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Table 2 Levels of the factors evaluated in the \(2_{\text{V}}^{{ 5 { - 1}}}\) fractional factorial design, sample identification with the corresponding experimental conditions and the main response evaluated in the acid–alkali pretreatment applied to elephant grass leaves (EA)

From: Optimization of biomass pretreatments using fractional factorial experimental design

 

Low level (−)

High level (+)

Central (0)

Factor levels

 A-ball mill time (h)

0

10

5

 B-[H2SO4] (%v/v)

None

2

1

 C-[NaOH] (%w/v)

0.5

4.5

2.5

 D-temperature (°C)

85

125

105

 E-time (min)

20

80

60

Samples and experimental conditions

Response

Sample name

Ball mill time (h)

[H2SO4] step 1 (% v/v)

[NaOH] step 2 (% m/v)

Temp step 2 (°C)

Time step 2 (min)

Reducing sugar release (mg/g)

EA1

0

None

0.5

85

100

86.4

EA2

10

None

0.5

85

20

84.3

EA3

0

2

0.5

85

20

103.7

EA4

10

2

0.5

85

100

108.0

EA5

0

None

4.5

85

20

168.0

EA6

10

None

4.5

85

100

204.5

EA7

0

2

4.5

85

100

179.7

EA8

10

2

4.5

85

20

165.8

EA9

0

None

0.5

125

20

124.4

EA10

10

None

0.5

125

100

124.3

EA11

0

2

0.5

125

100

105.7

EA12

10

2

0.5

125

20

109.5

EA13

0

None

4.5

125

100

143.0

EA14

10

None

4.5

125

20

173.9

EA15

0

2

4.5

125

20

163.3

EA16

10

2

4.5

125

100

169.7

EA17

5

1

2.5

105

60

143.1

EA18

5

1

2.5

105

60

140.3

EA19

5

1

2.5

105

60

143.2