Effect of different sugar sources on P. rhodozyma Y1654 growth and astaxanthin production

Abstract

Phaffia rhodozyma (also known as Xanthophyllomyces dendrorhous) is one of the most promising natural sources of commercial astaxanthin. It has high growth rates, easy cultivation conditions and able to utilize different carbon substrates. This provides an opportunity to further lower production cost by using industrial waste such as molasses. This research therefore evaluates the growth dynamic and astaxanthin production of P. rhodozyma Y1654 growing on soy and sugar beet molasses-based media. Liquid growth media based on soy molasses (SM), sugar beet molasses (SBM) and glucose (control) as main sugar source with peptone and yeast extract supplementation were inoculated with 48 h old seed culture (grown in standard glucose media: 2.0% glucose, 1.0% peptone, 0.2% yeast extract) and incubated at 20 °C with stirring speed of 180 rpm for 7 days. Samples were taken daily throughout the study period to assess; cell count, dry cell weight (DCW) and amount of astaxanthin. Soy molasses-based media resulted in the highest biomass yield (7.7 g L) followed by SBM (5.8 g L). Generally, more than 90% of initial fermentable sugar was consumed at the end of the study. However, about 40% of total sugar in SM was unassimilable by P. rhodozyma Y1654. The highest astaxanthin yield was observed in the control media (77 µg g of DCW). Cultivation of P. rhodozyma Y1654 in SBM resulted in as much as twice (32.8 µg g of DCW) the astaxanthin yield of SM (12.4 µg g DCW). Molasses-based media are good for growth of P. rhodozyma Y1654 but for astaxanthin production, they need further optimization.