The demand for effective, low-cost vaccines increases research in next-generation biomanufacturing platforms and the study of new vaccine delivery systems (e.g., mucosal vaccines). Applied biotechnology in antigen production guides research toward developing genetic modification techniques in different biological models to achieve the expression of heterologous proteins. These studies are based on various transformation protocols, applied in prokaryotic systems such as Escherichia coli to eukaryotic models such as yeasts, insect cell cultures, animals, and plants, including a particular type of photosynthetic organisms: microalgae, demonstrating the feasibility of recombinant protein expression in these biological models. Microalgae are one of the recombinant protein expression models with the most significant potential and studies in the last decade. Unicellular photosynthetic organisms are widely diverse with biological and growth-specific characteristics. Some examples of the species with commercial interest are Chlamydomonas, Botryococcus, Chlorella, Dunaliella, Haematococcus, and Spirulina. The production of microalgae species at an industrial level through specialized equipment for this purpose allows for proposing microalgae as a basis for producing recombinant proteins at a commercial level. A specie with a particular interest in biotechnology application due to growth characteristics, composition, and protein production capacity is D. salina, which can be cultivated under industrial standards to obtain βcarotene of high interest to humans. D saline currently has advantages over other microalgae species, such as its growth in culture media with a high salt concentration which reduces the risk of contamination, rapid growth, generally considered safe (GRAS), recombinant protein biofactory, and a possible delivery vehicle for mucosal application. This review discusses the status of microalgae D. salina as a platform of expression of recombinant production for its potential mucosal application as a vaccine delivery system, taking an advance on the technology for its production and cultivation at an industrial level.

Biosynthesized silver nanoparticles (AgNPs) are widely used in varied applications, which are morphology dependent. Consequently, a morphology-controlled synthesis is mandatory. Although there are several studies focused on the plant extract-based biosynthesis of metallic nanoparticles, the use of extracts obtained from agro-wastes is scant. Furthermore, information regarding morphology modification through the use of additional agents is even more scarce. Thus, in this study, AgNPs were synthesized using a malt extract (ME) obtained from an artisanal beer brewing process residue. Additionally, sodium chloride (NaCl), gum arabic (GA), and talc (T) were used in an attempt to modify the morphology of AgNPs. XRD, DLS, SEM, and TEM results demonstrate that stable AgNPs of different sizes and shapes were synthesized. FTIR, HPLC analysis, and the quantification of total proteins, free amino acids, reducing sugars, and total polyphenols before and after AgNPs synthesis showed that ME biomolecules allowed them to act as a source of reducing and stabilizing agents. Therefore, this study provides evidence that ME can be successfully used to biosynthesize AgNPs. Additionally, the antibacterial activity of AgNPs against Gram-negative and Gram-positive bacteria was evaluated. Results indicate that AgNPs show a higher antibacterial activity against Gram-positive bacteria.

The use of zinc oxide nanoparticles (ZnONPs) in agriculture has increased due to their biostimulant potential; however, their effects on plant chemical communication and associated microbial communities are still poorly understood. This study presents a multi-perspective analysis contrasting the effects of ZnONPs with those of conventional ZnO (Bulk) on Capsicum annuum seedlings grown in a substrate with concentrations of 50 and 500 mg kg⁻¹. The results reveal that, at high doses, the bulk material (B500) generated a higher foliar accumulation of zinc (128.7 mg kg⁻¹) than ZnONPs (NP500, 119.7 mg kg⁻¹), a phenomenon attributed to the agglomeration of nanoparticles in the soil matrix, which limits their root absorption. At the physiological level, a critical divergence was observed: while bulk ZnO stimulated the activity of the enzyme superoxide dismutase (SOD), ZnONPs caused severe inhibition of the same (93% reduction), compromising the enzymatic antioxidant machinery and forcing the plant to rely on non-enzymatic mechanisms, such as an increase in total phenols. The volatilomic profile revealed a specific metabolic disturbance induced by ZnONPs in the green leaf volatiles (GLV) pathway. A significant accumulation of hexanal and suppression of hexanol and hexyl acetate were detected, suggesting that the nanomaterial inhibited alcohol dehydrogenase (ADH). In addition, ZnONPs suppressed the emission of methyl salicylate (MeSA)—a key messenger in acquired systemic resistance—whereas the Bulk treatment increased its abundance to 41.7%. Finally, metagenomic analysis indicated that zinc stress restructured the phyllosphere microbiota, promoting the proliferation of Actinobacteria and eliminating sensitive taxa such as Spirochaetes. Taken together, these findings demonstrate that ZnONPs act as multifactorial stressors that not only alter internal metabolism but also silence chemical communication and remodel plant ecology.