Biovalorization of agro-food wastes for the production of melanin pigment via a submerged fermentation process using Aspergillus niger: as a sustainable approach
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Date
2024
Journal Title
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Faculty of Science, University of Kelaniya Sri Lanka
Abstract
Biovalorization harnesses biological processes to convert waste materials into value added products, encouraging sustainability and resource efficiency. The current study aims to explore and optimize a sustainable method for the production of melanin pigment through the submerged fermentation (SMF) process by utilizing banana peel waste, affected Sesbania grandiflora leaves and stem wastes, and used tea dust waste using Aspergillus niger. The pH, moisture content, total organic carbon, and total ash contents of collected food wastes were measured using standard methods. Fungal cultures were incubated under the submerged fermentation process, at 25 °C with an agitation speed of 160 rpm for 14 days. Subsequently, the fungal-produced pigment was extracted using 1.0 mol/L KOH and subsequently characterized using physicochemical tests with water, organic solvents, alkaline and acidic solutions, and an oxidizing-reducing agent. Further, the pigment was confirmed based on ultraviolet-visible spectroscopic analysis and Fourier-transform infrared spectroscopic (FTIR) analysis. The extracted pigment was tested for toxicity, antibacterial, and antioxidant properties to the determination of the distinctive characteristics and quality of the extracted pigment, hence enabling their industrial use. The pigment yield from banana, Sesbania, and tea wastes were 597.2 ± 21.5 mg/L, 395.4 ± 39.1 mg/L, and 135 ± 12.9 mg/L, respectively. Compared to the control setup, a significant difference (p < 0.05) was observed between the pigment yields produced by A. niger when utilizing different types of food waste. In the physico-chemical analysis, the blackish brown colour of the pigment served as primary evidence for melanin. The pigment was insoluble in water and organic solvents (acetone, chloroform, ethanol, and sodium acetate), but it was readily soluble in KOH and NaOH, precipitated with HCl, and decolorized with H₂O₂. The UV-Vis spectrum indicated that the pigment possessed a λmax around 213–216 nm. The FTIR spectrum showed broad bands around 3000– 3500 cm⁻¹ (OH), 2924.7 and 1032.6 cm⁻¹ (saturated carbon and C-O), 2830–2930 cm⁻¹ (CH2 and CH3), 1500–1650 cm⁻¹ (aromatic C=C or C=O), 1320 and 1390 cm⁻¹ (C-N), and 1210–1230 cm⁻¹ (C-OH). The extracted pigment exhibited low toxicity to mung beans (4.4–6.7%) compared to the positive control (100% extraction solvent). In the antibacterial activity assay, inhibition zones ranged from 2.1 ± 0.1 to 2.6 ± 0.1 cm for Staphylococcus aureus and 2.1 ± 0.1 to 2.5 ± 0.1 cm for Escherichia coli. The antioxidant assay demonstrated an increase in the percentage of DPPH inhibition with increasing pigment concentration, suggesting the pigment's ability to scavenge free radicals. This study proposes a sustainable approach for the production of fungal-based pigment (melanin) through a submerged fermentation process utilizing agro-food wastes with Aspergillus niger strain, which was not documented in previous studies.
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Keywords
Agro-food waste, Aspergillus niger, Biovalorization, Melanin pigment, Submerged fermentation
Citation
Rasna N. F.; Jayathilake K. M. P. I.; Manage P. M.; Idroos F. S. (2024), Biovalorization of agro-food wastes for the production of melanin pigment via a submerged fermentation process using Aspergillus niger: as a sustainable approach, Proceedings of the International Conference on Applied and Pure Sciences (ICAPS 2024-Kelaniya) Volume 4, Faculty of Science, University of Kelaniya Sri Lanka. Page 40