Techno-Functional Properties of Crude Extracts from the Green Microalga Tetraselmis suecica

Ionic Liquid-Assisted Selective Extraction and Partitioning of Biomolecules from Macroalgae

Macroalgae are a promising feedstock for several industries due to their large content of proteins and carbohydrates and the high biomass productivities. A novel extraction and fractionation concept based on ionic liquids (ILs) using Ulva lactuca as model organism is presented. Biomolecules are first extracted by means of IL-assisted mechanical shear, followed by two-phase partitioning or ultrafiltration in order to fractionate proteins and carbohydrates and to recover the IL. Ethyl methyl imidazolium dibutyl phosphate ([Emim][DBP]) is strongly selective to proteins, leading to extraction yields up to 80.4% for proteins and 30.7% for carbohydrates. The complete process, including extraction and ultrafiltration, allowed protein recovery of up to 64.6 and 15.4% of the carbohydrates in the retentate phase, while a maximum of 85.7% of the IL was recovered in the permeate phase. The native structure of the extracted proteins was preserved during extraction and fractionation as shown by gel electrophoresis. Selective extraction of proteins from macroalgae under non-denaturing conditions using ILs followed by the recovery of IL using ultrafiltration is for the first time reported. The proposed extraction-fractionation approach is simple and can be potentially applied for the biorefinery of macroalgae at the commercial scale.

Recent advances in the application of microalgae and its derivatives for preservation, quality improvement, and shelf-life extension of seafood

Seafood is a highly perishable food product due to microbiological, chemical, and enzymatic reactions, which are the principal causes of their rapid quality deterioration. Therefore, ever-increasing consumers' demand for high-quality seafood along with a negative perception of synthetic preservatives creates opportunities for natural preservatives such as microalgae extracts. They are potential alternatives to reduce microbial growth, increase oxidative stability, and protect the sensorial properties of seafood. Research has shown that the inclusion of microalgae extracts into the aquatic animal's diet could enhance their meat quality and increase production. This review focuses on the direct application of various microalgae extracts as seafood preservative, and their functional properties in seafood, such as antioxidant and antimicrobial activities. Besides, the potential nutritional application of microalgae extracts as an alternative in aqua-feed and their impact on seafood quality (indirect application) are also presented. The safety aspects and regulatory issues of products from microalgae are highlighted.

Effect of Arthrospira platensis microalgae protein purification on emulsification mechanism and efficiency

In light of environmental concerns and changing consumer demands, efforts are increasing to replace frequently used animal-based emulsifiers. We demonstrate the interfacial network formation and emulsifying potential of Arthrospira platensis protein extracts and hypothesize a mechanistic change upon progressing purification. A microalgae suspension of A. platensis powder in phosphate buffer solution (pH 7, 0.1 M) was homogenized and insoluble components separated by centrifugation. Proteins were precipitated at the identified isoelectric point at pH 3.5 and diafiltrated. In interfacial shear rheology measurements, the build-up of an interfacial viscoelastic network was faster and final network strength increased with the degree of purification. It is suggested that isolated A. platensis proteins rapidly form an interconnected protein layer while coextracted surfactants impede protein adsorption for crude and soluble extracts. Emulsions with 20 vol % medium chain triglycerides (MCT) oil could be formed with all extracts of different degrees of purification. Normalized by protein concentration, smaller droplets could be stabilized with the isolated fractions. For potential applications in food, pharma and cosmetic product categories, the enhanced functionality has to be balanced against the loss in biomass while purifying microalgae proteins or other alternative single cell proteins.

A review on microalgae cultivation and harvesting, and their biomass extraction processing using ionic liquids

The richness of high-value bio-compounds derived from microalgae has made microalgae a promising and sustainable source of useful product. The present work starts with a review on the usage of open pond and photobioreactor in culturing various microalgae strains, followed by an in-depth evaluation on the common harvesting techniques used to collect microalgae from culture medium. The harvesting methods discussed include filtration, centrifugation, flocculation, and flotation. Additionally, the advanced extraction technologies using ionic liquids as extractive solvents applied to extract high-value bio-compounds such as lipids, carbohydrates, proteins, and other bioactive compounds from microalgae biomass are summarized and discussed. However, more work needs to be done to fully utilize the potential of microalgae biomass for the application in large-scale production of biofuels, food additives, and nutritive supplements.

Towards the Properties of Different Biomass-Derived Proteins via Various Extraction Methods

This study selected three representative protein-rich biomass-brewer's spent grain (BSG), pasture grass (PG), and cyanobacteria (Arthrospira platensis; AP) for protein extraction with different extraction methods (alkaline treatment, aqueous extraction, and subcritical water extraction). The yield, purity, molecular weight, oil-water interfacial tension, and thermal stability of the obtained proteins derived from different biomass and extraction methods were comprehensively characterized and compared. In the view of protein yield and purity, alkaline treatment was found optimal for BSG (21.4 and 60.2 wt.%, respectively) and AP (55.5 and 68.8 wt.%, respectively). With the decreased oil-water interfacial tension, the proteins from all biomass showed the potential to be emulsifier. BSG and AP protein obtained with chemical treatment presented excellent thermal stability. As a novel method, subcritical water extraction is promising in recovering protein from all three biomass with the comparable yield and purity as alkaline treatment. Furthermore, the hydrolyzed protein with lower molecular weight by subcritical water could promote its functions of foaming and emulsifying.