Phycobiliproteins from extreme environments and their potential applications

Synechococcus sp. PCC7335 responses to far-red enriched spectra and anoxic/microoxic atmospheres: Potential for astrobiotechnological applications

Recently, cyanobacteria have gained attention in space exploration to support long-term crewed missions via Bioregenerative Life Support Systems. In this frame, cyanobacteria would provide biomass and profitable biomolecules through oxygenic photosynthesis, uptaking CO2, and releasing breathable O2. Their growth potential and organic matter production will depend on their ability to photoacclimate to different light intensities and spectra, maximizing incident light harvesting. Studying cyanobacteria responses to different light regimes will also benefit the broader field of astrobiology, providing data on the possibility of oxygenic photosynthetic life on planets orbiting stars with emission spectra different than the Sun. Here, we tested the acclimation and productivity of Synechococcus sp. PCC7335 (hereafter PCC7335), capable of Far-Red Light Photoacclimation (FaRLiP) and type III chromatic acclimation (CA3), in an anoxic, CO2-enriched atmosphere and under a spectrum simulating the low energetic light regime of an M-dwarf star, also comparable to a subsuperficial environment. When exposed to the light spectrum, with few photons in the visible (VIS) and rich in far-red (FR), PCC7335 did not activate FaRLiP but acclimated only via CA3, achieving a biomass productivity higher than expected, considering the low VIS light availability, and a higher production of phycocyanin, a valuable pigment, with respect to solar light. Its growth or physiological responses of PCC7335 were not affected by the anoxic atmosphere. In these conditions, PCC7335 efficiently produced O2 and scavenged CO2. Results highlight the photosynthetic plasticity of PCC7335, its suitability for astrobiotechnological applications, and the importance to investigate biodiversity of oxygenic photosynthesis for searching life beyond Earth.

Narrative Review of the Current and Future Perspectives of Phycobiliproteins' Applications in the Food Industry: From Natural Colors to Alternative Proteins

Vivid-colored phycobiliproteins (PBPs) have emerging potential as food colors and alternative proteins in the food industry. However, enhancing their application potential requires increasing stability, cost-effective purification processes, and consumer acceptance. This narrative review aimed to highlight information regarding the critical aspects of PBP research that is needed to improve their food industry potential, such as stability, food fortification, development of new PBP-based food products, and cost-effective production. The main results of the literature review show that polysaccharide and protein-based encapsulations significantly improve PBPs' stability. Additionally, while many studies have investigated the ability of PBPs to enhance the techno-functional properties, like viscosity, emulsifying and stabilizing activity, texture, rheology, etc., of widely used food products, highly concentrated PBP food products are still rare. Therefore, much effort should be invested in improving the stability, yield, and sensory characteristics of the PBP-fortified food due to the resulting unpleasant sensory characteristics. Considering that most studies focus on the C-phycocyanin from Spirulina, future studies should concentrate on less explored PBPs from red macroalgae due to their much higher production potential, a critical factor for positioning PBPs as alternative proteins.

Thermophilic cyanobacteria-exciting, yet challenging biotechnological chassis

Thermophilic cyanobacteria are prokaryotic photoautotrophic microorganisms capable of growth between 45 and 73 °C. They are typically found in hot springs where they serve as essential primary producers. Several key features make these robust photosynthetic microbes biotechnologically relevant. These are highly stable proteins and their complexes, the ability to actively transport and concentrate inorganic carbon and other nutrients, to serve as gene donors, microbial cell factories, and sources of bioactive metabolites. A thorough investigation of the recent progress in thermophilic cyanobacteria reveals a significant increase in the number of newly isolated and delineated organisms and wide application of thermophilic light-harvesting components in biohybrid devices. Yet despite these achievements, there are still deficiencies at the high-end of the biotechnological learning curve, notably in genetic engineering and gene editing. Thermostable proteins could be more widely employed, and an extensive pool of newly available genetic data could be better utilised. In this manuscript, we attempt to showcase the most important recent advances in thermophilic cyanobacterial biotechnology and provide an overview of the future direction of the field and challenges that need to be overcome before thermophilic cyanobacterial biotechnology can bridge the gap with highly advanced biotechnology of their mesophilic counterparts. KEY POINTS: • Increased interest in all aspects of thermophilic cyanobacteria in recent years • Light harvesting components remain the most biotechnologically relevant • Lack of reliable molecular biology tools hinders further development of the chassis.

