Microbial formation of esters

Kluyveromyces marxianus is capable of converting lactose into ethyl acetate offering a chance for an economical reuse of whey. The microbial formation of ethyl acetate as a bulk product calls for an aerobic process and, thus, the highly volatile ethyl acetate is discharged from the aerated bioreactor. This stripping process was modeled and investigated experimentally. The stripping rate was proportional to the gas flow and nearly independent of the stirring rate since the stripping was governed by the absorption capacity of the exhaust gas rather than the phase transfer. Cooling the exhaust gas did not noticeably influence the stripping. One batch experiment is presented in detail to demonstrate the formation of ethyl acetate by K. maxianus DSM 5422 on whey. Further batch experiments showed that a substantial formation of ethyl acetate only occurred when the yeast growth was limited by a lack of trace elements. The highest product yield observed was 0.25 g ethyl acetate per g lactose which is nearly 50% of the theoretical maximum.

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“…[11][12][13]). Most research in this field has been aimed at the formation of esters as aroma compounds and is still ongoing [1,14,15].…”

Section: Introductionmentioning

confidence: 97%

Formation of ethyl acetate by Kluyveromyces marxianus on whey: studies of the ester stripping

Urit

Löser

Wunderlich

et al. 2010

Bioprocess Biosyst Eng

141

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“…According to their chemical structure, the esters can be divided into three groups: acetate esters, ethyl esters and other esters (Park et al, 2009). Among these esters, only ethyl decanoate was found to be significantly different among the wine closures tested.…”

Section: Analysis Of Volatile Compoundsmentioning

confidence: 99%

Effect of Wine Closures on the Aroma Properties of Chardonnay Wines after Four Years of Storage

Liu¹,

Song²,

Dang³

et al. 2015

SAJEV

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The effects of wine closures on the sensory properties and aroma profiles of fresh Chardonnay wines were evaluated after four years of bottle storage. Natural cork closure, technical cork closure, Nomacorc light, Nomacorc classic and Nomacorc premium were investigated. Among these wines sealing with different closures, the physicochemical parameters of the wine samples showed no significant differences, except that of the free and total sulphur dioxide. Nomacorc light with the highest OTR (oxygen transition rate) had the least residual free sulphur dioxide. Most of volatiles were generally stable, and seven compounds (acetoin, 1-butanol, 2-phenylethanol, 1-pentanol, (Z)-3-hexen-1-ol, 2-nonanol and ethyl decanoate) were significantly affected by the wine closures. The sensory analysis revealed that cork closures preserved more fruity/flowery characters of the fresh wines after four years' storage, as well as cork-tainted off-flavour. Two synthetic closures (Nomacorc light, Nomacorc classic) imparted some grilled attributes to the wines. Nomacorc premium highly reserved the fruity/flowery flavour without cork contamination or oxidised toasted characters.

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“…ethyl hexanoate is another important compound, with a fruity characteristic note (PASTore; PArK; MIN, 1995;YAMAUCHI;HASUo;AMACHI, 1989;YAMAUCHI, 1991;YoSHIZAWA et al, 1988). The formation of other microbial esters was recently described in a review (PArK et al, 2009). …”

Section: Bioflavorsmentioning

confidence: 99%