Abstract

ARA is a long-chain polyunsaturated fatty acid (LC-PUFA), classified in the n-6 (w-6) family, scarcely produced in animals and cannot be synthesized de novo in humans. It is considered a highly valued nutraceutical, as it is being increasingly added as dietary supplement in formulas for adults and infants. Thraustochytrids (TH), marine protists, are considered potential producers of ARA, due to their high content of total fatty acids and PUFAs, wide distribution and rapid cell growth. Adaptive laboratory evolution (ALE) is considered a biotechnological tool with great application in strain improvement in terms of growth rates and productivity. ALE consists of repeated or continuous cultures under environmental or nutritional stress for many generations, to obtain genetic or phenotypic changes with better tolerance to inhibitors. The objective of this study was to increase biomass and ARA yields in Ulkenia visurgensis Lng2 through ALE. Thus, ALE consisted of 30 cycles (30 c) of continuous cultivation under high salinity (ALES) and low temperature (ALET) for improving the antioxidant capacity and increasing the strain's PUFAs content respectively. Additionally, the simultaneous combination of both stress factors (ALETS) stimulated changes in cell growth and ARA production. The final evolved strain ALETS 30c produced a biomass of 3.05 g/L and an ARA yield of 4.78 mg/g dry biomass, an increase of 125.9 % and 14.66 %, respective, as compared to the control. Interestingly, ALET 30c presented the highest concentration of total antioxidants with 3.78 nmol Cu2+ reduced/ mu L being 2.6 times higher than the control strain (1.41 nmol Cu2+ reduced/mu L) suggesting oxidative damage prevention is connected to the tolerance to low temperatures and to the increase in PUFAs content and not to the high salinity stress. Overall, the evidence presented highlights the Ulkenia genus, for ARA production and a way to increase these yields and counteract peroxidation through ALE.