The bating process renders leather soft and pliable. For example, glove leather is highly bated whereas shoe sole leather is not bated at all. Traditional trypsin, a proteolytic enzyme extracted from the pancreas of animals, still dominates the bating enzyme market. The alternative is microbial enzymes made by fermentation and Novozymes is a leading supplier of these types of enzyme to the leather industry.

Advantages of the new enzymes  Mild and gentle bating Excellent scud loosening Fine and delicate grain High-quality leather

For many years, Pyrase® has been the major microbial enzyme sold for bating by Novozymes. However, Pyrase is not suitable for all bating applications due to the inherent nature of the enzyme action. Pyrase is not suitable for small skins, especially goat, and for leathers like floaters that require a more uniform grain pattern.

In future, Pyrase will continue to be sold for special applications, but in addition Novozymes is introducing two far more gentle and versatile enzymes for bating. The mildest is NovoBate 115 whereas new NovoBate 100 has been developed for a slightly speedier and more powerful bating effect. The new NovoBate products can be used to bate any type of hide or skin and they result in high-quality leather with a firm and delicate grain and they also give excellent scud loosening.

Safety issue
One of the advantages of microbial enzymes over trypsin is that they do not originate from an animal source and there is therefore no need for a health certificate. There is a risk of infection when animal bates are being handled in a tannery. Unless they are sterilised, the bates may contain pathogenic bacteria.

There is also a risk of cross-infection if tannery workers inadvertently take home traces of the bates on their clothing and then come into contact with livestock.

Another advantage is that microbial enzymes have a highly standardised activity that improves the quality of the final formulation.

Three kinds of evaluation were made: Bating effect (scud removal, float colour, thumb mark, etc.) DIN tests (lastometer, tear strength, tensile strength and elongation at break) General leather quality of crust (grain quality, colour uniformity, softness) A similar bating effect was achieved with a dosage of approximately 22,000 MTU per kg of pelt. A higher dosage may improve the bating process without damaging the quality of the final leather.

Trial results
The effect of NovoBate 115 was tested in a series of trials performed in collabor­ation with the famous Reutlingen Leather Research Institute in Germany. The enzyme was applied in a standard bating process (100% float, pH 8-8.5, 30°C for 45 minutes) compared to a bating process using a standard pancreatic trypsin product on bovine pelt for shoe uppers.

The figure shows the scores relative to those obtained by using the standard pancreatic bating enzyme. The new microbial enzyme is comparable in performance to trypsin at a dose rate of 22,000 MTU per kg of pelt and gives an even better bating performance at higher doses.

Arranging a trial
Tanneries are invited to test the two new approved bating enzymes that were first launched in June 2006 and are currently being used by a number of tanneries. Novozymes recommends using a prolonged bating process at normal bating pH and temperature in order to achieve a complete reaction, i.e. 60 to 90 minutes for tighter leathers and 120 minutes or longer for soft articles. With the new bating concept from Novozymes, a real bating effect can be obtained on all leathers.

Novozymes’ Customer Solutions experts around the world or local formulators can be on hand to offer technical support for a trial. They can advise on the optimal dosage and reaction time because the dosage is highly dependent on the raw material and the article to be produced. A good trial result will convince tanners that there is a viable and safe alternative to trypsin.