A high percentage (80–90%) of all the leather manufactured today is tanned using
basic chromium sulphate (Cr(OH)SO 4 ) because chrome tanning produces light and
inexpensive leather of high thermal and bacterial resistance [44]. Although proteolytic and other enzymes are not used in the tanning process, their applications in the
previous stage significantly influence the quality of tanned leather.
7.3.3 Shaving
The shaving process is carried out to reduce or standardize the thickness of hide or
skin. Machines with a rapidly revolving cylinder are used to cut fine, thin fragments
from the flesh side of the skin to achieve uniformity. This process can be undertaken
on tanned or crusted leather. Small pieces of leather waste which are cut off are
called shavings. Solubilizing of the chrome shaving using proteolytic enzyme assists
in chrome recovery and solid waste management.
8 Protease in Bioremediation of Waste
Effluent discharges from tanneries create health hazards and environmental problems.
When raw hides and skins are processed to leather, a number of by-products such as
claws, scales, trimmings, tails, fleshings, pelt cuts, gluestock and tanned material such as
cuts, buffing dust, dyed and chrome shavings are obtained [3]. As a result, the industry
generates huge quantities of proteinaceous waste, chromium containing waste and
wastewaters which pose serious environmental and pollution problems. Currently, the
most common way practiced in the management of solid wastes is by tanneries disposing
them in landfills. The disposal of untreated wastes into land and water bodies from
tanneries results in air and water pollution as well as emission of greenhouse gases like
methane and carbon dioxide [46]. Chromium leaching into the soil and groundwater
makes it unfit for cultivation and other uses. Discharge of coloured wastewater contaminated with organic dyes from tanneries into natural streams has caused severe pollution
problems, such as increased toxicity, BOD, COD and TDS of the effluent and also
reduced light penetration, which has adverse effects on photosynthesis [47, 48].
Exploitation of enzymes in treatment of chrome-tanned leather shavings (CTLSs)
at a commercial level is not fully developed. Studies have shown that protein is the
main component of most of the CTLSs generated in tanneries [12]. However, due to
non-biodegradability of CTLSs, their disposal poses a major problem for the leather
industry. Enzymatic hydrolysis of CTLS is a viable method and provides a 50–60%
yield of hydrolysate, which shows low ash content and a low content of chromic
Alkaliphilic Enzymes and Their Application in Novel Leather Processing. . .
213
basic chromium sulphate (Cr(OH)SO 4 ) because chrome tanning produces light and
inexpensive leather of high thermal and bacterial resistance [44]. Although proteolytic and other enzymes are not used in the tanning process, their applications in the
previous stage significantly influence the quality of tanned leather.
7.3.3 Shaving
The shaving process is carried out to reduce or standardize the thickness of hide or
skin. Machines with a rapidly revolving cylinder are used to cut fine, thin fragments
from the flesh side of the skin to achieve uniformity. This process can be undertaken
on tanned or crusted leather. Small pieces of leather waste which are cut off are
called shavings. Solubilizing of the chrome shaving using proteolytic enzyme assists
in chrome recovery and solid waste management.
8 Protease in Bioremediation of Waste
Effluent discharges from tanneries create health hazards and environmental problems.
When raw hides and skins are processed to leather, a number of by-products such as
claws, scales, trimmings, tails, fleshings, pelt cuts, gluestock and tanned material such as
cuts, buffing dust, dyed and chrome shavings are obtained [3]. As a result, the industry
generates huge quantities of proteinaceous waste, chromium containing waste and
wastewaters which pose serious environmental and pollution problems. Currently, the
most common way practiced in the management of solid wastes is by tanneries disposing
them in landfills. The disposal of untreated wastes into land and water bodies from
tanneries results in air and water pollution as well as emission of greenhouse gases like
methane and carbon dioxide [46]. Chromium leaching into the soil and groundwater
makes it unfit for cultivation and other uses. Discharge of coloured wastewater contaminated with organic dyes from tanneries into natural streams has caused severe pollution
problems, such as increased toxicity, BOD, COD and TDS of the effluent and also
reduced light penetration, which has adverse effects on photosynthesis [47, 48].
Exploitation of enzymes in treatment of chrome-tanned leather shavings (CTLSs)
at a commercial level is not fully developed. Studies have shown that protein is the
main component of most of the CTLSs generated in tanneries [12]. However, due to
non-biodegradability of CTLSs, their disposal poses a major problem for the leather
industry. Enzymatic hydrolysis of CTLS is a viable method and provides a 50–60%
yield of hydrolysate, which shows low ash content and a low content of chromic
Alkaliphilic Enzymes and Their Application in Novel Leather Processing. . .
213