Phenylalanine ammonia lyase (PAL) enzyme activity and antioxidant properties of some cyanobacteria isolates

Metabolomics Reveals Antioxidant Metabolites in Colored Rice Grains

Colored rice is richer in nutrients and contains more nutrients and bioactive substances than ordinary white rice. Moderate consumption of black (purple) rice has a variety of physiological effects, such as antioxidant effects, blood lipid regulation, and blood sugar control. Therefore, we utilized nontargeted metabolomics, quantitative assays for flavonoid and phenolic compounds, and physiological and biochemical data to explore the correlations between metabolites and the development of antioxidant characteristics in pigmented rice seeds. The findings indicated that, among Yangjinnuo 818 (YJN818), Hongnuo (HN), Yangchannuo 1 hao (YCN1H), and Yangzi 6 hao (YZ6H), YZ6H exhibited the highest PAL activity, which was 2.13, 3.08, and 3.25 times greater than those of YJN818, HN, and YCN1H, respectively. YZ6H likewise exhibited the highest flavonoid content, which was 3.8, 7.06, and 35.54 times greater than those of YJN818, HN, and YCN1H, respectively. YZ6H also had the highest total antioxidant capacity, which was 2.42, 3.76, and 3.77 times greater than those of YJN818, HN, and YCN1H, respectively. Thus, purple rice grains have stronger antioxidant properties than other colored rice grains. Receiver operating characteristic (ROC) curve analysis revealed that trans-3,3',4',5,5',7-hexahydroxyflavanone, phorizin, and trilobatin in the YZ6H, HN, and YCN1H comparison groups all had area under the curve (AUC) values of 1. Phlorizin, trans-3,3',4',5,5',7-hexahydroxyflavanone, and trilobatin were recognized as indices of antioxidant capability in colored rice in this research. This research adds to the understanding of antioxidant compounds in pigmented rice, which can increase the nutritional value of rice and promote the overall well-being of individuals. This type of information is of immense importance in maintaining a balanced and healthy diet.

Metabolomics revealed metabolite biomarkers of antioxidant properties and flavonoid metabolite accumulation in purple rice after grain filling

The correlation between flavonoids, phenolic metabolites and the total antioxidant capacity is well established. However, specific biomarkers of metabolites with antioxidant properties in purple rice grains remain unidentified. This study integrated nontargeted metabolomics, quantitative detection of flavonoids and phenolic compounds, and physiological and biochemical data to identify metabolite biomarkers of the antioxidant properties of purple rice grains after filling. The findings demonstrated a significant enhancement in the biosynthesis of flavonoids during the middle and late filling stages in purple rice grains. Additionally, the pathways involved in anthocyanin and flavonoid biosynthesis were significantly enriched. Catalase (CAT), phenylalanine ammonia-lyase (PAL), total phenols (TP), flavonoids (FD), and oligomeric proanthocyanidin (OPC) were significantly correlated with philorizin, myricetin 3-galactoside, and trilobatin. Phlorizin, myricetin 3-galactoside, and trilobatin were metabolite biomarkers of antioxidant properties in purple rice grains. This study provides new ideas for the cultivation of high-quality coloured rice varieties with high antioxidant activity.

Transcriptomic Profiling of Tomato Leaves Identifies Novel Transcription Factors Responding to Dehydration Stress

Drought is among the most challenging environmental restrictions to tomatoes (Solanum lycopersi-cum), which causes dehydration of the tissues and results in massive loss of yield. Breeding for dehydration-tolerant tomatoes is a pressing issue as a result of global climate change that leads to increased duration and frequency of droughts. However, the key genes involved in dehydration response and tolerance in tomato are not widely known, and genes that can be targeted for dehydration-tolerant tomato breeding remains to be discovered. Here, we compared phenotypes and transcriptomic profiles of tomato leaves between control and dehydration conditions. We show that dehydration decreased the relative water content of tomato leaves after 2 h of dehydration treatment; however, it promoted the malondialdehyde (MDA) content and ion leakage ratio after 4 h and 12 h of dehydration, respectively. Moreover, dehydration stress triggered oxidative stress as we detected significant increases in H₂O₂ and O^2- levels. Simultaneously, dehydration enhanced the activities of antioxidant enzymes including peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), and phenylalanine ammonia-lyase (PAL). Genome-wide RNA sequencing of tomato leaves treated with or without dehydration (control) identified 8116 and 5670 differentially expressed genes (DEGs) after 2 h and 4 h of dehydration, respectively. These DEGs included genes involved in translation, photosynthesis, stress response, and cytoplasmic translation. We then focused specifically on DEGs annotated as transcription factors (TFs). RNA-seq analysis identified 742 TFs as DEGs by comparing samples dehydrated for 2 h with 0 h control, while among all the DEGs detected after 4 h of dehydration, only 499 of them were TFs. Furthermore, we performed real-time quantitative PCR analyses and validated expression patterns of 31 differentially expressed TFs of NAC, AP2/ERF, MYB, bHLH, bZIP, WRKY, and HB families. In addition, the transcriptomic data revealed that expression levels of six drought-responsive marker genes were upregulated by de-hydration treatment. Collectively, our findings not only provide a solid foundation for further functional characterization of dehydration-responsive TFs in tomatoes but may also benefit the improvement of dehydration/drought tolerance in tomatoes in the future.

Effects of Three Essential Oil Fumigation Treatments on the Postharvest Control of Botrytis cinerea and Their Efficacy as Preservatives of Cherry Tomatoes

Cherry tomatoes (Solanum lycopersicum) are becoming increasingly popular due to their nutrition and delicious flavor. However, cherry tomatoes are highly perishable and susceptible to various pathogenic microorganisms after harvest, such as Botrytis cinerea. In the pretest experiment, we screened out three kinds of plant essential oils (EOs) (Torreya grandis oil, Eriobotrya japonica oil, and Citrus medica oil) that have strong fungicidal activity on B. cinerea from cherry tomatoes. To further evaluate the postharvest preservation application prospect of these three oils for cherry tomatoes, the oils were extracted from different parts of three plants by hydrodistillation, and their chemical constituents were analyzed by gas chromatography-mass spectrometry. The main representative components of T. grandis oil, E. japonica oil, and C. medica oil were δ-cadinene (11.76%), transnerolidol (9.70%), and 5,7-dimethoxycoumarin (23.22%), respectively. These three EOs effectively inhibited the mycelial growth of B. cinerea in vitro, with EC50 values of 81.672, 144.046, and 221.500 μl/liter, respectively. Compared with the blank control and other oil treatments, the T. grandis oil (at a concentration of 200 µl/liter) fumigation treatment was more effective at inhibiting the growth rate of the pathogen. In addition, the phenolic content and phenylalanine ammonia lyase, β-1,3-glucanase, chitinase, and peroxidase activities of tomatoes significantly increased on the seventh day due to the T. grandis oil treatment. The present study shows that these three oils with high extraction rates have preservation potential for cherry tomatoes. Among these three EOs, T. grandis oil can be used to further develop preservative products as a fumigant.

