Specificities of proteases for use in leather manufacture

Proteases are used in leather manufacture in the processes of soaking, unhairing and bating of hides and skins. However proteases can be relatively non-specific in their usage, and for improved efficacy of enzyme biocatalysis within the industry, an analysis of specific activities of enzymes towards skin proteins was undertaken. Most commercial proteases for soaking showed substantial activity against the substrates elastin-Congo Red and Azocoll but little or no activity against keratin-azure and hide powder black. Enzymes used for unhairing in conjunction with 30% of the usual concentration of sulfide to effect chemical unhairing showed moderate activity against all substrates tested (selected as representative of skin proteins), while proteases used in bating showed activity against Azocoll and elastin-Congo Red but had no keratinase activity and little activity against hide powder black. Bating proteases and soaking proteases displayed similar activities at pH 8. Microbes isolated in the screening of organisms from putrefied skins included one fungal and two bacterial isolates whose extracellular enzymes had efficient unhairing activity without the addition of sulfide. Enzyme activities for these proteases included high activity measured against Azocoll with little or no activity against elastin-Congo Red, keratin-azure and hide powder black. Neither elastase nor keratinase activities were determined as being essential for unhairing. (c) 2005 Society of Chemical Industry