Production of citric acid by Aspergillus niger immobilized in Detarium microcarpum matrix

Aims: This study investigated the potential use of Detarium microcarpum as a support matrix for the immobilization of fungal cell and its subsequent use in the production of citric acid. Methodology and results: Conidia of Aspergillus niger were immobilized on Detarium microcarpum matrix crosslinked with glutaraldehyde (2.5% v/v). Effects of various immobilized conditions on citric acid yield were determined. Citric acid production was optimum at 9% gel concentration, 5.0 mm bead size and 400 mg spore load. Higher citric acid yield (82 g/L) was obtained by immobilized cells while free cells gave (61 g/L). Immobilized gels were stable for 15 days in the fermentation medium and retained about 75% of initial yield after five repeated cycles. Conclusion, significance and impact of study: This study therefore shows that D. microcarpum is a novel matrix for cell immobilization and will enhance production of citric acid in batch system.