Bioprospecting of fish scale waste as a cost effective substrate for crude protease production using Stenotrophomonas koreensis SH32 and its multifunctional applications: A sustainable strategy for circular bioeconomy

Abstract

In this study Stenotrophomonas koreensis SH32 bacterial strain previously isolated from waste dumped soil was screened for protease production through qualitative and quantitative methods. The protease enzyme production in based media was optimised using response surface methodology (RSM). Under optimised conditions 295.11 IU/mL of protease activity was recorded from the crude enzyme that marked a 5.76 fold increase in protease activity as compared to unoptimised condition (51.21 IU/mL). The crude enzyme was further explored for its dehairing activity using goat skin, destaining activity using chicken blood stained cloth and metal recovery property from old X-ray films. Further the plant growth promoting characteristics and antagonistic activity of the proteolytic strain against common phytopathogenic fungi was evaluated. The results suggested that the bacteria was positive for indole acetic acid, siderophore and ammonia production. The bacterial culture also showed antagonism against Cladosporium tennuisimum, Talaromyces albobiverticillius and Fusarium solani. The plant growth promotion activity of the bacteria was further confirmed by plant growth test using Solanum lycopersicum amended with fish scale hydrolysate produced through bacterial fermentation. A significant increase in length (8.3 cm) was observed in plants treated with fish scale hydrolysate as compared to the control (6.5 cm).