Effects of chitosan molecular weight and mass ratio with natural blue phycocyanin on physiochemical and structural stability of protein

Phycocyanin (PC), an algae-extracted colorant, has extensive applications for its water-solubility and fresh blue shade. When PC is added to acidified media, dispersions are prone to aggregate and decolorize into cloudy systems. For palliating this matter, chitosan with high, medium, and low molecular weights (HMC, MMC, and LMC) were adopted in PC dispersions, and their protective effects were compared based on physiochemical stabilities. The optimal mass ratio between chitosan and PC was identified as 1:5 based on preliminary evaluations and was supported by the higher ζ-potential (31.0-32.1 mV), lower turbidity (39.6-43.6 NTU), and polyacrylamide gel electrophoresis results. Through interfacial and antioxidant capacity analyses, LMC was found to display a higher affinity to PC, which was also confirmed by SEM images and the maximum increase in transition temperature of their complex (155.70 °C) in DSC measurements. The mechanism of electrostatic interaction reinforced by hydrophobic effects and hydrogen bonding was elucidated by FT-IR and Raman spectroscopy. Further comprehensive stability evaluations revealed that, without light exposure, LMC kept PC from internal secondary structure to external blueness luster to the maximum extent. While with light exposure, LMC was not so flexible as HMC, to protect chromophores from attack of free radicals.

Phycobiliproteins from microalgae: research progress in sustainable production and extraction processes

Phycobiliproteins (PBPs), one of the functional proteins from algae, are natural pigment-protein complex containing various amino acids and phycobilins. It has various activities, such as anti-inflammatory and antioxidant properties. And are potential for applications in food, cosmetics, and biomedicine. Improving their metabolic yield is of great interest. Microalgaes are one of the important sources of PBPs, with high growth rate and have the potential for large-scale production. The key to large-scale PBPs production depends on accumulation and recovery of massive productive alga in the upstream stage and the efficiency of microalgae cells breakup and extract PBPs in the downstream stage. Therefore, we reviewed the status quo in the research and development of PBPs production, summarized the advances in each stage and the feasibility of scaled-up production, and demonstrated challenges and future directions in this field.

Optimizing inorganic carbon and salinity for enhanced biomass and pigment production in Colaconema formosanum: Implications for sustainable carbon sequestration and stress responses

This study investigates a cultivation strategy for the macroalga Colaconema formosanum by determining optimal inorganic carbon concentration and salinity for maximizing biomass and photosynthetic pigment production while also facilitating carbon sequestration. The response surface method was used with a central composite design (CCD-RSM) to determine the optimal conditions. Results showed that adding 1.2 g/L of carbon increased the specific growth rate to 18%-19% per day. The maximum amount of pigment, including phycobiliprotein and chlorophyll, was achieved by adjusting both carbon content and salinity. This strategy enables mass pigment production and offers an eco-friendly approach to carbon sequestration while reducing culture period. This study also sheds light on algal mechanisms against enriched inorganic carbon and salinity content, contributing to an enhanced understanding of these vital processes.

The Unique Light-Harvesting System of the Algal Phycobilisome: Structure, Assembly Components, and Functions

The phycobilisome (PBS) is the major light-harvesting apparatus in cyanobacteria and red algae. It is a large multi-subunit protein complex of several megadaltons that is found on the stromal side of thylakoid membranes in orderly arrays. Chromophore lyases catalyse the thioether bond between apoproteins and phycobilins of PBSs. Depending on the species, composition, spatial assembly, and, especially, the functional tuning of different phycobiliproteins mediated by linker proteins, PBSs can absorb light between 450 and 650 nm, making them efficient and versatile light-harvesting systems. However, basic research and technological innovations are needed, not only to understand their role in photosynthesis but also to realise the potential applications of PBSs. Crucial components including phycobiliproteins, phycobilins, and lyases together make the PBS an efficient light-harvesting system, and these provide a scheme to explore the heterologous synthesis of PBS. Focusing on these topics, this review describes the essential components needed for PBS assembly, the functional basis of PBS photosynthesis, and the applications of phycobiliproteins. Moreover, key technical challenges for heterologous biosynthesis of phycobiliproteins in chassis cells are discussed.

