High-value Metabolites Research Articles

Evaluating stress resilience of cyanobacteria through flow cytometry and fluorescent viability assessment.

Cyanobacteria are prokaryotic organisms characterised by their complex structures and a wide range of pigments. With their ability to fix CO2, cyanobacteria are interesting for white biotechnology as cell factories to produce various high-value metabolites such as polyhydroxyalkanoates, pigments, or proteins. White biotechnology is the industrial production and processing of chemicals, materials, and energy using microorganisms. It is known that exposing cyanobacteria to low levels of stressors can induce the production of secondary metabolites. Understanding of this phenomenon, known as hormesis, can involve the strategic application of controlled stressors to enhance the production of specific metabolites. Consequently, precise measurement of cyanobacterial viability becomes crucial for process control. However, there is no established reliable and quick viability assay protocol for cyanobacteria since the task is challenging due to strong interferences of autofluorescence signals of intercellular pigments and fluorescent viability probes when flow cytometry is used. We performed the screening of selected fluorescent viability probes used frequently in bacteria viability assays. The results of our investigation demonstrated the efficacy and reliability of three widely utilised types of viability probes for the assessment of the viability of Synechocystis strains. The developed technique can be possibly utilised for the evaluation of the importance of polyhydroxyalkanoates for cyanobacterial cultures with respect to selected stressor-repeated freezing and thawing. The results indicated that the presence of polyhydroxyalkanoate granules in cyanobacterial cells could hypothetically contribute to the survival of repeated freezing and thawing.

Reappraisal of different agro-industrial waste for the optimization of cellulase production from Aspergillus niger ITV02 in a liquid medium using a Box-Benkhen design.

High-value metabolites, such as enzymes and biofuels, can be produced from various agro-industrial waste containing high percentages of cellulose and hemicellulose. Aspergillus niger ITV02 demonstrates high potential in cellulases production, the key enzyme for converting lignocellulosic materials into fermentable sugars to produce second-generation bioethanol (bioethanol 2G). This study evaluated five lignocellulosic residues of agricultural importance: sugarcane bagasse (SCB), sorghum bagasse (SB), corn stubble (CS), barley straw (BS) and rice husk (RH) as substrates for cellulase production. The temperature, pH and stirring conditions were optimized using a Box-Behnken design to identify the most suitable conditions for cellulase production while minimizing nitrogen concentrations. The results indicate that the best way of propagation A. niger ITV02 is through the use of spores as an inoculant, in conjunction with the use of materials with a high cellulose/lignin ratio, such as CS and SB for the generation of cellulases. These conditions promote the expression of cellulases towards β-glucosidase production, unlike materials with lower cellulose/lignin ratios like BS and RH, which exhibited lower cellulase activity. The optimal conditions for cellulase production by A. niger ITV02 were determined to be 33 °C, pH 5.3, and 200rpm, resulting in a 1.7-fold increase in Exoglucanase (FPase activity) (from 0.127 to 0.215 U/mL). These findings demonstrate the potential to enhance FPase activity by utilizing substrates with high cellulose/lignin content and implementing optimal operational conditions without the need to raise the nitrogen content of the basal medium, thus mitigating the economic impact of cellulase production.

No two clones are alike: characterization of heterologous subpopulations in a transgenic cell line of the model diatom Phaeodactylum tricornutum

