Antioxidant capacity and lipid composition of Brachionus plicatilis and Artemia enriched with a mixture of different post-processing formats of Navicula salinicola and Isochrysis galbana and lipid emulsions

Abstract

Live prey used by the aquaculture industry are usually poor in some essential nutrients including long chain polyunsaturated fatty acids (LC-PUFA) and must be enriched to improve their nutritional value prior to larval feeding. Standard enrichment protocols are commonly based on lipid emulsions, being associated to a high oxidative stress condition. The combination of microalgae and lipid emulsion can palliate this situation, where the oxidative stress can be partially compensated by the antioxidant compounds present in microalgae. The maintenance of living microalgae in culture facilities is laborious, and the produced biomass may present fluctuating properties, leading to a serious bottleneck in the cultivation of live prey. Hence, substitutes for live microalgae including pastes or dried formats are receiving increasing research attention due to its nutritional stability, longer shelf-life and easy handling. In this study four different microalgae formats combined with a lipid emulsion are tested as enrichment products for Brachionus plicatilis and Artemia. Thus, fresh, frozen and spray-dried Navicula salinicola (NFRE, NFRO and NSD, respectively), and spray-dried Isochrysis galbana (ISD) were mixed with a commercial oil concentrate (IncromegaTM) or a marine lecithin (LC 60®), and added for 5 h to the rotifer or Artemia culture media. The antioxidant capacity of the microalgae extracts and the live prey activity of antioxidant enzymes, peroxides index (PxI) and thiobarbituric acid reactive substances (TBARS) were evaluated. The lipid profile of microalgae formats and enriched live preys was also determined. Ethyl acetate extract was the most antioxidant active extract of all microalgae formats. In addition, overall, I. galbana seems to be better than any N. salinicola format for a more effective protection against oxidative stress and for live prey lipid enrichment. Both rotifer and Artemia cultured with the mixture of I. galbana and the lipid emulsion generally showed higher DHA/EPA and EPA/ARA ratios. Moreover, the combination of the microalgae with LC 60® lipid emulsion highly favored Artemia´s polar lipid and DHA incorporation. Among microalgae products, both spray-dried formats better enhanced live prey n-3 LC-PUFA content. Our results highlight the great potential of new microalgae-derived products to improve effectiveness of current live prey lipid enrichment protocols used in aquaculture.