Phycobiliproteins from algae: Current updates in sustainable production and applications in food and health

Phycobiliproteins are light-harvesting complexes found mainly in cyanobacteria and red algae, playing a key role in photosynthesis. They are extensively applied in food, cosmetics, and biomedical industry due to bright color, unique fluorescence characteristics and diverse physiological activities. They have received much attention in the past few decades because of their green and sustainable production, safe application, and functional diversity. This work aimed to provide a comprehensive summary of parameters affecting the whole bioprocess with a special focus on the extraction and purification, which directly determines the application of phycobiliproteins. Food grade phycobiliproteins are easy to prepare, whereas analytical grade phycobiliproteins are extremely complex and costly to produce. Most phycobiliproteins are denatured and inactivated at high temperatures, severely limiting their application. Inspired by recent advances, future perspectives are put forward, including (1) the mutagenesis and screening of algal strains for higher phycobiliprotein productivity, (2) the application of omics and genetic engineering for stronger phycobiliprotein stability, and (3) the utilization of synthetic biology and heterologous expression systems for easier phycobiliprotein isolation. This review will give a reference for exploring more phycobiliproteins for food and health application development.

Characterization of Molecular Diversity and Organization of Phycobilisomes in Thermophilic Cyanobacteria

Thermophilic cyanobacteria are cosmopolitan and abundant in the thermal environment. Their light-harvesting complexes, phycobilisomes (PBS), are highly important in photosynthesis. To date, there is limited information on the PBS composition of thermophilic cyanobacteria whose habitats are challenging for survival. Herein, genome-based methods were used to investigate the molecular components of PBS in 19 well-described thermophilic cyanobacteria. These cyanobacteria are from the genera Leptolyngbya, Leptothermofonsia, Ocullathermofonsia, Thermoleptolyngbya, Trichothermofonsia, Synechococcus, Thermostichus, and Thermosynechococcus. According to the phycobiliprotein (PBP) composition of the rods, two pigment types are observed in these thermophiles. The amino acid sequence analysis of different PBP subunits suggests several highly conserved cysteine residues in these thermophiles. Certain amino acid contents in the PBP of thermophiles are significantly higher than their mesophilic counterparts, highlighting the potential roles of specific substitutions of amino acid in the adaptive thermostability of light-harvesting complexes in thermophilic cyanobacteria. Genes encoding PBS linker polypeptides vary among the thermophiles. Intriguingly, motifs in linker apcE indicate a photoacclimation of a far-red light by Leptolyngbya JSC-1, Leptothermofonsia E412, and Ocullathermofonsia A174. The composition pattern of phycobilin lyases is consistent among the thermophiles, except for Thermostichus strains that have extra homologs of cpcE, cpcF, and cpcT. In addition, phylogenetic analyses of genes coding for PBPs, linkers, and lyases suggest extensive genetic diversity among these thermophiles, which is further discussed with the domain analyses. Moreover, comparative genomic analysis suggests different genomic distributions of PBS-related genes among the thermophiles, indicating probably various regulations of expression. In summary, the comparative analysis elucidates distinct molecular components and organization of PBS in thermophilic cyanobacteria. These results provide insights into the PBS components of thermophilic cyanobacteria and fundamental knowledge for future research regarding structures, functions, and photosynthetic improvement.

CIPDB: A biological structure databank for studying cation and π interactions

As major forces for modulating protein folding and molecular recognition, cation and π interactions are extensively identified in protein structures. They are even more competitive than hydrogen bonds in molecular recognition, thus, are vital in numerous biological processes. In this review, we introduce the methods for the identification and quantification of cation and π interactions, provide insights into the characteristics of cation and π interactions in the natural state, and reveal their biological function together with our developed database (Cation and π Interaction in Protein Data Bank; CIPDB; http://chemyang.ccnu.edu.cn/ccb/database/CIPDB). This review lays the foundation for the in-depth study of cation and π interactions and will guide the use of molecular design for drug discovery.

