Optimization of citrinin production by endophytic Penicillium citrinum isolated from Ziziphus jujuba

Citrinin is a common mycotoxin produced by different fungi. Although considerable endeavors have been made to increase citrinin output to meet the requirements of research and industrial needs, few methods are effective, owing to potential safety concerns and technical limitations. In this study, a blue fungus that produces a yellow pigment was isolated from Ziziphus jujuba. The strain was then identified as Penicillium citrinum and named HR-087. Preparative liquid chromatography was used to extract the yellow pigment. Both LC-MS and NMR assays showed that it was citrinin. To enhance the citrinin production of this strain, the culture medium was optimized through orthogonal experiments, as well as batch and fed-batch process. The final titer and productivity of citrinin reached 9.62 g/L and 0.1 g/(L x h), respectively. The high titer achieved indicates the possibility of large-scale production of high purity citrinin for low-cost supply for both academic and diagnostic analysis standard.