Project

Enhancing Mild Extraction: Utilizing a Combination of Bio-based Solvent and External Field

Microalgae primary metabolites are useful ingredients suitable for a wide range of industry applications such as foods, nutraceuticals, and cosmetics. However, the current extraction approaches are harsh, require hazardous chemicals, and focused on a single product – with the rest of the active components being lost in the process. The hypothesis is that the use of mild extraction methods consisting of bio-based solvents in conjunction with external fields could recover most of these compounds while maintaining their structure and activity intact.

Background

Microalgae are unicellular species that use light energy and nutrients to produce valuable biomass components, including proteins, carbohydrates, lipids, and carotenoids, which can be used as a feedstock for many products. In addition to the long-chain polyunsaturated fatty acids (PUFA) such as EPA and DHA that are typically used for cosmetics and nutraceuticals application, algal proteins are a suitable substitute for traditional dietary supplements because of their high nutritional content and distinctive amino acid profiles. Algal polysaccharides can also be used to produce biopolymers such as viscosifiers, stabilizers, flocculants, and gelling agents to support food and cosmetics industry. Furthermore, along with the primary metabolites, a considerable number of secondary metabolites are present, whose industrial use potentially strengthens a bio-based economy. Among these secondary metabolites, the carotenoid pigment such as fucoxanthin is considered to be one of the most valuable algal compounds with a wide range of applications in the food, feed, cosmetics and pharmaceutical sector.

Despite their immense potential, the industrial application of microalgae is still restricted to very high-valueapplications due to a number of operational constraints. The biggest disadvantage of producing microalgae, however, is that the processes involved are energy-intensive for cultivation and downstream processing which makes it economically unattractive, meaning that the goal is to maximize the biomass value of the microalgae while utilizing the least amount of energy possible. One way to achieve this is to shift from current single-product concepts, towards multiproduct biorefineries. Therefore, using the biorefinery approach, one can improve the economic viability of primary production by sequentially separating different microalgae compounds, especially certain high-value compounds. Mild extraction methods must be used to fully use the biomass of the microalgae without damaging one or more of the product fractions. For example, conventional lipid extraction using organic solvent will harm and denature the protein fraction. Homogenizers, bead milling, high pressure, heating, osmotic shock, and chemicals are examples of traditional extraction and separation methods that are typically developed to extract only one product at the expense of the other fractions. Therefore, the choice of solvent and extraction method is critical to obtaining improved yields and selectivity.

Apart from looking for a milder extraction solvent to preserve the functionality of the remainder of the biomass, the use of green solvents for the extraction of bioactive molecules has gained attention in industry and academia due to the growing concern about the need for more sustainable resource use in the present day. For example, ethyl lactate, 2-methyl­tetrahydrofuran (MeTHF), and cyclopentyl methyl ether (CPME) have been investigated as an extraction solvent for bioactive compounds, such as carotenoids, fatty acids, and derivates from microalgae and food. Currently, extraction of valuable compounds from microalgae, is commonly carried out with conventional techniques, including maceration, Soxhlet, and conventional solid-liquid extraction (SLE). However, these techniques present several disadvantages, such as lack of temperature control, poor extraction selectivity, and high waste generation in term of solvent usage. New extraction approach for the recovery of high-value compounds from microalgae have been proposed as alternatives, namely ultrasound-assisted extraction (UAE); microwave-assisted extraction (MAE); and supercritical CO2 extraction (SC-CO2). These extraction methods have numerous advantages, including greater penetration of the solvent into the matrix, higher extraction yields, shorter processing and residence time, lower solvent expenditure, energy saving, etc. "Green" extraction methods are more in line with sustainable development plans because they need less time, energy, and solvent. Furthermore, the use of "green" solvents enables the production of chemical-free compounds that are seen as safe and preferred by customers.

Project description

Extraction technologies play a pivotal role in successfully separating components from biomass. The challenge is that traditional petrochemical solvents have issues such as high energy consumption, flammability, toxicity, and expensive recovery. Furthermore, to lower the production costs by improving the economic utilization of each biomass compound, the severe extraction method is not preferred as it can cause denaturation for sensitive compounds. Therefore, the combination of bio-based solvents and external fields, including ultrasound and microwave, for greener and milder extraction could potentially overcome these limitations and maintain the economic viability of multi components.

The main objective is to develop a novel and more sustainable extraction method to recover bioactive compounds from T-iso using biorefinery approach. Thus, the specific objectives are:

  1. Establish a library of bio-based solvents to specifically recover fucoxanthin and PUFAs from hydrophobic fraction and further valorize the defatted biomass as a source of proteins and carbohydrates based on their solubility and hydrophobicity;
  2. Evaluate alternative mild extraction approaches using bio-based solvents and both external fields (such as ultrasound and microwave) and supercritical CO2 to maintain their biomolecule functionalities;
  3. Design an integrated multiproduct microalgal biorefinery and perform the techno-economic and life-cycle assessments.

The highlighted objectives tackled will shed light on a number of critical research questions:

  • To what extent most of the microalgal components can be recovered by the combination of bio-based solvents with external fields and supercritical CO2 extraction methods to allow for better extraction yields without compromising the mild extraction conditions and the functionality of targeted biomolecules such as proteins, fucoxanthin, and DHA?
  • Which sequential extraction approach is more suitable for obtaining both functional proteins as well as fucoxanthin and DHA among other compounds?
  • Is the new approach more sustainable and economically competitive?