Ultrasonic extraction is the superior method to disrupt algae cells effectively and rapidly. Sonication can release the complete amount of the bioactive compounds, which makes the ultrasonic technique highly efficient.

How To Extract Proteins, Lipids and Phenolics from Algae with Ultrasonics

Algal and microalgal species are rich in biologically active compounds such as proteins, lipids, carotenoids, pigments (e.g., phycocyanins, astaxanthin etc.), phenolics and polysaccharides (e.g., carrageenans). This makes them a widely used natural material to produce extracts for foods and dietary supplements. Commonly used algae species for nutritional supplements are Arthrospira maxima and (also known as spirulina), Chlorella vulgaris, Haematococcus pluvialis, and Ulva spp. Algae are known to be a good source of high-quality proteins, lipids, long-chain PUFAs (i.e. omega-3), polysaccharides (e.g. alginate, carrageenan, β-glucans), vitamins, and antioxidants.
Spirulina is a commonly used type of algae, that is rich in high valued bioactive compounds such as proteins (with 50–70% dry wt). Since Spirulina is approved by the FDA (Food Drug Administration of the United States) as GRAS (Generally Recognized As Safe), spirulina and spirulina extracts can be used in commercialized foods or as food supplements.

Advantages of Ultrasonic Algae Extraction

Ultrasonic extraction excels alternative extraction methods in manifold points, such as high yield, reliability, safety, simplicity, and environmental-friendliness.

Full Extraction Yield

High-performance ultrasonicators break the algae cells open and disrupt them so that the intracellular material is released. Ultrasonic extraction releases thereby the full spectrum of bioactive compounds, such as phycobiliproteins, carotenoids and lipids and phenolics.
Phycobiliproteins can be differentiated into three major groups, namely chloro-phycocyanins, allophycocyanins and phycoerythrins. C-Phycocyanin is a natural blue pigment, which is widely used in food and pharmaceutical products. Ultrasonic extraction releases the full spectrum of proteins.

High Extraction Efficiency

Duangsee et al. (2009) tested two different methods of extraction (ultrasonically-assisted solvent extraction and extraction by repeated freezing and thawing) of bioactive compounds from Arthospira biomass and found that ultrasonic solvent extraction resulted in a higher extraction efficiency (22.1%) than freezing and thawing (15.6%). Cell rupture comparison between sonication and repeated freezing and thawing shows that sonication is more effective. Ultrasonic cavitation disrupt algae cells rapid and effectively which results in a higher cell disruption when compared to the spirulina cells treated by repeated freezing and thawing.
Sonication was more effective in breaking the cell envelope when compared to repeated freezing and thawing. The extraction yield of phycocyanin showed that processing temperature influenced extraction efficiency.

Rapid Extraction Process

High-performance ultrasonic systems can apply high ultrasound power via high amplitudes into the algae suspension. This makes the ultrasonic extraction a very fast processing method.

Temperature Control

Ultrasonication is a non-thermal, purely mechanical extraction technique. The extraction temperature can be precisely controlled using a pluggable temperature sensor, which is wired to the digital Hielscher ultrasonicator. The software of Hielscher’s digital ultrasonicators allow to set temperature limits, so that the ultrasonic homogeniser pauses when the temperature limit is reached. The precise temperature control allows to prevent the thermal degradation of heat-sensitive materials such as phycobiliproteins, vitamins, polyphenols, polysaccharides, lipids and other bioactive compounds.

Compatible with Various Solvents

Ultrasonication is compatible with almost any solvent. Ultrasonic extraction in combination with green solvents such as water or ethanol produce clean extracts. These ultrasonic extracts can be safely incorporated into foods since the extraction solvents ethanol and water have GRAS (Generally Recognized As Safe) status.

Reproducibility and Process Standardization

Hielscher’s digital ultrasonicators come with an intelligent software and an elaborated variety of settings for the ideal extraction parameters. The software protocols all ultrasonic process parameter (e.g., amplitude, net power, total power, temperature, pressure, time, date) and writes the sonication data into a CSV file on the built-in SD-card. This allows you to standardise your extraction process and to monitor sonication and quality output closely. These features help you fulfil process stadandization requirements as well as Good Manufacturing Practices (GMP), which are both highly important when the extracts are produced for supplements, food or pharmaceutical products.

