As current methods of production of phycocyanobilin, a photosynthetic blue pigment derived from phycocyanin of filamentous cyanobacteria, Pseudanabaena sp. ABRG5-3, Limnothrix sp. SK1-2-1, and Spirulina sp., exhibit a low extraction efficiency, a new extraction method using ethanol extraction as a type of solvolysis with an autoclave (130 ℃, 5.7bar, 10min) was developed in this study. This method exhibited high efficiency and enabled easy recovery of the three types of phycocyanobilins. The identity of the three types of phycocyanobilins was confirmed by high-performance liquid chromatography and electrospray ionization-tandem mass spectrometry. Phycocyanobilins were stable at high temperatures (80 ℃) and acidic (pH 3) conditions. Phycocyanobilins also possessed a remarkable antioxidant property. This is the first time that a simple phycocyanobilin extraction method with a recovery rate of more than 60% and approximately 1% per dry cell weight of filamentous cyanobacteria has been demonstrated. This novel production method is thus convenient and effective for obtaining high-purity phycocyanobilins.

The red macroalgae Porphyra, commonly known as Nori, is widely used as food around the world due to its high nutrient content, including the significant abundance of colored phycobiliproteins (PBPs). Among these, R-phycocyanin (R-PC) stands out for its vibrant purple color and numerous bioactive properties, making it a valuable protein for the food industry. However, R-PC\'s limited thermal stability necessitates alternative processing methods to preserve its color and bioactive properties. Our study aimed to investigate the in-situ stability of oligomeric R-PC under high pressure (HP) conditions (up to 4000 bar) using a combination of absorption, fluorescence, and small-angle X-ray scattering (SAXS) techniques. The unfolding of R-PC is a multiphase process. Initially, low pressure induces conformational changes in the R-PC oligomeric form (trimers). As pressure increases above 1600 bar, these trimers dissociate into monomers, and at pressures above 3000 bar, the subunits begin to unfold. When returned to atmospheric pressure, R-PC partially refolds, retaining 50% of its original color absorbance. In contrast, heat treatment causes irreversible and detrimental effects on R-PC color, highlighting the advantages of HP treatment in preserving both the color and bioactive properties of R-PC compared to heat treatment.

BACKGROUND: A water-in-oil-in-water (W/O/W) double emulsion can simultaneously load hydrophilic and hydrophobic substances due to its unique two-membrane, three-phase structure. However, thermodynamic instability greatly limits the application of double emulsions in food processing. Further development of Pickering emulsions based on proteins, etc., can improve the stability and loading capacity. It is of great significance to promote their practical application.
RESULTS: Herein, we prepared ultrasound pretreatment complex glycation-modified phycocyanin (UMPC) to stabilize a W/O/W Pickering emulsion for the codelivery of vitamin B12 (VB12) and vitamin E (VE). First, an inner water phase and oil phase containing polyglycerin polyricinoleate were homogenized to prepare a W/O emulsion. Subsequently, the W/O emulsion was homogenized with an outer water phase containing UMPC to obtain a W/O/W Pickering emulsion. A gel-like inner phase emulsion with excellent storage and thermal stabilities was obtained under the condition that the W/O emulsion volume ratio was 80% and the UMPC was stabilized by 10 g kg-1. The double emulsion after loading VB12 and VE showed good encapsulation effect during the storage period, the encapsulation rate could reach more than 90%, it also showed excellent protection effect under long-time storage and UV irradiation and the retention rate increased by more than 65%. In addition, the bioavailability of VB12 and VE significantly increased during simulated gastrointestinal digestion and reached 46.02% and 52.43%, respectively.
CONCLUSIONS: These results indicate that the UMPC-stabilized W/O/W Pickering emulsion is an effective carrier for the codelivery of hydrophilic and hydrophobic bioactive molecules and also provides a means for useful exploration of an efficient and stable emulsion system stabilized by biological macromolecules. © 2024 Society of Chemical Industry.

The challenge of applying chlorophyll(Chl) in aqueous media has been a significant obstacle to the diversified development of Chl a-related industries. This study presents the first report on the true-solution-scale utilization of Chl in aqueous media through the construction of chlorophyll a-phycocyanin (Chls-PC) composite nanoparticles. This study determined the optimal conditions for Chls-PC preparation: a composite ratio of 1:25, a solvent ratio of 1:4, and a stirring time of 1 h. Fluorescence spectroscopy, transmission electron microscope, and confocal microscopy confirmed Chl a and PC aggregation. Surface hydrophobicity and contact angle measurements showed that Chls-PC water solubility was similar to PC and much higher than Chl. Infrared spectroscopy, quantum chemical calculations, X-ray photoelectron spectroscopy, and molecular dynamics simulations elucidated the water solubilization mechanism of Chls-PC both experimentally and theoretically. This research provides theoretical guidance for the development and production of water-based products using Chl as a raw material.

