Pulsed electric field treatment of sugar beet tails as a sustainable feedstock for bioethanol production

Sugar beet tails are a sustainable feedstock for bioethanol production. This work discusses a new process to produce a fermentable juice of sugar beet tails using pulsed electric field (PEF) and solid-liquid expression. The impact of PEF intensity E and duration tPEF on the expression kinetics of solutes from sugar beet tails was investigated. The optimal PEF intensity and duration were respectively E = 450 V/cm and tPEF = 10 ms corresponding to an energy input Q = 1.91 W h/kg. At these PEF parameters, the yield of solutes was increased from 16.8% to 79.85% and the dryness of pressed cake was increased from 15% to 24% in comparison with the untreated tails. Moreover, the PEF expressed juice was more concentrated (10% vs. 5.2%) and had higher sucrose content (8.9 vs. 4.5 °S) than the juice expressed from untreated tails. Batch fermentation experiments with commercial Saccharomyces cerevisiae yeast were realized using raw juices expressed from untreated and PEF treated sugar beet tails. It was found that the higher content of fermentable sugars in PEF expressed juice leads to a higher ethanol content in distillate (6.1% vs. 2.95% v/v) and a higher CO2 weight loss (57.2 vs. 28.3 g/L) than that obtained from raw juice of untreated tissue. The obtained results are promising and open new opportunities for valorization of sugar beet by-products.