Use of cider waste for the formulation of an economic culture medium for the production of yeast biomass

JOSEFINA MAGDALENA FONTANINI; ANDREA C. ORIGONE; MARCELA P. SANGORRÍN; M. EUGENIA RODRÍGUEZ

Los Cocos

Congreso; XVII Congreso Argentino de Microbiología General; 2022

Sociedad Argentina de Microbiología General - SAMIGE

The fermented beverage industries, particularly cider, generate large tons of waste per year, including bagasse and lees. It was shown that these wastes represent a potential source of nutrients for the formulation of culture media when the apple bagasse was chemically treated in order to increase the amount of free sugars (SAMIGE 2021). Therefore, the objective of this work was to optimize the lees autolysis method to increase the availability of nitrogen and the subsequent formulation of an economical culture medium using both substrates that could be useful for the propagation of unconventional yeast strains of Saccharomyces uvarum NPCC 1420 and Saccharomyces eubayanus NPCC 1292. To optimize autolysis of lyophilized lees a central composite design was used to evaluate the effect of the variables: incubation time (24-48 h), lees g/L of solution (20-40 g/L) and pH (3.5-6.5) adjusted with NaOH. The assays were carried out at a final volume of 200 mL in constant agitation (150 rpm), at 50°C (water bath equipment). Yeast assimilable nitrogen (YAN) concentration was determined as the response variable. The optimal conditions obtained forthis design were: pH 6.5 and concentration 20 g/L for 36 h, obtaining a value of 97,6 mg N/100 g lees. To increase the yield of YAN, a new CCD Split Plot was performed with the following factors: temperature (40-60 °C), pH (3.5-6.5) and time (24-48 h), being YAN concentration the responsevariable. Lees concentration was set at 30 g/L. The highest nitrogen concentration reached (192 mg N/100 g lees) was obtained under the conditions pH 5.33 at 60°C for 24h.In order to evaluate the growth of unconventional yeast strains using the treated residues as substrate, a statistical design of mixtures was used. The design showed 14 runs with different proportions of the residues. The assays were carried out in 30 mL of substrate and growth was followed by DO640nm. The response variables for both strains were dry weight (g/L) and maximum biomass reached (A). The cultures were adjusted to pH 5 and incubated at 20°C and shaking (150 rpm). The strain NPCC 1420 showed the best growth under the following conditions: 20% Bagasse + 80% lees, showing a dry weight of 4.2 g/L and an A of 5.1, while the strain NPCC 1292 evidenced better weight dry values and A -3.2 g/L and 4.8, respectively- at 35.8% Bagasse + 64.2% lees. The results obtained suggest the possibility of using these two residues - bagasse and lees - as carbon and nitrogen sources for the formulation of economic culture media for biomass production of yeasts.