| | Substrate | Organism | Fermentation conditions | Citric acid content | Reference |
| | Apple pomace | A. niger van Tieghem MTCC 281 | 30°C and 120 h | 46 g·kg−1 | Kumar et al. [13] | | Banana peel | A. niger UABN 210 | 30°C, 96 h, 10 g·L−1 methanol, and 10 ppm copper ions | 82 g·kg−1 | Kareem and Rahman [14] | | Cassava peel | A. niger mutant strain | 30°C, 0.5% consistency, pH 4.5, 6% inoculum, and 84 h | 89 g·L−1 | Adeoye et al. [15] | | Coffee husk | A. niger | 30°C, pH 4.5, 72 h, and 50% moisture content | 150 g·kg−1 | Shankaranand and Lonsane [16] | | Corn cob | A. niger | 28°C, 144 h, 150 g·kg−1 sucrose, and 50% consistency | 138 g·kg−1 | Addo et al. [17] | | Corn grains | A. niger ATCC 9142 | 25°C, 240 h, and 82% moisture content | 6 g·kg−1 | Xie and West [18] | | Coconut husk | A. niger KLCN2 | 30°C, 168 h, and 55% moisture content | 128.6 g·kg−1 | Lingappa et al. [19] | | Mango peels | A. niger | 32°C, pH 5, 192 h, and 11% consistency | 30 g·L−1 | Abbas et al. [20] | | Oat bran | A. niger | 28°C, pH 4.5, 72 h, 20% fructose, and 2.5 g·L−1 NH4NO3 | 62 g·kg−1 | Rao and Reddy [21] | | Orange peel | A. niger CECT-2090 | 30°C, 84 h, and 70% moisture content | 193 g·kg−1 | Torrado et al. [22] | | Sweet orange peels | A. niger | 32°C, pH 4, 144 h, and 11% consistency | 11 g·L−1 | Abbas et al. [20] | | Pineapple waste | A. niger KS-7 | 30°C, 120 h, and 65% moisture content | 6 g·kg−1 | Kareem et al. [23] | | Sugar cane bagasse | A. niger | 30°C, pH 5, and 65% moisture content | 3.5 g·kg−1 | Sharan et al. [24] | | Beet root pulp waste | A. niger ATCC 16404 | Room temperature (min 22°C–max 32°C), 192 h, and 6% moisture content | 3.4 g·kg−1 | Bezalwar et al. [25] | | Guava pulp waste | 4.8 g·kg−1 | | Indian jujube pulp waste | 4 g·kg−1 | | Papaya pulp waste | 3.8 g·kg−1 | | Pineapple pulp waste | 5 g·kg−1 | | Wood apple pulp waste | 5.5 g·kg−1 | | Grape residues | A. niger | 30°C, pH 2.1–3.1, after 24 h, 40 g·L−1 methanol, and 70% moisture content | 34.4 g·kg−1 | Goud et al. [26] | | Mosambi peel | 28.6 g·kg−1 | | Sugar cane bagasse | 24.9 g·kg−1 |
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These substrates beet root pulp waste, guava pulp waste, Indian jujube pulp waste, papaya pulp waste, pineapple pulp waste, wood apple pulp waste, belong to the reference Bezalwar et al. [ 25]. The substrates grape residues, mosambi peel, sugar cane bagasse belong to the reference Goud et al. [ 26] |
