Near-complete removal of non-cellulosic components from bamboo by 1-pentanol induced organosolv pretreatment under mild conditions for robust cellulose enzymatic hydrolysis

Based on Hildebrand solubility parameter (delta(H)) theory, a novel organosolv pretreatment medium (OPM), 1-pentanol (80%, v/v)-water mixture with a delta(H) value of 27.4 (J/cm(3))(-1/2), was discovered. This OPM achieved near-complete removal of non-cellulosic components (hemicellulose 96.2% and lignin 87.8%) from bamboo under mild conditions [130 degrees C, 20 min, 4% (w/w) H2SO4]. For the OPMs with similar delta(H) values [DMSO (80%, v/v)- and 1-pentanol (80%, v/v)-water, 30.9 vs. 27.4 (J/cm(3))(-1/2)] to that of bamboo lignin [28.3 (J/cm(3))(-1/2)] used in this study, the effect of the delta(h) value (contribution of hydrogen-binding force to the delta(H)) on lignin removal was also discussed. After overcoming the negative effect of lignin deposits on enzymes with biocompatible soy protein (SP), a decent cellulose enzymatic conversion (EC) of 92.6% was achieved by 1-pentanol (80%, v/v)-water induced organosolv pretreatment at a low cellulase loading (5 FPU/g glucan). This cellulose EC was much higher than those of other OPMs (<63%) with the delta(H) values very different from that of bamboo lignin. Integration of organosolv pretreatment with an ideal OPM and enzymatic hydrolysis using SP as an additive can be thereby viewed as a viable way to achieve the robust cellulose EC at low enzyme loading, which shows great potential for improving the economics of organosolv pretreatment-based lignocellulose biorefinery.