BackgroundConjugation-based episome delivery is a highly efficient method used to transfer DNA into the diatom Phaeodactylum tricornutum, facilitating the production of recombinant proteins and high-value metabolites. However, previous reports have indicated phenotypic heterogeneity among individual cells from clonally propagated exconjugant cell lines, potentially affecting the stability of recombinant protein production in the diatom.ResultsHere, we characterized the differences between subpopulations with distinct fluorescence intensity phenotypes derived from a single exconjugant colony of P. tricornutum expressing the enhanced green fluorescent protein (eGFP). We analyzed the expression cassette sequence integrity, plasmid copy number, and global gene expression. Our findings reveal that lower copy numbers and the deletion of the expression cassette in part of the population contributed to low transgene expression. Gene co-expression analysis identified a set of genes with similar expression pattern to eGFP including a gene encoding a putative Flp recombinase, which may be related to variations in fluorescence intensity. These genes thus present themselves as potential candidates for increasing recombinant proteins production in P. tricornutum episomal expression system.ConclusionsOverall, our study elucidates genetic and transcriptomic differences between distinct subpopulations in a clonally propagated culture, contributes to a better understanding of heterogeneity in diatom expression systems for synthetic biology applications.

24-Epibrassinolide promoted growth and organic compounds accumulation in Dunaliella parva by enhancing photosynthesis

As a commonly used type of the sixth class of phytohormones brassinosteroids (BRs), 24-epibrassinolide (EBL) plays the important roles in plant growth and development. Dunaliella parva (D. parva) is an important lipid-producing microalga, and its growth and accumulation of organic compounds need to be further improved for higher application value. However, the effects of EBL on D. parva are still unclear now. In this study, D. parva was treated with different concentrations of 24-epibrassinolide (EBL) to evaluate its influence. Cell density of 0.5 mg/L EBL treated group was 1.28-fold of control at 18 d. The contents of chlorophyll, carotenoid, carbohydrate, starch, protein of 0.5 mg/L EBL treated group were 1.31-, 1.18-, 1.49-, 1.35-, and 1.54-fold of control. The highest mRNA levels of rbcS, rbcL, RuPE, PRK, TPI, FBPA, FBPase, SBPase, DpME, CA in EBL treated group were 1.94-, 2.43-, 2.14-, 1.76-, 1.97-, 2.21-, 1.48-, 1.96-, 2.06-, and 1.89-fold of control. The highest enzymatic activities of ME, CA and RuBisCO in EBL-treated group were 1.27-, 1.23-, and 1.37-fold of control. Lipid content of 0.4 mg/L EBL treated group was 1.44-fold of control. This study demonstrated the great potential of EBL to obtain higher biomass and organic compounds accumulation. Our study indicates that EBL treatment is valuable for the subsequent commercial production of biofuel and other high-value metabolites using microalgal biomass as raw material.

Increase in polyunsaturated fatty acids and carotenoid accumulation in the microalga Golenkinia brevispicula (Chlorophyceae) by manipulating spectral irradiance and salinity.

Microalgal biotechnology offers a promising platform for the sustainable production of diverse renewable bioactive compounds. The key distinction from other microbial bioprocesses lies in the critical role that light plays in cultures, as it serves as a source of environmental information to control metabolic processes. Therefore, we can use these criteria to design a bioprocess that aims to stimulate the accumulation of target molecules by controlling light exposure. We study the effect on biochemical and photobiological responses of Golenkinia brevispicula FAUBA-3 to the exposition of different spectral irradiances (specifically, high-fluence PAR of narrow yellow spectrum complemented with low intensity of monochromatic radiations of red, blue, and UV-A) under prestress and salinity stress conditions. High light (HL) intensity coupled to salinity stress affected the photosynthetic activity and photoprotection mechanisms as shown by maximal quantum yield (Fv/Fm) and non-photochemical quenching (NPQmax) reduction, respectively. HL treatments combined with the proper dose of UV-A radiation under salinity stress induced the highest carotenoid content (2.75 mg g dry weight [DW]- 1) composed mainly of lutein and β-carotene, and the highest lipid accumulation (35.3% DW) with the highest polyunsaturated fatty acid content (alpha-linolenic acid (C18:3) and linoleic acid (C18:2)). Our study can guide the strategies for commercial indoor production of G. brevispicula for high-value metabolites.

