(239c) Enzymatic Hydrolysis of Waste Rejects from OCC Mills – Effect of Minerals and Optimal Methods to Reduce Inhibition

Fines are produced while recycling OCC (Old Corrugated Containerboards) and are usually rejected into the solid waste stream that further requires landfilling. The major component of fines rejects is primarily cellulose that can be hydrolyzed into sugars and thus present a ready cellulosic source which is a waste stream and does not require any complex pretreatment processes typical of lignocellulosic substrates such as wood chips and cereal straws or stover. However, the high content (over 30%) of ash in fines has inhibitory potential to enzymatic hydrolysis. Especially, PCC among fillers was the most powerful inhibitor reducing hydrolysis yield by adsorbing cellulase and changing pH of buffer solution. In this study, addition of anionic surfactants (SDS), cationic surfactant (CTAB) and nonionic surfactant (Tween-80) were investigated to improve enzymatic hydrolysis yield of reject fines from a recycled OCC mill. Nonionic surfactant reduced the requirement of enzyme (Trichoderma reesei ATCC 26921) from 50 FPU to 30 FPU for the maximum hydrolysis yield of 43% sugar (g/g-OD fines). The activity of Tween-80 reducing inhibitory potential of fillers was revealed by enzyme adsorption test and the Langmuir isotherm resulted in reduction of the affinity of fillers to enzyme.  pH adjustment of buffer with acid was also studied to make a optimal hydrolysis condition for cellulase. Presence of calcium carbonate increased the pH of buffer solution with fines over 6. Addition of acid to make the buffer to pH 5 increased hydrolysis yield and combination method with nonionic surfactant reduced enzyme dosage to 20 FPU for the maximum yield. A model for the enzymatic hydrolysis of such complex mixtures was developed and applied.