Enhanced 2-phenylethanol and co-production of pullulan from synthetic medium by Aureobasidium pullulans

Abstract

2-phenylethanol (2-PE) and its derivatives play crucial roles in food flavoring and fine chemical synthesis. However, their industrial-scale production yields remain a key constraint for broader industrial implementation. To overcome this challenge, we implemented an integrated in-situ product adsorption (ISPR) strategy combined with nitrogen source restriction and a high-glucose medium formulation during 2-PE biosynthesis using Aureobasidium pullulans (A. pullulans) A5. Notably, this approach enabled simultaneous co-production of 2-PE and the commercially valuable exopolysaccharide pullulan. The experimental protocol comprised two phases: First, we established a basal production medium (medium-1) containing 20 % (w/v) glucose and 1.8 % (w/v) Yeast Nitrogen Base (YNB). Subsequently, we systematically screened adsorption agents, identifying Trialkylphosphine Oxide (TRPO) as an optimal extractant that demonstrated selective 2-PE adsorption capacity but not for L-phenylalanine (L-phe). In the optimized system, supplementation of 10 mL TRPO to 50 mL medium-1 (pH 6.0) supplemented with 4 g/L of L-phe as precursor resulted in 2.39 g/L 2-PE production (60 % molar conversion efficiency) and 5.16 g/L pullulan accumulation after 48 h fermentation. Process analysis revealed that TRPO-mediated ISPR enhanced 2-PE volumetric productivity, while the high-carbon medium configuration synergistically increased both target metabolite titers. These technical improvements significantly improved process economics while simultaneously streamlining downstream processing for industrial-scale operations