Effects of temperature and pH on polyunsaturated fatty acid production by Aurantiochytrium sp. L3W when cultivated on unsterile pomace

Abstract Aurantiochytrium sp. strain L3W produces polyunsaturated fatty acids, particularly docosahexaenoic acid (DHA). This study investigated the feasibility of unsterile cultivation of strain L3W using pomace from tomato, lemon, and yellow carrot as substrates at different temperatures (25 °C, 30 °C, and 35 °C) and pH (4 and 7). Toward this end, the effects of temperature and pH on the growth of L3W, DHA production, and co-existing bacterial dynamics were examined. The cultivation of strain L3W at 25 °C and pH 4 resulted in the highest cell growth on both tomato pomace and yellow carrot pomace and the resultant biomass mixtures contained DHA at 8.20 mg/g and 5.63 mg/g, respectively. This result may be due to reduction of competitive bacterial dominance by the pH shock load. At 25 °C, the lemon pomace yielded a biomass mixture containing DHA at 5.59 mg/g and 8.89 mg/g at pH 4 and pH 7, respectively. Even at 35 °C, lemon pomace and yellow carrot pomace supported relatively high DHA production at 5.13 mg/g and 8.13 mg/g, respectively, at pH 4. The DHA levels in the biomass mixtures exceeded those in the diet previously shown to enrich chicken eggs with DHA, indicating their potential as functional eco-feed.