SCALING UP THE BIOMASS PRODUCTION OF Vishniacozyma victoriae AND BIOCONTROL EFFICACY IN SEMI-COMMERCIAL ASSAY IN THE CONTROL OF PEAR POSTHARVEST DECAYS

SANGORRIN; MARCELA PAULA; GORORDO, M.F.; LUCCA, M.E.

Simposio; SAMIGE XIX; 2023

Biological control agents (BCA) are widely proposed as an alternative to chemical fungicides to prevent fungal diseases in organic pear production. Vishniacozyma victoriae yeast was previously isolated and selected because of its biocontrol effectiveness of pear postharvest decays. To obtain high amounts of BCA it is necessary to scale up the production process using different reactor configurations and low-cost culture medium. In the laboratory we have evaluated residues for the biomass production in batch at 12L (BC12), 100 L (BC100) and semicontinuous (SC) culture using cheese whey powder (CWP) from the lactic industry.The culture media employed in different reactor was optimized using a central composite design (DCC): CWP 80 g/L, NH4(SO2)4 1.2 g/L, KH2PO4 10 g/L. BC12 and SC fermentations were carried out in a 15 L stirred-tank bioreactor with 12 L of working volume. The SC was fed three times at 24-h intervals, before feeding, 5 L of culture contents was removed, and 5 L of fresh culture was then added reaching 27 L volume production. BC12 and SC fermentations were carried out at 20°C, 300 rpm and 0.64 vvm of aeration. BBC100 fermentation was carried out in a 140 L stirred-tank bioreactor with 100 L of working volume (PROIMI), at 20°C, 200 rpm and 1 vvm of aeration.In BC12 cultures the dry weight (DW) was 103.6 g and the CFU was 3.3.1013 reaching a 1.4 g/L.h productivity in 65 h of incubation. In SC culture, we obtained a total of 221.2 g DW and 1.8.1014 CFU after 105 h of incubation reaching a productivity of 0.31 g/h. In BC100 we obtained a total of 2070 g DW and 2.6.1015 CFU after 70 h of incubation reaching a productivity of 0.30 g/h. The results showed that SC culture improves BCA production comparted to BC12, since it doubles the volumetric productivity and reduces the total downtime (harvest, cleaning, sterilize and prepare) between successive reactors for biomass production. Using BC100 increases three orders of magnitude the UFC and 20 fold the dry weight with respect to SC12.The efficacy of V. victoriae for controlling postharvest decay of pear fruits was evaluated in semicommercial packing-house conditions with the application of 108 CFU mL-1 on two pear cultivars. After 150 days of storage, fresh (BC12, BC100 and SC) and lyophilized-rehydrated biomass treatment reduced the incidence caused by B. cinerea, P. expansum and Cladosporium spp. The treatment yeasts were able to control decay (40-85% control) and colonize the surface of the fruits during the postharvest period, with an estimated increase in the population density of approximately three log units independently of the treatment applied.This study provides evidence of the suitability of the developed scaling process, highlighting its high volumetric productivity. Furthermore, the effectiveness of both fresh and dried biomass in reducing the incidence of diseases caused by major pathogenic fungi during the post-harvest conservation of pears has been verified