title: Mechanisms of the inhibition of enzymatic hydrolysis of waste pulp fibers by calcium carbonate and the influence of nonionic surfactant for mitigation.
abstract: Recycled paper mills produce large quantities of fibrous rejects and fines which are usually sent to landfills as solid waste. These cellulosic materials can be enzymatically hydrolyzed into sugars for the production of biofuels and biomaterials. Paper mill wastes also contain large amounts of calcium carbonate which inhibits cellulase activity. The calcium carbonate (30%, w/w) decreased 40-60% of sugar yield of unbleached softwood kraft pulp. The prime mechanisms for this are by pH variation, competitive and non-productive binding, and aggregation effect. Addition of acetic acid (pH adjustment) increased the sugar production from 19 to 22 g/L of paper mill waste fibers. Strong affinity of enzyme-calcium carbonate decreased free enzyme in solution and hindered sugar production. Electrostatic and hydrogen bond interactions are mainly possible mechanism of enzyme-calcium carbonate adsorption. The application of the nonionic surfactant Tween 80 alleviated the non-productive binding of enzyme with the higher affinity on calcium carbonate. Dissociated calcium ion also inhibited the hydrolysis by aggregation of enzyme.
authors.affiliation: Department of Paper and Bioprocess Engineering, Empire State Paper Research Institute, College of Environmental science and Forestry, State University of New York, 1 Forestry Drive, Syracuse, NY, 13210, USA.
authors.forename: Byeong Cheol
authors.initials: BC
authors.lastname: Min
authors.affiliation: Department of Paper and Bioprocess Engineering, Empire State Paper Research Institute, College of Environmental science and Forestry, State University of New York, 1 Forestry Drive, Syracuse, NY, 13210, USA. bvramara@esf.edu.
authors.forename: Bandaru V
authors.initials: BV
authors.lastname: Ramarao
mesh_terms: D002119:Calcium Carbonate / Q000378:metabolism*; D002480:Cellulase; D002482:Cellulose; D006868:Hydrolysis; D010209:Paper; D013501:Surface-Active Agents
chemical_list: D013501:Surface-Active Agents; D002482:Cellulose; D002480:Cellulase; D002119:Calcium Carbonate
keywords: Calcium carbonate; Cellulase adsorption; Enzymatic hydrolysis; Inhibitors; Non-ionic surfactants; Waste fibers