Determination of Storage (Starch/Glycogen) and Total Saccharides Content in Algae and Cyanobacteria by a Phenol-Sulfuric Acid Method

A Comprehensive Study of Light Quality Acclimation in Synechocystis Sp. PCC 6803

Cyanobacteria play a key role in primary production in both oceans and fresh waters and hold great potential for sustainable production of a large number of commodities. During their life, cyanobacteria cells need to acclimate to a multitude of challenges, including shifts in intensity and quality of incident light. Despite our increasing understanding of metabolic regulation under various light regimes, detailed insight into fitness advantages and limitations under shifting light quality remains underexplored. Here, we study photo-physiological acclimation in the cyanobacterium Synechocystis sp. PCC 6803 throughout the photosynthetically active radiation (PAR) range. Using light emitting diodes (LEDs) with qualitatively different narrow spectra, we describe wavelength dependence of light capture, electron transport and energy transduction to main cellular pools. In addition, we describe processes that fine-tune light capture, such as state transitions, or the efficiency of energy transfer from phycobilisomes to photosystems (PS). We show that growth was the most limited under blue light due to inefficient light harvesting, and that many cellular processes are tightly linked to the redox state of the plastoquinone (PQ) pool, which was the most reduced under red light. The PSI-to-PSII ratio was low under blue photons, however, it was not the main growth-limiting factor, since it was even more reduced under violet and near far-red lights, where Synechocystis grew faster compared to blue light. Our results provide insight into the spectral dependence of phototrophic growth and can provide the foundation for future studies of molecular mechanisms underlying light acclimation in cyanobacteria, leading to light optimization in controlled cultivations.

Tailoring nitrogen and phosphorus levels for tunable glycogen and protein production in halophilic Cyanobacterium aponinum PCC10605

Cyanobacteria hold promise for simultaneous carbon capture and chemicals production, but the regulation and effect of nitrogen (N) and phosphorus (P) remains unclear. This study investigates major productions of glycogen, protein, and C-phycocyanin (C-PC) in Cyanobacterium aponinum PCC10605 under different N/P levels, alongside changes in light and CO2. Increasing nitrate (NO3-) from 2 to 6 mM resulted in a 9.7-fold increase in C-PC and reduced glycogen to 8.9 %. On the other hand, elevating phosphorus from 0.1 to 2 mM under limited nitrogen enhanced biomass and glycogen through the upregulation of carbonic anhydrase, ADP-glucose pyrophosphorylase, and glycogen phosphorylase. Changes in phosphorus levels and CO2 inlet concentrations affected metabolites accumulation and carbon capture efficiency, leading to the best condition of 76 % uptake capacity in direct air capture (DAC). All findings underscore the trade-off between glycogen and protein, representing the importance of N/P levels in nutrient modulation of PCC10605.

The Discovery, Molecular Cloning, and Characterization of Dextransucrase LmDexA and Its Active Truncated Mutant from Leuconostoc mesenteroides NN710

Dextransucrases play a crucial role in the production of dextran from economical sucrose; therefore, there is a pressing demand to explore novel dextransucrases with better performance. This study characterized a dextransucrase enzyme, LmDexA, which was identified from the Leuconostoc mesenteroides NN710. This bacterium was isolated from the soil of growing dragon fruit in Guangxi province, China. We successfully constructed six different N-terminal truncated variants through sequential analysis. Additionally, a truncated variant, ΔN190LmDexA, was constructed by removing the 190 amino acids fragment from the N-terminal. This truncated variant was then successfully expressed heterologously in Escherichia coli and purified. The purified ΔN190LmDexA demonstrated optimal hydrolysis activity at a pH of 5.6 and a temperature of 30 °C. Its maximum specific activity was measured to be 126.13 U/mg, with a Km of 13.7 mM. Results demonstrated a significant improvement in the heterologous expression level and total enzyme activity of ΔN190LmDexA. ΔN190LmDexA exhibited both hydrolytic and transsaccharolytic enzymatic activities. When sucrose was used as the substrate, it primarily produced high-molecular-weight dextran (>400 kDa). However, upon the addition of maltose as a receptor, it resulted in the production of a significant amount of oligosaccharides. Our results can provide valuable information for enhancing the characteristics of recombinant dextransucrase and potentially converting sucrose into high-value-added dextran and oligosaccharides.

