Valorization of agro-industrial wastes by producing 2-phenylethanol via solid-state fermentation: Influence of substrate selection on the process

Abstract

2-phenylethanol (2-PE) is a value-added compound widely used in industry due to its rose-like odor and antibacterial properties that can be bioproduced using wastes as raw materials. This study presents the valorization of nine agro-industrial wastes as potential substrates for 2-PE production using an isolated 2-PE producer Pichia kudriavzevii, and the solid-state fermentation (SSF) technology as an alternative approach. The assessed substrates comprised wastes of varied traits such that each of them provided different characteristics to the fermentation. Thus, by using a principal component analysis (PCA), it was possible to identify the most significant characteristics associated with the substrates affecting the 2-PE production. Results show that L-phenylalanine biotransformation was more efficient than de novo synthesis for producing 2-PE. Besides, from the evaluated set, the maximum 2-PE production was achieved with red apple pomace, reaching 1.7 and 25.2 mg_2PE per gram of used waste through de novo and L-phenylalanine biotransformation, respectively. In that scenario, volumetric productivity and precursor yield were 39.6 mg_2PE L^-1h^-1 and 0.69 g_2PE per gram of L-phenylalanine added_, respectively. From the PCA, it was identified that the reducing sugars content of the substrate, the air-filled porosity of the bed and the L-phenylalanine availability were the most critical parameters (associated with the substrates) influencing the microbial activity and 2-PE production. These results suggest that the desirable traits a solid media needs for promoting 2-PE production via SSF could be reached by using a combination of wastes in a synergistic approach.

Keywords: Aroma compounds; Pichia kudriavzevii; Rose-like compounds; Solid-state fermentation; Substrate screening; Waste valorization.