β-Carotene production by Flavobacterium multivorum in the presence of inorganic salts and urea

Abstract

Flavobacterium multivorum, a non-fermenting Gram-negative bacteria, normally produces zeaxanthin (3R, 3′ R-β, β-carotene-3, 3′ diol) as its main carotenoid. The effect of supplementation of various inorganic salts and urea on the growth, total carotenoid production, and proportion of β-carotene (β, β-carotene), β-cryptoxanthin (β, β-caroten-3-ol), and zeaxanthin produced by F. multivorum was investigated. Urea and several salts, such as calcium chloride, ammonium chloride, lithium chloride, and sodium carbonate, improved total carotenoid production by 1.5- to 2.0-fold. Urea and sodium carbonate had an unexpectedly strong positive effect on β-carotene production at the expense of zeaxanthin formation. The effect was found to be independent of incubation time, and β-carotene represented 70% (w/w) of the total carotenoid content. The cumulative effect of urea and sodium carbonate was further studied using response surface methodology. An optimum medium was found to contain 4,000 and 4,070 mg l-1 urea and sodium carbonate, respectively. The maximum β-carotene level was 7.85 μg ml-1 culture broth, which represented 80% (w/w) of the total carotenoid produced. Optimization resulted in 77- and 88-fold improvements in the volumetric and specific β-carotene levels, respectively, accompanied by a simultaneous decrease in the zeaxanthin level as compared to the control medium. The carotenoid production profile in the optimized medium indicated that β-carotene was produced maximally during the late exponential phase at 0.41 μg ml-1 h-1. It is possible that this organism could be an excellent commercial source of either β-carotene or zeaxanthin, depending on initial culture conditions. © Society for Industrial Microbiology 2004.