Table 1 Pretreatment methods of lignocellulose

Physical pretreatment

Ultrasonic pretreatment, steam pretreatment, explosion pretreatment, etc.

Simple principle; convenient operation, high energy consumption, and high cost

Succinic acid (45.7 kg/100 t)

Glucose (89.55%)

[98]

[99]

Chemical pretreatment

Acid pretreatment, alkaline pretreatment, Ionic liquid pretreatment, etc.

Simple operation; high efficiency; potential secondary pollution

Succinic acid (71%)

Succinic acid (63.8%)

Succinic acid (57.1%)

[100]

[101]

[102]

Biological pretreatment

Germ pretreatment, fungus pretreatment, enzyme pretreatment, etc.

Time-consuming; pollution-free; mild conditions; low energy consumption

Lignin removals (38.7%)

Free carbon (97%)

Enzyme activity (5.6–24.0 U/g)

[103]

[104]

[105]

Combined pretreatment

Physicochemical pretreatment, biochemical pretreatment, etc.

High efficiency; low cost and energy consumption; environment- friendly

Succinic acid (79.0%)

Succinic acid (83.0%)

Succinic acid (19.3 g/L)

[42]

[106]

[107]