Bacterial bioeffectors modify bioactive profile and increase isoflavone content in soybean sprouts (Glycine max var Osumi)

Endophytic Pseudomonas fluorescens promotes changes in the phenotype and secondary metabolite profile of Houttuynia cordata Thunb

The interactions between microbes and plants are governed by complex chemical signals, which can forcefully affect plant growth and development. Here, to understand how microbes influence Houttuynia cordata Thunb. plant growth and its secondary metabolite through chemical signals, we established the interaction between single bacteria and a plant. We inoculated H. cordata seedlings with bacteria isolated from their roots. The results showed that the total fresh weight, the total dry weight, and the number of lateral roots per seedling in the P. fluorescens-inoculated seedlings were 174%, 172% and 227% higher than in the control seedlings. Pseudomonas fluorescens had a significant promotional effect of the volatile contents compared to control, with β-myrcene increasing by 192%, 2-undecanone by 203%, decanol by 304%, β-caryophyllene by 197%, α-pinene by 281%, bornyl acetate by 157%, γ-terpinene by 239% and 3-tetradecane by 328% in P. fluorescens-inoculated H. cordata seedlings. the contents of chlorogenic acid, rutin, quercitin, and afzelin were 284%, 154%, 137%, and 213% higher than in control seedlings, respectively. Our study provided basic data to assess the linkages between endophytic bacteria, plant phenotype and metabolites of H. cordata to provide an insight into P. fluorescens use as biological fertilizer, promoting the synthesis of medicinal plant compounds.

Bacillus H47 triggers Olea europaea metabolism activating DOXP and shikimate pathways simultaneously and modifying leaf extracts’ antihypertensive activity

Improvement of plant adaptation by beneficial bacteria (PGPB) may be achieved by triggering multiple pathways to overcome the environmental stress on plant’s growth cycle, activating plant’s metabolism. The present work reports the differential ability of three Bacillus strains to trigger olive tree metabolism, among which, only H47 was outstanding increasing iridoid and flavonol concentration. One-year old olive seedlings grown open air, under harsh conditions of water shortage in saline soils, were root-inoculated with three Bacillus PGPB strains throughout a 12-month period after which, photosynthesis was determined; photosynthetic pigments and bioactive secondary metabolites (iridoids and flavonols) were analyzed, and a study of gene expression of both pathways involved was undertaken to unravel molecular targets involved in the activation. All three strains increased plant fitness based on photosynthetic values, increasing energy dissipation capacity to lower oxidative stress; only H47 increased CO2 fixation and transpiration. Bacillus H47 was found to trigger synthases in the DOXP pathway (up to 5-fold in DOXP-synthase, 3.5-fold in Iridoid synthase, and 2-fold in secologanin synthase) associated to a concomitant increase in iridoids (up to 5-fold in oleuropein and 2-fold in its precursor secologanin). However, despite the 2-fold increases detected in the two predominant flavonols, gene expression was not enhanced, suggesting involvement of a pulse activation model proposed for innate immunity. Furthermore, the activity of leaf extracts to inhibit Angiotensin Converting Enzyme was evaluated, to explore further uses of plant debris with higher added value. Despite the increases in iridoids, leaf extracts from H47 did not increase ACE inhibition, and still, increased antihypertensive potential in oil obtained with this strain is to be explored, as leaves are the source for these metabolites which further translocate to fruits. In summary, Bacillus H47 is an effective strain to increase plant adaptation to dry and saline environments, activates photosynthesis and secondary metabolism in olive tree.

Occurrence of isoflavones in soybean sprouts and strategies to enhance their content: A review

Sprouting is a common strategy to enhance the nutritional value of seeds. Here, all the reports regarding the occurrence of isoflavones in soybean sprouts have been covered for the first time. Isoflavones were detected with concentrations ranging from 1 × 10-2 to 1 × 101  g/kg in soybean sprouts. Isoflavone concentration depends on the cultivar, germination time, part of the sprout, light, and temperature. Aglycon isoflavones increased during germination, especially in the hypocotyl, while 6″-O-malonyl-7-O-β-glucoside isoflavones decreased in the hypocotyl and increased in the cotyledon and root. Cooking reduced total isoflavone content. Regarding the strategies to enhance isoflavone contents, fermentation with Aspergillus sojae and external irradiation with UV-A or far-infrared were the methods that caused the greatest increases in aglycon, 7-O-β-glucoside, and total isoflavones. However, the largest increases in 6″-O-malonyl-7-O-β-glucoside and 6″-O-acetyl-7-O-β-glucosides isoflavones were detected after treatment with chitohexaose and calcium chloride, respectively. PRACTICAL APPLICATION: Soybean sprouts are widely consumed and provide essential proteins, antioxidants, and minerals. They are rich in isoflavones, which exhibit numerous health benefits, and have been studied as alternative therapies for a range of hormone-dependent conditions, such as cancer, menopausal symptoms, cardiovascular disease, and osteoporosis. Despite numerous reports being published to date regarding the occurrence of isoflavones in soybean sprouts, the publications in this field are highly dispersed, and a review has not yet been published. This review aims to (1) highlight the particular isoflavones that have been detected in soybean sprouts and their concentrations, (2) compared the effects of temperature, light, cooking and soybean cultivar affect the isoflavone levels on the different parts of the sprout, and (3) discuss the efficacy of the methods to enhance isoflavone contents. This review will provide a better understanding of the current state of this field of research by comparing the general trends and the different treatments for soybean sprouts.

Seed Treatment with Illite Enhanced Yield and Nutritional Value of Soybean Sprouts

Soybean sprouts, a nutritional food product, can contribute to food security because they can be grown within a week and do not require sophisticated technology. The yield and quality of soybean sprouts are influenced by various factors, including seed priming and growing conditions. The objective of this study was to investigate the effects of seed soaking in different concentrations of illite, a clay mineral, on the yield and quality of soybean sprouts. Soybean seeds soaked in five concentrations (0.5%, 1%, 3%, 5%, and 10%, w/v) of illite or tap water for 8 h were named IP-0.5, IP-1, IP3, IP-5, IP-10, and control, respectively. The highest sprout yield was found in IP-3, followed by IP-1, and IP-5, which had 11.1%, 8.8%, and 7.4% increments, respectively, compared to the control. The content of vitamin C, mineral element, isoflavone, total polyphenol, and total flavonoid was higher in many of the illite-treated soybean sprouts than in the control. The overall results indicated that pre-soaking soybean seeds in lower concentrations (0.5-3%, w/v) of illite could be helpful to enhance the yield and nutritional value of soybean sprouts in an easy and inexpensive way.

Elicitation: a new perspective into plant chemo-diversity and functional property

Sprouts are consumed as fresh foods or their flours can be added in processed products as determinants of sensory perception, product differentiation, and shelf life. Elicitation technique can be used to accumulate phytochemicals in plant sprouts thereby improving their functionality. This review summarized the recent state of knowledge on the use of elicitors to produce sprouts with improved functional properties. Elicitation using abiotic or biotic elicitors has been applied to increase the yield of sprout secondary metabolites (glucosinolates, aminobutyric acid, phenolic compounds), biological activities (antioxidant, anti-obesity, antidiabetic properties), and growth. Elicitors trigger the synthesis of plant metabolites by changing enzyme activities or gene expression related to the plant defence system. They also promote sprout growth by enhancing the levels of plant growth hormones. Elicitation is an effective method to produce sprouts with improved health benefits, and enhance their growth. Future studies are needed to identify early plant signaling pathways to fully understand elicitors' mechanisms on plant metabolites. Moreover, further investigation can be impetus in revealing the lower and upper limits of elicitor that can be applied in sprouts without compromising health and environmental safety.

Nutritional Improvement of Bean Sprouts by Using Chitooligosaccharide as an Elicitor in Germination of Soybean (Glycine max L.)

Soybean sprouts are among the healthiest foods consumed in most Asian countries. Their nutritional content, especially bioactive compounds, may change according to the conditions of germination. The purpose of this study was to test the effect of chitooligosaccharide with different molecular weight and dosage on nutritional quality and enzymatic and antioxidant activities of soybean sprouts. The chitooligosaccharide elicitor strongly stimulated the accumulation of vitamin C, total phenolics, and total flavonoid. The stimulation effect was correlated with the molecular weight and concentration of chitooligosaccharide. With treatment of 0.01% of 1 kDa chitooligosaccharide, the nine phenolic constituents and six isoflavone compounds were significantly increased. The antioxidant capacity (DPPH radical and hydroxyl radical scavenging activity) and antioxidase activities (catalase and peroxidase) of soybean sprouts were also enhanced after treatment with chitooligosaccharide. The degree of chitooligosaccharide-induced elicitor activity increased as the molecular weight of chitooligosaccharide decreased. These results suggest that soaking soybean seeds in a solution of chitooligosaccharide, especially in 0.01% of 1 kDa chitooligosaccharide, may effectively improve the nutritional value and physiological function of soybean sprouts.

