Enzymatic Hydrolysis of Gelatin Layers of X-Ray Films and Release of Silver Particles Using Keratinolytic Serine Proteases from Purpureocillium lilacinum LPS # 876

Abstract

Enzymatic decomposition of gelatin layers on used X-ray films and repeated utilization of the 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℃. Under the conditions of 6.9 U/ml, 60℃, and pH 9.0, hydrolysis of the 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 increased 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 with 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 recycling is (at the present time) needed and imperative, it can be remarked that, in this research, three wastes were successfully used: hair waste in order to produce serine proteases; glycerol in order to enhance enzyme thermal stability; and used Xray films in order to recover silver and PET films.

Plant Growth Promotion Activity of Keratinolytic Fungi Growing on a Recalcitrant Waste Known as “Hair Waste”

“…P. lilacinum LPS #876 was previously reported as a keratinolytic fungus capable of producing keratinases when hair waste was used as substrate under submerged fermentation. Keratinases of P. lilacinum could be used for several purposes as it was stated early [ 2 , 5 , 12 ]. This report describes experiments that suggest that P. lilacinum LPS #876 is able to produce a cell-free supernatant that can be considered as a multifunctional crude extract with keratinolytic, antifungal, and plant growth-promoting activities.…”

“…The biotransformation of hair waste could give rise to a partially degraded organic material with high nitrogen content due to extent of the proteolysis when microorganisms act. This new biomaterial could have different potential uses, that is, as a highly digestible protein source for animal feeding, as a raw material in the fertilizing or chemical industry, and as substrate for the production of enzymes such as proteases and keratinases [ 2 , 4 , 5 ].…”

Two novel protocols for cleaning residual simethicone and fluid in patient‐ready duodenoscopes

“…The efficacy of enzymatic detergent with simethicone cleaning was evaluated by a surrogate X-ray film hydrolysis model. 18 X-ray films with gelatin layers (Kodak medical X-ray film general purpose green, Kodak Company, Colorado, USA) were cut into small pieces of size 5 × 4 cm, immersed in the 0.06% w/v simethicone solution for 30 min, and then transferred to a sonicator containing enzymatic detergent (1:100) for 1 or 8 min. X-ray film was then removed, dried at room temperature, and placed over a green color surgical towel.…”

Potential application spectrum of microbial proteases for clean and green industrial production

“…Around 18-20% of the world's silver needs are supplied by recycling photographic waste (Shankar et al 2010). Nearly 2.0 billion radiographs are taken each year, including chest X-rays, mammograms and CT scans (Cavello et al 2013). …”

“…B. lehensis (Joshi and Satyanarayana 2013), B. subtilis (Nakiboglu et al 2001;Kumaran et al 2013), B. cereus ) and B. licheniformis (Pathak and Deshmukh 2012), B. subtilis K-5 ) and B. licheniformis K-3 (Singh and Bajaj 2017), have been demonstrated to possess good gelatinolytic activity for efficient silver recovery from X-ray films. Proteases from other sources like Aspergillus versicolor (Choudhary 2013) and Purpureocillium lilacinum (Cavello et al 2013) have also shown good gelatin hydrolysing ability. High temperature and slightly alkaline conditions favour stripping off of the gelatin layer.…”