Regulation of Intracellular Reactive Oxygen Species Levels after the Development of Phallus rubrovolvatus Rot Disease Due to Trichoderma koningii Mycoparasitism

Phallus rubrovolvatus is a unique mushroom used for medicinal and dietary purposes in China. In recent years, however, the rot disease of P. rubrovolvatus has seriously affected its yield and quality, becoming an economically important threat. In this study, samples of symptomatic tissues were collected, isolated, and identified from five major P. rubrovolvatus production regions in Guizhou Province, China. Based on combined analyses of phylogenies (ITS and EF1-α), morphological characteristics and Koch's postulates, Trichoderma koningiopsis and Trichoderma koningii were identified as the pathogenic fungal species. Among these, T. koningii exhibited stronger pathogenicity than the other strains; thus, T. koningii was used as the test strain in the follow-up experiments. Upon co-culturing T. koningii with P. rubrovolvatus, the hyphae of the two species were intertwined, and the color of the P. rubrovolvatus hyphae changed from white to red. Moreover, T. koningii hyphae were wrapped around P. rubrovolvatus hyphae, leading to their shortening and convolution and ultimately inhibiting their growth due to wrinkling; T. koningii penetrated the entire basidiocarp tissue of P. rubrovolvatus, causing serious damage to the host basidiocarp cells. Further analyses revealed that T. koningii infection resulted in the swelling of basidiocarps and significantly enhanced the activity of defense-related enzymes, such as malondialdehyde, manganese peroxidase, and polyphenol oxidase. These findings offer theoretical support for further research on the infection mechanisms of pathogenic fungi and the prevention of diseases caused by them.

New Insights into the Mechanism of Trichoderma virens-Induced Developmental Effects on Agrostis stolonifera Disease Resistance against Dollar Spot Infection

Trichoderma is internationally recognized as a biocontrol fungus for its broad-spectrum antimicrobial activity. Intriguingly, the crosstalk mechanism between the plant and Trichoderma is dynamic, depending on the Trichoderma strains and the plant species. In our previous study, the Trichoderma virens 192-45 strain showed better pathogen inhibition through the secretive non-volatile and volatile substrates. Therefore, we studied transcriptional and metabolic responses altered in creeping bentgrass (Agrostis stolonifera L.) with T. virens colonization prior to a challenge with Clarireedia homoeocarpa. This fungal pathogen causes dollar spot on various turfgrasses. When the pathogen is deficient, the importance of T. virens to the enhancement of plant growth can be seen in hormonal production and microbe signaling, such as indole-3-acrylic acid. Therefore, these substrates secreted by T. virens and induced genes related to plant growth can be the ‘pre-defense’ for ensuing pathogen attacks. During C. homoeocarpa infection, the Trichoderma–plant interaction activates defense responses through the SA- and/or JA-dependent pathway, induced by T. virens and its respective exudates, such as oleic, citric, and stearic acid. Thus, we will anticipate a combination of genetic engineering and exogenous application targeting these genes and metabolites, which could make creeping bentgrass more resistant to dollar spot and other pathogens.

Genomic analysis and biochemical profiling of an unaxenic strain of Synechococcus sp. isolated from the Peruvian Amazon Basin region

Cyanobacteria are diverse photosynthetic microorganisms able to produce a myriad of bioactive chemicals. To make possible the rational exploitation of these microorganisms, it is fundamental to know their metabolic capabilities and to have genomic resources. In this context, the main objective of this research was to determine the genome features and the biochemical profile of Synechococcus sp. UCP002. The cyanobacterium was isolated from the Peruvian Amazon Basin region and cultured in BG-11 medium. Growth parameters, genome features, and the biochemical profile of the cyanobacterium were determined using standardized methods. Synechococcus sp. UCP002 had a specific growth rate of 0.086 ± 0.008 μ and a doubling time of 8.08 ± 0.78 h. The complete genome of Synechococcus sp. UCP002 had a size of ∼3.53 Mb with a high coverage (∼200x), and its quality parameters were acceptable (completeness = 99.29%, complete and single-copy genes = 97.5%, and contamination = 0.35%). Additionally, the cyanobacterium had six plasmids ranging from 24 to 200 kbp. The annotated genome revealed ∼3,422 genes, ∼ 3,374 protein-coding genes (with ∼41.31% hypothetical protein-coding genes), two CRISPR Cas systems, and 61 non-coding RNAs. Both the genome and plasmids had the genes for prokaryotic defense systems. Additionally, the genome had genes coding the transcription factors of the metalloregulator ArsR/SmtB family, involved in sensing heavy metal pollution. The biochemical profile showed primary nutrients, essential amino acids, some essential fatty acids, pigments (e.g., all-trans-β-carotene, chlorophyll a, and phycocyanin), and phenolic compounds. In conclusion, Synechococcus sp. UCP002 shows biotechnological potential to produce human and animal nutrients and raw materials for biofuels and could be a new source of genes for synthetic biological applications.

Effect of Melatonin on Fruit Quality via Decay Inhibition and Enhancement of Antioxidative Enzyme Activities and Genes Expression of Two Mango Cultivars during Cold Storage

The postharvest deterioration of mango fruits is a critical issue limiting mango storage and preservation due to its climacteric nature. This study evaluated the storage behavior of two mango cultivars and their response to exogenous melatonin (MT, 1000 μmol L⁻¹) treatment in attenuating fruit decay and enhancing fruits’ physiological and metabolic processes and gene relative expression subjected to cold storage. MT treatment in both mango cultivars significantly delayed weight loss, firmness, respiration rate, and decay incidence. However, MT did not influence the TSS, TA, and TSS:TA ratio regardless of the cultivar. Moreover, MT inhibited the decrease in total phenol and flavonoid content and AsA content while delaying the increase in the MDA content of mango during storage in both cultivars. In addition, MT dramatically inhibited the enzyme activity of PPO. In contrast, an increase in the activities of antioxidant enzymes (SOD and APX) and PAL and their genes’ relative expression was noticed in MT-treated fruits versus control in both cultivars. However, MT treatment was cultivar dependent in most parameters under study. These results demonstrated that MT treatment could be an essential postharvest treatment in minimizing decay, maintaining fruit quality, and extending mango fruits’ postharvest shelf life by enhancing the physiological and metabolic processes during cold storage.