Transcriptome analysis reveals the effect of cold storage time on the expression of genes related to oxidative metabolism in Chinese black truffle

Chinese black truffle (Tuber indicum) is a hypogenous fungus of great value due to its distinctive aroma. In this study, both transcriptome and physicochemical analyses were performed to investigate the changes of nutrients and gene expression in truffle fruiting bodies during cold storage. The results of physicochemical analysis revealed the active metabolism of fruiting bodies in cold storage, showing the decreased contents of protein and soluble sugar, the variations in both polyphenol oxidase activity and total phenol content, and the detrimental effect of reactive oxygen species production caused by heavy metals (cadmium and lead) in truffles. Transcriptome analysis identified a total of 139,489 unigenes. Down-regulated expression of genes encoding the catalase-like domain-containing protein (katE), glutaredoxin protein (GRX), a copper/zinc superoxide dismutase (Sod_Cu), and aspartate aminotransferase (AAT) affected the degradation metabolism of intracellular oxides. Ribulose-5-phosphate-3-epimerase (RPE) was a key enzyme in response to oxidative stress in truffle cells through the pentose phosphate pathway (PPP). A total of 51,612 simple sequence repeats were identified, providing valuable resources for further genetic diversity analysis, molecular breeding, and genetic map-ping in T. indicum. Transcription factors GAL4 and SUF4-like protein were involved in glucose metabolism and histone methylation processes, respectively. Our study provided a fundamental characterization of the physicochemical and molecular variations in T. indicum during the cold storage at 4°C, providing strong experimental evidence to support the improvement of storage quality of T. indicum.

An effective moisture interference correction method for maize powder NIR spectra analysis

The detection of maize starch content is of great significance for maize processing industry and near-infrared spectroscopy (NIRS) is an ideal rapid detection technology. However, the interference of moisture in maize is a bottleneck problem that affects the accuracy of NIRS quantitative analysis. In this study, we proposed methods based on external parameter orthogonalization (EPO) combined with wavelength selection algorithms to bring more accurate analytical results. Two groups of maize starch samples with different moisture content distributions were investigated to compare the predictive performance of NIRS models. The results showed that the model built using EPO combined with the synergy interval partial least squares (EPO-siPLS) algorithm exhibited the superior prediction accuracy, whose RMSEP/RMSEPck is improved by 9.7 % compared with that of siPLS model, 25.3 % compared with that of EPO-PLS, and 45.8 % compared with that of the PLS model. This study provides a more accurate and robust new method for rapid detection of maize starch and offers new insights for its application.

Sugarcane leaf polysaccharide exerts a therapeutic effect on cardiovascular diseases through necroptosis

Background

Necroptosis, a novel form of programmed cell death wherein the necrotic morphology is characterized by swelling of the cells, rupture of the plasma membrane, and dysfunction of the organelle, has been always observed in cardiovascular diseases. Sugarcane leaf polysaccharide (SLP) are primary components present in sugarcane leaves that exert cardiovascular protective effects. However, the positive effect of SLP and underlying mechanisms in myocardial ischemia-reperfusion (MI/R) remain unexplored.

Aim

In this study, the protective effects of SLP on MI/R injury were investigated under in vitro and in vivo conditions.

Methods

The protective effects of SLP on MI/R injury were assessed using tertiary butyl hydrogen peroxide (TBHP)-stimulated-H9c2 cells in the in vitro assay and using Sprague Dawley rats in the in vivo assay.

Results

In vitro, SLP significantly reversed TBHP-induced H9c2 cell death by inhibiting necroptosis and oxidative stress. SLP exerted antioxidant activity through the Nrf2/HO-1 pathway. SLP suppressed necroptosis by decreasing phosphorylation of RIP1, RIP3, and MLKL in TBHP-stimulated H9c2 cells. In vivo, SLP attenuated MI/R injury by decreasing the myocardial infarct area; increasing myeloperoxidase and superoxide dismutase levels; and reducing malondialdehyde, interleukin-6, and tumor necrosis factor-α levels.