Evaluating the Performance of Yarrowia lipolytica 2.2ab in Solid-State Fermentation under Bench-Scale Conditions in a Packed-Tray Bioreactor

Solid-State Fermentation (SSF) offers a valuable process for converting agri-food by-products (AFBP) into high-value metabolites, with Yarrowia lipolytica 2.2ab (Yl2.2ab) showing significant potential under laboratory-scale controlled conditions; however, its assessment in larger-scale bioreactor scenarios is needed. This work evaluates Yl2.2ab’s performance in a bench-scale custom-designed packed-tray bioreactor. Key features of this bioreactor design include a short packing length, a wall-cooling system, and forced aeration, enhancing hydrodynamics and heat and mass transfer within the tray. Preliminary studies under both abiotic and biotic conditions assessed Yl2.2ab’s adaptability to extreme temperature variations. The results indicated effective oxygen transport but poor heat transfer within the tray bed, with Yl2.2ab leading to a maximum growth rate of 28.15 mgx gssdb−1 h−1 and maximum production of proteases of 40.10 U gssdb−1 h−1, even when temperatures at the packed-tray outlet were around 49 °C. Hybrid-based modeling, incorporating Computational Fluid Dynamics (CFD) and Pseudo-Continuous Simulations (PCSs), elucidated that the forced-aeration system successfully maintained necessary oxygen levels in the bed. However, the low thermal conductivity of AFBP posed challenges for heat transfer. The bioreactor design presents promising avenues for scaling up SSF to valorize AFBP using Yl2.2ab’s extremophilic capabilities.

Biotransformation of ferulic acid into vanillyl alcohol and vanillic acid employing thermophilic bacterium Caldimonas thermodepolymerans

Caldimonas thermodepolymerans, a Gram-negative, moderately thermophilic bacterium, exhibits a remarkable biotechnological potential. Given the presence of genes in its genome dedicated to the metabolization of ferulic acid (FA), this study aimed to explore the bacterium's capability for biotransforming FA into high-value metabolites. The results unequivocally demonstrate the bacterium's proficiency in the efficient and rapid conversion of FA into vanillyl alcohol (VOH) and vanillic acid (VA). By manipulating key cultivation parameters, such as adjusting initial FA doses and varying cultivation periods, the product profile can be tailored. Higher initial doses and shorter cultivation periods favor the production of VOH, while lower FA doses and extended cultivation periods lead to the predominant formation of VA. Furthermore, the process can be operated in a repeated-batch scenario. This underscores the potential of C. thermodepolymerans for industrial biotransformation of FA, presenting a promising avenue for leveraging its capabilities in practical applications.

Exploring the impact of microalgal fatty acid content on anaerobic digestion and methane production: An experimental and mathematical modeling study

Microalgal biomass can potentially be valorized for several purposes, targeting either high added-value metabolites or biofuels. In case the cultivation conditions are inappropriate for the production of high-value metabolites, or the produced yields are insufficient for extraction and further valorization, there is the alternative of the anaerobic digestion (AD) process for biogas production. In the current study, Chlorella vulgaris biomass was treated through the process of AD, focusing on the effect of fatty acids (FAs) content (5–30 %) on biomethane production. Mixotrophic and heterotrophic conditions were used to produce biomass samples with different FAs content. The biochemical methane potential (BMP) assays of the biomass samples followed, targeting the evaluation of the process, taking into account the FAs concentration effect. The BMP yields varied between 304 (5 % FAs) and 502 NmL CH4 gVSadded−1 (30 % FAs). The next step in this work was the mathematical modeling of CH4 production, where the proposed model could satisfactorily simulate the biological process with R2 = 0.94 for all the studied experiments. Such a model can be a valuable tool for deciding on the most appropriate biomass utilization option and the description of AD with dual-stage CH4 production.

Progress on metabolites of Astragalus medicinal plants and a new factor affecting their formation: Biotransformation of endophytic fungi.

