Extractive Bioconversion of 2‐Phenylethanol from l‐Phenylalanine by Saccharomycescerevisiae

Abstract

The bioconversion of L-phenylalanine (L-Phe) to 2-phenylethanol (PEA) by the yeast Saccharomyces cerevisiae is limited by the toxicity of the product. PEA extraction by a separate organic phase in the fermenter is the ideal in situ product recovery (ISPR) technique to enhance productivity. Oleic acid was chosen as organic phase for two-phase fed-batch cultures, although it interfered to some extent with yeast viability. There was a synergistic inhibitory impact toward S. cerevisiae in the presence of PEA, and therefore a maximal PEA concentration in the aqueous phase of only 2.1 g/L was achieved, compared to 3.8 g/L for a normal fed-batch culture. However, the overall PEA concentration in the fermenter was increased to 12.6 g/L, because the PEA concentration in the oleic phase attained a value of 24 g/L. Thus, an average volumetric PEA production rate of 0.26 g L(-1) h(-1) and a maximal volumetric PEA production rate of 0.47 g L(-1) h(-1) were achieved in the two-phase fed-batch culture. As ethanol inhibition had to be avoided, the production rates were limited by the intrinsic oxidative capacity of S. cerevisiae. In addition, the high viscosity of the two-phase system lowered the k(l)a, and therefore also the productivity. Thus, if a specific ISPR technique is planned, it consequently has to be remembered that the productivity of this bioconversion process is also quickly limited by the k(l)a of the fermenter at high cell densities.

Elevated production of the aromatic fragrance molecule, 2‐phenylethanol, using Metschnikowia pulcherrima through both de novo and ex novo conversion in batch and continuous modes

“…Stark et al . reported a S. cerevisiae strain to produce 2.35 g L −1 of 2PE from 6 g L −1 l‐phenylalanine in a batch culture, this was increased to 12.6 g L −1 in a fed‐batch culture when removal of the 2PE was applied, bringing the average 2PE production rate to 0.26 g L −1 h ‐1 , with a maximum value of 0.47 g L −1 h ‐1 13. Using a hybrid system involving an immersed hollow fibre membrane module in an air‐lift reactor, the 2PE production in S. cerevisiae was reported to reach 18.6 g L −1 after 72 h in a fed‐batch culture supplemented with 9 g L −1 l‐phenylalanine.…”

“…This was demonstrated by Stark et al . to increase the production 10‐fold with extraction with oleic acid 13. Solid adsorbents also show promise with the hydrophobic polystyrene resin HZ818 boosting production of 2PE to 6.6 g L −1 from S. cerevisiae .…”

Wytwarzanie homo- i heterogenicznych mikrokapsułek oraz ich zastosowanie

“…Such systems are promoting rapid mass transfer thanks to a high surface area. Preventing the formation of stabilized emulsions and problems with toxic effect of organic phases for microorganisms are omitted by the separation of organic phase (core) by the capsule membrane from an aqueous environment [45]. The predominance of the core-shell system over beads is a much larger surface area.…”

“…It helps to overcome respiratory inhibition by both phenylethanol and dibutyl sebacate. As an organic phase core, dibutyl sebacate was used and it was entrapped in calcium alginate hydrogel to form autoclavable liquid-core capsules [45].…”

Lindnera saturnus Kullanılarak Hücresel Biyodönüşüm Yolu ile Fuzel Yağından Muz Aroması Eldesi

“…ISPR using adsorption processes have been mostly applied for the concentration and separation of various bioproducts like proteins, flavours, secondary metabolites etc. Especially, adsorbent resins are used in bioproduction of natural flavours and antibiotics, which are toxic to the producing organisms [20,21]. Adsorption resins have many advantages including high loading capacity, concentration of targeted components, higher adsorption specificities and easier desorption, better mechanical strength and re-uses [21].…”