03.08.2015   Pretreatment Techniques for Biofuels and Biorefineries

Further Processing of Hemicellulose and the Derived Lignin

The economical conversion of lignocellulosic biomass to higher value products re­quires efficient recovery of cellulose, lignin, and hemicellulose components during the fractionation process. Organosolv pretreatment can meet the requirement due to the selective dissolving ability of the solvent employed in the process. In addition to the cellulose-rich materials, it produces organosolv lignin and hemicellulose sugars that is environmentally friendly.

The hemicellulose sugars recovered from the water-soluble stream can be con­centrated for fermentation using special organisms to convert the five-carbon aldose to ethanol or other products [33]. Organosolv lignin is a suitable feedstock for the production of phenolic resins/adhesives [73], antioxidant [74], bio-based polymer

3.04% mannose, 0.93 % galactose, 0.48 % arabinose)

Species of biomass

Reaction factors

Deligni-

fication

Hemicel-

lulose

removal

Cellulose

Biomass

Effect on enzymatic hydrolysis

Temperature Time

Solvents

Biomass

Loading

(w/v)

Catalyst

and

contents

recovery

recovery

cellulose-

to-glucose

conversion

Enzyme loading

Time

Refer­

ence

190 °С

70 min

50 % ethanol/ water (v/v)

20 g/

200 ml

2 % NaOH

(w/v)

55.20%

80%

NA

75%

60 FPU cellulase 64 pNPGU (3- glucosidase/of pretreated material

72 h

[68]

Pinus contorta

170 °С

60 min

65 % ethanol/ water

200 gl 2L

1.1 %

h2so4

79%

~90 %

79%

NA

93-97 %

20 FPU cellulase 40 Ш |3- glucosidase/g ocellulose

48 h

[69]

Beech

184 °С

~100min

37.5 % cyclohexan/ water (v/v)

4g/

40 ml

95.00%

NA

NA

NA

61 %

420,000 FPU cellulase/g of pretreated material

30 h

[70]

Akamatsu pine

184 °С

~100min

37.5 % cyclohexan/ water (v/v)

4g/

40 ml

92.00%

NA

NA

NA

53 %

420,000 FPU cellulase/g of pretreated material

30 h

[70]

Bagasse

184 °С

~100min

37.5 %/ cyclohexan water (v/v)

4g/40ml

78%

NA

NA

NA

69%

420,000 FPU cellulase/g of pretreated material

30 h

[70]

sugarcane bagasse (49% cellulose, 15.8 % hemi — cellulose, 27.2 % lignin, 5.6 %

175 °С

60—90 min

50 % ethanol/ water (v/v)

500 gl 2.5L

1.5%

NaOH

(w/w)

NA

NA

NA

NA

9.3-13.9 g glucose per lOOg substrate

15-25 FPU/g biomass, xylanase 0-300 UFg biomass (3-glucosidase 100-250 IU/g biomass

24 h

[71]

14 Status and Perspective of Organic Solvent Based Pretreatment of Lignocellulosic… 323

composites [75], and even hydrocarbon products for blending with gasoline [76], owing to its unique high purity, low molecular weight, and abundance of reactive groups [21, 77].

However, the water-insoluble property of organosolv lignin may limit its appli­cations [78]. Therefore, conversion of the lignin dissolved in the organic solvents by catalyst or organic-solvent-stable enzymes may be a potential technological approach to resolve the problem [79-81].