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The scope of the project was to develop a method to induce soil bacteria to biosynthesize compounds that retard the effects of ethylene induced ripening in climacteric fruits. Thestudy was randomized. Organic bananas selected for the study were visibly inspected to ensure the fruit was unripen with no visible signs of bruising, spotting, or infection from a local distributor. Four trials were conducted from June 5th - August 5th 2014 with 3 replicates (3-4 bananas per experimental unit) in 4 trial studies for 3 days at room temperature. A mixed culture of plant growth promoting rhizobacteria (PGPR) were collected from soil surrounding the roots of young fruit bearing trees. Microbes were mixed with no-carbon source media, and cultured with an ethylene for 3 d at room temperature in a closed container. Induced soil was used to delay ripening. Microbes induced with media and ethylene delayed ripening 100% of the time in all experimental units compared to control samples, while microbes cultured with media (no ethylene) delayed ripening less than 10% of the time compared to the control. These cells also appeared to increase the incidence of fungal infection in the fruit. The findings suggest induced microbes may convert ethylene into ethanol then acetaldehyde. The two compounds may form an acetaldehyde/ethanol vapor that delays ripening, and a secondary nitrile compound that inhibits fungal growth.
The updated preprint includes additional fruit images, GC Mass Spec data, and new references. A new conclusion includes an altered proposed mechanism used by the bacteria to delay fruit ripening based on the original findings and new data.