Combining metabolite doping and metabolic engineering to improve 2-phenylethanol production by engineered cyanobacteria

2-Phenylethanol (2-PE) is a rose-scented aromatic compound, with broad application in cosmetic, pharmaceutical, food and beverage industries. Many plants naturally synthesize 2-PE via Shikimate Pathway, but its extraction is expensive and low-yielding. Consequently, most 2-PE derives from chemical synthesis, which employs petroleum as feedstock and generates unwanted by products and health issues. The need for “green” processes and the increasing public demand for natural products are pushing biotechnological production systems as promising alternatives. So far, several microorganisms have been investigated and engineered for 2-PE biosynthesis, but a few studies have focused on autotrophic microorganisms. Among them, the prokaryotic cyanobacteria can represent ideal microbial factories thanks to their ability to photosynthetically convert CO2 into valuable compounds, their minimal nutritional requirements, high photosynthetic rate and the availability of genetic and bioinformatics tools. An engineered strain of Synechococcus elongatus PCC 7942 for 2-PE production, i.e., p120, was previously published elsewhere. The strain p120 expresses four heterologous genes for the complete 2-PE synthesis pathway. Here, we developed a combined approach of metabolite doping and metabolic engineering to improve the 2-PE production kinetics of the Synechococcus elongatus PCC 7942 p120 strain. Firstly, the growth and 2-PE productivity performances of the p120 recombinant strain were analyzed to highlight potential metabolic constraints. By implementing a BG11 medium doped with L-phenylalanine, we covered the metabolic burden to which the p120 strain is strongly subjected, when the 2-PE pathway expression is induced. Additionally, we further boosted the carbon flow into the Shikimate Pathway by overexpressing the native Shikimate Kinase in the Synechococcus elongatus PCC 7942 p120 strain (i.e., 2PE_aroK). The combination of these different approaches led to a 2-PE yield of 300 mg/gDW and a maximum 2-PE titer of 285 mg/L, 2.4-fold higher than that reported in literature for the p120 recombinant strain and, to our knowledge, the highest recorded for photosynthetic microorganisms, in photoautotrophic growth condition. Finally, this work provides the basis for further optimization of the process aimed at increasing 2-PE productivity and concentration, and could offer new insights about the use of cyanobacteria as appealing microbial cell factories for the synthesis of aromatic compounds.

UV-C treatment inhibits browning, inactivates Pseudomonas tolaasii and reduces associated chemical and enzymatic changes of button mushrooms

BACKGROUND

Button mushrooms with completely white appearance are popular with consumers. However, button mushrooms are susceptible to infection with Pseudomonas tolaasii, which results in browning. This study evaluates the effects of ultraviolet-C (UV-C) treatment on the inactivation of P. tolaasii in vitro and in vivo and on the physiological and chemical changes of button mushrooms during storage for 21 days at 4 °C.

RESULTS

UV-C doses of 0.5 to 9.0 kJ m^-2 resulted in 3.91-6.26 log CFU mL^-1 reduction of P. tolaasii populations in vitro, and UV-C treatment reduced P. tolaasii populations inoculated on mushroom cap surfaces and browning severity. Moreover, P. tolaasii increased polyphenol oxidase (PPO) activity, and decreased phenylalanine ammonia-lyase (PAL) activity, the accumulation of phenolics and contents of brown melanin precursors, including γ-l-glutaminyl-4-hydroxybenzene (GHB), γ-l-glutaminyl-3,4-dihydroxybenzene (GDHB), and tyrosine in button mushrooms. UV-C treatment was found to reduce the negative changes due to P. tolaasii infection.

CONCLUSION

These results indicated that the application of UV-C treatment inhibited browning, inactivated P. tolaasii and reduced P. tolaasii - associated chemical and enzymatic changes of button mushrooms. © 2021 Society of Chemical Industry.

Biochemical Characterization of Novel Phenylalanine Ammonia-Lyase from Spirulina CPCC-695

Phenylalanine ammonia lyase (PAL) catalyzes the deamination of phenylalanine to cinnamic acid and ammonia. It plays a crucial role in the formation of secondary metabolites through the phenylpropanoid pathway. Recently there has been growing interest in exploring the biochemical properties of PAL for its clinical and commercial applications. PAL as a key component has been used in metabolic engineering and synthetic biology. Due to its high substrate specificity and catalytic efficacy, PAL has opened a new area of interest in the biomedical field. PAL has been frequently used in the enzyme replacement therapy of phenylketonuria, cancer treatment and microbial production of l-phe the precursor of noncalorific sweetener aspartame (Methyl L-α-aspartyl-l-phenylalaninate), antimicrobial and health supplements. PAL occurs in few plants, fungi, bacteria, and cyanobacteria. The present investigation is a preliminary study in which an attempt has been made for the isolation, partial purification, and biochemical characterization of PAL (crude and partially purified) from Spirulina CPCC-695. Partially purified PAL exhibited higher enzymatic activity and protein content than the crude enzyme. Molecular weight of the crude and partially purified PAL was ~ 66 kDa. The optimum temperature and pH for PAL activity was observed as 30 ℃ and 8.0 respectively. l-Phe was the most preferred substrate (100 mM) whereas gallic acid showed maximum inhibition of PAL activity. Enzyme kinetics suggested good catalytic efficacy of the PAL enzyme and affinity towards substrate. Both the enzyme (crude and partially purified) showed less than 5% haemolysis suggesting the biocompatible nature of PAL.

Seed-Borne Erwinia persicina Affects the Growth and Physiology of Alfalfa (Medicago sativa L.)

Seed-borne Erwinia persicina can be transmitted globally via alfalfa (Medicago sativa L.) seed trade, but there is limited information about the impact of this plant-pathogenic bacterium on alfalfa plants. In this study, strain Cp2, isolated from alfalfa seeds, was confirmed by whole-genome sequencing to belong to E. persicina. Subsequently, the effects of Cp2 on alfalfa growth and physiology were evaluated by constructing a rhizosphere infection model. Strain Cp2 had a strong inhibitory effect on the elongation and growth of alfalfa roots, which was very unfavorable to these perennial plants. Furthermore, an increased number of leaf spots and yellowing symptoms were observed in plants of the Cp2 group from day 10 to day 21 and the strain Cp2 was re-isolated from these leaves. Correlation between growth and photosynthetic parameters was analyzed and the significant decreases in fresh weight and root and plant lengths in the Cp2 group were related to the marked reduction of chlorophyll b, carotenoid, transpiration rate, and stomatal conductance of leaves (r > 0.75). In addition, nine physiological indicators of root, stem, and leaf were measured in the plants 21 days after treatment with Cp2. The physiological response of root and leaf to Cp2 treatment was stronger than that of stem. The physiological indicators with the greatest response to Cp2 infection were further explored through principal component analysis, and superoxide dismutase, peroxidase, ascorbate peroxidase, and soluble protein showed the greatest changes in roots, stems, and leaves (P < 0.001). Among tissues, the commonality was the change of soluble protein. Therefore, soluble protein is speculated to be a physiological marker during alfalfa–E. persicina interactions. These findings indicate that once E. persicina spreads from alfalfa seeds to the rhizosphere, it can invade alfalfa roots and cause disease. This study demonstrates that this plant pathogenic bacterium may be a potential threat to new environment when they spread via seed trade and these “dangerous hitchhikers” warrant further attention, especially in the study of bacterial diseases in pasture-based production systems.

