2.3. Pretreatment of hydrol, SCR, and malt
Unless otherwise stated, fermentation was carried out by using hydrol and hydrolyzate of SCR and malt as the main nutrients. Liquid hydrol was kindly provided by Samyang Genex Co. (Seoul, Korea). It contained 65–66% dry matter, of which 94–95% was reducing sugars and 5–6% was salts, including 2–3% sodium chloride. In this study, liquid hydrol was dried and powdered, which was then used as the carbon source. The hydrol concentration used in this work indicates the amount of dried hydrol.
SCR (150 g/L) and malt (20–150 g/L) were slurried in 0.5% (w/v) phosphoric acid and pretreated on an autoclave at 121 C for 1 h. The pretreated SCR and malt was adjusted to pH 7.0 with 10 M NaOH. The liquid was collected by centrifugation at 15,000 g for 10 min, and then the resulting supernatant was used as the nitrogen source.