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

Phaffia rhodozyma (also known as Xanthophyllomyces dendrorhous) is one of the mostpromising natural sources of commercial astaxanthin. It has high growth rates, easy cultivationconditions and able to utilize different carbon substrates. This provides an opportunity to furtherlower production cost by using industrial waste such as molasses. This research thereforeevaluates the growth dynamic and astaxanthin production of P. rhodozyma Y1654 growing onsoy 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 yeastextract supplementation were inoculated with 48 h old seed culture (grown in standard glucosemedia: 2.0% glucose, 1.0% peptone, 0.2% yeast extract) and incubated at 20 °C with stirringspeed of 180 rpm for 7 days. Samples were taken daily throughout the study period to assess; cellcount, dry cell weight (DCW) and amount of astaxanthin. Soy molasses-based media resulted inthe highest biomass yield (7.7 g L-1) followed by SBM (5.8 g L-1). Generally, more than 90% ofinitial fermentable sugar was consumed at the end of the study. However, about 40% of totalsugar in SM was unassimilable by P. rhodozyma Y1654. The highest astaxanthin yield wasobserved in the control media (77 µg g-1 of DCW). Cultivation of P. rhodozyma Y1654 in SBMresulted in as much as twice (32.8 µg g-1 of DCW) the astaxanthin yield of SM (12.4 µg g-1DCW). Molasses-based media are good for growth of P. rhodozyma Y1654 but for astaxanthinproduction, they need further optimization.