Improved astaxanthin production by Xanthophyllomyces dendrorhous growing on enzymatic wood hydrolysates containing glucose and cellobiose

Eucalyptus wood samples were treated with NaOH solutions and subjected to enzymatic hydrolysis with a commercial, β-glucosidase-deficient, cellulase complex or with a mixture of cellulase and β-glucosidase. Hydrolysates containing glucose or glucose and cellobiose were supplemented with KNO3 and nutrients, and used as culture media for the proliferation of Xanthophyllomyces dendrorhous (formerly Phaffia rhodozyma) ATCC 24228. For comparative purposes, similar experiments were carried out with media made from commercial sugars. All the bioconversion experiments were carried out in a batch fermenter. At selected fermentation times, the concentrations of substrate (or substrates), biomass and carotenoids were determined. Under the best conditions assayed (hydrolysates obtained with cellulases supplemented with an inorganic nitrogen source), biomass concentrations in the vicinity of 10 g litre−1, with volumetric carotenoid concentration of 2.14 mg litre−1, were reached after 74 h of fermentation. These results compare favourably with those reported for carotenoid production from enzymatic hydrolysates containing glucose as the sole carbon source..