Insights into the biosynthesis pathway of phenolic compounds in microalgae

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Microalgal PCs are important bioactive molecules beneficial for human health.

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Bioinformatic comparative exploration predicts PCs synthesis in microalgae.

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Ten groups of prokaryotic and eukaryotic microalgae reveal a conserved pathway core.

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Featured PCs can be restricted to diverse microalgae due to ecological implications.

Among the most relevant bioactive molecules family, phenolic compounds (PCs) are well known in higher plants, while their knowledge in microalgae is still scarce. Microalgae represent a novel and promising source of human health benefit compounds to be involved, for instance, in nutraceutical composition. This study aims to investigate the PCs biosynthetic pathway in the microalgal realm, exploring its potential variability over the microalgal biodiversity axis. A multistep in silico analysis was carried out using a selection of core enzymes from the pathway described in land plants. This study explores their presence in ten groups of prokaryotic and eukaryotic microalgae.. Analyses were carried out taking into account a wide selection of algal protein homologs, functional annotation of conserved domains and motifs, and maximum-likelihood tree construction. Results showed that a conserved core of the pathway for PCs biosynthesis is shared horizontally in all microalgae. Conversely, the ability to synthesize some subclasses of phenolics may be restricted to only some microalgal groups (i.e., Chlorophyta) depending on featured enzymes, such as the flavanone naringenin and other related chalcone isomerase dependent compounds.

Cyanobacteria-From the Oceans to the Potential Biotechnological and Biomedical Applications

Cyanobacteria are photosynthetic prokaryotic organisms which represent a significant source of novel, bioactive, secondary metabolites, and they are also considered an abundant source of bioactive compounds/drugs, such as dolastatin, cryptophycin 1, curacin toyocamycin, phytoalexin, cyanovirin-N and phycocyanin. Some of these compounds have displayed promising results in successful Phase I, II, III and IV clinical trials. Additionally, the cyanobacterial compounds applied to medical research have demonstrated an exciting future with great potential to be developed into new medicines. Most of these compounds have exhibited strong pharmacological activities, including neurotoxicity, cytotoxicity and antiviral activity against HCMV, HSV-1, HHV-6 and HIV-1, so these metabolites could be promising candidates for COVID-19 treatment. Therefore, the effective large-scale production of natural marine products through synthesis is important for resolving the existing issues associated with chemical isolation, including small yields, and may be necessary to better investigate their biological activities. Herein, we highlight the total synthesized and stereochemical determinations of the cyanobacterial bioactive compounds. Furthermore, this review primarily focuses on the biotechnological applications of cyanobacteria, including applications as cosmetics, food supplements, and the nanobiotechnological applications of cyanobacterial bioactive compounds in potential medicinal applications for various human diseases are discussed.

Antimicrobial activity and metabolite profiling of endophytic fungi in Digitaria bicornis (Lam) Roem. and Schult. and Paspalidium flavidum (Retz.) A. Camus

Endophytic fungal occurrences were studied in aerial regions of Digitaria bicornis and Paspalidium flavidum by three isolation methods: potato dextrose agar (PDA), malt extract agar (MEA), and moist blotters. Seventy species of 29 genera of endophytic fungi in D. bicornis and 71 species of 30 genera in P. flavidum were documented. Endophytic fungal communities were grouped into 40 and 43 anamorphic ascomycetes (21 and 23 genera) and 20 teleomorphic ascomycetes (6 and 7 genera) in D. bicornis and P. flavidum, respectively. PDA supported the expression of larger number of fungal communities than MEA and MB; and P. flavidum hosted more number of endophytic fungi than D. bicornis. Seasons played an important role in supporting the assemblage of fungal endophytes. Endophytic fungal species richness and assemblages in plant regions were determined for alpha, beta, and gamma diversities. The ethyl acetate followed by methanolic extracts of certain fungal species showed good antagonistic and antibacterial activities. Among fungal endophytes, Curvularia protuberata and Penicillium citrinum exhibited high antagonistic and antibacterial activities. The high-resolution orbitrap liquid chromatography-mass spectrometry of ethyl acetate crude extracts of C. protuberata and P. citrinum revealed the presence of antifungal and antimicrobial, besides a host of compounds in the extracts. The present study indicated that grass endophytes are the sources of compounds with antimicrobial and other pharmacological activities.

Exploitation of Filamentous and Picoplanktonic Cyanobacteria for Cosmetic Applications: Potential to Improve Skin Structure and Preserve Dermal Matrix Components

The use of natural products in skin care formulations gained interest as a concern for modern societies. The undesirable side effects of synthetic compounds, as well as the associated environmental hazards, have driven investigation on photosynthetic organisms as sustainable sources of effective and environmentally friendly ingredients. The use of natural extracts in cosmetics has been highlighted and, along with plants and algae, cyanobacteria have come into focus. Due to their low culture demands, high grow rates and ability to produce a wide variability of bioactive metabolites, cyanobacteria emerged as an economic and sustainable base for the cosmetic industry. In this study, we evaluated the potential of ethanol extracts of picocyanobacteria strains of the genera Cyanobium and Synechocystis and filamentous strains of the genera Nodosilinea, Phormidium and Tychonema for skin applications, with focus in the field of anti-aging. The extracts were analyzed for their pigment profile, phenolic content, antioxidant potential, cytotoxicity against keratinocytes (HaCat), fibroblasts (3T3L1), endothelial cells (hCMEC/D3) and capacity to inhibit hyaluronidase (HAase). The total carotenoid content ranged from 118.69 to 383.89 μg g⁻¹ of dry biomass, and the total phenolic content from 1.07 to 2.45 mg GAE g⁻¹. Identified carotenoids consisted of zeaxanthin, lutein, canthaxanthin, echinenone and β-carotene, with zeaxanthin and lutein being the most representative (49.82 and 79.08 μg g⁻¹, respectively). The highest antioxidant potential was found for Phormidium sp. LEGE 05292 and Tychonema sp. LEGE 07196 for superoxide anion radical (O₂^•−) scavenging (IC₅₀ of 822.70 and 924 μg mL⁻¹, respectively). Low or no cytotoxicity were registered. Regarding HAase inhibition, Tychonema sp. LEGE 07196 and Cyanobium sp. LEGE 07175 showed the best IC₅₀ (182.74 and 208.36 μg mL⁻¹, respectively). In addition, an increase in fibroblast proliferation was registered with these same strains. From this work, the ethanol extracts of the species Tychonema sp. and Cyanobium sp. are particularly interesting for their potential application in anti-aging formulations, once they stimulated fibroblast proliferation and inhibit hyaluronic acid digestion.

