2. Methods
2.1. Preparation of feed solution
Three sugar solution (glucose solution, diluted sugar beet
molasses, and liquid hydrolysate of dilute acid-pretreated rice
straw) were used as feeds. 10 g L–1 of glucose (Nacalai Tesque, Kyoto,
Japan) solution was prepared. Sugar beet molasses (Wada Sugar
Refining Co., Ltd., Tokyo, Japan) was diluted with distilled water
(5% v v–1 molasses). The pH of the glucose and sugar beet molasses
solutions was maintained at 5.0 using 1 N HCl or NaOH solution.
Rice straw (Nipponbare) was harvested in 2009 in Kasai, Hyogo,
Japan. Naturally dried rice straw was shredded into pieces less
than 2 mm long. Rice straw (75 g L–1) was immersed in 4% (v v–1)
sulfuric acid solution and autoclaved (135 C, 0.2 MPa) for 2 h.
The resulting solution of dilute acid-pretreated rice straw was
filtered through a membrane (No.1, Advantec, Osaka, Japan). The
obtained liquid hydrolysate was neutralized to pH 5.0 by the addition
of calcium hydroxide and stored in a refrigerator (4 C) until
the membrane separation experiments.