TY - JOUR
T1 - A Cation Study on Rice Husk Biomass Pretreatment with Aqueous Hydroxides
T2 - Cellulose Solubility Does Not Correlate with Improved Enzymatic Hydrolysis
AU - Lau, Benjamin B.Y.
AU - Yeung, Tracey
AU - Patterson, Robert J.
AU - Aldous, Leigh
PY - 2017/4/19
Y1 - 2017/4/19
N2 - Biomass pretreatment is a key first step in converting recalcitrant lignocellulosic biomass into value-added products. Aqueous hydroxide solutions can be effective biomass pretreatment media, and the cation of the hydroxide salt can have an extremely significant effect upon the physicochemical behavior of the hydroxide solution. However, the cation effect has not been comprehensively investigated with respect to biomass pretreatment. Here, we investigated pretreatment of rice husks (from Oryza sativa) and show that the cation indeed has a significant effect upon downstream enzymatic hydrolysis of the cellulose (with cellulase). In particular, the ability of the solution to dissolve cellulose was negatively correlated with pretreatment effectiveness, as judged by the downstream glucose yield. This was observed by investigating aqueous solutions of lithium, potassium, cesium, tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, and tetrahexylammonium hydroxide. Silica solubility was almost cation-independent, lignin solubility was moderately cation-dependent, while cellulose solubility was strongly cation-dependent. The rate of lignin extraction was inversely correlated with the size of the cation. As cellulose dissolution is a demanding chemical process, it initially limited the ability of the solution to disrupt the whole biomass, necessitated extensive washing of the pretreated rice husk, and still resulted in significant cation contamination downstream. Overall, lithium hydroxide was found to be the most effective hydroxide.
AB - Biomass pretreatment is a key first step in converting recalcitrant lignocellulosic biomass into value-added products. Aqueous hydroxide solutions can be effective biomass pretreatment media, and the cation of the hydroxide salt can have an extremely significant effect upon the physicochemical behavior of the hydroxide solution. However, the cation effect has not been comprehensively investigated with respect to biomass pretreatment. Here, we investigated pretreatment of rice husks (from Oryza sativa) and show that the cation indeed has a significant effect upon downstream enzymatic hydrolysis of the cellulose (with cellulase). In particular, the ability of the solution to dissolve cellulose was negatively correlated with pretreatment effectiveness, as judged by the downstream glucose yield. This was observed by investigating aqueous solutions of lithium, potassium, cesium, tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, and tetrahexylammonium hydroxide. Silica solubility was almost cation-independent, lignin solubility was moderately cation-dependent, while cellulose solubility was strongly cation-dependent. The rate of lignin extraction was inversely correlated with the size of the cation. As cellulose dissolution is a demanding chemical process, it initially limited the ability of the solution to disrupt the whole biomass, necessitated extensive washing of the pretreated rice husk, and still resulted in significant cation contamination downstream. Overall, lithium hydroxide was found to be the most effective hydroxide.
KW - cellulase
KW - kinetics
KW - onium hydroxides
KW - rice hulls
UR - http://www.scopus.com/inward/record.url?scp=85020181660&partnerID=8YFLogxK
U2 - 10.1021/acssuschemeng.7b00647
DO - 10.1021/acssuschemeng.7b00647
M3 - Article
AN - SCOPUS:85020181660
SN - 2168-0485
VL - 5
SP - 5320
EP - 5329
JO - ACS SUSTAINABLE CHEMISTRY & ENGINEERING
JF - ACS SUSTAINABLE CHEMISTRY & ENGINEERING
IS - 6
ER -