Estimation of total bacteria on mango surface by using ATP bioluminescence

This paper presents a rapid ATP assay for monitoring the total bacterial load associated with mango fruit surface. Conventional methods such as total plate count for the determination of total microbial counts are time consuming and prone to contamination resulting in low accuracy. Thus the need for quick and accurate methods for determination of total microbial count has led to development of many rapid techniques such as ATP bioluminescence. In this study the potential of ATP bioluminescence method for the determination of total bacterial count on mango surface has been evaluated using two types of luminescence techniques based on fluorescence spectroscopy and bioluminescence. Various mechanical and chemical extraction processes were employed for the extraction of ATP from bacterial cells and the best extraction was achieved with 0.03 M TCA. Minimum level of detection of ATP using fluorescence spectrophotometer and bioluminometer was found to be 10−8 M and 10−13 M, respectively. This ATP concentration was correlated with the number of bacterial cells present on mango surface. The minimum level of detection of bacterial cells in fluorescence spectroscopy and bioluminescence was found to be 107 cfu/ml and 102 cfu/ml, respectively.

► ATP extraction methods evaluated; 0.03 M and 0.06 M TCA, 0.2 M Tris–EDTA, sonication.
► Extraction using 0.03 M TCA yielded the best results.
► The detectable range of ATP; 10−4 to 10−8 M for fluorescence spectroscopy.
► The detectable range of ATP; 10−4 to 10−13 M for bioluminometer.
► LOD for bacterial cells using bioluminometer was 102 cfu/ml.