Classifications

• • C—CHEMISTRY; METALLURGY
  • C14—SKINS; HIDES; PELTS; LEATHER
  • C14C—CHEMICAL TREATMENT OF HIDES, SKINS OR LEATHER, e.g. TANNING, IMPREGNATING, FINISHING; APPARATUS THEREFOR; COMPOSITIONS FOR TANNING
  • C14C1/00—Chemical treatment prior to tanning
  • C14C1/06—Facilitating unhairing, e.g. by painting, by liming
  • C14C1/065—Enzymatic unhairing

Definitions

• the invention relates to a microbial process for the production of pelts from animal skin using agents which have been obtained from lactic acid bacteria.
• Obtaining bare skin from animal hides and skins consists, on the one hand, of depilation, and, on the other hand, of a skin disruption.
• epidermis made of keratin and non-collagen components from the hair follicles are also removed.
• Aqueous solutions of sodium sulfide (called sulfur sodium) and lime are used throughout.
• concentrations of more than 1% sodium sulfide or, if appropriate, proportions of sodium sulfhydrate the hair and all other keratinous components are destroyed and rubbed off as a slimy, structureless mass when treating the skins in the barrel.
• the keratin of the hair roots is preferably attacked, so that the more or less well-preserved hair can be mechanically stripped off on a machine. This formerly very common procedure is hardly used today for reasons of rationalization.
• Sulfide is a poison.
• the destroyed hair represents the greatest pollution of the wastewater of the tanneries with organic matter.
• the lime - always used in excess - produces high insoluble components and requires considerable effort to neutralize the high alkalinity. For these reasons alone, we are looking for other techniques for the extraction of bare skin.
• Hair can also be loosened by using proteolytic enzymes in such a way that you can either roll it off in the barrel or slide it down on the machine. Frequently, however, parts of sulfide are also used with the enzymes acting in the alkaline region, so that eventually hair breakdown also occurs.
• Oxidative hair removal as e.g. In practice, when using sodium chlorite in an acidic area, peracetic acid or sodium peroxide in an alkaline area have not become established.
• the problems in the production of ready-to-tan pelts are not only of a purely technological nature: the microbiological attack on the skins represents at least a latent danger.
• the microorganisms, in particular the bacteria, can be detrimental to the point of irreversible damage to the skin quality enzymes released to the microorganisms are responsible.
• the softened animal hides or skins are treated in a liquor which contains depilatory agents from lactic acid bacteria and the hair is removed in a manner known per se.
• an aqueous liquor which contains a culture of lactic acid bacteria.
• the depilatory agents obtained from lactic acid bacteria in a fleet which is free of lactic acid bacterial cells.
• the lactic acid bacteria to be used according to the invention are Laetobacteriaceae, in particular of the homofermentative type. These belong to the 16th group according to "Bergey's Manual of Determinative Bacteriology", 8th Edition (Ed. R.E. Buchanan & N.E. Gibbons, William & Wilkins, Baltimore). Lactobacillus species, especially Lactobacillus plantorum, are mentioned. (See Kirk-Othmer 3rd Ed. Vol. 13, 84, J. Wiley, 1981; H.-J. Rehm & G. Reed in "Biotechnology", Vol. 1, pg. 185; Vol. 3, pg. 411-418, Verlag Chemie
• the culture of the bacteria is favored by relatively high temperatures, i.e. approx. 30 ° C and above.
• Bacteria grow between 20 and 40 ° C, preferably the bacterial cultures according to the invention are used at a temperature of 33 + 3 ° C.
• lactic acid in the tannery has a tradition in decalcification.
• aqueous infusions of carbohydrate-containing substances that had passed into fermentation were used.
• Lactic acid fermentation is also a classic Side effect of herbal tannin extracts, in which yeast and mold growth have always occurred as an undesirable side effect.
• the pellet and bran stains, which were used for fur production are particularly noteworthy.
• the lactic acid has a kind of pimple effect.
• all of these uses have nothing to do with the process according to the invention, which is a substitute for the mostly alkaline liming process.
• Lactic acid bacteria have been used in food technology - in the dairy, vegetable and meat industry - since time immemorial and are also very widespread in nature. The production of vaccine cultures is also known. (See H.J. Rehm & G. Reed in "Biotechnology", Vol. 5, Verlag Chemie, 1983).
• the production and treatment of the lactic acid bacterial culture is based on and using the experience of the latter prior art. These bacteria are known to use carbohydrates for nutrition.
• the bacterial growth in the liquor is preferably started first. Ideal growth conditions are created by setting a temperature of 33 + 3 ° C, approx. 35 ° C as a guideline, and providing bacterial food. Lactose or lactose-containing, fermentatively usable products such as e.g. Whey, for example in proportions of 0.5 to 3% by weight. Has proven successful the use of a whey solution (as it is produced) that has been diluted to 3 times the volume.
