TITLE:
Citric Acid Production Potential of Aspergillus niger Using Chrysophyllum albidum Peel
AUTHORS:
Blessing Nteimam Dienye, Ihuoma Ahaotu, Obioma Kenechukwu Agwa, Ngozi Nma Odu
KEYWORDS:
Aspergillus niger, Citric Acid, Chrysophyllum albidum, Substrate, Solid State Fermentation (SSF)
JOURNAL NAME:
Advances in Bioscience and Biotechnology,
Vol.9 No.4,
April
30,
2018
ABSTRACT: The
production of citric acid using Chrysophyllum albidum an indigenous under-utilized fruit waste peel and
genetically characterized strains of Aspergillus 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 capability
of the isolates revealed a wide yellow zone around the inoculated colonies. 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 cultural/growth optimal
conditions were determined through Solid State Fermentation 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 reducing 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 Cu2+ and Fe2+ stimulated citric acid production; while other ions reduced citric acid
production. There was a statistically significant difference (P > 0.05) between the citric acid produced with the
various parameters investigated in this research. From the study, it has been found
that Chrysophlum albidum is suitable for the cultivation of Aspergillus niger and has great potential for citric
acid production and could be exploited to promote certain industrial applications
of underutilized fruits in Nigeria. This can be an application of waste to
wealth as well as a way of minimizing agro-based environmental pollution for a
cleaner environment.