Antioxidant and Cytoprotective Properties of Cyanobacteria: Potential for Biotechnological Applications

Antioxidant compounds from cyanobacteria may constitute a natural alternative to current synthetic antioxidants, which contain preservatives and suspected toxicity. In this work, we evaluate the antioxidant potential of cyanobacterial strains of distinct species/genus isolated from freshwater (n = 6), soil (n = 1) and wastewater (n = 1) environments. Lyophilized biomass obtained from in-vitro cultures of those strains was extracted with ethanol and methanol. The antioxidant potential was evaluated by chemical (DPPH scavenging method, β-carotene bleaching assay, determination of total phenolic and total flavonoid compounds) and biological (H₂O₂-exposed HEK293T cell line model) approach. Some strains showed high yields of antioxidant activity by the DPPH assay (up to 10.7% IP/20.7 TE μg/mL) and by the β-carotene bleaching assay (up to 828.94 AAC), as well as significant content in phenolic (123.16 mg EAG/g DW) and flavonoid (900.60 mg EQR/g DW) compounds. Normalization of data in a “per cell” or “per cell volume” base might facilitate the comparison between strains. Additionally, most of the cyanobacterial extracts conferred some degree of protection to HEK293T cells against the H₂O₂-induced cytotoxicity. Freshwater Aphanizomenon gracile (LMECYA 009) and Aphanizomenon flos-aquae (LMECYA 088), terrestrial Nostoc (LMECYA 291) and wastewater Planktothrix mougeotii (LEGE 06224) seem to be promising strains for further investigation on cyanobacteria antioxidant potential.

A plant biostimulant made from the marine brown algae Ascophyllum nodosum and chitosan reduce Fusarium head blight and mycotoxin contamination in wheat

Fusarium head blight (FHB) caused by Fusarium graminearum is a disease that results in yield loss and mycotoxin contamination in wheat globally. This study assessed the effect of a plant biostimulant prepared from a brown macroalga Ascophyllum nodosum (Liquid Seaweed Extract; LSE) alone and in combination with chitosan in controlling Fusarium. Wheat seedlings drenched with LSE and chitosan in combination showed reduced severity of F. graminearum infection on leaves as evidenced by a significant reduction in necrotic area and fewer number of conidia produced in the necrotic area. Gene expression studies showed that the combination of LSE and chitosan amplified the response of pathogenesis-related genes (TaPR1.1, TaPR2, TaPR3, TaGlu2) in wheat seedlings infected with Fusarium spores above that observed for the individual treatments. The combination treatments were more effective in enhancing the activity of various defense related enzymes such as peroxidase and polyphenol oxidase. FHB studies on adult plants showed a reduction of bleached spikes in wheat heads treated with the combination of LSE and chitosan. Mycotoxin content appeared to be correlated with FHB severity. Combination treatments of LSE and chitosan reduced the levels of mycotoxins deoxynivalenol and sambucinol in wheat grains. Systemic disease resistance appears to be induced by LSE and chitosan in response to F. graminearum in wheat by inducing defense genes and enzymes.

The Effect of Tartary Buckwheat Flavonoids in Inhibiting the Proliferation of MGC80-3 Cells during Seed Germination

Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn) is rich in functional compounds such as rutin, quercetin, d-chiro-inositol, dietary fiber, and essential amino acids. Electric field (EF) treatment before sprout germination results in physiological and chemical changes, and some alterations might lead to positive applications in plant seeds. MTT assay showed that the effect of total flavonoids on human gastric cancer cell line MGC80-3 was significantly changed after EF treatment for different germination days (3-7 days). Among them, the total flavonoids of tartary buckwheat (BWTF) on the third day had the most obvious inhibitory effect on MGC80-3 (p < 0.01). In addition, flow cytometry evidenced that different ratios of quercetin and rutin had effects on the proliferation of MGC80-3. The same content of quercetin and rutin had the best effect, reaching 6.18 ± 0.82%. The anti-cancer mechanism was mainly promoted by promoting the expression of apoptotic proteins. The expression of Bax/Bcl-2 and caspase-8 in MGC80-3 cells was mediated by BWTFs. This study has good research value for improving the biological and economic value of tartary buckwheat.

Hydroponic grown tobacco plants respond to zinc oxide nanoparticles and bulk exposures by morphological, physiological and anatomical adjustments

Zinc oxide nanoparticles (NPs) are the third highest in terms of global production among the various inorganic nanoparticles, and there are concerns because of their worldwide availability and accumulation in the environment. In contrast, zinc is an essential element in plant growth and metabolism, and ZnO NPs (nano-ZnO) may have unknown interactions with plants due to their small sizes as well as their particular chemical and physical characteristics. The present study examined the effect of nano-ZnO (25nm) and bulk or natural form (<1000nm, bulk-ZnO), compared with zinc in the ionic form (ZnSO4) on Nicotiana tabacum seedlings in a nutrient solution supplemented with either nano-ZnO, bulk-ZnO (0.2, 1, 5 and 25µM) or ZnSO4 (control) for 21 days. Results showed that nano-ZnO at most of the levels and 1µM bulk-ZnO positively affected growth (root and shoot length/dry weight), leaf surface area and its metabolites (auxin, phenolic compounds, flavonoids), leaf enzymatic activities (CAT, APX, SOD, POX, GPX, PPO and PAL) and anatomical properties (root, stem, cortex and central cylinder diameters), while bulk-ZnO caused decreases at other levels. The activities of enzymes were induced to a greater extent by intermediate nano-ZnO levels than by extreme concentrations, and were higher in nano-ZnO treated than in bulk treated tobacco. As the ZnO level increased, the vascular expansion and cell wall thickening of the collenchyma/parenchyma cells occurred, which was more pronounced when treated by NPs than by its counterpart. The Zn content of root and leaf increased in most of ZnO treatments, whereas the Fe content of leaves decreased. Our findings indicate that tobacco responded positively to 1µM bulk-ZnO and to nearly all nano-ZnO levels (with the best levels being at 0.2µM and 1µM) by morphological, physiological and anatomical adjustments.

The potent therapeutic effect of novel cyanobacterial isolates against oxidative stress damage in redox rats

AIMS

Cyanobacteria are immense sources of several pharmacological active compounds such as flavonoids and carotenoids with anti-inflammatory and antioxidant activity. The potential therapeutic effect of two novel cyanobacterial isolates, Cronbergia siamensis (KY296358.1) and Sphaerospermopsis aphanizomenoides (KU212886.1), against hydrogen peroxide (H₂ O₂ )-induced oxidative stress damage in the rat model was determined in this study.