It is generally believed that the main influencing factors of plant metabolism are genetic and environmental factors. However, the transformation and catalysis of metabolic intermediates by endophytic fungi have become a new factor and resource attracting attention in recent years. There are over 2000 precious plant species in the Astragalus genus. In the past decade, at least 303 high-value metabolites have been isolated from the Astragalus medicinal plants, including 124 saponins, 150 flavonoids, two alkaloids, six sterols, and over 20 other types of compounds. These medicinal plants contain abundant endophytic fungi with unique functions, and nearly 600 endophytic fungi with known identity have been detected, but only about 35 strains belonging to 13 genera have been isolated. Among them, at least four strains affiliated to Penicillium roseopurpureum, Alternaria eureka, Neosartorya hiratsukae, and Camarosporium laburnicola have demonstrated the ability to biotransform four saponin compounds from the Astragalus genus, resulting in the production of 66 new compounds, which have significantly enhanced our understanding of the formation of metabolites in plants of the Astragalus genus. They provide a scientific basis for improving the cultivation quality of Astragalus plants through the modification of dominant fungal endophytes or reshaping the endophytic fungal community. Additionally, they open up new avenues for the discovery of specialized, green, efficient, and sustainable biotransformation pathways for complex pharmaceutical intermediates.

Qualitative and quantitative analysis of high-value metabolites from callus culture of Alcea rosea L.

Qualitative and quantitative analysis of high-value metabolites from callus culture of Alcea rosea L.

Efficient production of l-glutathione by whole-cell catalysis with ATP regeneration from adenosine.

l-glutathione (GSH) is an important tripeptide compound with extensive applications in medicine, food additives, and cosmetics industries. In this work, an innovative whole-cell catalytic strategy was developed to enhance GSH production by combining metabolic engineering of GSH biosynthetic pathways with an adenosine-based adenosine triphosphate(ATP) regeneration system inEscherichia coli. Concretely, to enhance GSH production in E. coli, several genes associated with GSH and l-cysteine degradation, as well as the branched metabolic flow, were deleted. Additionally, the GSH bifunctional synthase (GshFSA) and GSH ATP-binding cassetteexporter (CydDC) were overexpressed. Moreover, an adenosine-based ATP regeneration system was first introduced into E. coli to enhance GSH biosynthesis without exogenous ATP additions. Through the optimization of whole-cell catalytic conditions, the engineered strain GSH17-FDC achieved an impressive GSH titer of 24.19 g/L only after 2 h reaction, with a nearly 100% (98.39%) conversion rate from the added l-Cys. This work not only unveils a new platform for GSH production but also provides valuable insights for the production of other high-value metabolites that rely on ATP consumption.

Effects of Cultivation Stress on the Glaucophyte Cyanophora paradoxa and Bioactive Potential in Human Cancer Cell Lines

ABSTRACT The propensity to accumulate high-value metabolites under specific conditions makes microalgae promising candidates for commercial applications. Here, the freshwater microalga Cyanophora paradoxa CCAP 981/1 was cultivated under varying conditions (control, nitrogen limitation, NaCl supplementation and blue light exposure) and the biological activity of the corresponding biomass extracts was assessed against human breast (MCF-7) and lung (A549) cancer cell lines. The stress treatments hindered the growth of C. paradoxa, the control displaying the highest specific growth rate (0.16 d−1 ± 0.01). Biomass screening by GCMS and HPLC identified diverse bioactive compounds including pigments (chlorophylls, xanthophylls, carotenes) and fatty acids (e.g., EPA). The control cultivation conditions returned the highest yields of biomass (724 mg), zeaxanthin (6.8 mg g−1), EPA (1.1 mg g−1) and phycocyanin (113.9 mg g−1), while the blue light treatment enhanced the proportions of unsaturated forms of C18 (34.3%). Extracts of dried biomass obtained by cold maceration using solvents of increasing polarity were used in the treatment of MCF-7 and A549 cancer cells. Ethyl acetate extracts from nitrogen-limited cultures reduced MCF-7 viability (~70%) after 72 h. However, the diethyl ether and methanol extracts showed no impact on MCF-7 and A549 cell viability. Furthermore, acridine orange staining revealed no significant DNA damage in these cell lines upon exposure to C. paradoxa extracts. Overall, the minimal impacts on cell viability observed here supports considering C. paradoxa as a promising source of natural bioactive compounds with applications in various biotechnological sectors.

