Achira Mukhopadhyay1, Praveen V. Vadlani1, Ravi S. Mulukutla2, and Frederick J. Renk2. (1) Department of Grain Science and Industry, Kansas State University, 1980 Kimball Avenue, BIVAP Building., Manhattan, KS 66502, (2) MeadWestvaco Corporation, NC State University Centennial Campus, 1021 Main Campus Drive,, Raleigh, NC 27606
Paper mill (PM) sludge is a solid waste generated from pulping and paper-making industry. The presence of cellulose in the PM sludge makes it an attractive feedstock for bioconversion to useful products. The enzyme requirement for complete hydrolysis of the cellulose in PM sludge was compared to a purely cellulosic substrate, paper pulp. Cellulase requirements were found to be similar for both pulp and PM sludge. However, β-glucosidase requirement was much higher in case of PM sludge due to inhibition by the lignin present in the sludge. Enzyme adsorption pattern on the sludge components are being investigated. Response Surface Methodology (RSM) was used to study the effects of temperature, the above mentioned enzymes, and substrate loading on saccharification. The optimized conditions resulted in a glucose release of 0.94g/g cellulose within 20 hours.Lactic acid producing microbial cultures, Lactobacillus plantarum and Rhizopus oryzae were evaluated for fermentation of the sugars generated by hydrolysis of PM sludge at the shake flask and fermenter levels. Inhibition of bacterial growth occurred due to the presence of inhibitory compounds such as sulphides, organochlorines and lignin degradation products resulting in lower yields and productivities than that obtained in synthetic glucose media. On the other hand, fungal growth rate is enhanced due to the high solid content of PM sludge. At shake flask level, the yield of lactic acid produced in sludge hydrolyzate using Lactobacillus sp and Rhizopus sp was 0.75g/g and 0.55g/g of glucose respectively. Fermenter studies are ongoing and the results will be discussed.
