The effect of a strain of marine yeast Rhodosporidium paludigenum on postharvest blue mold and patulin accumulation in apples and pears stored at 23°C was evaluated. The occurrence and severity of apple and pear decay caused by Penicillium expansum were significantly inhibited by R. paludigenum. However, the application of the yeast at a high concentration (10 8 cells per ml) enhanced patulin accumulation after 7 days of storage; the amount of patulin increased 24.2 times and 12.6 times compared to the controls in infected apples and pears, respectively. However, R. paludigenum reduced the patulin concentration in the growth medium by both biological degradation and physical adsorption. Optimal in vitro patulin reduction was observed at 30°C and at pH 6.0. R. paludigenum incubated at 28°C was tolerant to patulin at concentrations up to 100 mg/liter. In conclusion, R. paludigenum was able to control postharvest decay in apples and pears and to remove patulin in vitro effectively. However, because the yeast induced patulin accumulation in fruit, the assessment of mycotoxin content after biological treatments in postharvest decay control is important. R. paludigenum may also be a promising source of gene(s) and enzyme(s) for patulin degradation and may be a tool to decrease patulin contamination in commercial fruit-derived products.
Zehua Zhang,Shuhua Li,Dandan Sun,Ying Yang,Zhanhai Wei,Changlu Wang,Laifeng Lu
Penicillium digitatum acidifies the extracellular environments of fruit during decay development, this pH fluctuation decreased the efficacy of biological approaches under commercial conditions. Here, we explored the interaction between P. digitatum and an antagonistic yeast Rhodosporidium paludigenum to investigate potential mechanism behind the battle. P. digitatum was found in acidified citrus fruit tissue at pH 4.25 to 3.98 as mold infection progressed. Metabonomic data showed that gluconic, glucaric, and malic acids markedly increased upon infection at pathogen-fruit interaction sites. At concentrations > 1 × 10 6 cells mL −1 in liquid culture containing glucose or fructose instead of lactose, R. paludigenum could effectively control green mold. High concentrations of six different acids suppressed yeast growth even in the presence of sufficient glucose. Conversely, at ≤200 mmol L −1 , malic and gluconic acids promoted yeast growth in reverse. Cultivation of R. paludigenum with gluconic acid enhanced its ability to control green mold. This study provides new insights into the mechanisms by which extracellular acidification caused by acids produced by P. digitatum discriminates against competing microbes, thereby enhancing antagonistic yeast biocontrol of green mold in citrus.
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