Enhanced carbon capture, lipid and lutein production in Chlamydomonas reinhardtii under meso-thermophilic conditions using chaperone and CRISPRi system

Microalgae are widely recognized as a promising bioresource for producing renewable fuels and chemicals. Microalgal biorefinery has tremendous potential for incorporation into circular bioeconomy, including sustainability, cascading use, and waste reduction. In this study, genetic engineering was used to enhance the growth, lipid and lutein productivity of Chlamydomonas reinhardtii including strains of CC400, PY9, pCHS, and PG. Notably, CRISPRi mediated on phosphoenolpyruvate carboxylase (PEPC1) gene to down-regulate the branch pathway from glycolysis to partitioning more carbon flux to lipid was explored under meso-thermophilic condition. The best chassis PGi, which has overexpressed chaperone GroELS and applied CRISPRi resulting in the highest biomass of 2.56 g/L and also boosted the lipids and lutein with 893 and 23.5 mg/L, respectively at 35 °C. Finally, all strains with CRISPRi exhibited higher transcriptional levels of the crucial genes from photosynthesis, starch, lipid and lutein metabolism, thus reaching a CO₂ assimilation of 1.087 g-CO₂/g-DCW in mixotrophic condition.

Ti3C2Tx MXene nanosheets enhance the tolerance of Torreya grandis to Pb stress

As a 2D nanomaterial, MXene (Ti₃C₂T_x) has shown enormous potential for use in fields such as biomedical and environmental pollution. However, the utilization of MXene materials in plants has received little attention thus far. The efficient use of MXene materials in agriculture and forestry is first highlighted in this study. Phenotypic and physiological analyses indicated that MXene application significantly enhanced the tolerance of Torreya grandis to Pb stress by reducing Pb accumulation. Furthermore, we illustrated two independent mechanisms of MXene material in reducing Pb accumulation in T. grandis: 1) MXene converted the available form of Pb into stable forms via its strong Pb adsorption ability, resulting in a decrease of the available form of Pb in soils, and 2) MXene application obviously increased the cell wall pectin content to restrict more Pb in the cell wall by regulating the expression of pectin synthesis/metabolism-related genes (TgPLL2, TgPLL11, TgPG5, TgPG30, TgGAUT3 and TgGAUT12) in T. grandis roots. Overall, this finding provides insight into the application of MXene material in modern agriculture and forestry, which will facilitate the rapid development of nanotechnology in sustainable agriculture and forestry.

Comparison of the Antioxidant Activities and Polysaccharide Characterization of Fresh and Dry Dendrobium officinale Kimura et Migo

It is generally believed that fresh Dendrobium officinale (FDO) has more significant pharmacological activity than dried Dendrobium officinale (DDO); however, the difference has not been clearly shown. Our study compared their antioxidant properties both in vitro and in vivo, and the molecular weight arrangement and monosaccharide composition of the fresh Dendrobium officinale polysaccharides (FDOPs) and the dried Dendrobium officinale polysaccharides (DDOPs) were analyzed by HPLC-GPC and GC-MS. The results showed that the FDO and its polysaccharides had more significant effects on scavenging DPPH, ABTS, and hydroxyl radicals than the DDO. In addition, both the FDO and DDO significantly reduced lipid peroxidation levels and increased the SOD, T-AOC, CAT, and GSH levels in mice with acute liver damage caused by CCl₄, while the FDO and its polysaccharides were more effective. Histopathological analysis further verified the protective effect of the Dendrobium polysaccharides on CCl₄-induced liver injury. The determination of the polysaccharides revealed that the polysaccharide and mannose contents of the FDO were significantly higher than their dried counterparts, and the homogeneous arrangement of the polysaccharides in the FDO was degraded into three polysaccharide fragments of different molecular weights in the DDO. Overall, our data identified differences in the antioxidant activities of the FDO and DDO, as well as the reasons for these differences.

The Lebanese Red Algae Jania rubens: Promising Biomolecules against Colon Cancer Cells

Colorectal cancer (CRC) is ranked the second most lethal type of tumor globally. Thus, developing novel anti-cancer therapeutics that are less aggressive and more potent is needed. Recently, natural bioactive molecules are gaining interest as complementary and supportive antineoplastic treatments due to their safety, effectiveness, and low cost. Jania rubens (J. rubens) is a red coral seaweed abundant in the Mediterranean and bears a significant pharmacological essence. Despite its therapeutic potential, the natural biomolecules extracted from this alga are poorly identified. In this study, the proximal analysis revealed high levels of total ash content (66%), 11.3% proteins, 14.5% carbohydrates, and only 4.5% lipids. The elemental identification showed magnesium and calcium were high among its macro minerals, (24 ± 0.5 mg/g) and (33 ± 0.5 mg/g), respectively. The Chlorophyll of J. rubens was dominated by other pigments with (0.82 ± 0.02 mg/g). A 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay identified effective antioxidant activity in various J. rubens extracts. More importantly, a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) tetrazolium reduction and wound healing assays indicate that organic extracts from J. rubens significantly counteract the proliferation of colon cancer cell lines (HCT-116 and HT-29) and inhibit their migratory and metastatic properties in a dose and time-dependent manner. Overall, this study provides insight into the physicochemical properties of red seaweed, J. rubens, and identifies its significant antioxidant, cytotoxic, and anti-migratory potential on two colorectal cell lines, HCT-116 and HT-29.