Histochemistry in Advanced Cytometry: From Fluorochromes to Mass Probes

For over half a century, fluorescence has been the milestone of most of the quantitative approaches in various fields from chemistry and biochemistry to microscopy. This latter also evolved into cytometry, thanks to the development of fluorescence techniques. The dyes of classical cytochemistry were replaced by fluorochromes, and the pioneer microphotometry was replaced by microfluorometry. The latter has great advantages in terms of simplicity, sensitivity, and accuracy. The extensive research and availability of new fluorochromes as well as the technological evolution contributed to the success of microfluorometry. The development of flow cytometry in the 1960s gave a giant boost to cell analysis and in particular to the clinical diagnostics. The synergy between flow cytometry and the subsequent development of monoclonal antibodies allowed the setup of multiparametric analytical panels that are today popular and irreplaceable in many clinical and research laboratories. Multiparametric analysis has required the application of an increasing number of fluorochromes, but their simultaneous use creates problems of mutual contamination, hence the need to develop new fluorescent probes. Semiconductor and nanotechnology research enabled the development of new probes called nanocrystals or quantum dots, which offered great advantages to the multiparametric analysis: in fact, thanks to their spectrofluorometric peculiarities, dozens of quantum dots may be simultaneously used without appreciable crosstalk between them. New analytical horizons in cytometry seem to be associated with a new concept of analysis that replaces fluorescence toward new markers with (non-radiative) isotopes of heavy metals. Thus, the mass flow cytometry was born, which seems to guarantee the simultaneous compensation-free analysis of up to 100 markers on a single sample aliquot.

Autofluorescence-based high-throughput isolation of nonbleaching Cyanidioschyzon merolae strains under nitrogen-depletion

Photosynthetic organisms maintain optimum levels of photosynthetic pigments in response to environmental changes to adapt to the conditions. The identification of cyanobacteria strains that alleviate bleaching has revealed genes that regulate levels of phycobilisome, the main light-harvesting complex. In contrast, the mechanisms of pigment degradation in algae remain unclear, as no nonbleaching strains have previously been isolated. To address this issue, this study attempted to isolate nonbleaching strains of the unicellular red alga Cyanidioschyzon merolae after exposure to nitrogen (N)-depletion based on autofluorescence information. After four weeks under N-depletion, 13 cells from 500,000 cells with almost identical pre- and post-depletion chlorophyll a (Chl a) and/or phycocyanin autofluorescence intensities were identified. These nonbleaching candidate strains were sorted via a cell sorter, isolated on solid medium, and their post-N-depletion Chl a and phycocyanin levels were analyzed. Chl a levels of these nonbleaching candidate strains were lower at 1-4 weeks of N-depletion similar to the control strains, however, their phycocyanin levels were unchanged. Thus, we successfully isolated nonbleaching C. merolae strains in which phycocyanin was not degraded under N-depletion, via autofluorescence spectroscopy and cell sorting. This versatile method will help to elucidate the mechanisms regulating pigments in microalgae.

In Living Color: Pigment-Based Microbial Ecology At the Mineral-Air Interface

Pigment-based color is one of the most important phenotypic traits of biofilms at the mineral-air interface (subaerial biofilms, SABs), because it reflects the physiology of the microbial community. Because color is the hallmark of all SABs, we argue that pigment-based color could convey the mechanisms that drive microbial adaptation and coexistence across different terrestrial environments and link phenotypic traits to community fitness and ecological dynamics. Within this framework, we present the most relevant microbial pigments at the mineral-air interface and discuss some of the evolutionary landscapes that necessitate pigments as adaptive strategies for resource allocation and survivability. We report several pigment features that reflect SAB communities' structure and function, as well as pigment ecology in the context of microbial life-history strategies and coexistence theory. Finally, we conclude the study of pigment-based ecology by presenting its potential application and some of the key challenges in the research.

Phycobiliproteins, the pigment-protein complex form of natural food colorants and bioactive ingredients

Currently, the use of synthetic pigments in foods is restricted since synthetic pigments are proven and suspected to be harmful to human health. Phycobiliproteins (PBPs), existed in phycobilisomes (PBSs) of algae, are a kind of pigment-proteins with intense color. The specific color of PBPs (red and blue) is given by the water-soluble open-chained tetrapyrrole chromophore (phycobilin) that covalently attaches to the apo-protein via thioether linkages to cysteine residues. According to the spectral characteristics of PBPs, they can be categorized as phycoerythrins (PEs), phycocyanins (PCs), allophycocyanins (APCs), and phycoerythrocyanins (PECs). PBPs can be used as natural food colorants, fluorescent substances, and bioactive ingredients in food applications owing to their color characteristics and physiological activities. This paper mainly summarizes the extraction and purification methods of the PBPs and reviews their characteristics and applications. Moreover, the use of several strategies such as additives, microencapsulation, electrospray, and cross-linking to improve the stability and bioavailability of PBPs as well as the future outlooks of PBPs as natural colorants in food commercialization are elucidated.

