Bioeffects of Static Magnetic Fields on the Growth and Metabolites of C. pyrenoidosa and T. obliquus

Production of biomass and biomolecules in Limnospira indica PCC 8005 cultivation under magnetic fields and polymeric nanofibers

Researchers often apply physical, chemical, or biological stresses to cyanobacteria cultivation to enhance biomass production by triggering cellular adaptation mechanisms, increasing growth or boosting target compound synthesis. Static magnetic fields (SMF) offer a non-toxic, cost-effective way to modulate microalgal growth, alter biomass composition, and promote metabolite production. Polymeric nanofibers (Nano) function as a physical barrier in cultivation, while monoethanolamine (MEA) acts as a chemical absorbent, reducing CO₂ loss and enhancing biofixation. This study investigated the effects of SMF and nanofibers on the biomass yield and molecular composition of Limnospira indica PCC 8005. The combined SMF and Nano treatment achieved the highest biomass yield (5.87 ± 0.06 g L⁻¹), a 28 % increase compared to the control. SMF application increased protein content by 16 % but reduced carbohydrate levels by 73 % relative to the nanofiber-only treatment (39.58 ± 0.98 % ww⁻¹). Exopolysaccharide (EPS) produced under the SMF+NanoMEA treatment contained 39.9 % uronic acid, while the Nano-only treatment had the highest sulphate content (8.4 %) but the lowest uronic acid concentration (25.4 %). The EPS were identified as acidic, sulphated polysaccharides. SMF and nanofibers significantly enhances biomass production, alters the carbohydrate and protein proportions in biomass, and influences the composition of sugars, acids, and sulphate in exopolysaccharides.

A Review of Electromagnetic Fields in Cellular Interactions and Cacao Bean Fermentation

The influence of magnetic fields on biological systems, including fermentation processes and cocoa bean fermentation, is an area of study that is under development. Mechanisms, such as magnetosensitivity, protein conformational changes, changes to cellular biophysical properties, ROS production, regulation of gene expression, and epigenetic modifications, have been identified to explain how magnetic fields affect microorganisms and cellular processes. These mechanisms can alter enzyme activity, protein stability, cell signaling, intercellular communication, and oxidative stress. In cacao fermentation, electromagnetic fields offer a potential means to enhance the sensory attributes of chocolate by modulating microbial metabolism and optimizing flavor and aroma development. This area of study offers possibilities for innovation and the creation of premium food products. In this review, these aspects will be explored systematically and illustratively.

Traditional and new trend strategies to enhance pigment contents in microalgae

Microalgae are a source of a wide variety of commodities, including particularly valuable pigments. The typical pigments present in microalgae are the chlorophylls, carotenoids, and phycobiliproteins. However, other types of pigments, of the family of water-soluble polyphenols, usually encountered in terrestrial plants, have been recently reported in microalgae. Among such microalgal polyphenols, many flavonoids have a yellowish hue, and are used as natural textile dyes. Besides being used as natural colorants, for example in the food or cosmetic industry, microalgal pigments also possess many bioactive properties, making them functional as nutraceutical or pharmaceutical agents. Each type of pigment, with its own chemical structure, fulfills particular biological functions. Considering both eukaryotes and prokaryotes, some species within the four most promising microalgae groups (Cyanobacteria, Rhodophyta, Chlorophyta and Heterokontophyta) are distinguished by their high contents of specific added-value pigments. To further enhance microalgae pigment contents during autotrophic cultivation, a review is made of the main related strategies adopted during the last decade, including light adjustments (quantity and quality, and the duration of the photoperiod cycle), and regard to mineral medium characteristics (salinity, nutrients concentrations, presence of inductive chemicals). In contrast to what is usually observed for growth-related pigments, accumulation of non-photosynthetic pigments (polyphenols and secondary carotenoids) requires particularly stressful conditions. Finally, pigment enrichment is also made possible with two new cutting-edge technologies, via the application of metallic nanoparticles or magnetic fields.

Improving microbial production of value-added products through the intervention of magnetic fields

The magnetic field application is emerging as an auxiliary physical strategy to facilitate rapid biomass accumulation and intracellular production of compounds. However, the underlying mechanisms and principles governing the application of magnetic fields for microbial growth and biotransformation are not yet fully understood. Therefore, a better understanding of interdisciplinary technologies integration, expanded magnetic field application, and scaled-up industrial implementation is crucial. In this review, the magnetic field characteristics, magnetic field-assisted fermentation devices, and the working mechanism of magnetic field have been reviewed comprehensively from both physical and microbiological perspectives. The review suggests that magnetic fields affect the biochemical processes in microorganisms by mediating nutrient transport across membranes, electron transfer during photosynthesis and respiration, enzyme activity and gene expression. Moreover, the recent advances in magnetic field application for microbial fermentation and conversion in biochemical, food and agricultural fields have been summarized.

Influence of Cell Wall on Biomolecules Biosynthesis in Chlamydomonas reinhardtii Strains Exposed to Magnetic Fields

The application of magnetic fields (MF) has attracted the attention of researchers due to their efficiency to change cell metabolism. Chlamydomonas reinhardtii is a biotechnologically useful microalga with versatile metabolism that may be a valuable organism to study the effects of the MF in biology. Therefore, two C. reinhardtii strains, one with cell wall (2137) and other which lacks the cell wall (Wt-S1-cc4694), were evaluated that a new sensitivity factor in the analysis could be included. Comparative studies were undertaken with the two C. reinhardtii strains under the MF intensities of 0.005 mT (terrestrial MF - control), 11  and 20 mT. Results indicated that the physical cell wall barrier protected cells against the MF applied during the assays. Only with the highest MF applied (20 mT) a slight increase in lipid concentration in the cell wall strain was detected. The lowest growth of the strain that lacks cell wall (Wt-S1) indicated that these cells are under a negative effect. To cope with the two MF stresses conditions, Wt-S1 cells produced more pigments (chlorophylls and carotenoids) and lipids and enhanced the antioxidant defense system. The raise of these compounds under MF could potentially have a positive biotechnological impact on algal biomass.

Update on the application of magnetic fields to microalgal cultures

Several studies have shown that any magnetic field (MF) applied to microalgae modifies its cultivation conditions and may favor biomolecule production since it interacts with the microorganisms and affect their growth. As a result, there are changes in concentrations and compositions of biomass and biomolecules. This review aims at updating MF applications to microalga cultures that were reported by studies conducted in the last 5 years. It shows the main studies that reached positive results of carbohydrate, lipid, protein and pigment production. Effects of MFs may be positive, negative or null, depending on some factors, such as intensity, exposure time, physiological state of cells and application devices. Therefore, this review details cultivation conditions used for reaching high concentration of biomolecules, explains the action of MFs on microalgae and describes their applicability to the biorefinery concept.