Evaluation of metabolites in Iranian Licorice accessions under salinity stress and Azotobacter sp. inoculation

Licorice (Glycyrrhiza glabra L.) is an industrial medicinal plant that is potentially threatened by extinction. In this study, the effects of salinity (0 and 200 mM sodium chloride (NaCl)) and Azotobacter inoculation were evaluated on 16 licorice accessions. The results showed that salinity significantly reduced the fresh and dry biomass (FW and DW, respectively) of roots, compared to plants of the control group (a decrease of 15.92% and 17.26%, respectively). As a result of bacterial inoculation, the total sugar content of roots increased by 21.56% when salinity was applied, but increased by 14.01% without salinity. Salinity stress increased the content of glycyrrhizic acid (GA), phenols, and flavonoids in licorice roots by 104.6%, 117.2%, and 56.3%, respectively. Integrated bacterial inoculation and salt stress significantly increased the GA content in the accessions. Bajgah and Sepidan accessions had the highest GA contents (96.26 and 83.17 mg/g DW, respectively), while Eghlid accession had the lowest (41.98 mg/g DW). With the bacterial application, the maximum amounts of glabridin were obtained in Kashmar and Kermanshah accessions (2.04 and 1.98 mg/g DW, respectively). Bajgah and Kashmar accessions had higher amounts of rutin in their aerial parts (6.11 and 9.48 mg/g DW, respectively) when their roots were uninoculated. In conclusion, these results can assist in selecting promising licorice accessions for cultivation in harsh environments.

Optimization of environmental factors in a dual in vitro biofilm model of Candida albicans-Streptococcus mutans

The biofilm formation of Streptococcus mutans-Candida albicans is an important virulence factor for dental caries. The purpose of this study was to determine the effect of some environmental conditions on the biofilm formation like inoculation concentration, temperature, sugar, amino acid, metal ions and saliva, and then establish a persistent in vitro biofilm model for further research. Based on the single factor experiment, the factors participating in the biofilm formation including sugar, inoculation concentration, and saliva increased the biofilm mass, while amino acid, metal ions, temperatures reduced biofilm mass. Optimal conditions for biofilm formation were the inoculation dosage of S. mutans and C. albicans of 10⁸ and 10⁷ , respectively, the addition of 0·3 g l^-1 sucrose and sterile saliva. These results contribute to a deep understanding of the factors involved in oral biofilm formation of the important cariogenic pathogen S. mutans and the opportunistic pathogen C. albicans to study better for biofilm and promote the design of new therapeutic approaches. The present research also provides a model for evaluating the therapeutic potential for drugs in the future.

Physiological and metabolic responses of Microcystis aeruginosa to a salinity gradient

Microcystis is a well-known toxic cyanobacterium in eutrophic environments, and an increasing number of Microcystis blooms have emerged in salty reservoirs and coastal rivers. This study observed that many Microcystis were identified in a coastal river in June 2020. The relative abundance of Microcystis decreased from 81.2 to 10.2% in the sampling sites from a salinity of 0 (Sal. 0) to a salinity of 12 (Sal. 12). Hepatotoxic microcystins (MCs) were identified in the coastal river and its estuary. Of the samples, those with a salinity of 5 (Sal. 5) had the highest concentration of MCs at 7.81 ± 0.67 μg L^-1. In a saline water simulation experiment, the results showed that salt inhibited Microcystis (M.) aeruginosa growth, enhanced the activity levels of superoxide dismutase (SOD) and catalase (CAT) and stimulated microcystin production. Transcription analysis showed that the expression levels of the psaB and rbcL genes controlling photosymbiotic processes were downregulated, and capD and csaBgene-related polysaccharide productions were upregulated by salt incubation. Notably, metabolism analysis showed that the total polysaccharides, proteins and small molecular matter, such as sucrose, methionine and N-acetyl-D-glucosamine, in the Microcystis cells increased substantially to resist the extracellular hyperosmotic pressure caused by the high salinity levels in culture. These findings indicate that increased salt in a natural aquatic body shifts the phytoplankton community by influencing the physiological metabolism of cyanobacteria and poses a high risk of microcystin exposure during cyanobacterial blooms in coastal rivers.