Natural Substrates and Culture Conditions to Produce Pigments from Potential Microbes in Submerged Fermentation

Pigments from bacteria, fungi, yeast, cyanobacteria, and microalgae have been gaining more demand in the food, leather, and textile industries due to their natural origin and effective bioactive functions. Mass production of microbial pigments using inexpensive and ecofriendly agro-industrial residues is gaining more demand in the current research due to their low cost, natural origin, waste utilization, and high pigment stimulating characteristics. A wide range of natural substrates has been employed in submerged fermentation as carbon and nitrogen sources to enhance the pigment production from these microorganisms to obtain the required quantity of pigments. Submerged fermentation is proven to yield more pigment when added with agro-waste residues. Hence, in this review, aspects of potential pigmented microbes such as diversity, natural substrates that stimulate more pigment production from bacteria, fungi, yeast, and a few microalgae under submerged culture conditions, pigment identification, and ecological functions are detailed for the benefit of industrial personnel, researchers, and other entrepreneurs to explore pigmented microbes for multifaceted applications. In addition, some important aspects of microbial pigments are covered herein to disseminate the knowledge.

Effects of tebufenpyrad on freshwater systems dominated by Neocaridina palmata, Physa fontinalis, and Ceratophyllum demersum

Tebufenpyrad are widely used for control leaf mites in orchard and may enter freshwater systems through runoff, spray drift, and so on. Few papers have reported the side effect of the pesticide on population dynamics of aquatic taxa such as shrimps, gastropods, macrophytes, phytoplankton, and bacteria. Here, we tested the effect of a single application of tebufenpyrad on Neocaridina palmata, Physa fontinalis, Ceratophyllum demersum, Simocephalus vetulus, Dolerocypris sinensis, and so on, by indoor systems. The TWA (Time-weighted average)-based highest no observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) for Neocaridina palmata, which were counted by the wet weight, were 0.67 and 2.33 μg/L, respectively, and the dose-related effect lasted 21 d. According to our study, chitobiase could be used to quantify the effects of the pesticide on shrimp despite the interference from P. fontinalis, which was finally corrected by employing of antibodies. The NOEC and LOEC were thus determined to be 1.41 and ≤ 5.64 μg/L, respectively, which were higher than the values that was counted by the wet weight. Principal component analysis (PCA) and principal response curve (PRC) investigation showed that the pesticide suppressed population of C. demersum, and phytoplankton, while the Physa fontinalis, S. vetulus, and D. sinensis were stimulated by the pesticide. Illumina MiSeq was used to determine the alteration in bacterial community within the systems. The results of PRC and PCA analyses showed that tebufenpyrad induced flora of nitrate reducing, nitrate denitrifying, thiosulfate oxidation, ureolysis, and methanol oxidation, while it suppressed flora of cellulolysis. Tebufenpyrad was found to have a negative effect on water quality indicators such as pH, DO, NO₃^-, NO₂^-, and SO₄^2-, and a positive effect on PO₄^3-, NH₄⁺, and EC. This suggested that the tebufenpyrad led to water quality deterioration.

Enhanced Colaconema formosanum biomass and phycoerythrin yield after manipulating inorganic carbon, irradiance, and photoperiod

Due to an increasing CO₂ concentration leading to global warming, the techniques as carbon capture utilization and storage are currently critical issues. This study aimed to investigate a cultivation strategy using optimal inorganic carbon level, irradiance, and photoperiod for producing the highest biomass and photosynthesis pigment contents (chlorophyll and phycobiliprotein) in the macroalga Colaconema formosanum. The results revealed that adding 1 g L^-1 carbon increases phycoerythrin ratio by 12.52-13.74% and decreases allophycocyanin by 10.4-9.57%. Optimal conditions can increase algal growth by 60%, providing 5-6 mg g^-1 total phycobiliprotein and 650-680 µg g^-1 total chlorophyll. The results in this study illustrate the sensitivity of photosynthesis pigment after treatment with carbon, and suggest a hypothesis explaining the mechanism. The results also provide a feasible use of carbon for high-value large-scale production of pigment in the macroalgae industry.

