**Abstract**

Cellulase is an enzyme which depolymerizes the cellulose into glucose. Cellulases are produced by a diverse array of microbes including fungi, bacteria, yeast and actinomycetes. Considerable research for understanding the mechanism of cellulases began in early 1950s because of the significant use of these enzymes in various industries. This review provides a general account structure and availability of lignocellulosic biomass, pretreatment strategies for effective digestion, cellulase producing organisms, cellulase activity assay, and enzymology of cellulose degradation. Cellulase production, optimization, purification and characterization studies in addition to the industrial application of cellulase have also been discussed. At last a brief account of present market scenario of cellulases and future prospects of the study are also taken into account.

**Keywords:** cellulases, lignocellulosic biomass, fungi, pretreatment

### **1. Introduction**

Cellulases are inducible enzymes which breakdown cellulose (the most widely available source of fermentable sugars on earth) into glucose and synthesized during the growth of microorganisms on cellulosic substrates [1, 2]. Cellulase is biotechnological important enzyme due to various industrial applications including biofuel production [3]. Variety of microorganism having cellulose degrading capability, few of them produce considerable quantity of extracellular enzymes. Fungi are the main cellulase producing microorganisms. *Trichoderma* and *Aspergillus* are found to be most potent cellulase producers, to be used for agricultural and industrial purpose [4, 5].

A large number of industries are based upon the agricultural raw materials and it alone accounts for about 10% of the total wages from export. At present, in terms of agricultural production, country holds 2nd position in world (http://www.agrifest.in/aboutagrifest.php). Availability of lignocellulosic

biomass varies from one region to another region in our country because of specific patterns of cultivation of crops in different regions. As estimated by the Ministry of New and Renewable Energy (MNRE), Report 2009, Government of India (GOI) every year about 500 Mt/yr residues are generated in India. Out of total residue generated, highest contributor is Utter Pradesh (60 Mt/yr), followed by Punjab (55 Mt/yr) and Maharashtra (46 Mt/yr). Among different crops, cereals crops contribute for the generation of 352 Mt residue followed by fiber crops (66 Mt/yr), oilseed (29 Mt/yr), pulses (13 Mt/yr) and sugarcane (12 Mt/yr). Among the cereal crops up to 70% is contributed by rice, wheat, maize and millets. Rice crop alone accounts for 34% followed by wheat contributing 22% of total residue generated by cereal crops. As depicted above, out of total residues generated from all crops, 13% is contributed by fiber crops. Among fibers, cotton holds 1st position by generating 53 Mt/yr (11% of crop residues) and coconut ranks 2nd with 12 Mt/yr of residue generation. The sugarcane residue (foliage and tops) generates 12Mt/yr, i.e., 2% of crop residues (**Figure 1**) (www.nicra.iari.res.in/Data/FinalCRM.doc).

The amount of crop residues, which have not any valuable uses is either left in the fields to rot or burnt away as such, is termed as surplus biomass. A brief idea about the amount of residue generated in different states of India, surplus residues left behind after conventional use, residue burned as reported by IPCC and [6] is shown in **Table 1**. Two reports dictated the burnt surplus agricultural biomass approximately 83.66 Mt/yr and 92.81 Mt/yr respectively. The data from two reports vary by 11% and this difference can be due to the climatic conditions, geographic separation, sample size and time of sampling used in above mentioned studies. However, in comparison to the total surplus residues, observed difference can be considered as insignificant. Besides biomass a massive quantity of industrial residues is disposed off as such in environment generating pollution and other related problems [7]. This huge amount of lignocellulosic biomass can likely be converted into different valuable products including biofuels, cheap energy sources for microbial fermentation, enzyme production and useful fine chemicals [8].

**59**

**Table 1.**

**2. Lignocellulosic biomass**

Lignocellulosic biomass is consist of cellulose, hemicelluloses, lignin, water, protein and other compounds (**Table 2**). Cellulose and hemicelluloses provide strength

to fiber and lignin act as the concrete which hold the fibers [9].

