Enzymes for Leather
One of the oldest applications of industrial enzymes is processing
hides and skins for leather. Hides and skins contain proteins
and fat in between collagen fibres and before tanning; these substances
should be partially and fully removed. The proteins can be removed
by proteases and lipases as well as other chemicals can remove
the fat. Today, proteases and lipases are mainly used for soaking,
bating and enzyme assisted un-hairing. Using lipases to dissolve
and remove fat is a recent development and lipases are now extensively
used for leather processing in many parts of the world.
Maps is a major supplier of enzyme to the leather industry in
India and across the globe. We offer total enzyme solutions for
bating, un-haring, degreasing and soaking in the beam-house processes.
With the introduction of our new range of products based on Microorganisms,
we assure to provide clean and green leather tanneries.
To make leather pliable, the hides and skins require an enzymatic
treatment before tanning know as bating. During bating, scud is
loosened and other unwanted proteins are removed. Bating de-swells
swollen pelts and prepares leather for tanning. It makes the grain
surface of the finished leather clean, smooth and fine. Bating
with enzymes is an indispensable operation of leather processing
to obtain best quality of leather and cannot be substituted with
a chemical process.
Traditional methods for bating employed manure of dog, pigeon
or hen. These were very unpleasant, unreliable and slow methods.
Bio-technical developments in science have now completely replaced
these methods with use of industrial enzymes.
Maps offers a range of proteases for bating which work in different
||Protease for bating in alkaline pH conditions
||Protease for bating in acidic pH conditions
Soaking is first important operation of leather processing. Hides
and skins received into a tannery are in the four conditions,
as green or fresh, as wet salted, as dry salted or as dried. It
is advisable to carry out soaking for all types of skin and hides
to obtain best quality leather. Soaking cleans hides and skins
by removing dirt, blood, flesh, grease, dung etc. and most importantly,
re-hydrates them to bring skins as far as possible back to state
of green hides. Soaking agents fall into three categories, like
Chemical Agents, Surface-active agents and Enzymatic agents.
Enzymatic agents are biocatalyst. Specific protease and lipase
enzymes enhance water uptake by dissolving intrafibrillary proteins
that cement fibres together and disperse fats and oils together
with dirt and other contaminants present on skin.
Maps offers a range of protease and lipase for soaking which work
in different pH conditions.
||A mixture of protease and lipase for soaking in alkaline pH conditions
|| A mixture of protease and lipase for soaking in acidic pH conditions
The conventional and most wide spread way to remove hair from
bovine hides is to use lime and sodium sulphide in a hair-burning
process. They dissolve the hair and open up the fibre structure.
Most importantly, enzyme-assisted un-hairing results in a cleaner grain surface and improved area yield and softness. The use of a specific protease also offers tanneries a number of options. For instance, the sulphide and lime requirements can be reduced by as much as 40% while maintaining the same liming time. Alternatively tanners can shorten the liming time by at least half without any loss of quality. Another possibility is to avoid the use of amines, which can be converted into carcinogenic compounds.
The hair-burning process is the most widespread but a better alternative to this, is the hair-saving process, which is environment friendly, where the hair is not dissolved but can be filtered out from the liming float. It is possible to reduce the COD up to 50% and BOD up to 30% in waste discharges.
Maps offers a specific protease for un-hairing which can be used
either alone or in combination lime and sodium sulphide
||Protease for un-hairing in high alkaline pH conditions
Lipases are a type of enzyme that specifically degrades fat
and so cannot damage the leather itself. Lipases hydrolyse not
just the fat on the outside of the hides and skins, but also the
fat inside the skin structure. Once most of the natural fat has
been removed, subsequent chemical treatments such as tanning,
re-tanning and dyeing have a better effect.
The main advantages of using lipases are a more uniform colour
and a cleaner appearance. Lipases also improve the production
of hydrophobic (waterproof) leather; makers of leather for car
upholstery have commented that 'fogging' is reduced. This is the
term for the build-up of a film of chemicals on the inside of
Lipases represent a more environmentally sound method of removing
fat. For bovine hides, lipases allow tensides to be replaced completely.
For sheepskins, which contain up to 40% fat, the use of solvents
is very common and these can also be replaced with lipases and
surfactants. Solvents tend to dry out the skin and give it a pale
If surfactants are used for sheepskins, they are usually not
as effective and may be harmful to the environment. Stronger surfactants
such as nonyl phenol ethoxylate have a better effect but they
are more detrimental to the environment. When using lipases, the
original surfactant dosage can be reduced by at least 50% in the
case of both sheepskins and pigskins. In addition, nonyl phenol
ethoxylate can be substituted with more biodegradable surfactants.
Maps offers a range of lipases for degreasing which work in different
||Lipase for degreasing in neutral to alkaline pH conditions
|| Lipase for degreasing in acidic pH conditions