Enzymatic Hydrolysis of Waste Office Paper Using Viscosity as Operating Parameter Enoch Y. Park,* ,† A. Michinaka, † and N. Okuda ‡ Department of Applied Biological Chemistry, Faculty of Agriculture, Shizuoka University, 836 Ohya, Shizuoka 422-8529, and Technical Developments Department, Tsukishima Kikai Co., Ltd., 17-15, Tsukuda 2-Chome, Chuo-ku 104-0051, Japan Enzymatic hydrolysis of waste office (WO) paper with feeding WO paper in a reactor was investigated using apparent viscosity as operating parameter. Since the apparent viscosity was correlated with the concentration of pulping WO paper, the amount of hydrolyzed WO paper was assumed by measuring the decrease in the apparent viscosity. Then the amount of hydrolysis WO paper and the amount of enzyme corresponding to the desired ratio were fed into the reactor. When the WO paper and 1% (to the amount of WO paper) enzyme were fed to the hydrolytic reaction, 87 g/L of reducing sugar (RS) with a hydrolytic yield of 42.2% was obtained for a 24-h hydrolysis. However, when nonpulping WO paper and 5% (to the amount of WO paper) enzyme were fed to the hydrolytic reaction, 120 g/L of RS with a hydrolytic yield of 40% was obtained for a 24-h hydrolysis. Therefore, the RS concentration from this hydrolysis process feeding WO paper using apparent viscosity as operating parameter may be of sufficient concentration to serve as a carbon source in microorganism culture or chemical feedstock. Introduction Production of paper increased drastically this decade. Sixty percent of flammable solid waste materials was from waste papers. Recently, with the increase of under- standing about the recycling concept of resources, 50% of waste newspapers and 90% of cardboard have been recycled in Japan. The rest of the waste paper was sent for incineration or to a landfill. However, because of environmental restrictions, lack of suitable new sites, and the greenhouse effect of the earth, the incineration or disposal by landfill is probably impossible in a near future. The most severe problem is that available fossil resources are decreasing less and less. Our approach to this dilemma is to recycle a renewable resource. Cellulose, a major building block of waste paper, can be converted to sugars, including glucose, and subse- quently fermented to ethanol (1, 2). The potential for using cellulosic materials in bioconversion processes is well-recognized, but the high cost associated with enzy- matic hydrolysis remains a major problems (3). Concen- trated acid has been used in wood-to-ethanol processes, but yield is limited and implementation may require the development of new, cost-effective methods for acid recovery and reuse (3). Enzymatic hydrolysis provides an environmentally friendly means of depolymerizing cel- lulose and the potential for higher yields, but costs are also unfavorable. Moreover, the resulting reducing sugar (RS) concentration is not high enough to be used as carbon source in microorganism culture or chemical feedstock. This might be due to a low hydrolytic yield from waste paper. During the enzymatic hydrolytic process, it is most difficult to hydrolyze the waste paper in high concentration. Because the paper concentration is higher than 5%, it is difficult to mix the pulping solution in the reactor. Many researches have reported ways to avoid this problem and simultaneously to improve the hydrolytic yield. Zheng et al. (4) used supercritical carbon dioxide to increase the reactivity of cellulose and enhanced the hydrolytic rate of cellulosic material as well as the increase in glucose yield by as much as 50%. Wood et al. (5) reported that ultrasound stimulated ethanol produc- tion in the simultaneous saccharification and fermenta- tion of mixed waste paper. Wu and Ju (6) found that 2% addition of nonionic surfactants enhanced the cellulose conversion to 52% using pretreated newspaper. However, to reuse the waste paper as a renewable resource economically, it is preferable to hydrolyze the waste paper without additional reagents or additional process as above. In this work, we have tried to hydrolyze the waste paper and improve the hydrolytic yield without addition of any reagents or processes, except for paper disintegra- tion, if any. The enzymatic hydrolysis of waste papers was carried out in a reactor, in which the apparent viscosity was measured every 15-30 min during hydroly- sis. The efficient cellulose conversion in a reactor using viscosity as an operating parameter has investigated and discussed. Materials and Methods Pretreatments. Waste office (WO) paper was used for this experiment. The WO paper was cut using a shredder in rectangles 0.6 cm wide and 3 cm long. Then 75 g of shredded WO paper and 1450 mL of tap water were mixed in a pulp disintegrator (JIS P-8209, Kumagai Riki Kogyo Co. Ltd., Tokyo). The resulting pulps were centri- * Ph: (81)-54-238-4887. Fax: (81)-54-237-3028. E-mail: yspark@agr.shizuoka.ac.jp. † Shizuoka University. ‡ Tsukishima Kikai Co., Ltd. 379 Biotechnol. Prog. 2001, 17, 379-382 10.1021/bp0100070 CCC: $20.00 © 2001 American Chemical Society and American Institute of Chemical Engineers Published on Web 03/03/2001