Ivana Marova1, Milan Certik2 and Emilia Breierova3 1Brno University of Technology, Faculty of Chemistry, Centre for MaterialsResearch, Purkynova 118, 612 00 Brno, 2Slovak Technical University, Faculty of Chemical and Food Technology, Bratislava, 3Institute of Chemistry, Slovak Academy of Sciences, Bratislava, 1Czech Republic 2,3Slovak Republic

1. Introduction

Yeasts are easily grown unicellular eukaryotes. They are ubiquitous microorganisms, occuring in soil, fresh and marine water, animals, on plants and also in foods. The environment presents for yeast a source of nutrients and forms space for their growth and metabolism. On the other hand, yeast cells are continuously exposed to a myriad of changes in environmental conditions. These conditions determine the metabolic activity, growth and survival of yeasts. Basic knowledge of the effect of environmental factors on yeast is important for understanding the ecology and biodiversity of yeasts as well as for control the yeast physiology in order to enhance the exploitation of yeasts or to inhibit or stop their harmful and deleterious activity.

The overproduction of some metabolites as part of cell stress response can be of interest to the biotechnology. For instance carotenogenic yeasts are well known producers of biotechnologically significant carotenoid pigments — astaxanthin, P-carotene, torulen, torularhodin and under stress conditions this carotenoid accumulation was reported to be increased. Knowledge of molecular mechanism of the carotenoid production stimulation can then lead to improvement of such biotechnological process. Red yeasts are able to accumulate not only carotenoids, but also ergosterol, unsaturated fatty acids, Coenzyme Q10 and other, which can contribute to the biomass enrichment. The use of this stressed biomass in feed industry could have positive effect not only in animal and fish feeds because of high content of physiologically active substances, but it could influence nutritional value and organoleptic properties of final products for human nutrition.

Yeast biomass, mainly in the form of Saccharomyces cerevisiae, represents the largest bulk production of any single-celled microorganism throughout the world. In addition to use of

live yeast biomass for the leavening of bread dough, many other applications of yeast cells and yeast cell extracts have emerged. Most yeast biomass for industrial use is derived from Saccharomyces cerevisiae, but other yeasts have specific uses and may be grown on a range of substrates unavailable to S. cerevisiae. Some yeast strains are usable to industrial single-cell protein production from lignocellulose materials, methanol, n-alkanes, starch, oils and also other cheap carbon sources. Except compresses baker’s yeasts for baking, brewing, winemaking and distilling also other whole-cell yeast products are industrially used as animal feed, human and animal probiotics, as biosorbents for heavy metal sequestration and, also as nutritional trace element sources. Yeasts are rich sources of proteins, nucleic acids, vitamins and minerals but mostly with negligible levels of triglycerides.

Pigmented yeasts are used as feed and food colorants and, come of them, also as single cell oil producers. This chapter will be focused on controlled production of biomass and some interesting lipid metabolites of several non-traditional non-Saccharomyces yeast species. Growing interest in yeast applications in various fields coupled with significance of carotenoids, sterols and other provitamins in health and dietary requirements has encouraged "hunting" for more suitable sources of these compounds.