BIOMASS PRODUCTION OF Vishniacozyma victoriae USING AGRO-INDUSTRIAL WASTES IN BATCH AND SEMICONTINUOUS CULTURES

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

Congreso; XVII Congreso Argentino de Microbiología General; 2022

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. To obtain high amounts of BCA it is necessary to scale up the production process using different reactor configurations and low-cost culture media. This work aimed to evaluate the biomass production of V. victoriae in batch (BC) and semicontinuous (SC) culture using two agro-industrial wastes. Cheese whey powder (CWP), from the lactic industry and apple juice waste (AJW), from the juice industry.Two culture media were optimized using a central composite design (DCC), the composition for each was: AJW 44.4%(v/v), urea 2 g/L, KH2PO4 7.3 g/L, and CWP 80 g/L, NH4(SO2)4 1.2 g/L, KH2PO4 10 g/L. BC and SC fermentations were carried out in a 15 L stirred-tank bioreactor with 12 L of working volume with each culture medium. 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. All fermentations were carried out at 20°C, 300 rpm and 0.64 vvm of aeration. The colony forming unit (CFU) and dry weight (DW) of the yeast biomass were evaluated in both cultures. The DNS method was used to determine the total reducing sugar (RS) concentration and the ammonium content was analyzed using an enzymatic kit. In BC cultures with CWP, the dry weight was 103 g and the CFU was 3.3.1013 reaching a 1.5 g/h productivity in 68 h of incubation whereas with AJW we obtained 124 g DW and 3.1013 CFU after 62 h of incubation with a 2 g/h of productivity. 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 2.1 g/h and 300.8 g DW and 3.9.1019 CFU after 127 h of incubation reaching a productivity of 2.4 g/h using CWP and AJW respectively. The initial ammonium content was 0.44-0.55 g/L in CWP and the consumption was 0.33 g/L in BC and 0.48 g/L in SC, instead, using AJW the initial content was 0.87-1.1 g/L and the consumption was 0.41 g/L in BC and 0.54 g/L in SC. The initial RS concentration was 45-47 g/L using AJW and the consumption was 19 and 21 g/L for BC and SC respectively, instead, using CWP the initial RS concentration was 40-66 g/L and the consumption was 15 and 20 g/L for BC and SC respectively. The results showed that SC culture improves BCA production and reduces the total downtime (harvest, cleaning, sterilize and prepare) between successive reactors for biomass production. Using AJW increases 5 times the UFC and 1.4 times the dry weight, instead these parameters are similar in BC culture with both agro-industrial wastes. Future research will focus on evaluating and comparing the effectiveness of BCA biomass grown in both culture medium and in the two reactor configuration in semi-commercial-scale assays in a packaging line.