Citric acid production by cellulose decomposing black Aspergillus species isolated from sugarcane bagasse

Abstract

In the current investigation, the potentiality of black Aspergillus species isolated from sugarcane bagasse to produce cellulolytic enzymes, and citric acid was evaluated. Furthermore, the cellulolytic activity and citric acid production by the active producers were assayed on a carboxy methylcellulose medium. The study was extended to improve citric acid production from sugarcane bagasse using mixed cultures of the highest endo-cellulases (CMCase) and citric acid-producing isolates. All the tested fungal isolates exhibited varying amounts of acid production on Czapek’s dextrose (Cz-Dox) solid medium containing CaCO3. The highest concentration of citric acid produced using a Cz-Dox liquid medium was 8.49 ±2 g/L as recorded by A. brasiliensis Am 27. This amount of citric acid is equivalent to 29.22% of initial sugar. A.niger Am 270 showed the highest endo-cellulases production (0.73±0.2 IU/mL) whereas A. niger Am 258 exhibited the highest citric acid yield (14.74%). These isolates were chosen for the maximization of citric acid production from sugarcane bagasse. The highest amount of citric acid from sugarcane bagasse medium by A. niger Am 258 was obtained after 10 days of incubation, recording 34 g/L citric acid and by increasing the incubation period, the obtained amount of citric acid decreased. Whereas the mixed cultures of Am 270 and Am 258 strains revealed a slight enhancement of citric acid production recording 35.1 g/L citric acid after 8 days of the total incubation period. So the presented results may 82 Zohri et al. (2021), Egyptian Sugar Journal, Vol.17 ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ ــــــــــــــــــ provide a suitable strategy for citric acid production using sugarcane bagasse.