FUNGAL BIOTRANSFORMATION OF BOVINE HAIR: ASSESSMENT OF STRUCTURAL CHANGES

摘要

The hair-saving unhairing process generates another solid waste in the beamhouse area, regardless of the process used. Changes in unhairing technology have altered the problem of the high organic load and suspended solids of the beamhouse liquid effluent into a new problem: the disposal of the concentrated hair waste. Given that daily generation of 'hair waste' is considerable (approx. 2.5 tons per 1000 salted bovine hides processed) and that this waste can be considered as a raw material due to its physical and chemical properties, it is interesting to orientate our activities towards the investigation and development of technological alternatives to facilitate adding value. A typical analysis of the 'hair waste' after a hair saving unhairing process is within the following ranges. Total solids: 25-30%, total nitrogen: 11-15%, Ca~(++): 2-3%, Na~+: 1-2%, S: 3-5%, (% moisture-free basis), sulphides: 80-100mgH_2S/kg of recovered wet hair (filtered and drained, moisture 75%). The relevant organic component of the hair is the fibrous keratin protein which is very resistant to hydrolysis by chemical-physical and biological methods. Keratin has high stability as a consequence of the disulphide bridges of cysteine amino acid between adjacent protein chains. Biodegradation of hair by fungi is among the relevant alternatives to add value to 'hair waste'. Using the waste as a solid substrate for fungal growth, a higher bioavailability is achieved for further use in agricultural technology for example. Moreover, this process offers the attractive concept of 'feedback', because biodegradation generates an enzymatic extract with potential applications in leather technology.