Enzymatic Interesterification of Heterotrophic Microalgal Oil with Rapeseed Oil to Decrease the Levels of Tripalmitin

Abstract

High lipid heterotrophic microalgae (HM) Schizochytrium limacinum is a good dietary source of long‐chained polyunsaturated fatty acids. HM biomass has successfully been used in aquafeeds. However, the high saturated fatty acid content of the triacylglycerol (TAG) could limit the applications of HM as a main feed lipid source. Enzymatic interesterification of HM oil with unsaturated oils may increase the utilization efficiency and remove the technical challenges in using such oils. In the present study, extracted oil from HM biomass (Alltech Inc.) with rapeseed oil are mixed, and interesterified enzymatically with either Lipozyme RM IM or Lipozyme 435 in reactions with no, addition or 5% addition, of distilled water. The experimental oil mixes are formulated to target a total fatty acid profile similar to fish oil. No addition of water to the reaction mixture leads to more efficient TAG recovery after interesterification. Overall, enzymatic interesterification of HM and rapeseed oils with Lipozyme RM IM produces oils with lower levels of tri‐saturated TAG isomers, higher content of TAG isomers with unsaturated fatty acids and a lower slip melting point. Animal studies need to be performed to evaluate the biological effects of interesterified against unprocessed highly unsaturated oils. Practical Applications: Heterotrophic microalgal oil as a pure product could have limited application in feeds and foods due to its structural content of triacylglycerol (TAG) with saturated fatty acids in all three positions, due to both nutritional and practical reasons. Enzymatic interesterification of HM oil with rapeseed oil is in the present study shown to be an efficient technology to produce oils with more desirable TAG composition and reduced melting point for feed and food applications compared to the original raw material. Content of selected triacylglycerol (TAG) isomers in rapeseed oil (RO), extracted heterotrophic microalgae (HM) oil, and oil mixtures following enzymatic interesterification in reaction with no addition of water (Trial 2) by the use of Lipozyme 435 or Lipozyme RM IM.

Microalgal Schizochytrium limacinum Biomass Improves Growth and Filet Quality When Used Long-Term as a Replacement for Fish Oil, in Modern Salmon Diets

“…Nevertheless, though the diets were balanced for total SFA and EPA + DHA, at slaughter FO fish had higher levels of SFA and lower levels EPA + DHA compared to the ScB fish. As recently identified, S. limacinum biomass contains high levels tripalmitin (16:0/16:0/16:0) with high melting point (Bogevik et al, 2018) and low digestibility, explaining the differences in the whole-body SFA levels and retention efficiency of the dietary SFA. Early in the trial both dietary DHA and EPA were slightly more digestible in the FO diet, and at slaughter ADC of EPA but not that of DHA had higher ADC compared to that of the ScB diet.…”

Atlantic Salmon (Salmo salar) Performance Fed Low Trophic Ingredients in a Fish Meal and Fish Oil Free Diet

“…The FCR in the PM treatment was numerically lowest among that of the other treatments with single novel ingredient dietary inclusion, though not statistically significantly, and equal to that of the FMFO. ADC of lipids was lowest in the HM diet, as reported in short term trials before ( Kousoulaki et al, 2015 ) due to the high levels of tripalmitin in S. limacinum oil ( Bogevik et al, 2018 ). The HM diet had also slightly lower ADC of MUFA, n-6PUFA, n-3PUFA and EPA ± DHA as compared to the FMFO and other test diets, except the 0FM0FO which had surprisingly the highest levels among all the groups ( Table 6 ).…”

“…Ingredients produced from arthropods contain significant exoskeleton chitin amounts shown to limit performance in fish species like rainbow trout ( Lindsay et al, 1984 ) whereas being well digested by others, like cod ( Toppe et al, 2006 ) possessing lower gastric pH ( Danulat, 1987 ), and high chitinolytic enzyme activity both in the stomach, and in the intestinal contents ( Danulat and Kausch, 1984 ). Schizochytrium limacinum ( S. limacinum ) is a DHA rich fungal protist, often referred to as microalgae or microalgae - like organism, known to store fully saturated triglycerides, such as tripalmitin, whereas only one or two but not 3 saturated fatty acids are present in FO triglycerides ( Bogevik et al, 2018 ). Fully saturated fatty acids are less digestible in fish farmed in low water temperatures, such as Atlantic salmon ( Kousoulaki et al, 2016 ).…”

Fractionation of Oil from Black Soldier Fly Larvae (Hermetia illucens)

“…[ 20 ] Common for these is a high inclusion of palmitic acid (16:0), which is known to be digested slower than lauric acid. Furthermore, the high melting point due to a large fraction of triacylglycerols (TAG) with saturated fatty acids at all three sn ‐positions, [ 21 ] makes these structures less soluble in bile. This affects content viscosity and digestibility in the gut, [ 22 ] and may thus pose technical challenges in feed and food applications.…”