Marine thraustochytrid: exploration from taxonomic challenges to biotechnological applications

Thraustochytrids, as a distinct group of heterotrophic protists, have garnered considerable attention owing to their remarkable adaptability in extreme marine environments, pronounced capacity for metabolic regulation and prolific production of high-value metabolites. The taxonomic classification of these microorganisms presents a substantial challenge due to the variability in morphological characteristics under different culture conditions. And this undermines the efficacy of traditional classification systems on physiological and biochemical traits. The establishment of a polyphasic taxonomic system integrating genomic characteristics in the future will provide new avenues for more accurate classification and identification. Thraustochytrids can effectively accumulate bioactive substances such as docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), squalene and carotenoids. Through fermentation optimization and genetic modification, scientists have significantly enhanced the production of these metabolites. Moreover, the application of thraustochytrids in aquaculture, poultry and livestock feed has significantly improved animal growth and physiological indicators meanwhile increasing their DHA content. Natural bioactive substances in thraustochytrids, such as terpenoid compounds with antioxidant properties, have been proposed for application in the cosmetics industry. In the field of pharmacology, thraustochytrids have shown certain anti-inflammatory and anti-cancer activities and provide potential for the development of new oral vaccines. Additionally, they can degrade various industrial and agricultural wastes for growth and fatty acid production, demonstrating their potential in environmental bioremediation. Therefore, thraustochytrids not only exhibit tremendous application potential in the field of biotechnology, but also hold significant value in environmental protection and commercialization.

Combined effect of LED light color and nitrogen source on growth, pigments composition and oxidative stress in Arthrospira platensis

Artificial lighting with light-emitting diodes (LED) is proposed as a suitable solution to reach stable yearly production of high value molecules from microalgae under unfavorable climates. However, available studies are inconsistent regarding the effect of LED color on cultures performance. This study examined the response of Arthrospira platensis to three different LED lighting conditions (white, red, and red-blue 70:30) when is grown in three media with different nitrogen composition. Growth, phycobiliproteins and lipophilic pigments content were determined. In addition, antioxidant enzymes (GST, lipid peroxidation) and morphology were analyzed to enlighten new perspectives on the health status of microalgae production.The highest biomass production (2.13 g/L) was achieved under red LED when Zarrouk medium was supplemented with urea. Regarding pigment production (phycobilins, chlorophyll a and β- carotene), the most desirable combination was red: blue together with urea supplementation. In addition, this combination showed a high biomass production (2.03 g/L) and low expression of antioxidant enzymatic activity. This research shows a novel combination of LED technology and nutrients to enhance microalgae biomass production and high value metabolites with a lower economic cost.

Effect of In Vitro Micropropagation on the Chemical, Antioxidant, and Biological Characteristics of Senecio nutans Sch. Bip., an Endemic Plant of the Atacama Desert Andean Region.

The species Senecio nutans Sch. Bip., commonly called "chachacoma", is widely used as a medicinal plant by the Andean communities of Northern Chile. Ethanolic extracts of S. nutans and the main compound, 4-hydroxy-3-(3-methyl-2-butenyl) acetophenone, have shown interesting biological activity. However, due to the high-altitude areas where this species is found, access to S. nutans is very limited. Due to the latter, in this work, we carried out micropropagation in vitro and ex vitro adaptation techniques as an alternative for the massive multiplication, conservation, and in vitro production of high-value metabolites from this plant. The micropropagation and ex vitro adaptation techniques were successfully employed, and UHPLC-DAD analysis revealed no significant changes in the phenolic profile, with acetophenone 4 being the most abundant metabolite, whose antioxidant and antibacterial activity was studied. Independently of the applied culture condition, the ethanolic extracts of S. nutans presented high activity against both Gram-positive and Gram-negative bacteria, demonstrating their antimicrobial capacity. This successful initiation of in vitro and ex vitro cultures provides a biotechnological approach for the conservation of S. nutans and ensures a reliable and consistent source of acetophenone 4 as a potential raw material for pharmacological applications.

