Background - The leather industry contributes vast amounts of pollution damaging to aquatic and terrestrial environments. Leather dust is a chromium-contaminated waste produced from the shaving and buffering processes involved in leather tanning. Microorganisms have been investigated for their usefulness in bioremediation and recycling of waste materials. Solid leather waste is the current focus of material to be remediated in this study.
Objective - The present work focuses on the development of a process to degrade the leather dust protein with the aim of removing the chromium bound within the protein. As part of the study, detecting the presence of biosurfactant production was performed to fuel further interest in value-added by-products of the process.
Method - Bacillus subtilis SA-6 was used to treat the leather dust over a 10 day shake flask study. Daily samples were taken and analysed for chromium content by Atomic Absorption Spectrometry. The surface tension of the shake flask cultures was also investigated to detect for any valuable by-products such as biosurfactants for future prospects of developing an economically viable process.
Results - Chromium concentration demonstrated an exponential increase between 0-120 h in shake flask experiments. In the presence of B. subtilis SA-6 chromium concentration in cell free supernatant increased from 0.13±0.09 mg/L to 190.81±20.18 mg/L compared to when B. subtilis SA-6 was absent. Surface tension decreased during fermentation from 53.23±0.92 mN/m to 30.13±0.15 mN/m in 24 h.
Conclusion - This study demonstrates a waste management process,which detoxifies solid tannery waste to reduce environmental pollution,whilst yielding value-added products (such as biosurfactant) to provide an economically viable bioprocess with potential for large-scale development.
- Atomic absorption spectrometry
- Bacillus subtilis
- Leather dust
- Surface tension