Geotrichum candidumAGRC-GC1 prevented the decay of pulp from Citri Reticulatae Pericarpium production by inhibiting the growth of spoilage microorganisms

The increasing production of Citri Reticulatae Pericarpium (Chenpi) has led to a surge in the generation of citrus pulp byproducts; however, its recycling remains inadequate due to rapid spoilage. Developing sustainable storage methods to facilitate recycling initiatives is essential. In this study, a newly isolated strain, Geotrichum candidumAGRC-GC1, characterized by its robust ability to occupy ecological niches and suppress other microorganisms, was employed to inhibit spoilage in citrus pulp. AGRC-GC1 rapidly colonized the pulp, comprising 98.5% of the fungal microbiota, thereby protecting it from invasion by spoilage microorganisms including Saccharomyces, Torulaspora, Podosphaera, and Aureobasidium. This colonization slowed sugar consumption, preventing acidification and maintaining a pH of 3.86, compared to a control value of 3.48. Key molecules associated with the sour odor of spoilage, namely 3-aminoisobutyric acid (AIBA) and D-gluconic acid (GA), were significantly reduced by AGRC-GC1 treatment, effectively eliminating the sour odor. Additionally, two esters, glycerol-AIBA and erythritol-GA, were found to exhibit a strong sour odor associated with spoilage. Furthermore, AGRC-GC1 demonstrated the ability to synthesize a 3.45-fold increase in tyrosol, which enhanced the antioxidant activity in the pulp. Moreover, AGRC-GC1 regulated water activity by synthesizing glucitol and erythritol, with increases of 11.11- and 2.27-fold, respectively. These findings offer new insights into the citrus spoilage process in natural environments and highlight the potential of AGRC-GC1 in the recycling and utilization of citrus pulp byproducts.