ABSTRACT

A major producer of wet blue leather suddenly started experiencing outbreaks of mold growth in the wet blue stock after only a few days of storage and despite the proper use of a leading TCMTB fungicide. The fungicide supplier was unable to solve the mold problem, and the tannery consulted Zenith Industrial Chemicals for assistance. Zenith conducted thorough investigations on-site at the tannery operation and in Zenith’s laboratories. They identified the problem as being caused by an uncommon strain of fungus against which TCMTB has limited effectiveness. Zenith made the recommendation to use a new fungicide from their range of products which is based on novel technology and has efficacy against a wider range of fungal species. The Zenith product was tried in production and was found to effectively prevent all fungal growth on the wet blue leather. The tannery switched all of their production to the new product and the fungal problem was solved. They have not experienced any further outbreaks of mold in their wet blue leather for over six months since they changed to the Zenith product.

MOLD OUTBREAK

An important producer of quality wet blue leather in Northern India processes 150,000 pieces of sheepskin and goatskin from raw to wet blue per month and supplies quality wet blue leather to numerous big name customers. This company was using a leading fungicide based on 2(thiocyanomethylthio) benzothiazole (TCMTB). This solvent-based formulation contains 30% active TCMTB and was applied at the rate of 0.12%. This treatment level had been sufficient to provide adequate protection against mold growth for several months under the conditions present.
In early 2007 the tannery started seeing mold growth on some of the wet blues after a few weeks of storage. Tannery staff reacted immediately to seek advice from the supplier on the possible cause of the problem. No satisfactory corrective action was offered by the supplier and the problem worsened to the point that mold started appearing only days after the wet blues were produced. The tannery then consulted Zenith to try to help solve this serious and worsening problem.

INVESTIGATION OF ROOT CAUSE

Upon invitation by the tannery’s management, Zenith technicians visited the tanning operation for the purpose of identifying the root cause of the fungal outbreak problem. Initial investigation focused on the tanning process in order to uncover possible contributing factors. However, this disclosed nothing unusual or suspect.
Zenith then conducted a microbiological survey of the tannery and the storage areas, with particular emphasis on identifying sources of mold contamination. High levels of fungal contamination can contribute to higher levels of fungicide being required. Therefore, good housekeeping is important in the tannery to keep contamination levels low. Air sampling was also done throughout the operation and airborne fungal spore counts were determined. The microbiological survey revealed only low levels of contamination. Furthermore, no areas were found with actively growing mold. Thus, high fungal contamination levels in the operation were definitely not a factor that could have contributed to the fungal outbreak. On the contrary, except for the wet blue leather itself, the tannery and storage areas had very low levels of fungal activity, indicating good housekeeping was being done.

Despite the low level of contamination found, a sanitation procedure was carried out throughout the plant with a fungicidal sanitizer. All key areas were sprayed with this sanitizer to eradicate any fungus that may be present.
Several samples of molded skins were also taken from different areas and sent to Zenith’s laboratories for detailed microbiological analysis.

FINDINGS

The fungi present on the molded wet blue samples were cultured in Zenith’s laboratory to qualitatively and quantitatively analyze the different fungi present on the leather. Each fungus present was identified as to its type and as to the relative degree of its presence.
The analysis revealed the presence of three different types of fungi: Aspergillus niger, Aspergillus tamari and Trichoderma sp., most likely Trichoderma viride. Aspergillus species are commonly found on leather. However, Trichoderma is far less common.
In terms of their relative degree of presence, Trichoderma was 90%, Aspergillus tamari was 7% and Aspergillus niger was 3% of the fungus mix found on the leather.
This analysis provided Zenith with the answer to the root cause of the mold outbreak, namely the presence of Trichoderma in the tannery. It is known that TCMTB is not very effective against this particular type of fungus, and therefore very high concentrations of TCMTB are required to have any effect on this fungus. Consequently, normal dosage levels of a 30% TCMTB fungicide have little or no effect to control the growth of this mold. In a similar case at another tannery, increasing the dosage of 30% TCMTB up to 0.7% did not control an outbreak of Trichoderma.

