Optimization of Bromelain extraction from green papaya (Carica papaya) peel waste and its application in the recovery of silver from waste of X-ray photographic films.

As bromelain is a proteolytic enzyme present in many fruits, this study utilises the bromelain content present in unripe papaya (Carica papaya L.) by extraction and characterisation of bromelain extract from the unripe papaya peel waste. The extracted bromelain was utilised in the recovery of silver from waste of X-ray films, since the toxicity of silver directly impacts on the environment to treat and recover silver bromelain enzyme was used as a biocatalyst in this study. Response surface methodology with Box-Behnken design was used to optimise both the parameters included in the recovery of bromelain from papaya waste and silver from X-ray waste. Parameters involved in the recovery of bromelain include incubation time, pH of solution, temperature of solution and concentration of solution; for silver recovery along with the parameters selected for bromelain, recovery weight of X-rays is also considered in the study. Characterisation techniques like XRD, SEM, TGA, BET, FTIR and GC/MS were performed for the samples of bromelain and recovered silver from X-rays. At 30 min of incubation time, pH of 8, with 15 mL of bromelain solution maintained at 80 ℃ with 0.6 g of X-rays gives optimum silver recovery. The optimum recovery of silver was observed to be 96.6%.