Variation in Flavonoid Compounds, Volatiles and Yield Related Traits in Different Iranian Rosa damascena Mill. Cultivars Based on SPME Arrow and LC-MS/MS.

Damask rose (Rosa damascena Mill.) is an aromatic industrial plant with different applications. Selection of cultivars with high-value metabolites such as flavonoids-with acceptable yields-can lead to elite cultivars for mass propagation in various industries. A field experiment was carried out in a randomized complete block design (RCBD) to evaluate metabolites and some yield-related morphological data. In the present investigation, for the first time 13 flavonoid components of nine Iranian damask rose cultivars were compared using LC-MS/MS. As a result, 13 flavonoids were identified, most of which were reported for the first time in rose petals. Phloridzin (72.59-375.92 mg/100 g dw), diosmetin (82.48-153.16 mg/100 g dw) and biochanin A (0-1066.89 mg/100 g dw) were the most abundant, followed by trans-chalcone (0-106.29 mg/100 g dw) and diosmin (41.55-84.57 mg/100 g dw). Levels of naringenin also ranged from 3.77 in B111 to 54.70 mg/100 g dw in C294, while luteolin varied from 4.37 in B111 to 28.87 mg/100 g dw in C294. The SPME Arrow technique also was applied to determine the real aroma of the studied cultivars. Phenethyl alcohol was the most abundant compound, in the range of 69.28 to 77.58%. The highest citronellol/geraniol (C/G) was observed in D234 (4.52%) and D237 (4.30%), while the lowest amount belonged to A104 (1.28%). Rose oxide, as the most crucial factor for odor, ranged from 0.06% in D237 to 0.15% in D211. Based on cluster and principal component analysis (PCA), D234 cultivar can be suggested as a promising cultivar with high yield, high C/G content and high rose oxide, while D234 and C294 were the most valuable cultivars in terms of flavonoids with high yield. Finally, these cultivars can be introduced for further breeding programs and industrial cultivation.

Optimization of xylitol production through Candida tropicalis in xylose hydrolysate from rice husk

AbstractOwing to the extensive cultivation and production of rice, which consequently generates a high amount of rice husk, rice husk is an easily available lignocellulosic waste; however, the applications it currently has do not entirely exploit its potential. This study aims the production of xylitol as an opportunity to value this residue through fermentation of rice husk hydrolysate. For it, the best particle size of rice husk among 0.25–0.6 mm, 0.6–1.2 mm, and unmilled rice husk (URH) for dilute acid hydrolysis was determined by using a randomized complete block design (RCBD) to select the particle size that produced the highest amount of xylose release; subsequently, adaptation of Candida tropicalis was carried out as an alternative to common detoxification methods, by increasing the concentration of hydrolysate in the medium in 20% every 2 days, and then, xylitol fermentation from the best particle size hydrolysate with C. tropicalis was optimized performing a central composite design (CCD) 22. The best particle size for dilute acid hydrolysis was URH and produced a xylose concentration of 12.85 g/L, and the optimal conditions for xylitol fermentation were 4.41 g/L of inoculum and 68.28 g/L of xylose and accomplished a concentration of 36.74 g/L of xylitol, a yield of 0.58 g/g xylose, and a volumetric productivity of 0.34 g/L/h, providing evidence that rice husk has the potential to be valorized as a source of fermentable sugars for the production of xylitol as a high-value metabolite and proving adaptation method as a viable alternative for the strain’s growth as well as xylitol production.