METHODS AND RESULTS

In vitro antioxidant activity of the two studied isolates was evaluated by radical scavenging assay and ferric reducing power. The possible prophylactic activity of S. aphanizomenoides (KU212886.1) against H₂ O₂ -induced oxidative stress in the rat model was assessed in vivo. Serum alanine transaminase and aspartate transaminase were measured for the liver functions in redox rats. Liver malondialdehyde (MDA), glutathione, oxidized glutathione, nitric oxide, superoxide dismutase (SOD) and catalase (CAT) were assessed as oxidative stress markers. The effect of S. aphanizomenoides on the transcripts level of superoxide dismutase (Mn-SOD) and catalase (CAT) genes in the rat's liver tissues was measured using qRT-PCR. Oral administration of S. aphanizomenoides extract in low and high doses (100, 200 mg kg^-1 b.w) resulted in significant improvement in biochemical parameters of liver functions and oxidative stress markers. Also, the endogenous antioxidant defence enzymes and the expression of their related genes (Mn/SOD, CAT) were upregulated. Immunohistochemistry of Caspase-3, an apoptotic marker, showed potent amelioration in the liver tissues.

CONCLUSIONS

The novel isolate S. aphanizomenoides proved in vitro and in vivo antioxidant activity against redox rat model.

SIGNIFICANCE AND IMPACT OF THE STUDY

This isolate provides a new source of pharmacological compounds with great importance in pharmacological and medical fields.

A comprehensive in silico characterization of bacterial signal peptides for the excretory production of Anabaena variabilis phenylalanine ammonia lyase in Escherichia coli

Anabaena variabilis double mutant (C503S/C565S) phenylalanine ammonia-lyase (PAL) is an appealing enzyme in the enzyme-replacement therapy of phenylketonuria. Yet abundant production of this enzyme has been of concern for industrial production. In this study, we have characterized 1175 bacterial signal peptides (SPs) and identified the most efficient ones for the excretory production of mutant AvPAL. Analysis by SignalP 4.1 revealed that more than 61% of SPs had a D-score greater than 0.7, denoting to be highly efficient. The optimum length of a bacterial SP was 25-30. The preferable net positive charge and the second residue of N-region were + 2 and Lys/Arg, respectively. Highly efficient SPs possessed 3-5 Leus in their H-region and A/L/VXA-FF cleavage site. Highly efficient SPs were from Escherichia coli, corroborating the necessity of an agreement between SPs and the host. Physiochemical characterization of mutant AvPAL conjugates via ProtParam and PROSOII, revealed that ~ 99.5% of proteins would not be entraped in inclusion bodies. Secretory pathways were identified by EffectiveDB and more than 98% of SPs were cleavable. Chimeras were modeled using the I-TASSER program, being evaluated by the Ramachandran plots. The mRNA secondary structure of mutant AvPAL upon linkage to SPs was assessed using the mfold program. It was shown that the linkage of a SP does not affect mutant AvPAL's stability at the protein or mRNA level. AllergenFP tool demonstrated that chimeras were not allergen. SPs, including FMF4_ECOLX, E2BB_ECOLX, and LPTA_ECOLI exhibited the highest propensity for secretion and appropriate features in all analyses.

Genome duplication improves the resistance of watermelon root to salt stress

Salinity is a major abiotic stress factor that affects crop productivity. Roots play an important role in salt stress in plants. Watermelon is a salt-sensitive crop; however, tetraploid watermelon seedlings are more tolerant to salt stress than their homogenotype diploid ancestors. To obtain insights into the reasons underlying the differences in salt tolerance with respect to the ploidy of plants, self-grafted and cross-grafted diploid and tetraploid watermelon seedlings were exposed to 300 mM NaCl for 8 days. After the treatment, the tetraploid rootstock-grafted watermelon plants showed higher salt stress tolerance than the diploid plants. There were no significant differences in the physiological effects between the rootstocks with the same ploidy. The tetraploid rootstock-grafted watermelon plants exhibited higher net photosynthetic rate, leaf stomatal conductance and transpiration rate than the diploid rootstock-grafted watermelon plants throughout the salt treatment process. The activities of antioxidant enzymes and contents of osmoregulatory compounds in the roots were higher in the tetraploid rootstock-grafted watermelon plants than in the diploid plants during the entire salt response process. Higher Na⁺/K⁺ ratio was found in all parts of diploid rootstock-grafted watermelon, especially in the roots, K⁺ and Na⁺ were preferentially accumulated in the aerial parts (leaves and stem) than in the roots, which might be driven by the Na⁺/H⁺ antiporter, as evidenced by the higher transcript levels for SOS, PMA1, HKT1 and NHX1 in the roots. Taken together, our results suggest that genome duplication improves the resistance of watermelon root to salt stress.

Nostoc calcicola extract improved the antioxidative response of soybean to cowpea aphid

BACKGROUND

Soybean (Glycine max (L.) Merr. cv. "Nam Dan") is one of the most valuable crops in agricultural production in Nghe An province (Vietnam). Our previous study revealed that extract of the cyanobacterium strain Nostoc calcicola HN9 expressed positive effect on growth and development, and raised soybean productivity (Tran et al. in Proceeding of Vietnam national conference of research on biology, Da Nang, 2016). We hypothesized that N. calcicola HN9 would improve the defense responses of G. max cv. "Nam Dan" to cowpea aphid (Aphis craccivora Koch)-a serious pest of leguminous crops.

RESULTS

Infestation of A. craccivora caused oxidative stress in leaves of G. max cv. "Nam Dan". A strong generation of endogenous reactive oxygen species (ROS) such as superoxide anion radical (O ₂^·- ) and hydrogen peroxide (H₂O₂) resulted in the cellular damages in the aphid-infested leaves through high levels of injury percentage and lipid peroxidation. To protect from aphid attack themselves, soybean plants triggered the antioxidant defense systems, in which, enzymatic antioxidants such as superoxide dismutase (SOD, 1.15.1.1), catalase (CAT, 1.11.1.6) and GPx (EC 1.11.1.9) were strongly accumulated to reduce the toxic effects of ROS. Components of N. calcicola HN9 extract might strengthen the defensive capability of G. max cv. "Nam Dan" to cowpea aphid infestation via establishing the chemical constraints on oxidative stress. Under effect of cyanobacteria extract, generation of O ₂^·- and H₂O₂ was strictly limited, activities of SOD, CAT and GPx were remarkably accumulated in the aphid-infested leaves leading to a significant reduction of oxidative damages.

CONCLUSIONS

Nostoc calcicola HN9 extract probably not only controlled the generation and effects of O ₂^·- and H₂O₂ but also augmented the accumulated activity of SOD, CAT and GPx in soybean leaves that allowed them to control oxidative stress, contributed to increase the resistance of G. max cv. "Nam Dan" to A. craccivora. The improvement of cyanobacteria extract on the antioxidative response of soybean "Nam Dan" to cowpea aphid can be a novel aspect to contribute to current knowledge regarding the soybean-aphid interaction.

