Impact of mixed feedstock of wheat straw, willow and Miscanthus on enzymatic hydrolysis and inhibitor production after microwave hydrothermal pre-treatment in Europe

Abstract

Lignocellulosic feedstocks for biorefinery are likely to be seasonal and the supply of feedstock to cellulosic biorefineries remains a challenge. One way to overcome this is by utilizing a mixed feedstock which facilitates the maintenance of a year-round feedstock supply. This study investigated the impact of mixing of three industrially relevant cellulosic feedstocks—wheat straw, willow and Miscanthus using two major performance indicators—sugar yield and fermentation inhibitor production. A microwave hydrothermal pre-treatment regime of 200 °C for 5 min was applied to each feedstock individually and to 1:1 (w/w) mixes and the predicted sugar yield in the mixes was compared to the observed values. All the mixes resulted in improved sugar yields with willow + Miscanthus (15.4%, p = 0.015) and wheat + willow (13.6%, p = 0.010) showing a statistically significant improvement. Saccharification kinetics, inhibitor production, impact on yeast metabolic activity and growth were compared and no adverse impacts of mixing were observed. The use of mixed feedstocks in a hot water based commercial production of biofuels is unlikely to have any adverse effects on productivity and may indeed prove beneficial.

Keywords:

• Lignocellulosic feedstock mix
• microwave hydrothermal pre-treatment
• enzymatic saccharification
• fermentation inhibitors
• yeast response
• biorefining

Acknowledgements

We would like to thank the University of Nottingham's Bioenergy and Brewing Sciences (BABS) technical team for the use of analytical facilities such as HPLC, the Microwave reactor and the Phenotypic Microarray Omnilog reader. We are grateful to Prof Iain Donnison from Aberystwyth University, UK, for kindly providing the Willow and Miscanthus samples; Dr Kirsty Jewell, from the University of Nottingham, UK, for assistance with the yeast growth measurement; and Novozyme A/S, Denmark for kindly providing the Cellic CTec3 enzyme.

Disclosure statement

The authors indicate no potential conflicts of interest.