A FACTORIAL APPROACH FOR A SUGARCANE JUICE-BASED LOW-COST CULTURE-MEDIUM - INCREASING THE ASTAXANTHIN PRODUCTION BY THE RED YEAST PHAFFIA-RHODOZYMA

A sugarcane juice-based low cost culture medium was previously explore d to produce the carotenoid pigment astaxanthin in liquid culture by t he red yeast Phaffia rhodozyma (1300 mu g astaxanthin/g of dry yeast a nd 6500 mu g/l whole culture medium). Two peculiar limitations in Phaf fia are growth temperature (<26 degrees C) and lack of sugar osmotoler ance. Two advantages are the wide biochemical ability for the assimila tion and metabolization of disaccharides and the prompt utilization of simple nitrogen sources. For instance, the sucrolytic/ureolytic enzym atic activities deserves exploration. In order to improve the culture medium composition and the conditions of fermentation for highly oxyge nated carotenoids (e.g., astaxanthin) a study was carried out with a f actorial design in two steps. As a first step, the production of astax anthin was studied as a function of the nutrient concentration levels and their interactions. The production increase (mu g/l) obtained was 23.0% but at the expense of 16.0% pigment content decrease (mu g/g). I n the second step, the variables pH and agitation level (OTR, oxygen t ransfer rate) were optimized and then, both goals were attained: the i ncrease of pigment content (418 mu g astaxanthin/g of yeast) as well a s the absolute pigment production enhancement (1987 mu g/l).