Integrating sugar beet pulp storage, hydrolysis and fermentation for fuel ethanol production

Sugar beet pulp (SBP) as received has a fairly high moisture content of 75–85%, which makes SBP storage a challenge. Ensilage was studied over 90 days and was found to effectively preserve SBP without lactic acid bacterium inoculation. Higher packing density yielded a slightly better silage quality. Ensilage improved sugar yield upon enzymatic hydrolysis of ensiled SBP washed with water. However, neither washing nor sterilization improved ethanol production from ensiled SBP using Escherichia coli KO11, suggesting ensiled SBP could be used directly in fermentation. The ethanol yield from ensiled SBP was nearly 50% higher than raw SBP. Fed-batch fermentation obtained approximately 30% higher ethanol yield than batch. Fed-batch could also be carried out at 12% solid loading with a 50% lower enzyme dosage compared to batch at the same solid loading, indicating opportunities to improve the economics of SBP conversion into liquid fuels.