Enzymatic hydrolysis of gelatin layers of X-ray films and release of silver particles using keratinolytic serine proteases from Purpureocillium lilacinum LPS # 876

CAVELLO, IVANA; HOURS, ROQUE ALBERTO; CAVALITTO, SEBASTIÁN FERNANDO

JOURNAL OF MICROBIOLOGY AND BIOTECHNOLOGY

KOREAN SOC MICROBIOLOGY & BIOTECHNOLOGY

Lugar: Seul; Año: 2013 vol. 23

1017-7825

Enzymatic decomposition of gelatin layers on used X-ray films and repeated utilization of enzyme for potential application in silver recovery were investigated using keratinolytic serine proteases from Purpureocillium lilacinum LPS # 876. At pH 9.0, the enzymatic reaction was enhanced by the increase of enzyme concentration or by the increase of the temperature up to 60 ºC. Under the conditions of 6.9 U/ml, 60 ºC and pH 9.0, hydrolysis of gelatin layers and the resulting release of silver particles were achieved within 6 min. The protective effect of polyols against thermal denaturation was investigated. The presence of glycerol and propylene glycol increases enzyme stability. When the reusability of the enzyme for gelatin hydrolysis was tested it could be seen that it could be effectively reused for more cycles when glycerol was added compared to the enzyme without protective agents. The results of these repeated treatments suggested that a continuous process of recycling silver from used X-ray is feasible. Keeping in mind that recycle is -at the present time- needed and imperative, it can be remark that, in this research, three wastes were used: hair waste in order to produce serine proteases; glycerol in order to enhance enzyme thermal stability and used X-ray films in order to recover silver and PET films.