OBJECTIVE: Evaluation of the effect of phycocyanin (PC) and toluidine blue (TBO) along with sodium fluoride varnish (FV) or titanium tetrafluoride (TiF4) under the conditions of antimicrobial photodynamic therapy (PDT) on a dual-species cariogenic biofilm and on remineralization process.
METHODS: After the development of Streptococcus mutans and Lactobacillus acidophilus dual-species biofilms on the human enamel disks, they were divided into 11 groups (n = 9): Control (0.9% saline), PC, TBO, FV, and TiF4 alone, PC and TBO in combination with a 635 nm diode laser (PDT treatment), PC-PDT+ (PC + FV or TiF4 + 635 nm diode laser), and TBO-PDT+ (TBO + FV or TiF4 + 635 nm diode laser). After the treatment, crystal violet assay was performed to determine the reduction of cariogenic biofilms. Enamel remineralization changes were analyzed using energy dispersive X-ray spectroscopy (EDX) and field emission scanning electron microscopy (FESEM) for the calcium and phosphorus (Ca/P) ratio.
RESULTS: Only TBO-PDT+ showed superior antibiofilm activity when TiF4 was applied. Furthermore, the highest Ca/P ratio was found after treatment of enamel surfaces with TiF4-TBO-PDT+. The FESEM images showed that the enamel disks treated with TiF4 plus TBO-mediated PDT exhibited surface coating. However, TiF4 plus PC-mediated PDT cannot repair demineralized enamel.
CONCLUSIONS: These data suggest that TBO-PDT along with TiF4 can effectively reduce cariogenic biofilms and significantly remineralize enamel disks, opening new avenues in caries prevention.

Cyanobacteriochromes (CBCRs) are unique cyanobacteria-specific photoreceptors that share a distant relation with phytochromes. Most CBCRs contain conserved cysteine residues known as canonical Cys, while some CBCRs have additional cysteine residues called second Cys within the DXCF motif, leading to their classification as DXCF CBCRs. They typically undergo a process where they incorporate phycocyanobilin (PCB) and subsequently isomerize it to phycoviolobilin (PVB). Conversely, CBCRs with conserved Trp residues and without the second Cys are called extended red/green (XRG) CBCRs. Typical XRG CBCRs bind PCB without undergoing PCB-to-PVB isomerization, displaying red/green reversible photoconversion, and there are also atypical CBCRs that exhibit diverse photoconversions. We discovered novel XRG CBCRs with Cys residue instead of the conserved Trp residue. These novel XRG CBCRs exhibited the ability to isomerize PCB to PVB, displaying green/teal reversible photoconversion. Through sequence- and structure-based comparisons coupled with mutagenesis experiments, we identified three amino acid residues, including the Cys residue, crucial for facilitating PCB-to-PVB isomerization. This research expands our understanding of the diversity of XRG CBCRs, highlighting the remarkable molecular plasticity of CBCRs.

BACKGROUND: Beet filter cake (BFC) is a food-grade solid waste produced by the sugar industry, constituting a permanent source of pollution. Cyanobacteria are considered a sustainable resource for various bioactive compounds such as phycocyanin pigment with valuable applications. This study aimed to use beet filter cake extract (BFCE) as an alternative medium for the economic cultivation of cyanobacterium Leptolyngbya sp. SSI24 PP723083, then biorefined the bioactive component such as phycocyanin pigment that could be used in the production of selenium nanoparticles.
RESULTS: The results of the batch experiment displayed that the highest protein content was in BG11medium (47.9%); however, the maximum carbohydrate and lipid content were in 25% BFCE (15.25 and 10.23%, respectively). In addition, 75% BFCE medium stimulated the phycocyanin content (25.29 mg/g) with an insignificant variation compared to BG11 (22.8 mg/g). Moreover, crude phycocyanin extract from Leptolyngbya sp SSI24 cultivated on BG11 and 75% BFCE successfully produced spherical-shaped selenium nanoparticles (Se-NPs) with mean sizes of 95 and 96 nm in both extracts, respectively. Moreover, XRD results demonstrated that the biosynthesized Se-NPs have a crystalline nature. In addition, the Zeta potential of the biosynthesized Se-NPs equals - 17 mV and - 15.03 mV in the control and 75% BFCE treatment, respectively, indicating their stability. The biosynthesized Se-NPs exhibited higher effectiveness against Gram-positive bacteria than Gram-negative bacteria. Moreover, the biosynthesized Se-NPs from BG11 had higher antioxidant activity with IC50 of 60 ± 0.7 compared to 75% BFCE medium. Further, Se-NPs biosynthesized from phycocyanin extracted from Leptolyngbya sp cultivated on 75% BFCE exhibited strong anticancer activity with IC50 of 17.31 ± 0.63 µg/ml against the human breast cancer cell line.
CONCLUSIONS: The BFCE-supplemented medium can be used for the cultivation of cyanobacterial strain for the phycocyanin accumulation that is used for the green synthesis of selenium nanoparticles that have biological applications.

