Fermentable sugars from primary sludge by innovative enzymatic hydrolysis

Cellulose is one of the main components of raw municipal wastewater, in which it is mainly present as toilet paper. Due to its recalcitrant structure, the biodegradation process results very slow. Cellulose hydrolysis can be exploited for the circular approach of low-cost raw materials recovery from waste. In the present study the application of commercial (hemi)cellulolytic enzymes, for the conversion to fermentable sugars of the cellulose fraction of primary sludge from two different plants, was explored. A high glucose recovery of 68.1% was reached in 72 h of primary cellulosic sludge bioconversion at a solid load of 7%, 50 °C and pH 5.0, using commercial enzymes. Moreover, the bioprocess was carried out utilizing a cellulose from an extremophilic microorganism. The glucose recovery of 43.8%, obtained after bioconversion of 5% primary sludge for 72 h, in the same condition previously reported, was comparable to that achieved with the commercial enzyme.