Bioethanol production by recycled Scheffersomyces stipitis in sequential batch fermentations with high cell density using xylose and glucose mixture

Here, it is shown three-step investigative procedures aiming to improve pentose-rich fermentations performance, involving a simple system for elevated mass production by Scheffersomyces stipitis (I), cellular recycle batch fermentations (CRBFs) at high cell density using two temperature strategies (fixed at 30 °C; decreasing from 30 to 26 °C) (II), and a short-term adaptation action seeking to acclimatize the microorganism in xylose rich-media (III). Cellular propagation provided 0.52 gdry cell weight gRS−1, resulting in an expressive value of 45.9 gdry cell weight L−1. The yeast robustness in CRBF was proven by effective ethanol production, reaching high xylose consumption (81%) and EtOH productivity (1.53 g L−1 h−1). Regarding the short-term adaptation, S. stipitis strengthened its robustness, as shown by a 6-fold increase in xylose reductase (XR) activity. The short fermentation time (20 h for each batch) and the fermentation kinetics for ethanol production from xylose are quite promising.