(266b) Lignocellulosic Biomass Pretreatment Using Radical Species

Currently, much effort is directed at moving away from fossil fuel based economy towards renewable feedstocks and the development of biorefineries. The major challenge for refining the complex chemical structure of biomass to biofuel is the separation of lignin from cellulose and hemicellulose. Wood-eating termites provide an excellent model for degradation of biomass and separation of lignin from cellulose and hemicellulose by the presence of radical species and hydroxyl radical intermediates. In order to validate the suspected effect of radical on degrading lignin and carbohydrate, activated persulfate systems were applied to produce different reactive oxygen species. Persulfate system is a combination of powerful oxidative agents, reductive species, and nucleophilic ones, which all in all make this system outstanding to attack lignin, and makes noteworthy changes which are ideal for biomass pretreatment.
The base-activated and heat-activated persulfate were used to treat 60 mesh wheat straw particles for different reaction time (30min-7 h), and the formation of radicals was confirmed by chemical probes including nitrobenzene and anisole. The results from FTIR spectra, SEM images, compositional analysis, and enzymatic hydrolysis showed that the lignin structure was removed and in somehow modified, leading to higher sugar yield from 20% in raw material to 40% and 70% corresponding to heat-activated persulfate and base-activated persulfate, respectively. The better sugar yield obtained in base-activated persulfate was correlated to the capability of this system to generate an array of different radicals such as sulfate radical anion, hydroxyl radical, superoxide radical anion and hydroperoxide anion. These diverse groups of radicals make persulfate system a widely-reactive oxidant that can potentially penetrate in biomass pores to remove lignin and make cellulose accessible.