Isolation and screening for fungi producing citric acid from composting banana peels

Citric acid is a key element in food, drinks, pharmaceutical preparations, and detergents. Fungal fermentation with Aspergillus niger has long been recognized as one of the most effective methods for producing citric acid when compared to chemical approaches. The purpose of this study was to isolate, screen, and identify suitable fungal strains that produce citric acid using banana peel as a substrate. The samples were collected from Clifford University. The samples were then left to composte for two weeks. A 10-fold serial dilution was performed by suspending 1g of the material in 9ml of sterile distilled water. Thereafter, 0.1ml dilution of the sample was plated on a Potato dextrose agar (PDA) plate and incubated at room temperature (25 degrees Celsius) for four days, during which it was monitored and evaluated. The isolated fungi were subcultured and viewed under a microscope to identify the microorganism by slide culture technique using lactophenol blue. The Isolates were screened for citric acid production using Czepeck-dox agar containing bromocresol green as an indicator. Out of the two fungal isolates that were screened, only Aspergillus niger demonstrated the ability to produce citric acid. It was assessd base on the diameter of the colour change zone diameter caused by citric acid on the agar plate. The effect of pH was also determined from pH range of 4.5 to 8.5 and pH 5.0 was the optimal for production of citric acid with a value of 4.18g/L citric acid. This result show that banana peels is a good substrate for the production of citric acid.