Effect of different D-amino acids on biofilm formation of mixed microorganisms

This study aimed to determine the effects of D-tyrosine, D-aspartic acid, D-tryptophan and D-leucine on biofilm formation of mixed microorganisms. Results showed that, in the attachment stage, D-amino acids caused significant reduction in adhesion efficiency of mixed microorganisms to the membrane surface. Moreover, D-amino acids have a promoting effect on the reversible adhesion of mixed microorganisms. The addition of D-amino acid generally inhibited the biofilm biomass, of which D-tyrosine has the best inhibition effect. With the effect of D-tyrosine, D-aspartic acid, D-tryptophan and D-leucine, the protein in extracellular polymeric substance (EPS) decreased by 8.21%, 7.65%, 3.51% and 11.31%, respectively. The carbohydrates in EPS decreased by 29.53%, 21.44%, 14.60% and 10.54%, respectively. The results of excitation-emission matrix spectra (EEMs) suggested that the structural properties of the tyrosine-like proteins, tryptophan-like protein and humic-like acid might have changed by the D-amino acids.

Quantifying Cyanothece growth under DIC limitation

The photoautotrophic, unicellular N₂-fixer, Cyanothece, is a model organism that has been widely used to study photosynthesis regulation, the structure of photosystems, and the temporal segregation of carbon (C) and nitrogen (N) fixation in light and dark phases of the diel cycle. Here, we present a simple quantitative model and experimental data that together, suggest external dissolved inorganic carbon (DIC) concentration as a major limiting factor for Cyanothece growth, due to its high C-storage requirement. Using experimental data from a parallel laboratory study as a basis, we show that after the onset of the light period, DIC was rapidly consumed by photosynthesis, leading to a sharp drop in the rate of photosynthesis and C accumulation. In N₂-fixing cultures, high rates of photosynthesis in the morning enabled rapid conversion of DIC to intracellular C storage, hastening DIC consumption to levels that limited further uptake. The N₂-fixing condition allows only a small fraction of fixed C for cellular growth since a large fraction was reserved in storage to fuel night-time N₂ fixation. Our model provides a framework for resolving DIC limitation in aquatic ecosystem simulations, where DIC as a growth-limiting factor has rarely been considered, and importantly emphasizes the effect of intracellular C allocation on growth rate that varies depending on the growth environment.

Potential of the Red Alga Dixoniella grisea for the Production of Additives for Lubricants

There is an increasing interest in algae-based raw materials for medical, cosmetic or nutraceutical applications. Additionally, the high diversity of physicochemical properties of the different algal metabolites proposes these substances from microalgae as possible additives in the chemical industry. Among the wide range of natural products from red microalgae, research has mainly focused on extracellular polymers for additive use, while this study also considers the cellular components. The aim of the present study is to analytically characterize the extra- and intracellular molecular composition from the red microalga Dixoniella grisea and to evaluate its potential for being used in the tribological industry. D. grisea samples, fractionated into extracellular polymers (EPS), cells and medium, were examined for their molecular composition. This alga produces a highly viscous polymer, mainly composed of polysaccharides and proteins, being secreted into the culture medium. The EPS and biomass significantly differed in their molecular composition, indicating that they might be used for different bio-additive products. We also show that polysaccharides and proteins were the major chemical compounds in EPS, whereas the content of lipids depended on the separation protocol and the resulting product. Still, they did not represent a major group and were thus classified as a potential valuable side-product. Lyophilized algal fractions obtained from D. grisea were found to be not toxic when EPS were not included. Upon implementation of EPS as a commercial product, further assessment on the environmental toxicity to enchytraeids and other soil organisms is required. Our results provide a possible direction for developing a process to gain an environmentally friendly bio-additive for application in the tribological industry based on a biorefinery approach.

Effect of salt stress on physiological parameters of microalgae Vischeria punctata strain IPPAS H-242, a superproducer of eicosapentaenoic acid

The strain IPPAS H-242 is an eustigmatophycean alga with good growth characteristics and high content of the long chain polyunsaturated eicosapentaenoic fatty acid (EPA) - a very-long-chain fatty acid with high nutraceutical value. In this study, based on 18S rRNA gene and ITS1-5.8S-ITS2 sequences the strain IPPAS H-242 was identified as an authentic strain of Vischeria punctata. The effect of salt stress (0.5 M NaCl) on growth, cell morphology, ultrastructure, and biochemical composition with the emphasis on the fatty acid (FA) profile was investigated in batch cultures. Under salt stress, biomass accumulation and cell division were severely inhibited; cells were bigger, with higher chloroplast volume and numerous mitochondria, they had more proteins (73 % from the initial concentration as compared to 23 % in control) and their lipids had higher EPA proportion (13.6 % of total FA as compared to 6.4 % of total FA in control). In salt-stressed cells, thylakoid organization and photosynthetic activity were impaired, and D1 protein content decreased to trace amounts. In spite of an increase in EPA proportion in total FA, salt stress causes a decrease in total EPA productivity (49 mg/L as compared to 130 mg/L in control).

