Enhancing enzymatic saccharification of waste newsprint by surfactant addition

Several nonionic surfactants, Pluronic F68 and F88 (BASF) as well as Tween 20 and 80, were found in this study to enhance the enzymatic hydrolysis of pretreated newsprint. Pluronic F68 was the most effective among the surfactants studied. With 2% (w/v) F68 the cellulose (10 g/L) conversion achieved with 2 g/L cellulase reached 52%, about the same as the 48% conversion achieved with 10 g/L cellulase in a surfactant-free system. An empirical model, x = Kt0. 5-(t/tau)1/2, has been developed to describe the extended hydrolysis, where x is conversion, t is reaction time, and K and tau correspond to the initial saccharification rate and the characteristic time for its tendency to deviate from the initial power-law (exponent = 0.5) behavior. The best-fit K and tau in the extended hydrolysis experiments confirmed that F68 significantly enhanced both the initial rate and long-term hydrolysis. A study was also made to evaluate the compatibility of these surfactants, at concentrations up to 2% (w/v), with cultures of Saccharomyces cerevisiae and Dekkera clausenii. While Tween 20 was found strongly inhibitory to D. clausenii, the culture growth in all other surfactant-added systems was comparable to that in the surfactant-free controls.