Development of fermentation techniques for potential development of a lignocellulose biorefinery at a pulp mill

The University of Wisconsin-Stevens Point biorefinery research program aims to develop new processing technologies that will allow pulp and paper mills to produce renewable chemicals and fuels using existing infrastructure. In February of 2013, we began collaborating with Cosmo Specialty Fibers, an investor-owned dissolving wood pulp sulfite mill in Cosmopolis, Washington, to study the opportunities for increased revenue from conversion of mill residuals and low-cost biomass into renewable chemicals. WIST and mill staff analyzed potential feedstock for bio-based chemical production. The analysis identified 460,000 annual metric tons of carbohydrate in residual streams that are currently not processed. These streams have the potential to produce value added products by enzymatic hydrolysis and fermentation. Combined rejects are hemlock fibers that do not meet specification after digestion, they are 40% glucose and approximately 17.7 dry tons are produced/day correlating to 6500 kg/day glucose. We demonstrate the fermentation of sugars derived from the combined rejects residual stream to produce value added products lactic acid, ethanol and isoprene. Flask scale fermentation using transgenic E.coli strains for isoprene, Yeast Ferm pro for ethanol and L.rhamnosus for lactic acid production demonstrated that all three value added products could be successfully produced at concentrations that are industrially acceptable. Work is continuing with bench top bioreactor scale fermentations. These results show that the mill can benefit through reduced process costs, increased revenue streams through product sales, and potential renewable energy credits.