Biotechnology Letters 22: 313–316, 2000. © 2000 Kluwer Academic Publishers. Printed in the Netherlands. 313 Influence of medium composition and aeration on the synthesis of biosurfactants produced by Candida antarctica Marek Adamczak ∗ & Wlodzimierz Bednarski Institute of Food Biotechnology, Warmia and Masuria University in Olsztyn, Heweliusz St. 1, 10-718 Olsztyn, Poland ∗ Author for correspondence (Fax: +48 89 5273908; E-mail: marecki@art.olsztyn.pl) Received 23 August 1999; Revisions requested 21 September 1999/14 October 1999; Revisions received 8 October 1999/5 January 2000; Accepted 5 January 2000 Key words: aeration, biosurfactant, Candida antarctica, glycolipid, mannosylerythritol lipids Abstract Candida antarctica synthesised surface-active mannosylerythritol lipids at 46 g l −1 by adding 80 g soybean oil l −1 to the medium and maintaining the pO 2 at 50% with an air flow rate 1 vvm. Two-stage culturing of C. antarctica avoided medium foaming but the yield of biosurfactants synthesis was 28 g l −1 . The biosurfactants decreased the surface tension of water to 35 mN m −1 . Introduction With the aim of decreasing the amount of chemically- synthesised surface-active agents in food, cosmetics and pharmaceutical products and in environmental protection, microbial biosurfactants are increasingly considered (Banat 1995, Desai & Banat 1997). Mainly bacteria and yeasts are able to synthesise biosurfac- tants (Kosaric 1995). Microbial biosurfactants have an advantage over their chemical counterparts due to their better physical and chemical properties, e.g., foaming, environmen- tal compatibility and higher biodegradability. They may be used at extreme temperatures, acidity, and salt concentrations (Banat 1995). Microbial biosur- factants are divided into different groups. Their char- acteristics have been reviewed recently (Bednarski & Adamczak 1999). The major and best-known group of biosurfactants synthesised by micro-organisms are the glycolipids (Desai & Banat 1997). Microbial biosurfactants are either extra- or intra- cellular compounds. Their presence can be observed mainly during cell growth in medium containing lipid substrates (Desai & Banat 1997). For biosurfactants synthesis, by-products or wastes such as whey or even single cell oil can be used (Daniel et al. 1999). Microbial lipids can be ob- tained from yeasts cultivated in whey or beet molasses after extraction or cell disruption for this purpose (Bednarski et al. 1986, Daniel et al. 1999). Mannosylerythritol lipids are examples of micro- bial glycolipids synthesised by Candida spp. Extra- cellular mannosylerythritol lipids synthesised by Can- dida antarctica T-34 during submerged shake cultiva- tion were characterised by Kitamoto et al. (1990a,b, 1992, 1993). Currently, there is a lack of information on man- nosylerythritol lipids synthesised during submerged growth in fermenters. Therefore, it was decided to determine the conditions of biosurfactants synthesis by Candida antarctica cultured in submerged culti- vation in a fermenter. Particular attention was paid to the adjusting of aeration conditions and the related problem of medium foaming enhanced by synthesised biosurfactants. The aim of our experiments was also to release biosurfactants with foam from cultivation medium and to evaluate their physical and chemi- cal properties. It was very important to evaluate the physical and chemical properties of the biosurfactants extracted from medium.