Ultrasonic Phycocyanin Extraction Protocol

Mazumder et al. (2017) investigated the optimum processing parameters for the ultrasonic extraction of phycocyanin and phenolics from Arthospira platensis. The maximum yield of phycocyanin (29.9 mg/g) and total phenolics (2.4 mg/g) was obtained at 40% ethanol concentration, 34.9°C extraction temperature using the ultrasonicator UP50H (50 watts, 30kHz) at an amplitude of 95% for an extraction time of 104.7 sec.

Vernès et al. (2019) used a UIP1000hdT (1000W, 20kHz) ultrasonicator to extract proteins from spirulina. The ultrasonicator was equipped with a BS2d34 sonotrode and an ultrasonic flow reactor (see picture below for the exact ultrasonic extraction setup with flow cell and Seepex pump).

UIP1000hdT – Manothermosonication (MTS) setup und our protein extraction from spirulina at lab scale
source: Vernes et al. 2019

The research results show that ultrasonic extraction conditions optimised to protein yield involve slightly elevated temperature and pressure (so-called manothermosonication MTS). MTS promotes mass transfer and enables to get 229% more proteins (28.42 ± 1.15 g/100 g dry wt.) than conventional process without ultrasound (8.63 ± 1.15 g/100 g dry wt).
With 28.42 g of proteins obtained per 100 g of dry spirulina biomass in the extract, a protein recovery rate of 50% was achieved in only 6 minutes in a continuous sonication process. Microscopic imaging reveals that acoustic cavitation affects the spirulina filaments by different mechanisms such as fragmentation, sonoporation, detexturation. These various effects make extraction, release and solubilization of spirulina bioactive compounds easier and more effective, which results in a high protein yield of high quality.
Regarding quality of the ultrasonically extracted proteins, amino acids were not degraded by ultrasound treatment, but they are present in a larger quantity in the case of sonication when compared to conventional extraction.
When manothermosonication and ultrasonic extraction without elevated pressure and temperature are compared, the difference in extraction yield and efficiency is only minimal. Therefore, ultrasound alone is considered to be the most economical and easiest technique to produce a high-quality extract rich in spirulina proteins. Ultrasonic extraction is a green, environmental-friendly extraction technique suitable for protein extraction from spirulina at laboratory scale, which can easily scaled to pilot and industrial scale. (cf. Vernès et al. 2019)

High Performance Ultrasonic Extractors

All extraction results achieved on small scale, can be linearly scaled to larger production capacities. Hielscher Ultrasonics large product portfolio from lab to industrial extraction systems has the most suitable ultrasonicator for your envisaged process capacity. Our long-time experienced staff will assist you from feasibility tests and process optimisation to the installation of your ultrasonic system on final production level.

Hielscher Ultrasonics – Sophisticated Extraction Equipment

Hielscher Ultrasonics product portfolio covers the full range of high-performance ultrasonic extractors from small to large scale. Additional accessories allow for the easy assembly of the most suitable ultrasonic device configuration for your process. The optimal ultrasonic setup depends on the envisaged capacity, volume, raw material, batch or inline process and timeline. The robustness of Hielscher’s ultrasonic equipment allows for 24/7 operation at heavy duty and in demanding environments.The linear scalability of ultrasonic extraction processes allow the simple and reliable increase in production. Read more about the linear scale-up of ultrasonic extraction processes!

Choose from various accessories such as:

• sonotrodes with various sizes, diameters and shapes
• sonotrodes for high amplitude of 200µm and higher
• flow cell reactors with various volumes and geometries
• numerous booster horns to increase or decrease gains
• complete sonication setups such as the SonoStation, which include ultrasonic extractor, tank, agitator, and pump
• pluggable temperature sensors
• pluggable pressure sensors

Our well-trained, long-experienced staff will consult you and recommend you the most suitable ultrasonic system for your extraction process requirements!

The table below gives you an indication of the approximate processing capacity of our ultrasonicators: