Production of 2-phenylethanol by Geotrichum fragrans, Saccharomyces cerevisiae and Kluyveromyces marxianus in cassava wastewater

Abstract

2-Phenylethanol is the most used aroma in food, cosmetics and fragrances industry. Biotechnological production of this aroma is feasible and is studied with a wide variety of microorganisms. The use of agro industrial residues like cassava wastewater as substrates could make bioprocess economically viable. The aim of this study was to evaluate 2-phenylethanol production by Geotrichum fragrans, Kluyveromyces marxianus and Saccharomyces cerevisiae cultivation in cassava wastewater, analyzing the effect of two carbon sources on aroma production. Inoculum preparation was performed using 50 mL of cassava wastewater in 250 mL sterilized Erlenmeyer flask, under agitation at 150 rpm and 28°C for 24 hours. Cultivations were performed aerobically in a batch system in Erlenmeyer flasks containing 50 mL of medium in shaker at 150 rpm and 24±1°C. Cassava wastewater was supplemented with 50 g.L-1 of glucose and 3 g.L-1 of L-phenylalanine, inoculated with each organism and incubated for a period of 120 h. Another assay to determine carbon sources' effect consisted of cassava wastewater's complementation with 50.0 g.L-1 of glucose or fructose, keeping supplementation with 3.0 g.L-1 of L-phenylalanine. Media were inoculated with each organism and incubated for 72 h, under the same conditions adopted in the first cultivation. 2-Phenylethanol determination was carried out on a gas chromatograph equipped with flame ionization detector (FID) using fused silica capillary column Nukol. According to the results, all microorganisms studied produced the desired aroma, and S. cerevisiae stood out with the highest yield, 0.74 g.L-1, followed by K. marxianus, 0.19 g.L-1 in 120 h and finally by G. fragrans, 0.08 g.L-1 at 24 h. S. cerevisiae was the best producer of 2-phenylethanol. Glucose was the best carbon source for obtaining 2-phenylethanol to K. marxianus, whereas for G. fragrans and S. cerevisiae there was no statistical difference between the carbon sources for aroma production.