Abstract

In order to use purple non-sulfur bacteria as feed supplement in chicken industries, screening for red pigment-producing bacteria with proteinases was done using hen feces as a target. One isolate, P₄₁, with the highest proteinases activity was selected for further studies. Based on the data of biochemical and 16S rDNA sequence analysis, it was identified as Enterobacter sp. P₄₁. This strain produced 0.16 mg of β-carotene with red color per gram of cell dry weight. Addition of the dried cells ofEnterobacter sp. P₄₁ to chicken feeds did significantly intensify the egg yolk color (p = 0.000). Moreover, addition of the dried cells at the amount of 0.45 mg per kg of feed significantly increased the rate of egg-laying (p = 0.029). These results suggest that the dried cells of Enterobacter sp. P₄₁ might be useful as feed supplement for hens or other avian.

Key words: β-Carotene, Enterobacter sp., red carotenoid pigment, egg yolk, egg-laying rate, proteinase.