Cyanobacteria are photosynthetic prokaryotes that inhabit extreme environments by modifying their photosensitive chemoreceptors called cyanobacteriochromes (CBCRs) which are linear tetrapyrrole-linked phycobilin molecules. These light-sensitive phycobilin from Spirulina platensis is recognized as a potential photoreceptor tool in optogenetics for monitoring cellular morphogenesis. We prepared and extracted highly fluorescent cyanobacterial phycocyanin (C-PC) by irradiating the culture with ambient red light. The crude phycocyanin was subjected to ion exchange chromatography, and its purity was monitored using UV-visible, fluorescence, and FT-IR spectroscopy methods. In the conventional method, red light-induced C-PC exhibited strong antioxidant activity against H2O2, with 88.7% in vitro scavenging activity without requiring any other preservatives. Interestingly, this red light-acclimated phycocyanin was applied as a biosensing material for the detection of the free radical hydrogen peroxide (H2O2) using the enzyme horseradish peroxidase (HRP) as a mediator. The modified C-PC-HRP glassy carbon electrode (GCE) can detect H2O2 from 0.1 to 1600 µM. The lowest possible detection limit of the electrode for H2O2 was 19 nM. This electrode was used to detect free radical H2O2 in blood serum samples. The microstructure of the lyophilized PC under SEM showed a flat crystal pattern, which enabled the immobilization of HRP on the electrode surface and electron transfer.

In this study, a sustainable and environmentally friendly method was developed for the enrichment and purification of phycocyanin from Spirulina platensis. This was achieved by utilizing a temperature-sensitive polymer, Pluronic F68, in an aqueous two-phase solvent system. The phase behavior of the temperature-sensitive polymer-based biphasic system was evaluated. The extraction conditions were optimized by both single-factor experiments and response surface methodology. Under the optimal conditions, the upper polymer-rich phase was recycled for sustainable phycocyanin extraction, resulting in a grade of 3.23 during the third extraction cycle. Pluronic F68 could be efficiently recovered and reused during the extraction process. The interaction mechanism between Pluronic F68 and phycocyanin was systematically studied using FT-IR and fluorescence analysis. This was further complemented by static and dynamic calculation of molecular motion through molecular docking and molecular dynamics simulation, indicating that hydrophobic segment of Pluronic F68 played a key role in the binding process with phycocyanin.

Pulmonary fibrosis is a chronic and irreversible progressive lung disease caused by various factors, such as age and environmental pollution. With countries stepping into an aging society and the seriousness of environmental pollution caused by global industrialization, the incidence of pulmonary fibrosis is annually increasing. However, no effective drug is available for pulmonary fibrosis treatment. C-phycocyanin (C-PC), extracted from blue-green algae, has good water solubility and antioxidation. This study elucidated that C-PC reinforces autophagy to block pulmonary fibrogenesis by inhibiting long noncoding RNA (lncRNA) biogenesis in vivo and in vitro. Cleavage under targets and release using nuclease (CUT & RUN)-PCR, co-immunoprecipitation (Co-IP), and nuclear-cytoplasmic separation experiments clarified that C-PC blocked the nuclear translocation of activating transcription factor 3 (ATF3) to prevent the binding between ATF3 and transcription factor Smad3, thereby hindering lncIAPF transcription. Human antigen R (HuR) truncation experiment and RNA binding protein immunoprecipitation (RIP) were then performed to identify the binding domain with lncIAPF in the 244-322 aa of HuR. lncIAPF exerted its profibrogenic function through the binding protein HuR, a negative regulator of autophagy. In summary, C-PC promoted autophagy via down-regulating the lncIAPF-HuR-mediated signal pathway to alleviate pulmonary fibrosis, showing its potential as a drug for treating pulmonary fibrosis. Exploring how C-PC interacts with biological molecules will help us understand the mechanism of this drug and provide valuable target genes to design new drugs.