Hydrolysis Of Yeast-wall With Lytic Enzyme For Extraction Of Astaxanthin From Phaffia Rhodozyma And Inclusion Of Astaxanthin With β-Cyclodextrin

The rigid cell wall of Phaffia rhodozyma severely hampers the availability of astaxanthin because astaxanthin is accumulated in lipid droplets in the cytoplasmatic membranes, so its cell wall must be modified by suitable methods to enhance the absorption of pigment for animals and the extractability of astaxanthin. The present study investigated the production of lytic enzyme with Bacillus circulans, the extraction of astaxanthin after hydrolysis of yeast-walls with the lytic enzyme, the stability of astaxanthin and the encapsulation of astaxanthin with β-cyclodextrin for protecting it from oxidation. Some new technologies, viewpoints and results were suggested as follows:Bacillus circulans A1.383 producing lytic enzyme was mutagenized with UV and further screened through repeated shake flask experiments, and one plus-mutant with highly genetic stability was acquired. The lytic enzyme production of the plus-mutant(A 1.383-2) increased by 116.9% compared with that of the original strain. The effects of different factors on the lytic enzyme production of B. circulans A1.383-2 were studied in shake flask fermentation. Yeast glucan (10 g/L, water insoluble) was the best C sources and the mixture of peptone and (NH₄)₂SO₄ was the best N sources (total concentration equivalent to 4 g/L). The best inoculum concentration was 6%¹0%(v/v) and 40 mL medium volume in 250 mL triangle flask was benefit for B. circulans A1.383-2 to produce the lytic enzyme which had the high enzyme activity. The fermentation temperature and the best initial pH value of the culture medium were 30℃³5℃ and 6.5⁷.0, respectively. The lytic enzyme activity of fermentation fluid reached 74.6 u/mL when B. circulans A 1.383-2 was cultivated on the above-mentioned conditions, increasing 38.7% contrasted to the initial.The optimum reaction conditions of the lytic enzyme produced by B. circulans A1.383-2, which was used to hydrolyze the yeast-walls for extraction of astaxanthin from Phaffia rhodozyma, were studied by the single factor experiment and the uniform design. When the reaction temperature and pH for the astaxanthin extraction were 37℃ and 5.0, respectively, and 1614.5 u/(g dry yeast) lytic enzyme was added, over 98% of the astaxanthin could be extracted within 16.5 h. The lytic enzyme which mainly contained β-1,3-glucan, cellulose, casein, chitin, soluble starch hydrolyzing activity was stable below 50℃ and within the pH range 4.8⁹.8.2-deoxy-D-glucose, a glucose analogue, can hinder the cellular utilization of...