Special Issue Article Growth and by-product profiles of Kluyveromyces marxianus cells immobilized in foamed alginate Agnieszka Wilkowska 1 *, Dorota Kregiel 1 , Onur Guneser 2 and Yonca Karagul Yuceer 2 1 Institute of Fermentation Technology and Microbiology, Lodz University of Technology, Poland 2 Department of Food Engineering, Çanakkale Onsekiz Mart University, Turkey *Correspondence to: A. Wilkowska, Wolczanska 171/173, 90–924 Lodz, Poland. E-mail: agnieszka.wilkowska@p. lodz.pl Received: 18 March 2014 Accepted: 26 September 2014 Abstract The aim of this research was to study how the yeast cell immobilization technique influences the growth and fermentation profiles of Kluyveromyces marxianus cultivated on apple/chokeberry and apple/cranberry pomaces. Encapsulation of the cells was performed by droplet formation from a foamed alginate solution. The growth and meta- bolic profiles were evaluated for both free and immobilized cells. Culture media with fruit waste produced good growth of free as well as immobilized yeast cells. The fermentation profiles of K. marxianus were different with each waste material. The most varied aroma profiles were noted for immobilized yeast cultivated on apple/chokeberry pomace. Copyright © 2014 John Wiley & Sons, Ltd. Keywords: Kluyveromyces marxianus; encapsulation; foamed alginate; fruit waste Introduction Yeast strains belonging to the genus Kluyveromyces can be isolated from a wide variety of habitats, resulting in high levels of metabolic diversity and intraspecific polymorphism (Fonseca et al., 2008). A number of studies have been published on the biochemical and metabolic aspects of different Kluyveromyces spp. strains. Some of these have fo- cused on the regulation of respiration and fermenta- tion and on the so-called Crabtree-effect in yeasts (Van Urk et al., 1990; Verudyn et al., 1992). It has been shown that Kluyveromyces spp. are strongly Crabtree-negative and that their oxidoreductive metabolism is a function of increasing glycolytic flux. This yeast cannot grow under strictly anaerobic conditions and its production of ethanol is linked to oxygen limitation (van Dijken et al., 1993; Blank et al., 2005). The development of biotechnological applica- tions using Kluyveromyces marxianus has been motivated by the numerous advantages it offers in comparison to other species among the genus Kluyveromyces, most notably K. lactis. Its most im- portant features include: broad metabolic diversity; thermotolerance; high growth rate; absence of fer- mentative metabolism on sugar excess; and a broad substrate spectrum. Designated by the American Food and Drug Administration (FDA) as ‘generally regarded as safe’ (GRAS), K. marxianus is recog- nized as a potential industrial microorganism (Fonseca et al., 2008). The principal interest of K. marxianus lies in its ability to produce aroma compounds such as fruit esters, carboxylic acids, ketones, furanes, alcohols, etc. 2-Phenylethanol, which has a characteristic rose aroma, is the most desirable of these commercially (Wittmann et al., 2002; Leclercq-Perlat et al., 2004). The influence of the carbon source, level of aeration, media composition and cultivation conditions on aroma production by K. marxianus have been studied intensively (Medeiros et al., 2000, 2001; Etschmann et al., 2004). K. marxianus also manifests a natural ability to excrete different enzymes. This is an advantage in numerous cost-efficient processes using low-value enzymes: Yeast Yeast (2014) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/yea.3044 Copyright © 2014 John Wiley & Sons, Ltd.