to a different extent when paper sludge hydrolysate was used. Although the same batch of hydrolysate was used for all experiments under identical conditions, lactate production was observed from the early stage (Fig. 2, condition D2) of the fermentation or lactate was only found in the fermentation broth in the very late phase of the process (condition Dl). 

Results on the carbon balances for these fermentation experiments with paper sludge hydrolysate are presented in Table 3. Interference of unidentified components in the hydrolysate with the protein content determination disallowed accurate biomass content determination, resulting in an incomplete mass balance. However, similar OD was measured as observed for the mixture of pure sugars (condition C). 

Hydrogen and acetate yields on paper sludge hydrolysate were considerably higher than on pure sugars (Table 4, condition Dl). When a shift in metabolism toward lactic acid production occurred (condition D2), acetate and hydrogen yields became significantly lower. 

Previous experiments showed that C. saccharolyticus did not depend on nutrients for hydrogen production from paper sludge hydrolysate (15). 

Z., de Vrije, T., van Noorden, G., Budde, M.W., Szengyel, Z., Reczey, K., Claassen, P.M., 2004. Yields from glucose, xylose, and paper sludge hydrolysate during hydrogen production by the extreme thermophile Caldicellulosiruptor saccharolyticus. Applied Biochemistry and Biotechnology 114, 497—508. 

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