Abstract:
Perna canaliculus are a native New Zealand marine organism and one of the country’s largest marine exports. Due to their unique marine environment, New Zealand green-lipped mussels (NZGLM) contain a diverse range of valuable compounds, including omega-3 (n-3) polyunsaturated fatty acids (PUFAs). Known for their significant health benefits, marine-derived n-3 fatty acids are used in supplements across the pharmaceutical industry around the globe. Due to this, many processes have been developed to extract and recover these fatty acids from biomass matrices. However, these processes often use toxic and/or volatile solvents and have high costs or energy requirements. Due to the world’s seemingly exponential push to become more sustainable, traditional industrial processes are beginning to be replaced by green sustainable alternatives. In recent years, Deep eutectic solvents (DES) have emerged on the forefront of environmentally friendly solvent extraction. DESs are made up of a hydrogen bond acceptor (HBA) compound and a hydrogen bond donor (HBD) compound and DESs are characteristically green due to their negligible volatility, non-reactivity with water, adjustable viscosity, a wide range of polarity and a high degree of solubilization strength for different compounds. The selection of HBA and HBD compounds can allow the customisation of a DES's properties to suit specific extraction specifications. PUFAs derived from marine sources are efficient anti-inflammatory agents and have been proven to reduce the risks of cardiovascular diseases, cancer and have been proven to combat obesity. The most abundant n-3 PUFAs in perna canaliculus are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which make up over 80 % of total n-3 fatty PUFAs and are also largely accountable for the accredited health benefits. No previous studies based on DESs have been undertaken for the extraction of EPA and DHA from any marine organism. Therefore, for the first time, the extraction of EPA and DHA from NZGLMs was conducted using various DESs. Over fifty solvents were screened using a conductor-like screening model for real solvent software (COSMO-RS) based on their capacities for extracting EPA and DHA. From the COSMO-RS software, solvents with notable capacities (3 to 135) were selected for experimental screening. Menthol: decanoic acid, menthol: octanoic acid and menthol: lidocaine DESs all displayed better extraction efficiencies than ethanol as a benchmark solvent. Furthermore, the menthol: lidocaine DES (1:2 molar ratio) was selected to optimise the extraction process based on response surface methodology (RSM) coupled with Box-Behnken design (BBD) using the extraction parameters to produce an optimal extraction run of 2.11 hours, 60 ˚C and 5 weight per volume percent biomass. The optimal run extraction efficiency was 267.597 µg EPA/g DW and 1014.846 µg DHA/g DW The stability of the extract and the reusability studies of the solvent return positive results, with the extract concertation only slightly decreasing over a seven-day period and the solvent’s ability for extraction remaining relatively similar over five extraction cycles. Furthermore, some proof of concept for recovery of the extract was verified using a hydrochloric acid solution to switch the hydrophobicity of the solvent through protonation. The culmination of these results provides a window into the potential applications of DESs in the direct extraction of n-3 PUFAs from marine-derived biomass.