3.2. Yeast culture
The ability of the chosen yeast strain to proliferate in YM and media comprising liquor from steam exploded duckweed (SE media) was assessed by 96 h yeast cultures at small scale (200 μL) in a 96-well plate. Fig. 2 shows the growth kinetics of yeast in YM medium and a range of SE media. These were used “as produced” without any supplementation with fermentable sugars. The carbohydrate compositions of the SE liquors were reported previously (Zhao et al., 2015) and the concentrations of fermentable glucose were approximately 0.1 mg mL−1. Over a 96 h incubation, yeast growing in YM medium exhibited three growth phases: a very short lag phase, a short but rapid linear growing phase (less than 24 h) and a long stationary phase (72 h). Ciani and Picciotti (1995) observed similar growth kinetics for various yeasts used in wine production. In our study, yeast growing in the SE media generally exhibited a variable lag phase then underwent a linear growth phase longer than that observed in YM medium reflecting the presence of inhibitors and the lower concentration of fermentable glucose. The linear growing phase of SE liquor-based media continued throughout the entire 96 h incubation (after the lag phase) except for that derived after SE at 230 °C. Here, the growth phase terminated after 80 h with the turbidity of 0.65 (Fig. 2). The turbidities of cultures in 150, 170 and 190 °C SE media are all close to 0.5. The results show that the yeast used will effectively proliferate in all the SE liquors with similar growth curves to those reported by Field et al. (2015). Since SE for 10 min at 210 °C was already established as the optimal severity for duckweed pretreatment, (Zhao et al., 2015) a bulk quantity of such slurry was produced for SSF investigations.
3.2. ยีสต์วัฒนธรรมThe ability of the chosen yeast strain to proliferate in YM and media comprising liquor from steam exploded duckweed (SE media) was assessed by 96 h yeast cultures at small scale (200 μL) in a 96-well plate. Fig. 2 shows the growth kinetics of yeast in YM medium and a range of SE media. These were used “as produced” without any supplementation with fermentable sugars. The carbohydrate compositions of the SE liquors were reported previously (Zhao et al., 2015) and the concentrations of fermentable glucose were approximately 0.1 mg mL−1. Over a 96 h incubation, yeast growing in YM medium exhibited three growth phases: a very short lag phase, a short but rapid linear growing phase (less than 24 h) and a long stationary phase (72 h). Ciani and Picciotti (1995) observed similar growth kinetics for various yeasts used in wine production. In our study, yeast growing in the SE media generally exhibited a variable lag phase then underwent a linear growth phase longer than that observed in YM medium reflecting the presence of inhibitors and the lower concentration of fermentable glucose. The linear growing phase of SE liquor-based media continued throughout the entire 96 h incubation (after the lag phase) except for that derived after SE at 230 °C. Here, the growth phase terminated after 80 h with the turbidity of 0.65 (Fig. 2). The turbidities of cultures in 150, 170 and 190 °C SE media are all close to 0.5. The results show that the yeast used will effectively proliferate in all the SE liquors with similar growth curves to those reported by Field et al. (2015). Since SE for 10 min at 210 °C was already established as the optimal severity for duckweed pretreatment, (Zhao et al., 2015) a bulk quantity of such slurry was produced for SSF investigations.
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