**5. Purification of cellulase**

It is an important step to remove any contaminants that are found to be present in the mixture. Hence, it is a vital step required for improving performance/ functioning of an enzyme. Enzymes in the culture supernatant could be purified by the conventional methods which include ammonium sulfate precipitation and dialysis followed by column chromatography [117]. The most common matrix for gel exclusion chromatography is the Sephadex with different pore sizes which is employed in the purification of cellulase [118]. The purification folds and % yield are the two most important factors which are used to evaluate the efficiency of purification. First step (ammonium salt precipitation) is based upon difference in protein solubility. The solubility of protein firstly increase and then starts decreasing with increase in salt concentration and finally protein gets precipitate. This

**71**

*Overview of the Process of Enzymatic Transformation of Biomass*

process is called Salting out [119]. Ammonium sulfate ((NH4)2SO4) is often used for this purpose because of its high solubility in water. Devi et al. [120] reported protein precipitation by addition of solid ammonium sulfate up to 80% saturation. Chen et al. [121] reported precipitation with (NH4)2SO4 at 40–60% saturation. Precipitation is followed by a concentrating step that separates proteins from salts called dialysis. For next step chromatographic technique is most widely used for the direct recovery of protein and other charged molecules. Various types of chromatography methods (gel filtration: Sephadex G-100 [73], ion exchange: DEAE-Cellulose [122] and affinity: swollen avicel [123] have been used for purification of

Different researchers reported different temperatures for maximum cellulase production. It is reported that the optimal temperature for cellulase production varies from strain to strain of microorganisms [69]. The optimum temperature of fungal cellulases ranges from 40 to 60°C and pH found to be 4.8. A battery of thermophilic fungal strains are known to produce thermostable enzymes which are stable and active at such high temperature which are not optimum for the growth of the microorganism. Filamentous fungi, e.g., *Talaromyces emersonii*, *Thermoascus aurantiacus* and *Chaetomium thermophilum* are reported to produce cellulases having high-cellulase activity at elevated temperature [124]. The Km value is used for the measurement of enzyme affinity towards the substrate. An increase in substrate concentration made more binding sites available for the enzymes to adhere and the rate at which product formation would be achieved therefore would be faster [125]. In literature, different ranges of Km and Vmax for different fungal species have been reported. Genetic variability may be a factor for the above reported variation [126]. Taha et al. [127] reported cellulase showing optimum activity at pH 6 and 50°C with

According to Sajith et al. [87] on the global enzyme market cellulases occupy the third place (i.e., ≈15%) after amylase (≈25%) and protease (≈18%). Cellulases are currently being produced on commercial scale by several industries all over the

Today, 90% of paper pulp is made of wood. Recycling one ton of newsprint and printing or copier paper saves about 1 ton and more than 2 tons of wood respectively [129]. Usually, the industrial process for eradicating wastepaper pollutants involves re-pulping, screening, cleaning, washing and flotation [130]. According to Shrinath et al. [131] the conventional recycling of waste papers is costly and hazardous to the environment due to the use of chemicals (hydrogen peroxide, sodium hydroxide and sodium silicate). Cellulases are mainly used for the pulping and deinking of waste papers. Enzymatic deinking as whole is an environmental friendly process [132]. Cellulase based pulping process is not only energy efficient, environment-friendly but also improve mechanical strength of the final paper product by improving the inter-fiber bonding [133]. When used with hemicellulases, cellulases improve the brightness and quality of the recycled paper [134].

with its corresponding Km value of 2.5 × 10<sup>−</sup><sup>5</sup>

g/l.

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

cellulase from various fungal strains.

**6. Characterization of cellulase**

(Vmax) of 75 g l<sup>−</sup><sup>1</sup>

min<sup>−</sup><sup>1</sup>

**7. Applications of cellulases**

**7.1 Paper and pulp industries**

mg<sup>−</sup><sup>1</sup>

world and widely used in various industrial applications [128].

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

process is called Salting out [119]. Ammonium sulfate ((NH4)2SO4) is often used for this purpose because of its high solubility in water. Devi et al. [120] reported protein precipitation by addition of solid ammonium sulfate up to 80% saturation. Chen et al. [121] reported precipitation with (NH4)2SO4 at 40–60% saturation. Precipitation is followed by a concentrating step that separates proteins from salts called dialysis. For next step chromatographic technique is most widely used for the direct recovery of protein and other charged molecules. Various types of chromatography methods (gel filtration: Sephadex G-100 [73], ion exchange: DEAE-Cellulose [122] and affinity: swollen avicel [123] have been used for purification of cellulase from various fungal strains.
