Novel type of in situ extraction: Use of solvent containing microcapsules for the bioconversion of 2‐phenylethanol from L‐phenylalanine by Saccharomyces cerevisiae

Abstract

A novel in situ product removal (ISPR) method that uses microcapsules to extract inhibitory products from the reaction suspension is introduced into fermentation technology. More specifically, L-phenylalanine (L-Phe) was transformed by Saccharomyces cerevisiae to 2-phenylethanol (PEA), which is inhibitory toward the yeast. In order to continuously remove PEA from the vicinity of the cells, the reaction suspension was brought into contact with capsules of 2.2-mm diameter that had a hydrophobic core of dibutyl sebacate and an alginate-based wall. This novel process combines the advantages of a normal in situ extraction process (fast mass transfer and simple process set-up) with the benefits of a membrane-based process (reduction of the solvent toxicity and avoidance of stable emulsions). In particular, the microbial cells are shielded from the phase toxicity of the organic solvent by a hydrogel layer surrounding the organic core. By placing the microcapsules into the fermenter, the final overall concentration of PEA in a fed-batch culture was increased from 3.8 to 5.6 g/L because a part of the inhibitory product dissolved in the dibutyl sebacate core. In another fermentation experiment, the capsules were placed in a fluidized bed that was connected via a loop to the fermenter. In addition, the fluidized bed was connected via a second loop to a back-extractor to regenerate the capsules. By alternating the extraction and back-extraction cycles, it was possible to limit the PEA concentration of the fed-batch culture in the fermenter to 2.4 g/L while producing important quantities of PEA that accumulated in an external reservoir.

Bioproduction of the aroma compound 2‐Phenylethanol in a solid–liquid two‐phase partitioning bioreactor system by Kluyveromyces marxianus

“…Etschmann and Schrader (2006) achieved the highest 2-PE concentration (10.2 g/L overall) reported by using K. marxianus CBS 600. Other ISPR techniques such as microcapsulation (Serp et al, 2003;Stark et al, 2003); and organophilic pervaporation (Etschmann et al, 2005) have also been reported.…”

Ca-Alginate Liquid Core Capsule for Lactobacili Fermentation

“…Moreover, the alginate may be gelled and clogged at the orifice of the nozzle if the flow rate of the solutions was not properly determined. Even so, the clogging issue could be avoided if vibration force was applied to the nozzle (Whelehan et al 2010;Marison et al 2004;Wyss et al 2004;Stark et al 2003).…”

“…The tested neutralizing agents are Alamine-336 in oleyl alcohol and calcium carbonate (Lee et al 2013;Tik et al 2001). Since the capsules have low mass transfer resistance, the solutes/ions could be freely diffused between the inner liquid core and the fermentation media through the capsular membrane to react with the inhibitors (Lee et al 2013;Whelehan et al 2010;Marison et al 2004;Koyama and Seki 2004b;Chai et al 2004;Wyss et al 2004;Stark et al 2003). The neutralization could be achieved via liquid-liquid extraction (Whelehan et al 2010;Marison et al 2004;Wyss et al 2004Wyss et al , 2004Wyss et al , 2005Stark et al 2003).…”

“…Furthermore, the semi-porous membrane allows the solutes to diffuse into and out from the inner core of the capsule with minimum resistance. Since the capsules have low diffusion resistance, they have been used for medicinal drug delivery, nutritional supplements delivery and they also allow development of a new reactive perstraction system based on the principle of liquid-liquid extraction (Whelehan et al 2010;Marison et al 2004;Wyss et al 2004Wyss et al , 2004Wyss et al , 2005Stark et al 2003).…”

Supercritical Fluid Application in Food and Bioprocess Technology

“…End-product inhibition occurs in many fermentation processes and in situ removal of them typically enhances product formation rates, yields, and specificity (Christen et al, 1990;Gyamerah and Glover, 1996;Qureshi et al, 1998). Techniques that have been employed for in situ removal of fermentation products include liquid-liquid extractive fermentation (Adrian et al, 2000), use of selective membranes (Chang et al, 1992), cell recycling (Roca and Olsson, 2003), adsorption (Millitzer et al, 2002), microcapsule application (Stark et al, 2003) and vacuum fermentation (Qureshi et al, 1998). However, the intimate contact of an organic phase with the broth implies that the organic components of this phase may be present in the aqueous www.intechopen.com phase at saturation levels.…”