SOLUTION

Since the fungus on the wet blues was found to be composed almost completely of Trichoderma, the solution to this problem was to apply a fungicide that has good efficacy against this strain, as well as against the other fungal species known to attack leather.
Zenith recommended that the tannery try Zenith 399, the company’s newest fungicidal product. This product has a broader spectrum of activity than TCMTB fungicides. In other words, Zenith 399 is effective at controlling more different types of mold, and it is very effective against Trichoderma.
The tannery evaluated Zenith 399 by first running one batch with the product. It was applied at the same dosage level of 0.12%. Cuttings were given to Zenith for fungal resistance testing compared to cuttings from wet blue made using the TCMTB product. Zenith’s laboratory test results showed the wet blue with Zenith 399 had significantly better fungal resistance. In addition, the tannery’s own evaluations, keeping the wet blues from this batch isolated for observation in their storage area, revealed that none of the pieces developed any mold growth.
After concluding the evaluations, it was clear that Zenith 399 was the solution to the problem, and the tannery converted from the TCMTB fungicide to Zenith 399. This change was implemented around June 2007. Up to the writing of this paper (January 2008) all of the tannery’s wet blue production has remained completely free of mold growth through the use of Zenith 399.

CONCLUSION

This case study documents how a fungal outbreak can occur suddenly and unexpectedly in a tanning operation, despite good housekeeping practices and despite the proper use of an established fungicide, and cause major disruption to the operation and the inability to bring the outbreak under control. This case also illustrates that certain types of fungi, like Trichoderma, which are not commonly found in tanneries, can easily find their way into the tannery and then readily attack the leather. They may enter the tannery on the wooden pallets on which the leather will be stacked, stored and shipped; or on the rope used to tie the leather; etc. Therefore, a good fungicide for use in leather should ideally have efficacy against a wide range of fungi and not just against the common types normally found in tanneries. In this case, the uncontrollable mold outbreak occurred because the fungicide that was in use (TCMTB) is not very effective against the fungal species Trichoderma that found its way into the tannery. This case also documents that the fungicide Zenith 399 has a broader spectrum of fungicidal activity and was able to effectively control the common fungi present in the tannery as well as the “wild strain” Trichoderma that was responsible for the mold outbreak which could not be controlled by the TCMTB fungicide.

ABOUT ZENITH 399

Zenith 399 is a “new generation” fungicide developed by Zenith and first introduced commercially in selected leather markets in late 2006. The product is 100% TCMTB-free and offers several important benefits for tanners.
While TCMTB has been the widely used standard in the leather industry since the seventies, it does possess certain drawbacks. Consequently, chemical companies have long been attempting to develop the next generation of fungicide that could replace TCMTB without the drawbacks.
Zenith 399 is one of a series of new Zenith products based on azole antifungal technology. Azole derivatives are the most rapidly expanding group of antifungal agents. Major developments in research into the azole class of antifungal agents took place during the 1990s and these have provided expanded options for the treatment in humans of many fungal problems in the form of orally taken antifungals as well as topical creams. Besides their application in pharmaceuticals, this group of antifungal agents also has utility in industrial applications, such as the protection of processed hides and finished leather against fungal attack.
Zenith 399 was developed using the latest formulation technology from the pharmaceutical industry to render greater eco-friendly characteristics than traditional industrial fungicide products. Unlike TCMTB formulations, Zenith 399 does not have a strong irritating odor and is user-friendly in terms of its near odorless character for tannery staff who may work in proximity of open containers of the chemical. The product is also far less aggressive to the skin.
Full-scale comparative tannery trials, stringent longterm fungal resistance studies and successful commercial use by scores of tanneries have proven Zenith 399 possesses a broader, more effective spectrum of activity than TCMTB formulations.
Zenith 399 is recommended at the same dosage levels as 30% TCMTB formulations. However, at equal dosage levels, Zenith 399 exhibits better fungicidal effectiveness.
Zenith 399 is now commercially available from ZENITH in many areas. The company offers free fungal resistance testing of leathers using its ASTM tropical chamber method.