Abstract
Soil samples were collected from the different locations in Sathuragiri Hills (Western Ghats, Tamilnadu). The Total Fungal Counts in the soil samples of the different locations were analyzed. The percentage frequencies of occurrence of fungal isolates are identified. The fungal isolates were identified based on the morphological and cultural characteristics they were identified as Cladosporium sp, Aspergillus niger, Penicillium sp, Alternaria sp, Curvularia sp, Helminthosporium sp and Aspergillus flavus. Among the isolates maximum amount of citric acid levels was produced by Aspergillus niger (2.2 ± 0.001 g/l). The effect of different pH, temperature, carbon source, nitrogen source, incubation time and agricultural residues on citric acid production by Aspergillus niger was analysed. The maximum amount of citric acid production was recorded in pH - 6.0 (2.32 ± 0.09 g/l), temperature - 30℃ (2.85 ± 0.06 g/l), carbon source - Glucose (6.08 ± 0.10 g/l). Nitrogen source - ammonium chloride (10.22 ± 0.05g/l), incubation time - 72 hours (13.56 ± 0.04 g/l) and agricultural residue - corn ears (17.2 ± 0.14 g/l).
Highlights
Citric acid (C6H8O7, 2–hydroxy–1,2,3–propane tricarboxylic acid), a natural constituent and common metabolite of plants and animals, is the most versatile and widely used organic acid in the field of food (70%) and pharmaceuticals (12%)
It was proved that the increase in glucose concentration had a positive effect on citric acid production
Aspergillus niger found to produce the highest quantity of citric acid (2.20 ± 0.01 g/L)
Summary
Citric acid (C6H8O7, 2–hydroxy–1,2,3–propane tricarboxylic acid), a natural constituent and common metabolite of plants and animals, is the most versatile and widely used organic acid in the field of food (70%) and pharmaceuticals (12%) It has got several other applications in various other fields. The main reason for constant increase is the large number of applications that can be found for citric acid, mainly in the food and pharmaceutical industries Traditional processes, such as the submerged fermentation using the fungus Aspergillus niger, dominate the global production. Different techniques of production are continuously being studied showing new perspectives for the production of citric acid In this context, solid-state fermentation appears where agro-industrial residues can be used as substrate-supports to the filamentous fungi Aspergillus niger. Since the Second World War, the production of citric acid has increased rapidly, reaching about 1.7 million tons per annum in 2008 with 5% predicted annual increase in the rate of production in order to meet the growing needs of the global market [4]
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