The degree of concentration of fermentation inhibitors against
glucose was evaluated by their separation factor over glucose
(Table 5). The separation factor over glucose of acetate, formate,
furfural, and HMF was higher than 1, suggesting that glucose was
selectively concentrated by NTR-729HF, NTR-7250, and ESNA3.
The concentration of xylose in the permeates was under the detection
limit using HPLC, suggesting that xylose was also selectively
concentrated. Thus, the selective concentration of sugars against
fermentation inhibitors was favorable for subsequent fermentation
by S. cerevisiae (Hasunuma and Kondo, 2012).