Pilot scale production, extraction and purification of a thermostable phycocyanin from Synechocystis sp. PCC 6803

Phycocyanin (PC) is a soluble blue pigment-protein primarily harvested from the cyanobacterium Arthrospira platensis. PC is in high demand from several industries, but its narrow stability range limits potential applications. Here, a pilot scale (120 L total) batch production, extraction and purification process for thermostable PC (Te-PC) from a Synechocystis sp. PCC 6803 'Olive' strain expressing the PC operon cpcBACD from Thermosynechococcus elongatus BP-1 on a self-replicating vector is presented. Batch cultivation without antibiotics had no impact on growth or Te-PC production and optimisation of growth conditions resulted in Te-PC contents of 75.3 ± 1.7 mg g DW^-1. Wet biomass was harvested following chitosan-based flocculation with a 97 ± 2% efficiency, and Te-PC was extracted by high pressure homogenisation. Subsequent purification by heat-treatment and two-step ammonium sulfate precipitation removed chlorophyll and allophycocyanin contamination, resulting in Te-PC purities of 2.9 ± 0.7 and a mean Te-PC recovery of 84 ± 12%.

Photoglobin, a distinct family of non-heme binding globins, defines a potential photosensor in prokaryotic signal transduction systems

Globins constitute an ancient superfamily of proteins, exhibiting enormous structural and functional diversity, as demonstrated by many heme-binding families and two non-heme binding families that were discovered in bacterial stressosome component RsbR and in light-harvesting phycobiliproteins (phycocyanin) in cyanobacteria and red algae. By comprehensively exploring the globin repertoire using sensitive computational analyses of sequences, structures, and genomes, we present the identification of the third family of non-heme binding globins—the photoglobin. By conducting profile-based comparisons, clustering analyses, and structural modeling, we demonstrate that photoglobin is related to, but distinct from, the phycocyanin family. Photoglobin preserves a potential ligand-binding pocket, whose residue configuration closely resembles that of phycocyanin, indicating that photoglobin potentially binds to a comparable linear tetrapyrrole. By exploring the contextual information provided by the photoglobin’s domain architectures and gene-neighborhoods, we found that photoglobin is frequently associated with the B12-binding light sensor domain and many domains typical of prokaryotic signal transduction systems. Structural modeling using AlphaFold2 demonstrated that photoglobin and B12-binding domains form a structurally conserved hub among different domain architecture contexts. Based on these strong associations, we predict that the coupled photoglobin and B12-binding domains act as a light-sensing regulatory bundle, with each domain sensing different wavelengths of light resulting in switch-like regulation of downstream signaling effectors. Thus, based on the above lines of evidence, we present a distinct non-heme binding globin family and propose that it may define a new type of light sensor, by means of a linear tetrapyrrole, in complex prokaryotic signal transduction systems.

Phycobiliprotein as fluorescent probe and photosensitizer: A systematic review

Phycobiliprotein is a natural product with many biological activities in various seaweeds. Phycobiliproteins have been widely used for anti-oxidation, anti-tumor, anti-inflammatory and immune-enhancing activities as a functional factor. Phycobiliproteins with high purity are considerably more expensive than common. To provide with a systematic, deep and detailed information about those features of phycobiliproteins, we performed a relatively comprehensive analysis on structural composition, the application of phycobiliproteins in the fields of fluorescent probe and photodynamic therapy in this report.

Production of thermostable phycocyanin in a mesophilic cyanobacterium

Phycocyanin (PC) is a soluble phycobiliprotein found within the light-harvesting phycobilisome complex of cyanobacteria and red algae, and is considered a high-value product due to its brilliant blue colour and fluorescent properties. However, commercially available PC has a relatively low temperature stability. Thermophilic species produce more thermostable variants of PC, but are challenging and energetically expensive to cultivate. Here, we show that the PC operon from the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1 (cpcBACD) is functional in the mesophile Synechocystis sp. PCC 6803. Expression of cpcBACD in an 'Olive' mutant strain of Synechocystis lacking endogenous PC resulted in high yields of thermostable PC (112 ± 1 mg g-1 DW) comparable to that of endogenous PC in wild-type cells. Heterologous PC also improved the growth of the Olive mutant, which was further supported by evidence of a functional interaction with the endogenous allophycocyanin core of the phycobilisome complex. The thermostability properties of the heterologous PC were comparable to those of PC from T. elongatus, and could be purified from the Olive mutant using a low-cost heat treatment method. Finally, we developed a scalable model to calculate the energetic benefits of producing PC from T. elongatus in Synechocystis cultures. Our model showed that the higher yields and lower cultivation temperatures of Synechocystis resulted in a 3.5-fold increase in energy efficiency compared to T. elongatus, indicating that producing thermostable PC in non-native hosts is a cost-effective strategy for scaling to commercial production.

