Tuesday, April 20, 2010
11-51

Production of astaxanthin from cellulosic biomass sugars by mutants of the yeast Phaffia rhodozyma

Justin Montanti1, Nhuan P. Nghiem2, and David B. Johnston2. (1) Biosystems Engineering, Clemson University, 221 McAdams Hall, Clemson, SC 29634, (2) Crop Conversion Science and Engineering, Eastern Regional Research Center, Agricultural Research Service, USDA, 600 E Mermaid Ln, Wyndmoor, PA 19038

Astaxanthin is a carotenoid of high value to the aquaculture, nutraceutical, and pharmaceutical industries. Three mutant strains of the astaxanthin-producing yeast Phaffia rhodozyma, which were derived from the parent strain ATCC 24202 (UCD 67-210) and designated JTM166, JTM185, and SSM19, were tested for their capability of utilizing the major sugars found in cellulosic biomass, including glucose, xylose, and arabinose, for astaxanthin production. While all three strains were capable of metabolizing these sugars, both individually and in mixtures, JTM 185 demonstrated the greatest sugar utilization and astaxanthin production. The kinetics of sugar utilization was studied in fermenters using mixtures of glucose, xylose, and arabinose at varied concentrations. It was found that glucose was utilized preferentially, followed by xylose, and lastly, arabinose. The greatest astaxanthin production per total sugar consumption (0.21 mg/g) was observed when glucose was supplied in very low levels relative to xylose and arabinose, although the final astaxanthin concentration (8.3 mg/ml) was lower than when glucose was supplied at higher concentrations. Hydrolysates produced from corn fiber and barley hulls pretreated by the soaking in aqueous ammonia (SAA) method and hydrolyzed with the commercial cellulase enzyme product, Accellerase 1000, were used for astaxanthin production by the mutant strain JTM185. The results of sugar utilization and astaxanthin production from these hydrolysates will be discussed.    

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