As it can be observed in Table 1, a value close or even superior to 1 is obtained when the product yield is calculated considering glucose as the only substrate utilised, whereas the corrected yield accounting for total sugars consumption (0.9 g g−1 on RPS hydrolysate) is more realistic, which confirms the fact already pointed that cellobiose (and partially xylose) is also converted to lactic acid. Moreover, since theoretical yields from the three consumed cellobiose, glucose and xylose are 1.0, 1.0 and 0.6 g lactic acid per g of substrate, respectively, the fact that lactic yield achieved is near 1 g g−1 indicates that little of the substrate is used for cell growth and maintenance, and almost all is converted to product, as desired.