Pu-erh Tea Extract Treatment Could Be an Efficient Way to Enhance the Yield and Nutritional Value of Soybean Sprout

Soybean sprouts are one of the most inexpensive and nutritious food items that can be easily grown year-round. Several studies have been conducted to increase their yield and nutritional values. This study was carried out to examine the effects of Pu-erh tea extracts on the production and nutrients content of soybean sprouts. Soybean seeds were soaked in 1%, 2%, or 3% (w/v) tea extracts, or tap water, before keeping for sprout cultivation; the sprout samples were named PE-1, PE-2, PE-3, and the control, respectively. The sprout yields were increased by up to 17% in PE-2 and PE-3 than in the control. The vitamin C, total free amino acid, total mineral, total isoflavone, total polyphenol, and flavonoid contents as well as the antioxidant potentials of the tea extract-treated sprouts were higher than those of the control. The results indicated that pre-soaking soybean seeds in 2% Pu-erh tea extracts could offer an easy, inexpensive, and efficient way to improve the yield and nutritional value of soybean sprouts.

Management of Plant Physiology with Beneficial Bacteria to Improve Leaf Bioactive Profiles and Plant Adaptation under Saline Stress in Olea europea L

Global climate change has increased warming with a concomitant decrease in water availability and increased soil salinity, factors that compromise agronomic production. On the other hand, new agronomic developments using irrigation systems demand increasing amounts of water to achieve an increase in yields. Therefore, new challenges appear to improve plant fitness and yield, while limiting water supply for specific crops, particularly, olive trees. Plants have developed several innate mechanisms to overcome water shortage and the use of beneficial microorganisms to ameliorate symptoms appears as a challenging alternative. Our aim is to improve plant fitness with beneficial bacterial strains capable of triggering plant metabolism that targets several mechanisms simultaneously. Our secondary aim is to improve the content of molecules with bioactive effects to valorize pruning residues. To analyze bacterial effects on olive plantlets that are grown in saline soil, photosynthesis, photosynthetic pigments, osmolytes (proline and soluble sugars), and reactive oxygen species (ROS)-scavenging enzymes (superoxide dismutase-SOD and ascorbate peroxidase-APX) and molecules (phenols, flavonols, and oleuropein) were determined. We found photosynthetic pigments, antioxidant molecules, net photosynthesis, and water use efficiency to be the most affected parameters. Most strains decreased pigments and increased osmolytes and phenols, and only one strain increased the antihypertensive molecule oleuropein. All strains increased net photosynthesis, but only three increased water use efficiency. In conclusion, among the ten strains, three improved water use efficiency and one increased values of pruning residues.

Modulation of plant chemistry by beneficial root microbiota

Beneficial root microbiota modulate plant chemistry and represent an untapped potential to discover new pathways involved in the biosynthesis of high value natural plant products.

Persimmon Fruit Powder May Substitute Indolbi, a Synthetic Growth Regulator, in Soybean Sprout Cultivation

Soybean sprouts are a major food item in Korea. Various studies have been carried out to enhance their yield and nutritional values. The objective of the present study was to examine the influence of persimmon fruit powder and Indolbi, a synthetic plant growth regulator, on the yield and nutritional value of soybean sprouts. Seeds were soaked in tap water containing 0.5%, 1.0%, 2.5% and 5.0% (w/v) persimmon fruit powder and the samples were named as PT-1, PT-2, PT-3, and PT-4, respectively. The yield increment was almost doubled in PT-3 and PT-4 than in the Indolbi treated sprouts on basis of the control. Vitamin C, isoflavones, and total phenolic contents as well as antioxidant potentials (determined by 1,1-diphenyl-2-picrylhydrazyl and superoxide anion radical scavenging assays) were also significantly (p < 0.05) higher in PT-3 compared to the Indolbi treatment and the control. However, total free amino acid and magnesium contents of Indolbi- applied sprouts were higher than in the fruit powder treatments. The overall results of the present study showed that persimmon fruit powder can be an option to enhance the yield and nutritional value of soybean sprouts since, due to potential health hazards, the use of synthetic chemicals like Indolbi is less preferred than the natural products.

Analysis of isoflavones and coumestrol in soybean sprouts

High-performance liquid chromatography analysis is used to examine the distribution of isoflavones in different parts of soybean sprouts. Between the seed leaf and hypocotyl, the ratio of isoflavones differs depending on the aglycone type. Glycitein exists predominantly in the hypocotyl. Three compounds isolated from 4-day-old seed coats were identified as coumestrol and its glycosides.

Genomic Potential of Stenotrophomonas maltophilia in Bioremediation with an Assessment of Its Multifaceted Role in Our Environment

The gram negative bacterium Stenotrophomonas is rapidly evolving as a nosocomial pathogen in immuno-compromised patients. Treatment of Stenotrophomonas maltophilia infections is problematic because of their increasing resistance to multiple antibiotics. This article aims to review the multi-disciplinary role of Stenotrophomonas in our environment with special focus on their metabolic and genetic potential in relation to bioremediation and phytoremediation. Current and emerging treatments and diagnosis for patients infected with S. maltophilia are discussed besides their capability of production of novel bioactive compounds. The plant growth promoting characteristics of this bacterium has been considered with special reference to secondary metabolite production. Nano-particle synthesis by Stenotrophomonas has also been reviewed in addition to their applications as effective biocontrol agents in plant and animal pathogenesis.