Advanced Applications for Protein and Compounds from Microalgae

Algal species still show unrevealed and unexplored potentiality for the identification of new compounds. Photosynthetic organisms represent a valuable resource to exploit and sustain the urgent need of sustainable and green technologies. Particularly, unconventional organisms from extreme environments could hide properties to be employed in a wide range of biotechnology applications, due to their peculiar alleles, proteins, and molecules. In this review we report a detailed dissection about the latest and advanced applications of protein derived from algae. Furthermore, the innovative use of modified algae as bio-reactors to generate proteins or bioactive compounds was discussed. The latest progress about pharmaceutical applications, including the possibility to obtain drugs to counteract virus (as SARS-CoV-2) were also examined. The last paragraph will survey recent cases of the utilization of extremophiles as bio-factories for specific protein and molecule production.

Enhancing growth, phycoerythrin production, and pigment composition in the red alga Colaconema sp. Through optimal environmental conditions in an indoor system

Phycoerythrin (PE) is a compound with strong potential for both basic research and industrial applications, but short supply and high prices have so far hindered its development. One common problem is a shortage of biomass for extraction. The aim of the present study was to determine a cultivation strategy (optimizing temperature, irradiance, photoperiod, and light quality) to produce greater biomass and higher PE concentrations in the alga Colaconema sp. We found that an optimized culture process could increase algae growth 7-9 fold while allowing extraction of 9-10 mg g^-1 total phycobiliproteins, containing 60%-65% PE. Low energy costs make this approach economically feasible and competitive when compared with existing methods. Our results suggest an improved strategy for the large-scale production of PE and offer valuable applications in the algae industry.

MMP-9 and IL-1β as Targets for Diatoxanthin and Related Microalgal Pigments: Potential Chemopreventive and Photoprotective Agents

Photochemoprevention can be a valuable approach to counteract the damaging effects of environmental stressors (e.g., UV radiations) on the skin. Pigments are bioactive molecules, greatly attractive for biotechnological purposes, and with promising applications for human health. In this context, marine microalgae are a valuable alternative and eco-sustainable source of pigments that still need to be taken advantage of. In this study, a comparative in vitro photochemopreventive effects of twenty marine pigments on carcinogenic melanoma model cell B16F0 from UV-induced injury was setup. Pigment modulation of the intracellular reactive oxygen species (ROS) concentration and extracellular release of nitric oxide (NO) was investigated. At the cell signaling level, interleukin 1-β (IL-1β) and matrix metallopeptidase 9 protein (MMP-9) protein expression was examined. These processes are known to be involved in the signaling pathway, from UV stress to cancer induction. Diatoxanthin resulted the best performing pigment in lowering MMP-9 levels and was able to strongly lower IL-1β. This study highlights the pronounced bioactivity of the exclusively aquatic carotenoid diatoxanthin, among the others. It is suggested increasing research efforts on this molecule, emphasizing that a deeper integration of plant ecophysiological studies into a biotechnological context could improve the exploration and exploitation of bioactive natural products.

Demonstration of protein capture and separation using three-dimensional printed anion exchange monoliths fabricated in one-step

Three-dimensional printing applications in separation science are currently limited by the lack of materials compatible with chromatographic operations and three-dimensional printing technologies. In this work, we propose a new material for Digital Light Processing printing to fabricate functional ion exchange monoliths in a single step. Through copolymerization of the bifunctional monomer [2-(acryloyloxy)ethyl] trimethylammonium chloride, monolithic structures with quaternary amine ligands were fabricated. The novel formulation was optimized in terms of protein binding and recovery, microporous structure, and its swelling susceptibility by increasing its cross-link density and employing cyclohexanol and dodecanol as pore forming agents. In static conditions, the material demonstrated a maximum binding capacity of 104.2 ± 10.6 mg/mL for bovine serum albumin, in line with commercially available materials. Its anion exchange behavior was validated by separating bovine serum albumin and myoglobin on a monolithic bed with Schoen gyroid morphology. The same column geometry was tested for the purification of C-phycocyanin from clarified as well as cell-laden Arthrospira platensis feedstocks. This represents the first demonstration of one-step printed stationary phases to capture proteins directly from solid-laden feedstocks. We believe that the material presented here represents a significant improvement towards implementation of three-dimensional printed chromatography media in the field of separation science.