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<p>This study focused on strain improvement and fermentation optimization for enhanced citric acid production by <i>Aspergillus niger</i> using waste molasses as a substrate. Fifty strains were isolated from soil samples collected in Lahore, Pakistan, and the most productive strain was identified through cultural characteristics and slide culture confirmation. UV and gamma irradiation were employed for strain improvement, with UV treatment producing the most efficient mutant strain (ISO-18-UV-M-10). A molasses-based fermentation medium was optimized using the following conditions: 30&#xa0;°C, pH 5.5, 150&#xa0;g/L initial sugar concentration, and 144&#xa0;h fermentation time under shake flask conditions. To reduce the inhibitory effects of heavy metals, EDTA and K₄Fe(CN)₆ were tested as chelating agents. The best results were achieved with 150 ppm EDTA added at 72&#xa0;h and 200 ppm K₄Fe(CN)₆ added at 48&#xa0;h, respectively. Simultaneous addition of both chelators reduced productivity. The highest citric acid yield reached 70.5&#xa0;g/L using K₄Fe(CN)₆, representing a 15.67-fold increase over the original wild-type strain (4.5&#xa0;g/L). Under standard optimized conditions without chelators, the UV mutant produced 53.0&#xa0;g/L, equivalent to a 10.3-fold increase, establishing the effectiveness of mutagenesis and process optimization in boosting production.</p>

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Improved Citric Acid Productivity from Waste Molasses by Lowering Heavy Metal Concentration Through Soil-Inhabited Mutagen of Aspergillus Niger

  • 期刊论文

  • 发表日期：

    2025年8月27日

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  • Sikander Ali,
  • Mehwish Mahrukh Iqbal,
  • Muhammad Usman Ahmad,
  • Ifrah Shabbir,
  • Sadaf Saleem,
  • Dawood Ahmed,
  • Sumera Shaheen,
  • Sibtain Ahmed,
  • Khaled Fahmi Fawy,
  • Muhammad Arshad

摘要

This study focused on strain improvement and fermentation optimization for enhanced citric acid production by Aspergillus niger using waste molasses as a substrate. Fifty strains were isolated from soil samples collected in Lahore, Pakistan, and the most productive strain was identified through cultural characteristics and slide culture confirmation. UV and gamma irradiation were employed for strain improvement, with UV treatment producing the most efficient mutant strain (ISO-18-UV-M-10). A molasses-based fermentation medium was optimized using the following conditions: 30 °C, pH 5.5, 150 g/L initial sugar concentration, and 144 h fermentation time under shake flask conditions. To reduce the inhibitory effects of heavy metals, EDTA and K₄Fe(CN)₆ were tested as chelating agents. The best results were achieved with 150 ppm EDTA added at 72 h and 200 ppm K₄Fe(CN)₆ added at 48 h, respectively. Simultaneous addition of both chelators reduced productivity. The highest citric acid yield reached 70.5 g/L using K₄Fe(CN)₆, representing a 15.67-fold increase over the original wild-type strain (4.5 g/L). Under standard optimized conditions without chelators, the UV mutant produced 53.0 g/L, equivalent to a 10.3-fold increase, establishing the effectiveness of mutagenesis and process optimization in boosting production.