Advances in Bioscience and Biotechnology, 2018, 9, 190-203 http://www.scirp.org/journal/abb ISSN Online: 2156-8502 ISSN Print: 2156-8456 DOI: 10.4236/abb.2018.94013 Apr. 30, 2018 190 Advances in Bioscience and Biotechnology Citric Acid Production Potential of Aspergillus niger Using Chrysophyllum albidum Peel Blessing Nteimam Dienye * , Ihuoma Ahaotu, Obioma Kenechukwu Agwa, Ngozi Nma Odu Department of Microbiology, University of Port Harcourt, Port Harcourt, Nigeria Abstract The production of citric acid using Chrysophyllum albidum an indigenous under-utilized fruit waste peel and genetically characterized strains of Asper- gillus niger was carried out. The Chrysophyllum albidum peel was dried, sieved to remove dirt, dry milled and the powder used as substrate for citric acid production. Thirteen fungal isolates were obtained from soil samples and decayed agricultural waste by spread plate technique and screened for citric acid producing capabilities on Czapek dox agar. Citric acid producing capa- bility of the isolates revealed a wide yellow zone around the inoculated colo- nies. Two (F1 and F3) out of the thirteen isolates exhibited positive reactions and were identified based on their cultural, morphological and molecular characteristics. The fungal species were identified using PCR as Aspergillus niger DTO: 133-E8 and Aspergillus niger DTO: 131-H5. Their cul- tural/growth optimal conditions were determined through Solid State Fer- mentation of the substrate using two species of the test organism. The effects of fermentation period examined revealed, Aspergillus niger DTO: 133-E8 which produced the highest amount of citric acid 15.7 ± 0.08 g/l, lower re- ducing sugar and final pH of 2.1 and 121.5 ± 0.31 g/l respectively after 192 h of growth at 30˚C. Aspergillus niger DTO: 131-H5 showed highest amount of citric acid 10.2 ± 0.22 g/l, lower reducing sugar and final pH of 2.4 and 128.5 ± 0.15 g/l respectively after 192 h of growth at 30˚C. Maximum concentration of citric acid ranging between 16.3 ± 0.30 g/l and 12.6 ± 0.11 g/l with reducing sugar 125.4 ± 0.11 g/l and 127.2 ± 0.03 g/l was achieved at an initial pH of 5.5. Methanol was used to stimulate citric acid production (0% - 3% (v/v)) and was found to be effective at 2% (v/v) level with 21.2 ± 0.20 g/l of citric acid produced with residual sucrose concentration of 129.5 ± 0.44 g/l. The effect of trace element on citric acid production showed that Cu 2+ and Fe 2+ stimulated citric acid production; while other ions reduced citric acid production. There was a statistically significant difference (P > 0.05) between the citric acid pro- duced with the various parameters investigated in this research. From the How to cite this paper: Dienye, B.N., Ahaotu, I., Agwa, O.K. and Odu, N.N. (2018) Citric Acid Production Potential of Aspergillus niger Using Chrysophyllum albidum Peel. Advances in Bioscience and Biotechnology, 9, 190-203. https://doi.org/10.4236/abb.2018.94013 Received: February 10, 2018 Accepted: April 27, 2018 Published: April 30, 2018 Copyright © 2018 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution-NonCommercial International License (CC BY-NC 4.0) http://creativecommons.org/licenses/by-nc/4.0/ Open Access