This study addressed the key factors affecting the extraction and quantification of glycogen from floccular and granular mixed microbial cultures collected from activated sludge, nutrient removal systems and photosynthetic consortiums: acid concentration, hydrolysis time and concentration of biomass in the hydrolysis. Response surface modelling indicated that 0.9 M HCl and a biomass concentration of 1 mg mL(-1) were optimal conditions for performing acid hydrolysis. Floccular samples only needed a 2-h hydrolysis time whereas granular samples required as much as 5 h. An intermediate 3 h yielded an error of 10% compared to the results obtained with the hydrolysis times specifically tailored to the type of biomass and can thus be recommended as a practical compromise.
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