Antioxidant properties and polyphenolic content in terrestrial cyanobacteria

Cell-free extracts of twenty terrestrial cyanobacteria were evaluated for their antioxidant properties in terms of free-radical scavenging (DPPH and ABTS) and metal chelating activity and deoxyribose protection. Extract of Anabaena constricta was the most prominent antioxidant agent (IC50 for DPPH activity 0.91 mg ml-1, ABTS 0.23 mg ml-1, deoxyribose protection 0.63 mg ml-1 and Fe+2-ion chelating 0.9 mg ml-1). The extracts of cyanobacterial species contained high quantity of total phenol and total flavonoid that were supposed to impart prominent antioxidant properties. Cyanobacterial species also showed fairly high PAL activity. We reported varied quantities of polyphenolics gallic, chlorogenic, caffeic, vanillic and ferulic acids and flavonoids rutin, quercetin and kaempferol in cyanobacterial extracts. The presence of these polyphenolics was linked with the free radical scavenging, metal chelating and antioxidative damage protecting properties of the organisms. Cyanobacteria are the most feasible, promising and alternative candidates for searching out new chemical leads for industrial applications in pharmaceuticals, neutraceuticals and biomolecules of importance. Presence of biomolecules such as polyphenolics and their connection with the prominent biological functions (e.g., antioxidant properties) make these organisms a potential source of secondary metabolites with predominant biological activities. Additionally, dominant presence of polyphenols as antioxidant agents in cyanobacterial species may reflect their adaptation strategies against abiotic stresses for their ecological success in different habitats.

Biochemical analysis of Centaurea depressa phenylalanine ammonia lyase (PAL) for biotechnological applications in phenylketonuria (PKU)

CONTEXT

Phenylketonuria (PKU) is the most common hereditary defect of phenylalanine hydroxylase (PAH) enzyme achieving the hydroxylation of phenylalanine (Phe). Phenylalanine ammonia lyase (PAL) converts Phe to a harmless metabolite, trans-cinnamic acid (TCA) in plants and PAL enzyme activity is fairly high in plants rich in flavonoids.

OBJECTIVE

The study aimed the biochemical analysis of PAL form Centaurea depressa BIEB. (Asteraceae) a flavonoid rich plant. This study may form the main frame of future research efforts for the development of a plant preparation aimed for oral intake in PKU patients in an attempt to enrich their diet by allowing them to ingest some food stuff containing Phe without being exposed to complications.

MATERIALS AND METHODS

PAL was partially purified from the leaves of C. depressa. Enzyme activity was determined in comparison with that of other herbs that reportedly have a high PAL activity. Enzyme optimization was achieved and the PAL protein was detected by western blotting.

RESULTS

C. depressa PAL demonstrated high activity (34.9 ± 0.6 U/mg protein). The enzyme was purified by 1.92-fold, which resulted in an activity of 53.30 ± 0.2 U/mg protein. The high-performance liquid chromatography analyzes of the PAL activity both before and after purification were in agreement. Western blot of PAL exhibited a 70 kDa protein band. The optimum pH and temperature are pH 8.8 and 37 °C. The optimum activities under gastric and intestinal digestion conditions were observed at pH 4.0 and pH 8.0, respectively.

DISCUSSION AND CONCLUSION

PAL activity of C. depressa is high, and does not disappear under different environmental conditions. This enzyme could be used for the development of dietary foods and biotechnological products for patients with PKU.

Optimization of oligomeric enzyme activity in ionic liquids using Rhodotorula glutinis yeast phenylalanine ammonia lyase

Phenylalanine ammonia lyase (E.C.4.3.1.24, PAL) activity of Rhodotorula glutinis yeast has been demonstrated in four commonly used ionic liquids. PAL forward reaction was carried out in 1-butyl-3-methylimidazolium methyl sulfate ([BMIM][MeSO₄]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄]), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) and 1-butyl-3-methylimidazolium lactate ([BMIM][lactate]). Our experiments have revealed that PAL is catalytically active in ionic liquids and the enzyme activity in ([BMIM][PF₆]) is comparable to that obtained in aqueous buffer medium. Different conditions were optimized for maximal PAL forward activity including time of incubation (30.0min)_L-phenylalanine substrate concentration (30.0mM), nature of buffer (50.0mM Tris-HCl), pH (9.0), temperature (37°C), and speed of agitation (100 rev min^-1). Under these optimized conditions, about 83% conversion of substrate to product was obtained for the PAL forward reaction that was determined using UV spectroscopy at 290nm. PAL reverse reaction in ([BMIM][PF₆]) was determined spectrophotometrically at 520nm; and about 59% substrate conversion was obtained. This data provides further knowledge in enzyme biocatalysis in non-aqueous media, and may be of importance when studying the function of other oligomeric/multimeric proteins and enzymes in ionic liquids.

Antioxidant properties in some selected cyanobacteria isolated from fresh water bodies of Sri Lanka

Phytonutrients and pigments present in cyanobacteria act as antioxidants, which facilitate the formation of body's defense mechanism against free radical damage to cells. The aim of this investigation was to study the total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity, phycobiliproteins (PBPs), and active compounds in four cyanobacterial species, that is, Oscillatoria sp., Lyngbya sp., Microcystis sp., and Spirulina sp. isolated from fresh water bodies of Sri Lanka. In this study, Lyngbya sp., showed highest TPC (5.02 ± 0.20 mg/g), TFC (664.07 ± 19.76 mg/g), and total PBPs (127.01 mg/g) value. The ferric reducing antioxidant power (FRAP) was recorded highest in Oscillatoria sp. (39.63 ± 7.02), whereas the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity was also reported the highest in Oscillatoria sp. (465.31 ± 25.76) followed by Lyngbya sp. (248.39 ± 11.97). In FTIR spectroscopy, Lyngbya sp. does not show any N-H stretching band which is ultimately responsible for the inhibition of antioxidant activity. The study revealed that Lyngbya sp. and Oscillatoria sp. can be an excellent source for food, pharmaceutical, and other industrial uses.

Plant-growth regulators alter phytochemical constituents and pharmaceutical quality in Sweet potato (Ipomoea batatas L.)

Background

Sweet potato (Ipomoea batatas L.) is one of the most important consumed crops in many parts of the world because of its economic importance and content of health-promoting phytochemicals.

Methods

With the sweet potato (Ipomoea batatas L.) as our model, we investigated the exogenous effects of three plant-growth regulators methyl jasmonate (MeJA), salicylic acid (SA), and abscisic acid (ABA) on major phytochemicals in relation to phenylalanine ammonia lyase (PAL) activity. Specifically, we investigated the total phenolic content (TPC), total flavonoid content (TFC), total anthocyanin content (TAC), and total β-carotene content (TCC). Individual phenolic and flavonoid compounds were identified using ultra-high performance liquid chromatography (UHPLC). Antioxidant activities of treated plants were evaluated using a 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay and a β-carotene bleaching assay. Anticancer activity of extracts was evaluated against breast cancer cell lines (MCF-7 and MDA-MB-231) using MTT assay.

