Scaling up biomass production of Vishniacozyma victoriae and semi-commercial testing for post-harvest control of pome fruit disease

Postharvest losses of pome fruits such as apples and pears, primarily due to fungal pathogens, represent a significant challenge for global fruit production. Conventional chemical control strategies have raised concerns regarding food safety and environmental impact, highlighting the need for sustainable alternatives. This study aimed to scale up the biomass production of the epiphytic yeast Vishniacozyma victoriae NPCC 1263, a promising biological control agent (BCA) against postharvest diseases in pome fruits, and to evaluate its efficacy under semi-commercial conditions. BCA yeast biomass was produced using low-cost media based on cheese whey powder (CWP) and salts in laboratory (15 L) and pilot-scale (140 L) bioreactors, applying batch and semi-continuous cultivation modes. The volumetric oxygen transfer coefficient (k_La) was used as the scale-up criterion. The biomass yield, CFU/mL, and viability after drying and storage were assessed. At the pilot scale, the biomass concentration was 20.7 g/L, which was more than double the concentration obtained under batch conditions at the laboratory scale (8.89 g/L). This confirmed the scalability of the process. The freeze-dried yeast biomass retained 35.1% viability after 330 days of storage at room temperature, while spray-drying proved inadequate due to heat sensitivity. Both fresh and freeze-dried formulations were evaluated in two harvest seasons on Beurré D’Anjou and Packham’s Triumph pears, and Red Delicious apples. The treatments reduced the natural incidence of Penicillium expansum, Botrytis cinerea, and Alternaria–Cladosporium spp., by more than 42%. The results demonstrate the feasibility of large-scale production and application of V. victoriae, supporting its potential integration into sustainable postharvest disease management strategies.