Enzymatic hydrolysis of paper mill primary sludge as a potential source of simple sugars for lignocellulosic biorefinery

Author(s): Mylène Gagnon, Aïcha Debboub, Daniel Montplaisir

This study examined the enzymatic hydrolysis of lignocellulosic biomass materials extracted from the primary sludge of a pulp and paper mill. The main objective was to investigate residual primary sludge as low-cost feedstock for the production of ethanol and chemicals. Primary sludge was collected from a newspaper mill and treated with commercial cellulase. Two StatisticalDesigns of Experiment (DOE) were used to determine optimal reaction conditions. The sludge consistency, its pH, the use of acid or buffer to set the pH, the ionic strength, the need for biocide addition, and the enzyme dosage were the conditions analyzed to optimize the enzymatic hydrolysis. The first DOE determined the optimal pH control strategy. Sodium acetate buffer concentrations of 250 mM at pH 5 gave higher results compare to trials with sulphuric acid and acetic acid.Addition of biocide was proven to be ineffective under these conditions. The second DOE determined that the best conditions for hydrolysis yield are an enzyme concentration of 300 µL per gram of dried sludge and a 8.5% sludge consistency. Under optimal conditions, hydrolysis yield reached 58±3% with a sugar concentration of 68±4 mM mM.

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