Preliminary report on a catalyst derived from induced cells of Rhodococcus rhodochrous strain DAP 96253 that delays the ripening of selected climacteric fruit: bananas, avocados, and peaches

Abstract

Despite the use of refrigeration, improved packaging, adsorbents, and ethylene receptor blockers, on average, nearly 40% of all fruits and vegetables harvested in the US are not consumed. Many plant products, especially fruit, continue to ripen after harvesting, and as they do so, become increasingly susceptible to mechanical injury, resulting in increased rot. Other plant products during transportation and storage are susceptible to chill injury (CI). There is a real need for products that can delay ripening or mitigate the effects of CI, yet still permit full ripeness and quality to be achieved. Preliminary results are discussed where catalyst derived from cells of Rhodococcus rhodochrous DAP 96253, grown under conditions that induced high levels of nitrile hydratase, were able to extend the ripening and thus the shelf-life of selected climacteric fruits (banana, avocado, and peach). A catalyst, when placed in proximity to, but not touching, the test fruit delayed the ripening but did not alter the final ripeness of the fruit tested. Organoleptic evaluations conducted with control peaches and with peaches exposed to, but not in contact with, the catalyst showed that the catalyst-treated peaches achieved full, natural levels of ripeness with respect to aroma, flavor, sweetness, and juice content. Furthermore, the results of delayed ripening were achieved at ambient temperatures (without the need for refrigeration).

Delayed Ripening of Climacteric Fruit by Catalysts Prepared from Induced Cells ofRhodococcus rhodochrousDAP 96253: A Case for the Biological Modulation of Yang-Cycle Driven Processes by a Prokaryote

“…The maintenance, cultivation, and induction are detailed in Pierce et al [8][9][10][11] R. rhodochrous DAP 96253 cells were grown on yeast extract, malt extract agar (YEMEA) medium (ISP medium 2 as recommended by Dietz and Thayer). 12 Full induction was achieved by supplementing YEMEA with urea (7 g/L) and cobalt (as CoCl 2 ), at 10-88 ppm with 50 ppm preferred.…”

“…[5][6][7][8] It was also observed that the effects of chill injury in peaches, after extended periods of refrigeration at transport temperatures recommended by the United States Department of Agriculture, could be significantly mitigated by exposing the refrigerated peaches to induced cells of R. rhodochrous DAP 96253. 8 Initially, all experiments were conducted using live cells of induced R. rhodochrous DAP 96253. But, to investigate practical methods, the cells were immobilized using glutaraldehyde and then cross-linked using polyethylenimine (PEI), a method that renders the cells non-replicating.…”

“…But, to investigate practical methods, the cells were immobilized using glutaraldehyde and then cross-linked using polyethylenimine (PEI), a method that renders the cells non-replicating. [8][9][10][11] While no viable cells could be recovered from glutaraldehyde/PEI immobilization, the immobilized cells were still capable of delaying the ripening of peaches and/or bananas. [5][6][7][8] Materials and Methods…”

“…[8][9][10][11] While no viable cells could be recovered from glutaraldehyde/PEI immobilization, the immobilized cells were still capable of delaying the ripening of peaches and/or bananas. [5][6][7][8] Materials and Methods…”

The potential of plant microbiota in reducing postharvest food loss

“…Many bacteria in soil and plants possess ACC deaminase activity, which cleaves ACC to 2‐oxobutyrate and ammonia and can contribute to ethylene balancing in plants (Glick, 2005). An alternative role of ethylene in microbial‐driven modulation of ripening was introduced by a recent study exploring the potential of a Rhodococcus rhodochrous strain to delay ripening in different species of climacteric fruits (Pierce et al ., 2011). In this case, the proposed mechanism is that ethylene‐induced nitrile hydratase and/or nitrilase activity in the bacterium, which resulted in maintenance of fruit firmness and reduced spotting and spoilage (Perry, 2011).…”