Effects of an endophyte Aspergillus niger in controlling internal browning of pineapple and its biosafety assessment

Internal browning (IB), a critical postharvest physiological disorder in pineapple ( Ananas comosus L.), has caused significant economic losses to the pineapple industry. In our previous study, an endophytic strain, Aspergillus niger S ( A. niger S), was isolated and identified as a potent biological agent for attenuating IB in pineapple. The current study systematically characterizes its impact on fruit quality and provides a rigorous biosafety assessment regarding its application in pineapple preservation. The results demonstrated that postharvest treatment with A. niger S effectively retarded pineapple senescence and reinforced the cellular antioxidant defense system—specifically via the modulation of the ascorbate-glutathione cycle—thereby attenuating IB development and preserving the nutritional quality of pineapple during storage. Comprehensive morphological characterization revealed that A. niger S was phenotypically consistent with non-mycotoxigenic reference isolates, remaining distinctly divergent from the profiles of mycotoxigenic strains involved in the production of ochratoxin A (OTA) and fumonisin B (FB). Genomic PCR screening confirmed the absence of core genes for the biosynthesis of OTA (including PKS , HAL , P450 , bZIP , and NRPS ) and FB (including FUM1 , FUM3 , FUM6–8 , FUM10 , FUM13–15 , and FUM21 ). Furthermore, A. niger S exhibited no toxigenic potential for OTA or FB biosynthesis across a broad range of culture conditions. In conclusion, A. niger S is a non-mycotoxigenic strain, ensuring its biosafety and high efficacy as a bio-preservative for controlling IB in postharvest pineapples. • Postharvest A. niger S application retards pineapple ripening and senescence. • A. niger S treatment attenuates IB development and preserves pineapple quality. • A. niger S enhances antioxidant capacity of pineapple via modulating AsA-GSH cycle. • Core biosynthetic genes for OTA and FB mycotoxins are absent in the A. niger S genome. • A. niger S exhibited no potential for OTA or FB biosynthesis under diverse conditions.