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Table 2 Optimal cell ratio of S. stipitis/S. cerevisiae co-culture for maximized ethanol production from different biomass feedstock predicted by co-culture kinetic model

From: Model-based optimization of Scheffersomyces stipitis and Saccharomyces cerevisiae co-culture for efficient lignocellulosic ethanol production

Type of biomass

Sugar ratio

Opt. cell ratioa

R bETOH (g/l h)

[EtOH]c (g/l)

Glc/Xyl (g/g)

X 1/X 2 (g/g)

Co-culture

Improve (%)d

Co-culture

Improve (%)d

Rice straw

3.00

1.70

0.17

35

8.00

33

Corn stover

1.89

1.78

0.17

55

9.17

52

Cottonwood

3.23

1.70

0.17

33

7.86

30

Sugarcane bagasse

1.63

1.94

0.18

63

9.68

61

Corn cobs

1.29

1.86

0.19

79

10.65

77

Switch grass

1.45

1.86

0.18

71

10.14

68

Eucalyptus

4.90

1.63

0.17

23

7.22

20

Wheat straw

1.58

1.94

0.18

65

9.80

63

  1. Glucose and xylose ratio for each biomass feedstock is based on biomass feedstock composition and property database
  2. aOptimal cell ratio is defined as initial g cell of S. stipitis (X 1) per initial g cell of S. cerevisiae (X 2). The model simulation for each type of feedstock is based on glucose concentration of 15 g/l and xylose concentration according to sugar ratio for each feedstock for comparison purpose
  3. bRate of ethanol is defined as overall productivity which is total ethanol produced divided by required fermentation time of co-culture under optimal cell ratio. Fermentation time is the time required for completion of all glucose and xylose by co-culture
  4. cEthanol titer of co-culture under optimal cell ratio is predicted by the model based on total glucose and xylose available and 80 % of theoretical yield assumption
  5. dPercent improvement is calculated by comparing the performance of co-culture under optimal cell ratio with that of S. cerevisiae based on kinetic model