*Residue generated, surplus and burned (www.nicra.iari.res.in/Data/FinalCRM.doc).*

*Overview of the Process of Enzymatic Transformation of Biomass*

**(MNRE, 2009)**

**Residue surplus (MNRE, 2009)**

Andhra Pradesh 43.89 6.96 5.73 2.73 Arunachal Pradesh 0.4 0.07 0.06 0.04 Assam 11.43 2.34 1.42 0.73 Bihar 25.29 5.08 3.77 3.19 Chhattisgarh 11.25 2.12 1.84 0.83 Goa 0.57 0.14 0.08 0.04 Gujarat 28.73 8.9 6.69 3.81 Haryana 27.83 11.22 5.45 9.06 Himachal Pradesh 2.85 1.03 0.20 0.41

Jharkhand 3.61 0.89 1.11 1.10 Karnataka 33.94 8.98 2.85 5.66 Kerala 9.74 5.07 0.40 0.22 Madhya Pradesh 33.18 10.22 3.46 1.91 Maharashtra 46.45 14.67 6.27 7.41 Manipur 0.9 0.11 0.14 0.07 Meghalaya 0.51 0.09 0.10 0.05 Mizoram 0.06 0.01 0.01 0.01 Nagaland 0.49 0.09 0.11 0.08 Orissa 20.07 3.68 2.57 1.34 Punjab 50.75 24.83 8.94 19.62 Rajasthan 29.32 8.52 3.58 1.78 Sikkim 0.15 0.02 0.01 0.01 Tamil Nadu 19.93 7.05 3.55 4.08 Tripura 0.04 0.02 0.22 0.11 Uttarakhand 2.86 0.63 13.34 21.92 Uttar Pradesh 59.97 13.53 0.58 0.78 West Bengal 35.93 4.29 10.82 4.96 India 501.76 140.84 83.66 92.81

**Mt/yr**

1.59 0.28 0.35 0.89

**Residue burned (IPCC coeff.)**

**Residue burned [6]**

*DOI: http://dx.doi.org/10.5772/intechopen.85036*

**States Residue generation** 

Jammu and Kashmir


#### *Overview of the Process of Enzymatic Transformation of Biomass DOI: http://dx.doi.org/10.5772/intechopen.85036*

*Elements of Bioeconomy*

(www.nicra.iari.res.in/Data/FinalCRM.doc).

biomass varies from one region to another region in our country because of specific patterns of cultivation of crops in different regions. As estimated by the Ministry of New and Renewable Energy (MNRE), Report 2009, Government of India (GOI) every year about 500 Mt/yr residues are generated in India. Out of total residue generated, highest contributor is Utter Pradesh (60 Mt/yr), followed by Punjab (55 Mt/yr) and Maharashtra (46 Mt/yr). Among different crops, cereals crops contribute for the generation of 352 Mt residue followed by fiber crops (66 Mt/yr), oilseed (29 Mt/yr), pulses (13 Mt/yr) and sugarcane (12 Mt/yr). Among the cereal crops up to 70% is contributed by rice, wheat, maize and millets. Rice crop alone accounts for 34% followed by wheat contributing 22% of total residue generated by cereal crops. As depicted above, out of total residues generated from all crops, 13% is contributed by fiber crops. Among fibers, cotton holds 1st position by generating 53 Mt/yr (11% of crop residues) and coconut ranks 2nd with 12 Mt/yr of residue generation. The sugarcane residue (foliage and tops) generates 12Mt/yr, i.e., 2% of crop residues (**Figure 1**)

The amount of crop residues, which have not any valuable uses is either left in the fields to rot or burnt away as such, is termed as surplus biomass. A brief idea about the amount of residue generated in different states of India, surplus residues left behind after conventional use, residue burned as reported by IPCC and [6] is shown in **Table 1**. Two reports dictated the burnt surplus agricultural biomass approximately 83.66 Mt/yr and 92.81 Mt/yr respectively. The data from two reports vary by 11% and this difference can be due to the climatic conditions, geographic separation, sample size and time of sampling used in above mentioned studies. However, in comparison to the total surplus residues, observed difference can be considered as insignificant. Besides biomass a massive quantity of industrial residues is disposed off as such in environment generating pollution and other related problems [7]. This huge amount of lignocellulosic biomass can likely be converted into different valuable products including biofuels, cheap energy sources for microbial fermentation, enzyme production and useful fine

*Contribution of various crops in residue generation (www.nicra.iari.res.in/Data/FinalCRM.doc).*

**58**

**Figure 1.**

chemicals [8].

#### **Table 1.**

*Residue generated, surplus and burned (www.nicra.iari.res.in/Data/FinalCRM.doc).*
