Evaluating the use of biosensors for monitoring of Penicillium digitatum infection in citrus fruit

Penicillium digitatum is a major postharvest pathogen in citrus fruit that causes losses in all citrus-growing countries. In this study, a new whole-cell-based biosensor was developed to detect the fungus' presence in oranges. The approach was based on bacteria's luminescent responses to changes in volatile organic compounds (VOCs) following infection by a pathogenic microorganism in oranges. Differences between VOC patterns in the infected and noninfected fruit were monitored by GC-MS and then with four different genetically modified bioluminescent bacterial strains. GC-MS detected the changes in emitted VOC patterns during the first infection steps. Bioreporter strains allowed pathogen detection on the third day of infection, before the appearance of visible signs of fungal infection on the surface of the orange. Thanks to their increased sensitivity, portability and ease of use, whole-cell biosensors may serve as a new tool for monitoring rot. In the future, such technology will reduce food losses by enabling more efficient crop management throughout postharvest treatment, storage and transport.