270

17 Utilization of Microbial Potential for Bioethanol Production from Lignocellulosic Waste

Table 17.1

(Continued)

Sl. No. Pretreatment

Nature

Intermediate

operation

Advantages

Disadvantages

References

9.

Ammonium

fiber

explosion

Physico-

chemical

Liquid

ammonia at

high pressure

and

temperature

Swelling and

phase change in

cellulose

crystallinity,

modification of

lignin to increase

water holding

capacity and

degradability

Ammonia

could be

recovered, no

inhibitor

formation

[10]

10.

Whole cell or

enzyme

mediated

Biological White-rot fungi,

Brown-rot

fungi, bacteria,

and archaea

Energy efficient,

lignin and

hemicellulose

degradation,

economically

sound

Lower

hydrolysis rate

[2]

sugarcane bagasse rice straw, bamboo, wheat straw, cotton stalk, and sugarcane tops

are a few of the largely available agro-wastes. Most of these by-products are used for

the production of bioethanol [4].

Pretreatment of bioethanol generally uses bacterial strains or their enzymes. This

strategy is attracting consideration because of its capacity to work in the moderately

shorter response time, not only that, but also it needs low sustenance prerequisite

for the enzymatic responses [6, 8]. A few microorganisms, for example, Clostridium

sp., Cellulomonas sp., Bacillus sp., Thermomonospora sp., Streptomyces sp. and so

forth., and a few parasites such as Phanerochaete chrysosporium, Trichoderma reesei,

Trichoderma viride, Aspergillus niger are generally utilized in natural pretreatment

process [7, 9]. By utilizing the sugars, cellulose and hemicellulose degrading

microorganisms typically hydrolyze the complex molecules to monomeric sugars

[10]. Most significant benefits of natural strategies incorporate no compound

reusing after pretreatment, lower downstream handling charges, least inhibitor

arrangement, straightforward working, and lower vitality utilization [11]. In any

case, the amazingly low pace of hydrolysis is the principle hindrance in creating

bioprocessing (BP) strategies [12]. Furthermore, microscopic organisms can create

hydrolytic and oxidative catalysts which can break down unbending structures

of LCBs. Cellulase is the enzyme that is primarily added, and then 𝛽-glucosidase

and xylanase are added [13]. In light of the past investigations, enzyme-mediated

pretreatment improves the methane content more than 100%; consequently, the

viability of enzymatic pretreatment is dictated by various elements [14].

Fungal pretreatment requires higher brooding time, while enzymatic and bacterial

pretreatments need a couple of hours to end. Contagious pretreatment diminishes

the unmanageability of structure of LCBs [15]. For instance, Trametes versicolor has

been utilized for BP of grain harvests, for example, wheat, rye, and grain before