Continuous pressurized extraction versus electric fields-assisted extraction of cyanobacterial pigments

Microalgae Biomass Production from Rice Husk as Alternative Media Cultivation and Extraction of Phycocyanin Using 3D-Printed Ohmic Heating Reactor

Phycocyanin is a highly valued pigment present in Spirulina platensis biomass with applications in the food industry in terms of biorefinery concepts; specifically, its antioxidant and antimicrobial capacity are an advantage that could be incorporated into a food matrix. This study aims to use rice husk as an alternative culture medium for S. platensis biomass growth and phycocyanin extraction by ohmic heating processing using a 3D-printed reactor. S. platensis was cultivated in rice husk extract (RHE) from 0-100% (v/v). The highest content of microalgal biomass was 1.75 ± 0.01 g/L, with a specific growth rate of 0.125 ± 0.01 h-1. For the phycocyanin extraction under an ohmic heating process, a 3D-printed reactor was designed and built. To optimize phycocyanin extraction, a central composite rotatable design (CCDR) was evaluated, with three factors: time (min), temperature (°C), and pH. The highest phycocyanin content was 75.80 ± 0.98 mg/g in S. platensis biomass grown with rice husk extract. Ohmic heating is a promising method for rapid phycocyanin extraction, and rice husk as a culture medium is an alternative for the growth of S. platensis biomass in the integration of second- and third-generation biorefineries.

Microalgae biomass as an alternative source of biocompounds: New insights and future perspectives of extraction methodologies

Microalgae have characteristics that make them unique and full of potential. Their capacity to generate interesting bioactive molecules can add value to various industrial applications. However, most of these valuable compounds are intracellular, which makes their extraction a major bottleneck. Conventional extraction methodologies have some drawbacks, such as low eco-friendly character, high costs and energy demand, long treatment times, low selectivity and reduced extraction yields, as well as degradation of extracted compounds. The gaps found for these methods demonstrate that emergent approaches, such as ohmic heating, pulsed electric fields, ionic liquids, deep eutectic solvents, or high-pressure processing, show potential to overcome the current drawbacks in the release and extraction of added-value compounds from microalgae. These new processing techniques can potentially extract a variety of compounds, making the process more profitable and applicable to large scales. This review provides an overview of the most important and promising factors to consider in the extraction methodologies applied to microalgae. Additionally, it delivers broad knowledge of the present impact of these methods on biomass and its compounds, raising the possibility of applying them in an integrated manner within a biorefinery concept.

Combining high pressure and electric fields towards Nannochloropsis oculata eicosapentaenoic acid-rich extracts

Nannochloropsis oculata is naturally rich in eicosapentaenoic acid (EPA). To turn this microalga into an economically viable source for commercial applications, extraction efficiency must be achieved. Pursuing this goal, emerging technologies such as high hydrostatic pressure (HHP) and moderate electric fields (MEF) were tested, aiming to increase EPA accessibility and subsequent extraction yields. The innovative approach used in this study combined these technologies and associated tailored, less hazardous different solvent mixtures (SM) with distinct polarity indexes. Although the classical Folch SM with chloroform: methanol (PI 4.4) provided the highest yield concerning total lipids (166.4 mg_lipid/g_biomass), diethyl ether: ethanol (PI 3.6) presented statistically higher values in terms of EPA per biomass, corresponding to 1.3-fold increase. When SM were used in HHP and MEF, neither technology independently improved EPA extraction yields, although the sequential combination of technologies did result in 62% increment in EPA extraction. Overall, the SM and extraction methodologies tested (HHP-200 MPa, 21 °C, 15 min, followed by MEF processing at 40 °C, 15 min) enabled increased EPA extraction yields from wet N. oculata biomass. These findings are of high relevance for the food and pharmaceutical industries, providing viable alternatives to the "classical" extraction methodologies and solvents, with increased yields and lower environmental impact. KEY POINTS: • Et₂O: EtOH is a less toxic and more efficient alternative to Folch solvent mixture • HHP or MEF per se was not able to significantly increase EPA extraction yield • Combinations of HHP and MEF technologies increased both lipids and EPA yields.

Extraction of Nannochloropsis Fatty Acids Using Different Green Technologies: The Current Path

Nannochloropsis is a genus of microalgae widely recognized as potential sources of distinct lipids, particularly polyunsaturated fatty acids (PUFA). These may be obtained through extraction, which has conventionally been performed using hazardous organic solvents. To substitute such solvents with "greener" alternatives, several technologies have been studied to increase their extraction potential. Distinct technologies utilize different principles to achieve such objective; while some aim at disrupting the cell walls of the microalgae, others target the extraction per se. While some methods have been utilized independently, several technologies have also been combined, which has proven to be an effective strategy. The current review focuses on the technologies explored in the last five years to extract or increase extraction yields of fatty acids from Nannochloropsis microalgae. Depending on the extraction efficacy of the different technologies, distinct types of lipids and/or fatty acids are obtained accordingly. Moreover, the extraction efficiency may vary depending on the Nannochloropsis species. Hence, a case-by-case assessment must be conducted in order to ascertain the most suited technology, or tailor a specific one, to be applied to recover a particular fatty acid (or fatty acid class), namely PUFA, including eicosapentaenoic acid.

Algae biorefinery: a promising approach to promote microalgae industry and waste utilization

Microalgae have a number of intriguing characteristics that make them a viable raw material aimed at usage in a variety of applications when refined using a bio-refining process. They offer unique capabilities that allow them to be used in biotechnology-related applications. As a result, this review explores how to increase the extent to which microalgae may be integrated with various additional biorefinery uses in order to improve their maintainability. In this study, the use of microalgae as potential animal feed, manure, medicinal, cosmeceutical, ecological, and other biotechnological uses is examined in its entirety. It also includes information on the boundaries, openings, and improvements of microalgae and the possibilities of increasing the range of microalgae through techno-economic analysis. According to the findings of this review, financing supported research and shifting the focus of microalgal investigations from biofuels production to biorefinery co-products can help guarantee that they remain a viable resource. Furthermore, innovation collaboration is unavoidable if one wishes to avoid the high cost of microalgae biomass handling. This review is expected to be useful in identifying the possible role of microalgae in biorefinery applications in the future.

Emergent Proteins-Based Structures-Prospects towards Sustainable Nutrition and Functionality

The increased pressure over soils imposed by the need for agricultural expansion and food production requires development of sustainable and smart strategies for the efficient use of resources and food nutrients. In accordance with worldwide transformative polices, it is crucial to design sustainable systems for food production aimed at reducing environmental impact, contributing to biodiversity preservation, and leveraging a bioeconomy that supports circular byproduct management. Research on the use of emergent protein sources to develop value-added foods and biomaterials is in its infancy. This review intends to summarize recent research dealing with technological functionality of underused protein fractions, recovered from microbial biomass and food waste sources, addressing their potential applications but also bottlenecks. Protein-based materials from dairy byproducts and microalgae biomass gather promising prospects of use related to their techno-functional properties. However, a balance between yield and functionality is needed to turn this approach profitable on an industrial scale basis. In this context, downstream processing should be strategically used and properly integrated. Food solutions based on microbial proteins will expand in forthcoming years, bringing the opportunity to finetune development of novel protein-based biomaterials.