Development of a Continuous System for 2-Phenylethanol Bioproduction by Yeast on Whey Permeate-Based Medium

Abstract

2-Phenylethanol (2-PE) is an alcohol with a rosy scent and antimicrobial activity, and therefore, it is widely used in the food and cosmetic industries as an aroma and preservative. This work was aimed to draw up a technology for 2-PE bioproduction on whey permeate, which is waste produced by the dairy industry, rich in lactase and proteins. Its composition makes it a harmful waste to dispose of; however, with a properly selected microorganism, it could be converted to a value-added product. Herein, two yeast Kluyveromyces marxianus strains and one Kluyveromyces lactis, isolated from dairy products, were tested for 2-PE production, firstly on standard media and then on whey permeate based media in batch cultures. Thereafter, the 2-PE bioproduction in a continuous system in a 4.8 L bioreactor was developed, and subsequently, the final product was recovered from culture broth. The results showed that the yield of 2-PE production increased by 60% in the continuous culture compared to batch culture. Together with a notable reduction of chemical oxygen demand for whey permeate, the present study reports a complete, effective, and environmentally friendly strategy for 2-PE bioproduction with a space-time yield of 57.5 mg L^-1 h^-1.

Keywords: 2-phenylethanol; Kluyveromyces; batch culture; bioreactor; continuous culture; whey permeate; yeast.

Figure 1

Effect of the presence of exogenous 2-PE on the growth of (a) K. lactis WUT175, (b) K. marxianus WUT216, and (c) K. marxianus WUT240. For each strain, four 48 h batch cultures in SAB were conducted. When the cultures reached OD₆₀₀ values of 0.6–0.8 (indicated by a red arrow), 2-PE was added to three cultures to final concentrations of 2, 3, and 4 g L⁻¹, respectively. The fourth culture was not supplemented with 2-PE and served as a control. Analyses were performed in triplicate and data are presented as the mean ± SD. Statistical significance between values is marked with asterisks.

Figure 2

Schematic representation of continuous system for 2-PE bioproduction and its recovery from fermentation broth.

Figure 3

Reduction of COD load in K. marxianus WUT240 cultures over 48 h batch and 72 h continuous operation in a 4.8 L bioreactor.