Short communication Improved production of lycopene and b-carotene by Blakeslea trispora with oxygen-vectors Fang Xu, Qi-Peng Yuan * , Yan Zhu College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, P.O. Box 75, PR China Received 15 January 2006; received in revised form 26 July 2006; accepted 18 August 2006 Abstract Lycopene and b-carotene production were increased when oxygen-vectors, n-hexane and n-dodecane, were added to cultures of Blakeslea trispora because of the enhanced dissolved oxygen concentrations. With 1% (v/v) n-hexane or n-dodecane added in the medium, lycopene production was 51% or 78% higher and b-carotene production was 44% or 65% higher than that of the control, respectively. The highest lycopene and b-carotene production, 533 mg l À1 and 596 mg l À1 , were obtained when 1% (v/v) n-dodecane and 0.1% (w/v) Span 20 were added together, which were 2.1-fold and 1.8-fold of the control, respectively. # 2006 Elsevier Ltd. All rights reserved. Keywords: Lycopene; b-Carotene; Blakeslea trispora; Oxygen-vectors; Span 20 1. Introduction Lycopene and b-carotene, two kinds of important fat soluble carotenoids, are essential nutrients in human diet because they prevent cardiovascular diseases, regulate the immuno system and are considered as anti-carcinogenic agents and antioxidants [1,2]. The classical, natural sources of carotenoids are fruits, vegetables and microorganisms. The zygomycete, Blakeslea trispora, is used on an industrial scale to produce b-carotene [3,4], and a semi-industrial process has also been developed for lycopene production [5]. B. trispora is an aerobic microorganism and sufficient supply of oxygen can improve both cell growth and carotenoid synthesis [6,7]. However, the high viscosity of the fermentation broth, the intertwined mycelial growth of B. trispora and the low solubility of oxygen in water result in a deficiency of the dissolved oxygen in the fermentation medium [8,9]. How to increase the concentration of dissolved oxygen in the medium is very important for the culture of B. trispora. One approach to achieve better oxygen supply is by the addition of oxygen- vectors, which can increase the apparent solubility of oxygen in the medium [10,11]. Oxygen-vectors are hydrophobic liquids in which oxygen has a higher solubility than in water. Hemoglobin, perfluorochemicals and hydrocarbons are gen- erally used as oxygen-vectors in biotechnology [12,13]. Hydrocarbons are more favored for large-scale fermentation because they are cheaper compared to hemoglobin and perfluorochemicals. In this paper, the effects of two oxygen- vectors, n-hexane and n-dodecane, on the production of lycopene and b-carotene by B. trispora have been investigated in order to enhance the fermentation efficiency. 2. Material and methods 2.1. Microorganism and culture medium B. trispora ATCC 14271, mating type (+), and ATCC 14272, mating type (À), which were maintained on potato dextrose agar slants, were grown in the seed medium (starch 40 g l À1 , corn hydrolysate 50 g l À1 , KH 2 PO 4 1gl À1 , MgSO 4 0.1 g l À1 , Vitamin B 1 0.01 g l À1 , pH 6.5) at 28 8C for 40 h in 500 ml flasks containing 100 ml medium. The cultures were used for the inoculation of the fermentation medium. 2.2. Fermentation conditions The fermentation was carried out in 500 ml flasks with 100 ml medium including 10% inoculum, and the inoculum was a 1:2 (volume ratio) mixture of ATCC 14271 (+) and ATCC 14272 (À). The fermentation medium had the following composition (g l À1 ): starch 40; soybean meal 20; corn hydrolysate 25; KH 2 PO 4 1; MgSO 4 0.1; Vitamin B 1 0.01; pH 6.5. Before autoclaving the components of the medium were heated until dissolved completely. In addition to the control, sterilized n-hexane or n-dodecane was added to the fermentation medium at the concentration of 1% (v/v) and Span 20 at 0.1% (w/v) or as otherwise stated. The flasks were incubated at 28 8C in a rotary www.elsevier.com/locate/procbio Process Biochemistry 42 (2007) 289–293 * Corresponding author. Tel.: +86 10 64437610; fax: +86 10 64437610. E-mail address: yuanqp@mail.buct.edu.cn (Q.-P. Yuan). 1359-5113/$ – see front matter # 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.procbio.2006.08.007