Results

TPC, TFC, TAC, and TCC and antioxidant activities were substantially increased in MeJA-, SA-, and ABA-treated plants. Among the secondary metabolites identified in this study, MeJA application significantly induced production of quercetin, kaempferol, myricetin, gallic acid, chlorogenic acid, 3,5-dicaffeoylquinic acid, and 4,5-dicaffeoylquinic acid. Luteolin synthesis was significantly induced by SA application. Compared with control plants, MeJA-treated sweet potato exhibited the highest PAL activity, followed by SA and ABA treatment. The high DPPH activity was observed in MeJA followed by SA and ABA, with half-maximal inhibitory concentration (IC₅₀) values of 2.40, 3.0, and 3.40 mg/mL compared with α-tocopherol (1.1 mg/mL). Additionally, MeJA-treated sweet potato showed the highest β-carotene bleaching activity, with an IC₅₀ value of 2.90 mg/mL, followed by SA (3.30 mg/mL), ABA (3.70 mg/mL), and control plants (4.5 mg/mL). Extracts of sweet potato root treated with MeJA exhibited potent anticancer activity with IC₅₀ of 0.66 and 0.62 mg/mL against MDA-MB-231 and MCF-7 cell lines respectively, compared to that of extracts of sweet potato treated with SA (MDA-MB-231 = 0.78 mg/mL; MCF-7 = 0.90 mg/mL) and ABA (MDA-MB-231 = 0.94 mg/mL; MCF-7 = 1.40 mg/mL). The results of correlation analysis showed that anthocyanins and flavooids are corresponding compounds in sweet potato root extracts for anticancer activity against breast cancer cell lines.

Conclusions

MeJA has great potential to enhance the production of important health-promoting phytochemicals in sweet potato.

Rhodotorula glutinis Phenylalanine/Tyrosine Ammonia Lyase Enzyme Catalyzed Synthesis of the Methyl Ester of para-Hydroxycinnamic Acid and its Potential Antibacterial Activity

Biotransformation of L-tyrosine methyl ester (L-TM) to the methyl ester of para- hydroxycinnamic acid (p-HCAM) using Rhodotorula glutinis yeast phenylalanine/tyrosine ammonia lyase (PTAL; EC 4.3.1.26) enzyme was successfully demonstrated for the first time; progress of the reaction was followed by spectrophotometric determination at 315 nm. The following conditions were optimized for maximal formation of p-HCAM: pH (8.5), temperature (37°C), speed of agitation (50 rpm), enzyme concentration (0.080 μM), and substrate concentration (0.50 mM). Under these conditions, the yield of the reaction was ∼15% in 1 h incubation period and ∼63% after an overnight (∼18 h) incubation period. The product (p-HCAM) of the reaction of PTAL with L-TM was confirmed using Nuclear Magnetic Resonance spectroscopy (NMR). Fourier Transform Infra-Red spectroscopy (FTIR) was carried out to rule out potential hydrolysis of p-HCAM during overnight incubation. Potential antibacterial activity of p-HCAM was tested against several strains of Gram-positive and Gram-negative bacteria. This study describes a synthetically useful transformation, and could have future clinical and industrial applications.

Molecular Characterization of a Recombinant Zea mays Phenylalanine Ammonia-Lyase (ZmPAL2) and Its Application in trans-Cinnamic Acid Production from L-Phenylalanine

Phenylalanine ammonia-lyase (PAL) is one of the most extensively studied enzymes with its crucial role in secondary phenylpropanoid metabolism of plants. Recently, its demand has been increased for aromatic chemical production, but its applications in trans-cinnamic acid production were not much explored. In the present study, a putative PAL gene from Zea mays designated as ZmPAL2 was expressed and characterized in Escherichia coli BL21 (DE3). The recombinant ZmPAL2 exhibited a high PAL activity (7.14 U/mg) and a weak tyrosine ammonia-lyase activity. The optimal temperature of ZmPAL2 was 55 °C, and the thermal stability results showed that about 50 % of enzyme activity remained after a treatment at 60 °C for 6 h. The recombinant ZmPAL2 is a good candidate for the production of trans-cinnamic acid. The vitro conversion indicated that the recombinant ZmPAL2 could effectively catalyze the L-phenylalanine to trans-cinnamic acid, and the trans-cinnamic acid concentration can reach up to 5 g/l.

Phenylalanine ammonia-lyase, a key component used for phenylpropanoids production by metabolic engineering

Phenylalanine ammonia-lyase, a versatile enzyme with industrial and medical applications.

Detection of flavonoids in microalgae from different evolutionary lineages

Flavonoids are important secondary plant metabolites believed to be present mainly in land plants. As phenolics were detected previously in microalgae using photometric assays, we wanted to investigate the nature of these phenolics and verify whether flavonoids are present. Therefore, in this study, we used state-of-the-art ultra-high performance liquid chromatography-two-dimensional mass spectrometry (UHPLC-MS/MS) technology to investigate whether microalgae also contain flavonoids. For this, representative microalgal biomass samples from divergent evolutionary lineages (Cyanobacteria, Rhodophyta, Chlorophyta, Haptophyta, Ochrophyta) were screened for a set of carefully selected precursors, intermediates, and end products of the flavonoid biosynthesis pathways. Our data unequivocally showed that microalgae contain a wide range of flavonoids and thus must possess the enzyme pool required for their biosynthesis. Further, some of the microalgae displayed an intricate flavonoid pattern that is compatible with the established basic flavonoid pathway as observed in higher plants. This implies that the flavonoid biosynthesis pathway arose much earlier in evolution compared to what is generally accepted.

Biotechnological production and applications of microbial phenylalanine ammonia lyase: a recent review

Phenylalanine ammonia lyase (PAL) catalyzes the nonoxidative deamination of l-phenylalanine to form trans-cinnamic acid and a free ammonium ion. It plays a major role in the catabolism of l-phenylalanine. The presence of PAL has been reported in diverse plants, some fungi, Streptomyces and few Cyanobacteria. In the past two decades, PAL has gained considerable significance in several clinical, industrial and biotechnological applications. Since its discovery, much knowledge has been gathered with reference to the enzyme's importance in phenyl propanoid pathway of plants. In contrast, there is little knowledge about microbial PAL. Furthermore, the commercial source of the enzyme has been mainly obtained from the fungi. This study focuses on the recent advances on the physiological role of microbial PAL and the improvements of PAL biotechnological production both from our laboratory and many others as well as the latest advances on the new applications of microbial PAL.