Abstract
The study was conducted to investigate the potential of Parkia biglobosa fruit pulp as substrate for citric acid production by Aspergillus niger. Reducing sugar was estimated by 3,5-dinitrosalicylic acid and citric acid was estimated spectrophotometrically using pyridine-acetic anhydride methods. The studies revealed that production parameters (pH, inoculum size, substrate concentration, incubation temperature, and fermentation period) had profound effect on the amount of citric acid produced. The maximum yield was obtained at the pH of 2 with citric acid of 1.15 g/L and reducing sugar content of 0.541 mMol−1, 3% vegetative inoculum size with citric acid yield of 0.53 g/L and reducing sugar content of 8.87 mMol−1, 2% of the substrate concentration with citric acid yield of 0.83 g/L and reducing sugar content of 9.36 mMol−1, incubation temperature of 55°C with citric acid yield of 0.62 g/L and reducing sugar content of 8.37 mMol−1, and fermentation period of 5 days with citric acid yield of 0.61 g/L and reducing sugar content of 3.70 mMol−1. The results of this study are encouraging and suggest that Parkia biglobosa pulp can be harnessed at low concentration for large scale citric acid production.
Highlights
Citric acid is one of the most common products which have a never ending demand in the global market
The fermentation medium containing Parkia biglobosa fruit pulp 250 g, NH4NO3 10.0 g, KH2PO4 4.0 g, MgSO4⋅7H2O 1.0 g, and CaCO3 2.0 g was transferred to 1000 mL conical flask and using a measuring cylinder, sterile distilled water was used to make up the volume to 1000 mL. 100 mL of fermentation medium was transferred into 100 mL conical flasks (25 flasks) using a sterile measuring cylinder, cotton plugged, and corked with aluminium foil
The production of citric acid by Aspergillus niger cultured on Parkia biglobosa fruit pulp showed that the highest yield (1.15 g/L) of citric acid was obtained at pH 2 and it declined as the pH increased from being acidic to alkaline with the yield of (0.86 g/L)
Summary
Citric acid is one of the most common products which have a never ending demand in the global market. Parkia biglobosa (African locust bean) is a leguminous forest crop that belongs to the family Mimosaceae which provides to the West African population a range of products used in food and industrial and traditional medicine [4] It is rich in nutrients such as carbohydrate, proteins, carotenoids, ash, and fibre. Though proteins and fats provide energy, carbohydrates are much cheaper and more digested and absorbed [9] With this content of carbohydrate the African locust bean fruit pulp is a potential good source of energy given the recommended daily energy intake [8]. The main interest of this study is to use Parkia biglobosa fruit pulp as a substrate for the production of citric acid This is in order to explore its potentiality as a cheap raw material in the supply of citric acid for industrial usage and economic development
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