Influence of culture media used for biomass production of Vishniacozyma victoriae on the biocontrol activity on pear postharvest diseases

GRAMISCI BETINA; FERRARI ANA; LOPES CHRISTIAN ARIEL; SANGORRIN MARCELA P

Praga

Congreso; 28th International Conference on Yeast Genetics and Molecular Biology (ICYGMB; 2017

ICYGMB

Vishniacozyma victoriae NPCC 1263 yeast biomass, with antagonistic properties against fungal pathogens of postharvest pear fruits, was produced in a previous work using a not optimized molasses-based medium (NOM). The objective of this work was to obtain an optimized a medium (OM) for biomass production in a large-scale bioreactor and to compare the in situ effectiveness of the control agent obtained from the two preparations at commercial scale (organic packinghouse).Experimental Design using a molasses-based medium was employed for the optimization. Variables including molasses, urea, tiamine, KH2PO4 and ZnSO4 concentration as well as temperature were identified to show significant influence on the biomass production, and they were used to perform a Central Composite Experimental Design. According to these results, the highest biomass production was obtained with an optimize medium (OM) containing: 9% v/v molasses, 0.25% p/v KH2PO4, 0.25% p/v ZnSO4 ,0.25 ppm Tiamine and 1 g/l urea, at 13°C. Large scale biomass productions were carried out with both NOM (12.8% v/v molasses, 1 g/L urea, 20°C) and OM in a bioreactor (20L). Growth curves obtained in the bioreactor were fitted using the Gompertz model modified and kinetic parameters A and μmax were obtained (3.1 and 0.12 h-1 in OM medium and 2.6 and 0.04 h-1 in NOM medium, respectively) evidencing an improvement in culture parameters with the OM. Both cell viability following exposure of doses of H2O2 and intracellular ROS production were evaluated in yeast obtained from two preparations. The highest percentages of viability (60%) and the highest production ROS (33%) were obtained in cells from NOM compared with those cells from OM (30 and 3%, respectively). Finally, the biocontrol capacity of the two biomass preparations was evaluated in commercial conditions line-spray application with yeast (107 UFC/mL) in Packham´s pear (1000 fruit). Treated fruits were stored at 1°C, and grey and blue mold disease incidence was recorded after 6 months of storage.In efficacy trials on healthy pear fruit, C. victoriae grown in NOM effectively reduced incidence of Botrytis cinerea and Penicillium expansum in 66% and 86%, respectively while the same yeast grown in OM showed incidence reduction percentages of 63% and 26%, respectively. In conclusion, our findings suggest that resistance to oxidative stress could represent a mechanism by which V. victoriae regulates their viability and biocontrol efficacy when develops in NOM.