**3.4. Ethanol fermentation**

(a) (b)

174 Sustainable Degradation of Lignocellulosic Biomass - Techniques, Applications and Commercialization

(c)

**Figure 6.** Response surface plots of glucose yield as a function concentration of pulp and time (a), temperature and

The summary result from combination of each response surface plots showed that the optimum condition of enzyme hydrolysis for NaOH and KOH delignification were 54 FPU/g substrate, 65 FPU/g substrate enzyme concentation, 50 h, 60 h reaction time, 50ºC reaction temperature and 2.5% pulp concentration, respectively. The maximum glucose contents were 47.50% and 48.00% from NaOH and KOH delignification, respectively. The maximum glucose yield obtained were 85%, 81% and 75% from NaOH and KOH delignification and without delignification respectively. Both optimization conditions in enzyme hydrolysis of delignifi‐ cation pulp by NaOH and KOH used to hydrolyze undelignification pulp, the result showed

that percent glucose yield was lower than those from delignified pulp about 8-10%.

time (b), enzymatic loading and time (c), other fixed variables

)

#### *3.4.1. Production of ethanol from pure glucose*

S. Cerevisiae TISTR 5339 was grown in YMB containing 50 g/l glucose, 20 g/l peptone and 10 g/l yeast extract. The experiment was performed at room temperature. The result of ethanol production was shown in Table 7.


**Table 8.** Production of ethanol from 50 g/l of pure glucose by S. Cerevisiae TISTR 5339

Ethanol yield= ethanol from experiment Theoretical ethanol ×100

Table 8 showed the production of ethanol from 50 g/l of pure glucose by S. Cerevisiae TISTR 5339. The result showed that within 36 h of fermentation, the highest ethanol concentration was obtained at 21.92 g/l. The ethanol yield from calculation was 85.96%. This result indicated that S. Cerevisiae TISTR 5339 has 85.96% in capability to change pure glucose to ethanol.