Ultrasound Extraction Mediated Recovery of Nutrients and Antioxidant Bioactive Compounds from Phaeodactylum tricornutum Microalgae

In recent years, a growing interest has been shown in the use of microalgae due to their interesting nutritional and bioactive profiles. Green innovative processing technologies such as ultrasound-assisted extraction (UAE) avoid the use of toxic solvents and high temperatures, being a sustainable alternative in comparison with traditional extraction methods. The present study aims to evaluate the recovery of high added-value compounds from Phaedoactylum tricornutum assisted by ultrasound. To optimize the UAE of proteins, carbohydrates, pigments and antioxidant compounds, a response surface methodology was used. Carbohydrate extraction was positively affected by the temperature. However, for the extraction of carotenoids, the most influential factor was the extraction time. The total polyphenols were only significantly affected by the extraction time. Finally, the antioxidant capacity, measured by 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), was strongly modulated by the extraction time, while for the oxygen radical antioxidant capacity (ORAC) assay, the most important parameter was the temperature, followed by the extraction time. The optimal conditions for the maximum extraction of nutrients, bioactive compounds and antioxidant capacity were 30 min, 50 ºC and a pH of 8.5. Finally, it has been seen that with these conditions, the extraction of fucoxanthin is allowed, although no differences were found between an ultrasound-assisted extraction and a shaking extraction (control).

Purification and biochemical characterization of an extracellular fructosyltransferase enzyme from Aspergillus niger sp. XOBP48: implication in fructooligosaccharide production

An extracellular fructosyltransferase (Ftase) enzyme with a molar mass of ≈70 kDa from a newly isolated indigenous coprophilous fungus Aspergillus niger sp. XOBP48 is purified to homogeneity and characterized in this study. The enzyme was purified to 4.66-fold with a total yield of 15.53% and specific activity of 1219.17 U mg^-1 of protein after a three-step procedure involving (NH₄)₂SO₄ fractionation, dialysis and anion exchange chromatography. Ftase showed optimum activity at pH 6.0 and temperature 50 °C. Ftase exhibited over 80% residual activity at pH range of 4.0-10.0 and ≈90% residual activity at temperature range of 40-60 °C for 6 h. Metal ion inhibitors Hg²⁺ and Ag⁺ significantly inhibited Ftase activity at 1 mmol concentration. Ftase showed K _m, v _max and k _cat values of 79.51 mmol, 45.04 µmol min^-1 and 31.5 min^-1, respectively, with a catalytic efficiency (k _cat/K _m) of 396 µmol^-1 min^-1 for the substrate sucrose. HPLC-RI experiments identified the end products of fructosyltransferase activity as monomeric glucose, 1-kestose (GF₂), and 1,1-kestotetraose (GF₃). This study evaluates the feasibility of using this purified extracellular Ftase for the enzymatic synthesis of biofunctional fructooligosaccharides.

Quantitative insights into the cyanobacterial cell economy

Phototrophic microorganisms are promising resources for green biotechnology. Compared to heterotrophic microorganisms, however, the cellular economy of phototrophic growth is still insufficiently understood. We provide a quantitative analysis of light-limited, light-saturated, and light-inhibited growth of the cyanobacterium Synechocystis sp. PCC 6803 using a reproducible cultivation setup. We report key physiological parameters, including growth rate, cell size, and photosynthetic activity over a wide range of light intensities. Intracellular proteins were quantified to monitor proteome allocation as a function of growth rate. Among other physiological acclimations, we identify an upregulation of the translational machinery and downregulation of light harvesting components with increasing light intensity and growth rate. The resulting growth laws are discussed in the context of a coarse-grained model of phototrophic growth and available data obtained by a comprehensive literature search. Our insights into quantitative aspects of cyanobacterial acclimations to different growth rates have implications to understand and optimize photosynthetic productivity.