Perspectives for the biotechnological production of ethyl acetate by yeasts

Abstract

Ethyl acetate is an environmentally friendly solvent with many industrial applications. The production of ethyl acetate currently proceeds by energy-intensive petrochemical processes which are based on natural gas and crude oil without exception. Microbial synthesis of ethyl acetate could become an interesting alternative. The formation of esters as aroma compounds in food has been repeatedly reviewed, but a survey which deals with microbial synthesis of ethyl acetate as a bulk product is missing. The ability of yeasts for producing larger amounts of this ester is known for a long time. In the past, this potential was mainly of scientific interest, but in the future, it could be applied to large-scale ester production from renewable raw materials. Pichia anomala, Candida utilis, and Kluyveromyces marxianus are yeasts which convert sugar into ethyl acetate with a high yield where the latter is the most promising one. Special attention was paid to the mechanism of ester synthesis including regulatory aspects and to the maximum and expectable yield. Synthesis of much ethyl acetate requires oxygen which is usually supplied by aeration. Ethyl acetate is highly volatile so that aeration results in its phase transfer and stripping. This stripping process cannot be avoided but requires adequate handling during experimentation and offers a chance for a cost-efficient process-integrated recovery of the synthesized ester.

Efficient growth of Kluyveromyces marxianus biomass used as a biocatalyst in the sustainable production of ethyl acetate

“…Various yeast species can synthesize ethyl acetate (reviewed by Löser et al [9]), but only Pichia anomala, Candida utilis, and Kluyveromyces marxianus produce this ester in larger amounts. K. marxianus is the most promising candidate for large-scale ester production since this dairy yeast with GRAS status grows quickly, converts sugar directly into ethyl acetate without ethanol as an essential intermediate, and produces the ester with a high rate and yield [9][10][11][12][13][14][15][16][17]. The ester synthesis in K. marxianus is easy to control by the level of iron [11,13,[16][17][18].…”

“…Synthesis of ethyl acetate currently proceeds by petrochemical processes, which are based on crude oil constituents or natural gas, run at elevated temperature and pressure and commonly require catalysts [9]. The reactions are often incomplete, and the recovery of ethyl acetate and residual precursors needs a high input of energy.…”

“…The outstanding capability of K. marxianus for lactose utilization offers the chance for using whey as a resource of ester synthesis. K. marxianus converts whey-borne lactose with a high yield into ethyl acetate [9], but its ability for sucrose and glucose assimilation [19][20][21] enables production of ethyl acetate with this yeast from renewables like sugarcane, grain, and corn.…”

“…Although being an irritant and intoxicant at higher concentrations, ethyl acetate is less toxic to humans compared to many other solvents. Ethyl acetate is an environmentally friendly compound since the ester is easily degraded by bacteria [6][7][8] and is regarded as a non-persistent pollutant of the atmosphere [9].…”

A comparative study on the potential of epiphytic yeasts isolated from tropical fruits to produce flavoring compounds

“…The size of the market is ever increasing, with a sales revenue in US$8.6 billion to US 2000 to $23.9 billion in 2013 (http://www.leffingwell.com). Since 1923 (Omelianski, 1923), the microbial production of flavors has been extensively studied and many reviews on this field have been published (Abbas, 2006;Berger, 2009;Buzzini and Vaughan-Martini, 2006;Cheon et al, 2014;Dastager, 2009;Feron et al, 1996;Kim et al, 2014;Krings and Berger, 1998;Löser et al, 2014;Mdaini et al, 2006;Pires et al, 2014;Schrader, 2007;Styger et al, 2011). Yeasts and yeast-like fungi belonging to the genera Saccharomyces, Yarrowia, Geotrichum, Saprochaete, Pichia, Candida, Williopsis, and Kluyveromyces are recognized as reference yeast species for flavor production (Schrader, 2007;Willaert et al, 2005).…”