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International Journal of Research and Innovation in Applied Science (IJRIAS) |Volume VII, Issue XII, December 2022|ISSN 2454-6194

Production of Citric Acid from Aspergilus Niger

Nikolas Keith
School of Biological Sciences, University of Reading, Reading, United Kingdom

IJRISS Call for paper

Abstract: – Citric acid is a commercially important product used in several industrial processes. Solid state fermentation was used in this work to produce citric acid by using a locally isolated Aspergillus niger, from spoilt solidified pap (eko). About 25g of plantain peel was gelatinized and 100m1 of nutrient solution was added. Aspergillus niger spores of about 5×108 was added. The set-up was incubated for 15 days at room temperature. 1ml of the filtrate resulting from the fermentation was taken on 6th day, 8th day and 15th day into a test-tube. Pyridine and acetic anhydride were added and heated in water bath at 32°C for 30 minutes. The absorbance was taken using 420nm as wave length.
The concentration of the citric acid produced by the locally isolated Aspergillus niger on 6th day, 8th day and 15th day of incubation were 4.22g11, 2.29g/1, and 14.77g/1 respectively.

This result, which demonstrate the viability of citric acid production by Aspergillus niger isolated from spoilt solidified pap (eko) using plantain peel as a substrate can be of interest to possible future industrial applications.


1.1 Introduction
1.1.1 The discovery and production of citric acid

Citric acid was first isolated in 1784 by the Swedish chemist, Carl Wilhelm who
crystallized it from lemon juice (Frank et al., 2005). Industrial scale citric acid production began in 1890 based on the Italian citrus fruit industry but in 1893, C.Wehmer discovered that mold could produce citric acid from sugar. However, microbial production of citric acid did not become industrially important until World War I disrupted Italian citrus exports. In 1917, the American food chemist, Jane Currie discovered certain stains of the mold Aspergillus niger could be efficient citric acid producers, and the pharmaceutical company PFIZER began industrial-level production using this technique two years later, followed by Citrique Belge in 1929. This production technique is still the major industrial route to citric acid used today. Cultures of Aspergillus niger are fed on a sucrose or glucose containing medium to produce citric acid. The source of sugar is corn steep liquor, molasses, hydrolyzed corn starch or other inexpensive sugary solutions (Lotfy et al., 2007). After the mold is filtered out of the resulting solution, citric acid is isolated by precipitating it with lime (calcium hydroxide) to yield calcium citrate salt from which citric acid is regenerated by treatment with sulfuric acid (Lotfy et al ., 2007). Prior to the fermentative process, citric acid was isolated from citrus fruits. The juice was treated with lime (calcium hydroxide) to precipitate calcium citrate which was isolated and converted back to the acid (Frank et al., 2005).