Antioxidant and antimicrobial activity of natural phenolic extract from defatted soybean flour by-product for stone fruit postharvest application

BACKGROUND

Fresh fruit is highly perishable during storage and transport, so there has been growing interest in finding safe and natural antimicrobial compounds as a control tool. Phenolic compounds are secondary metabolites naturally present in vegetable material and have been associated with antimicrobial and antioxidant properties. Therefore, the aim of this study was to investigate the antioxidant capacity and potential antimicrobial effect of phenolic extract obtained from defatted soybean flour against selected pathogenic bacteria and microorganisms responsible of fruit decay.

RESULTS

Analysis of phenolic composition by HPLC-MS showed the presence of a wide range of compounds, with isoflavones and phenolic acids the main polyphenols identified. Furthermore, the phenolic extract had important antioxidant activity by two different assays. Related to antimicrobial activity, in vitro experiments demonstrated that phenolic extract displayed a high activity against the main foodborne pathogens, while a moderate inhibition was found against five spoilage yeasts and Monilia laxa and a scarce effect for Penicillium glabrum, Cladosporium uredinicola and Botrytis cinerea. Interestingly these compounds considerably inhibited the mycelial growth of Monilia laxa, in both in vitro and in vivo experiments.

CONCLUSION

The results of the present study revealed that defatted soybean flour is an important source of phenolic compounds with remarkable antimicrobial and antioxidant activity, suggesting the possibility of using them as natural additives in postharvest treatments to extend the shelf life of fruit.

The Stimulatory Effect of Strontium Ions on Phytoestrogens Content in Glycine max (L.) Merr

The amount of secondary metabolites in plants can be enhanced or reduced by various external factors. In this study, the effect of strontium ions on the production of phytoestrogens in soybeans was investigated. The plants were treated with Hoagland's solution, modified with Sr(2+) with concentrations ranging from 0.5 to 3.0 mM, and were grown for 14 days in hydroponic cultivation. After harvest, soybean plants were separated into roots and shoots, dried, and pulverized. The plant material was extracted with methanol and hydrolyzed. Phytoestrogens were quantified by HPLC. The significant increase in the concentration of the compounds of interest was observed for all tested concentrations of strontium ions when compared to control. Sr(2+) at a concentration of 2 mM was the strongest elicitor, and the amount of phytoestrogens in plant increased ca. 2.70, 1.92, 3.77 and 2.88-fold, for daidzein, coumestrol, genistein and formononetin, respectively. Moreover, no cytotoxic effects were observed in HepG2 liver cell models after treatment with extracts from 2 mM Sr(2+)-stressed soybean plants when compared to extracts from non-stressed plants. Our results indicate that the addition of strontium ions to the culture media may be used to functionalize soybean plants with enhanced phytoestrogen content.

The role of isoflavone metabolism in plant protection depends on the rhizobacterial MAMP that triggers systemic resistance against Xanthomonas axonopodis pv. glycines in Glycine max (L.) Merr. cv. Osumi

Glycine max (L.) Merr. plays a crucial role in both the field of food and the pharmaceutical industry due to their input as plant protein and to the benefits of isoflavones (IF) for health. In addition, IF play a key role in nodulation and plant defense and therefore, an increase in IF would be desirable for better field performance. IF are secondary metabolites and therefore, inducible, so finding effective agents to increase IF contents is interesting. Among these agents, plant growth promoting rhizobacteria (PGPR) have been used to trigger systemic induction of plant's secondary metabolism through their microbe associated molecular patterns (MAMPs) that fit in the plant's receptors to start a systemic response. The aim of this study was to evaluate the ability of 4 PGPR that had a contrasted effect on IF metabolism, to protect plants against biotic stress and to establish the relation between IF profile and the systemic response triggered by the bacteria. Apparently, the response involves a lower sensitivity to ethylene and despite the decrease in effective photosynthesis, growth is only compromised in the case of M84, the most effective in protection. All strains protected soybean against Xanthomonas axonopodis pv. glycines (M84 > N5.18 > Aur9>N21.4) and only M84 and N5.18 involved IF. N5.18 stimulated accumulation of IF before pathogen challenge. M84 caused a significant increase on IF only after pathogen challenge and N21.4 caused a significant increase on IF content irrespective of pathogen challenge. Aur9 did not affect IF. These results point out that all 4 strains have MAMPs that trigger defensive metabolism in soybean. Protection induced by N21.4 and Aur9 involves other metabolites different to IF and the role of IF in defence depends on the previous metabolic status of the plant and on the bacterial MAMP.