Enhanced bioconversion of L-phenylalanine into 2-phenylethanol via an oxygen control strategy and in situ product recovery

BACKGROUND: 2-Phenylethanol (PEA) production through bioconversion of L-phenylalanine (L-Phe) has been gaining increasing global interest in recent years. Studies have been conducted on the bioconversion of L-Phe into PEA using Saccharomyces cerevisiae. However, the influence of oxygen supply on the bioconversion has not been investigated thus far. In this research, we have attempted not only to explore the effects of oxygen on bioconversion of L-Phe, but also to develop strategies to enhance PEA production. RESULTS: Experimental results indicated that two-stage batch fermentation with oxygen supply control showed optimal operation for culture. The employment of a semi-continuous culture enhanced total PEA by 35.53% more in comparison to batch culture. In situ product recovery (ISPR) using polydimethylsiloxane (PDMS) sponge reduced the ethanol and PEA in the broth by approximately 4.2 and 0.50 g L⁻¹ for each operation, respectively. However, semi-continuous culture with ISPR failed to enhance total PEA because high glucose concentration and low oxygen supply triggered ethanol production. Based on these results, a novel three-stage ISPR fermentation by oxygen supply control was designed to maximize PEA production and minimize both the product feedback inhibition and ethanol formation. As a result, the total PEA concentration at 5.14 g L⁻¹ was achieved. CONCLUSION: We propose that a multi-stage fermentation strategy with both oxygen control and ISPR can be employed to enhance PEA formation by S. cerevisiae.