(452a) Two-Stage Pretreatment of Miscanthus with Alkaline Peroxide and Electrolyzed Water for Ethanol Production

Miscanthus x Giganteus, a C4 perennial grass, has been proven in recent studies to be twice as productive as switchgrass with regard to yields of biomass produced per acre (Long et al. 2004). Miscanthus' low nutrient and water requirements, as well as its productivity in marginal lands, make it an ideal energy crop. As a relatively new energy crop, the deconstruction of Miscanthus for bio-ethanol production is of interest.

The Miscanthus samples used in these experiments were grounded to pass a 50-70 mesh sieve, and are composed of 49.0% glucan, 22.5% xylan, 1.2% arabinan, 1.6% galactan and 21.6% lignin. The chemical composition analysis was performed following the NREL (National Renewable Energy Laboratory) methods.

Miscanthus was subjected to alkaline peroxide and electrolyzed water two-stage pretreatment. The electrolyzed water was produced by electrolysis of ordinary tap water containing low concentration of sodium chloride (0.1%). In the first stage, Miscanthus was soaked in an alkaline peroxide solution (pH=11.5) at five different concentrations (1-5% w/w) with a 5% solids loading at 50 C for 24 h, to partially remove hemicellulose and lignin. In the second stage, the cellulose-rich solids were pretreated with electrolyzed water at 121 C for 15 min, with a 7% solids loading.

After the second pretreatment, the slurries (6% solids) were hydrolyzed with 15 FPU/g glucan of cellulase and 40 U/g glucan of b-glucosidase at 50 C for 72 h. Following the enzymatic hydrolysis, sugar concentrations were determined by HPLC. Finally, a fermentation study was performed at 30 C and pH=5.5 for 72 h using Saccharomyces Cerevisiae to determine ethanol yield.

An enzymatic digestibility of up to 96% was achieved with the proposed two-stage pretreatment method, with relatively mild temperatures and shortened enzymatic hydrolysis times. With no detoxification performed, the hydrolysate produced from the two-stage process exhibited improved fermentability.

Keywords: Miscanthus, electrolyzed water, pretreatment, enzymatic digestibility

References

E. Heaton, T. Voight and S.P Long. A quantitative review comparing the yields of two candidate C4 perennial biomass crops in relation to nitrogen, temperature and water, Biomass and Bioenergy 27 (2004), pp. 21-30