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Table 4 Substrate, product and by-product concentrations and yields obtained from SHF (A) and SSF (B) experiments

From: Influence of bark on fuel ethanol production from steam-pretreated spruce

A)

 

Bark content (% of DM)

0

10

30

50

100

Enzymatic hydrolysis step in SHF

Glucose concentration (g/L)

80.6 ± 0.1

66.5 ± 0.7

61.8 ± 1.8

48.5 ± 0.5

34.0 ± 0.5

Glucose yield (% of the theoretical)

89.8 ± 0.3

81.6 ± 1.0

81.9 ± 3.3

67.9 ± 1.1

53.3 ± 0.9

Fermentation step in SHF

Total hexose sugar concentration (g/L)

3.5 ± 0

3.1 ± 0

2.9 ± 2.1

1.0 ± 0.7

1.1 ± 0

Glycerol concentration (g/L)

5.2 ± 0

4.5 ± 0.1

4.2 ± 0.1

3.6 ± 0

3.0 ± 0.1

Volumetric ethanol productivitya (g/Lh)

1.7 ± 0

2.0 ± 0

2.3 ± 1.2

2.8 ± 0.1

3.2 ± 0

Ethanol concentration (g/L)

41.5 ± 0.8

36.1 ± 1.8

32.8 ± 0.4

28.2 ± 0.1

18.1 ± 0

Ethanol yield (% of the theoretical)

93.1 ± 0.1

92.0 ± 0

93.8 ± 0.8

96.2 ± 0.9

95.0 ± 0.2

SHF

Overall ethanol yield (% of the theoretical)

83.6

75.1

76.8

65.3

50.7

B)

 

Bark content (% of DM)

0

10

30

50

100

SSF

Total hexose sugar concentration (g/L)

4.2 ± 0.3

1.9 ± 0.1

2.2 ± 0.1

2.4 ± 0.1

3.3 ± 0.1

 

Glycerol concentration (g/L)

4.8 ± 0.1

4.2 ± 0.2

3.8 ± 0.1

3.4 ± 0

3.6 ± 1.4

 

Volumetric ethanol productivitya (g/Lh)

1.7 ± 0.1

1.8 ± 0.3

2.5 ± 0

2.9 ± 0.1

4.0 ± 0.1

 

Ethanol concentration (g/L)

45.8 ± 0.8

39.3 ± 0.9

34.5 ± 0.4

29.4 ± 0.1

20.9 ± 0

 

Overall ethanol yield (% of the theoretical)

85.4 ± 1.9

81.1 ± 2.3

77.5 ± 1.3

70.5 ± 0.4

59.3 ± 0.1

  1. aCalculated for the first two hours.
  2. SSF and SHF experiments of steam-pretreated wood and bark mixtures were performed at 10% WIS loading, pH 5 using Cellic CTec3 enzyme cocktail (20 FPU/g WIS) and an industrial S. cerevisiae strain, Ethanol Red (5 g/L). DM, dry matter; SHF, separate hydrolysis and fermentation; SSF, simultaneous saccharification and fermentation; WIS, water-insoluble solids.