Faculty of Biology-Oriented Science and Technology, Kindai University.
Biocontrol Sci. 2020;25(4):215-222. doi: 10.4265/bio.25.215.
We initially correlated fluorescent pseudomonads and severity of enzymatic browning on fresh-cut potatoes. Subsequently, we determined the influence of inoculation with Pseudomonas fluorescens following its isolation from the brown tissues on the browning response on fresh-cut potatoes. Bacterial counts on potato slices were higher on browning tissues than on non-browning tissues. P. fluorescens that has been isolated only from the severely browning tissues developed brown discoloration on surface tissues when inoculated onto potato slices. When potato slices were initially inoculated with 10 colony-forming unit (CFU) per mL of P. fluorescens and then stored at 5ºC, bacterial counts, polyphenol oxidase (PPO) activity, phenolic content, and browning severity increased after 3 days of storage. We observed plant PPO derived from potatoes and bacterial PPO released by P. fluorescens and dictated that the plant PPO contributed to browning reactions because only the plant PPO was activated at pH 6-7 that lies in potato tissues. The PPO1 gene that contributed to browning on potatoes was expressed prominently in potato tissues following inoculation with P. fluorescens. These results indicated that P. fluorescens enhanced browning of fresh-cut potatoes by inducing the plant PPO gene, plant PPO activity, and accumulation of phenolics as a biocontrol agent.
我们最初将荧光假单胞菌与鲜切土豆的酶促褐变严重程度相关联。随后，我们确定了从棕色组织中分离出荧光假单胞菌并接种到鲜切土豆上对褐变反应的影响。在褐变组织上的土豆片细菌计数高于非褐变组织。仅从严重褐变组织中分离出的荧光假单胞菌在接种到土豆片上时，其表面组织会出现褐色变色。当土豆片最初用每毫升 10 个菌落形成单位（CFU）的荧光假单胞菌接种，然后在 5°C 下储存时，在储存 3 天后细菌计数、多酚氧化酶（PPO）活性、酚类含量和褐变严重程度增加。我们观察到来自土豆的植物 PPO 和荧光假单胞菌释放的细菌 PPO，并指出植物 PPO 促成了褐变反应，因为只有植物 PPO 在 pH 6-7 下被激活，而 pH 6-7 存在于土豆组织中。在接种荧光假单胞菌后，对土豆褐变有重要贡献的 PPO1 基因在土豆组织中表达明显。这些结果表明，荧光假单胞菌通过诱导植物 PPO 基因、植物 PPO 活性和酚类物质的积累作为生物防治剂来增强鲜切土豆的褐变。