Determination of Total Phenolic Content and Total Flavonoid Content of Nutmeg Flesh (Myristica Fragrans Houtt) Ethanol Extract from South Aceh Province

The nutmeg plant (Myristica fragrans Houtt) is often used as a medicinal ingredient and has medicinal efficacy. Nutmeg samples were obtained from South Aceh district, which is the main commodity obtained in the area. This study aims to measure the total phenolic content (TPC) and total flavonoid content (TFC) of the ethanol extract of nutmeg flesh. The dried nutmeg flesh was extracted (maceration) using an ethanol solvent, and the extract weight was 18.35%. The TPC and TFC analysis use the UV-visible spectrophotometer method and are measured at wavelengths of 759 nm and 495 nm, respectively. Gallic acid standards were used to measure total phenolic levels and quercetin standards to measure total flavonoid levels. Data of linearity, R square (R2), LoD, and LoQ were also calculated for each standard. The TPC and TFC contents in the ethanol extract of nutmeg flesh were found to be 76.972 ± 0.97 mg GAE/g and 15.625 ± 0.26 mg QE/g respectively. The presence of phenolic compounds and flavonoids shows that the ethanol extract of nutmeg flesh has high value metabolites that show good biological activity.

MetJ-Based Mutually Interfering SAM-ON/SAM-OFF Biosensors.

SAM (S-adenosylmethionine) is an important metabolite that operates as a major donor of methyl groups and is a controller of various physiological processes. Its availability is also believed to be a major bottleneck in the biological production of numerous high-value metabolites. Here, we constructed SAM-sensing systems using MetJ, an SAM-dependent transcriptional regulator, as a core component. SAM is a corepressor of MetJ, which suppresses the MetJ promoter with an increasing cellular concentration of SAM (SAM-OFF sensor). The application of transcriptional interference and evolutionary tuning effectively inverted its response, yielding a SAM-ON sensor (signal increases with increasing SAM concentration). By linking two genes encoding fluorescent protein reporters in such a way that their transcription events interfere with each other's and by placing one of them under the control of MetJ, we could increase the effective signal-to-noise ratio of the SAM sensor while decreasing the batch-to-batch deviation in signal output, likely by canceling out the growth-associated fluctuation in translational resources. By taking the ratio of SAM-ON/SAM-OFF signals and by resetting the default pool size of SAM, we could rapidly identify SAM synthetase (MetK) mutants with increased cellular activity from a random library. The strategy described herein should be widely applicable for identifying activity mutants, which would be otherwise overlooked because of the strong homeostasis of metabolic networks.

Synergic association of the consortium Arthrospira maxima with the microalga growth-promoting bacterium Azospirillum cultured under the stressful biogas composition.

The present study evaluates the association of the blue-green microalga Arthrospira maxima (Spirulina), which is known for its CO2 fixation, biomass, and high-value metabolite production, with the microalga growth-promoting bacterium Azospirillum brasilense under the stressful composition of biogas. The results demonstrated that A. maxima co-cultured with A. brasilense under the high CO2 (25%) and methane (CH4; 75%) concentrations of biogas recorded a CO2 fixation rate of 0.24 ± 0.03g L-1 days-1, thereby attaining a biomass production of 1.8 ± 0.03g L-1. Similarly, the biochemical composition quality of this microalga enhanced the attainment of higher contents of carbohydrates, proteins, and phycocyanin than cultured alone. However, metabolites other than tryptophan (Trp) and indole-3-acetic acid could have supported this beneficial interaction. Overall, the results demonstrate that this prokaryotic consortium of A. maxima-A. brasilense established a synergic association under biogas, which represents a sustainable strategy to improve the bio-refinery capacity of this microalga and increase the usefulness of A. brasilense in multiple economic sectors.