Impact of cultivar selection and process optimization on ethanol yield from different varieties of sugarcane

Table 4 Coefficient of determination, optimal conditions and predicted and validated maximum values for different optimization criteria

Model (in coded form)		R²	Optimal conditions		Max. values
Model (in coded form)		R²	Temperature	Time	Prediction	Value
5	X₅₅ = 77.15-3.77 T-4.12 t-5.64 T²	0.85	186	5	82.5	Na
6	X₇₀ = 82.33-4.80 T-2.50 t-6.15Tt-8.51 T²-5.94 t²	0.91	187	9	82.9	Na
7	X₇₄ = 78.99-2.20 T-2.99 t-4.88Tt-7.56 T²-5.50 t²	0.88	188	9	79.3	Na
8	X₁₂₀ = 76.18-8.00 T-7.02 t-6.01Tt-8.06 T²-10.66 t²	0.97	190	8	78.5	Na
9	G₅₅ = 38.05 + 3.63 T + 1.79 t-2.7 3 T²-2.91 t²	0.98	193	10	38.7	Na
10	G₇₀ = 34.99 + 2.73 T + 1.44 t-2.61Tt-2.61 T²	0.98	197	6	36.1	Na
11	G₇₄ = 26.54 + 3.24 T + 2.63 t	0.88	194	15	30.4	Na
12	G₁₂₀ = 27.67 + 2.25 T + 2.85 t-1.39Tt	0.97	198	14	31	Na
13	CSY₅₅ = 65.47 + 2.16 T + 1.04 t-4.90 T²-2.91 t²	0.96	189	10	65.3	65.8
14	CSY₇₀ = 63.73 + 1.80 T + 1.26 t-4.55Tt-5.29 T²-1.96 t²	0.99	188	11	63.5	64.5
15	CSY₇₄ = 52.67 + 3.05 T + 2.54 t-2.70Tt-2.85 T²-2.44 t²	0.95	189	12	53	52.7
16	CSY₁₂₀ = 49.24 + 0.35 T + 1.64 t-2.82Tt-2.19 T²-2.08 t²	0.92	192	12	49.7	50.3

X, G and CSY stands for xylose recovery after pretreatment (% of theoretical), glucose yield after enzymatic hydrolysis (g per 100 g dry material) and combined sugar yield (g per 100 g dry material); subscripts (55, 70, 74 and 120) stands for substrates.
T and t represents temperature and reaction time in coded form.
Optimal conditions: Temperature (°C) and time (minutes); acid concentration was kept constant at 0.5% (w/w).
Prediction. and Value stands for the maximum values predicted by the model and those obtained experimentally, respectively.
Na means not determined.
R², coefficient of determination.

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