• the liquor which contains the lactic acid bacterial culture is advantageously added with salts which promote bacterial growth, in particular in amounts of 0.1 to 1.5% by weight, based on the liquor.
• These salts generally contain sodium and / or potassium as the cation and chloride and / or phosphate, sulfate, carbonate in addition to lactate as anions.
• the liquor can also contain the depilatory agents obtained from the lactic acid bacterial cells in a manner known per se. The preparation takes place in accordance with this depilation effect.
• An advantageous embodiment of the present method also sees the presence in the fleet of agents which prevent yeast and mold growth, so that no undesired proteolytic activity of other microorganisms can spread, for example by adding parahydroxybenzoic acid, sorbic acid or propionic acid.
• the lactic acid environment created by the fermentation of sugars at pH values between 3.5 and 4.0 also prevents the spread and growth of almost all of the skin normally contaminating bacteria, so that the lactic acid bacteria monoculture alone, which is effective here, can spread freely.
• the well-soaked animal hides and skins are treated in the fleet described above, which contains depilatory agents from lactic acid bacteria in the form of the lactic acid bacterial culture itself and / or depilatory agents outside of (viable) lactic acid bacterial cells.
• the vessels and devices usually used for depilation are preferably used (cf. F. Stather, Gerschenemie und Gerfertechnologie, 4th edition, Akademie-Verlag, Berlin, 1967). It is advantageous to move occasionally.
• the duration of treatment usually extends over several days, for example 2 to 3 days.
• the pH of the liquor is advantageously kept at 3.5 to 5, preferably 3.5 to 4.3, especially 3.5 to 4.0. Then the hair is completely removed mechanically. The hair remains intact and can be used for other purposes. The excess acid production is counteracted by adding alkalis. Suitable are e.g. Sodium hydroxide solution, calcium carbonate or magnesium carbonate.
• Hair-free pelts can be chromed without any further treatment or, advantageously, are given a slight oxidative or reductive post-scrubber before chroming.
• a great advantage is that such skins do not swell during this treatment, that is to say do not show any scarring, and that they are mechanically protected because the skins only have to be moved occasionally during the treatment. At the same time, skin disruption takes place to the desired extent.
• the result is extremely surprising and is based on the selective digestion of carbohydrate components in the skin and in the basal layer of the epidermal cells and hair follicles. It is e.g. well known that the basement membrane contains a significant amount of proteoglycan. The same applies to the skin - especially in the scar layer - which contains keratin sulfate, dermatan sulfate and chrondroitin sulfate. However, it was not foreseeable that the removal of these substances would have such an effect. Of course, aqueous liquors containing lactic acid have no effect.
• chromium tanning agent of conventional type with 25% chromium oxide is added and the tanning is ended after 6 to 8 hours.
• Example 1 1000 kg of salted beef skins are - as in Example 1 - soaked, treated with a lactic acid culture and dehaired by machine after 3 days. Then the pelts are agitated in 3 m 3 of a bath containing 100 kg of hydrated lime in a barrel for 2 hours, then 50 kg of sodium sulfate are added and agitation is continued for 30 minutes. It is cremated for 24 hours - with only occasional movement. It is then washed, fleshed, split, pickled and, as in Example 1, chrome-tanned as usual.
• Example 1 1000 kg of salted beef skins are - as in Example 1 - soaked, then they are treated in 2 to 5 m 3 of a liquor, half of which consists of a previously used liquor, the lactobacillus treatment.
• the liquor is filled up with whey and water so that the whey portion of the total liquor is 33%.
• 20 to 100 liters of seed culture and 1 to 2.5 kg of sorbic acid are added and the reaction with the skins is started at 35 ° C.
• the work continues as in Example 1.
• the fermentation broth contains amino acids or proteins such as casein, collagen or gelatin or ammonium sulfate as the carbon source instead of the substrate "skin” as a carbon source, as mentioned lactose or other carbohydrates, as a nitrogen source.
• amino acids or proteins such as casein, collagen or gelatin or ammonium sulfate as the carbon source instead of the substrate "skin” as a carbon source, as mentioned lactose or other carbohydrates, as a nitrogen source.
• trace elements and vitamins are also added.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Cosmetics (AREA)
• Treatment And Processing Of Natural Fur Or Leather (AREA)
• Medicines Containing Material From Animals Or Micro-Organisms (AREA)

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Cited By (5)

Citations (3)

• 1984
  • 1984-10-27 DE DE19843439490 patent/DE3439490A1/de not_active Withdrawn
• 1985
  • 1985-10-23 EP EP85113439A patent/EP0180135A3/fr not_active Withdrawn

Patent Citations (3)

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