Solubilization Activity Research Articles

Isolation and Identification of New Soil Strains with Phosphate-Solubilizing and Exopolysaccharide-Producing Abilities in the Yellow River Wetland Nature Reserve of Luoyang City, China

The establishment of the Yellow River wetland nature reserves improves the local soil structure and fertility through the long-term succession of microorganisms. However, little is known about which indigenous microbial resources can accelerate the process of soil improvement and ecology restoration. To fill this gap, exopolysaccharides-producing bacteria and phosphate-solubilizing bacteria were isolated from soil samples of the wetland nature reserve with higher soil organic matter, available phosphorus, and available nitrogen content. 16S rRNA nucleotide sequence homology analysis and physiological-biochemical assay showed that the strain PD12 with the highest phosphate solubilization activity and higher EPS production was identified as Klebsiella variicola, and other high yield EPS-producing strains (EPS12, EPS15, EPS18, and EPS19) were identified as Pseudomonas migulae, Pseudomonas frederiksbergensis, Aeromonas media, and Pseudomonas vancouverensis, respectively. These results provided new potential microbial resources for the research and development of biofertilizers and added new insights into accelerating the restoration of physical, chemical, and biological properties of soil in the Yellow River basin.

Characterization of Plant Growth Promoting Rhizobacteria From Seasonal Flower Beds

The present investigations were carried out to screen the PGPR isolates from five separate seasonal flower beds (Catharanthus roseus, Portulaca grandiflora, Celosia argentea, Gomphrena globosa and Impatiens balsamina) of Curzon Hall, University of Dhaka. The bacterial load of the collected soil samples ranged in between 7.60 ± 6.01 × 106 and 9.49 ± 5.44× 108 cfu/g, 5.34 ± 4.06×106 and 13.4 ± 4.8×106 cfu/g and 1.01 ± 0.59×106 and 1.19 ± 0.95×108 cfu/g on Nutrient Agar (NA), Luria-Bertani (LB) and Yeast Extract Mannitol Agar (YEMA), respectively. All the selected eight isolates were Gram positive and rod shaped. All isolates were found to be IAA producer and 7 showed varying levels of phosphate solubilizing activity. IAA production and phosphate (P) solubilization of the selected isolates ranged in between 9.76 ± 5.98 to 17.99 ± 1.865 U/ml, and 1.17 ± 0.59 to 1.84 ± 0.499 mg/l. Maximum production of both IAA and phosphate solubilization was achieved in 24h of incubation period at 37°C and pH 7.0. Germination test against Mung Bean (Vigna radiata) revealed positive plant growth promoting activities and could be used as PGPR inoculant. Dhaka Univ. J. Biol. Sci. 31(2): 321-328, 2022 (July)

Evaluation of Soil Streptomyces spp. for the Biological Control of Fusarium Wilt Disease and Growth Promotion in Tomato and Banana

Fusarium oxysporum f. sp. lycopersici (Fol) and Fusarium oxysporum f. sp. cubense (Foc), are the causal agent of Fusarium wilt disease of tomato and banana, respectively, and cause significant yield losses worldwide. A cost-effective measure, such as biological control agents, was used as an alternative method to control these pathogens. Therefore, in this study, six isolates of the Streptomyces-like colony were isolated from soils and their antagonistic activity against phytopathogenic fungi and plant growth-promoting (PGP) activity were assessed. The results showed that these isolates could inhibit the mycelial growth of Fol and Foc. Among them, isolate STRM304 showed the highest percentage of mycelial growth reduction and broad-spectrum antagonistic activity against all tested fungi. In the pot experiment study, the culture filtrate of isolates STRM103 and STRM104 significantly decreased disease severity and symptoms in Fol inoculated plants. Similarly, the culture filtrate of the STRM304 isolate significantly reduced the severity of the disease and symptoms of the disease in Foc inoculated plants. The PGP activity test presents PGP activities, such as indole acetic acid production, phosphate solubilization, starch hydrolysis, lignin hydrolysis, and cellulase activity. Interestingly, the application of the culture filtrate from all isolates increased the percentage of tomato seed germination and stimulated the growth of tomato plants and banana seedlings, increasing the elongation of the shoot and the root and shoot and root weight compared to the control treatment. Therefore, the isolate STRM103 and STRM104, and STRM304 could be used as biocontrol and PGP agents for tomato and banana, respectively, in sustainable agriculture.

Mitigation of water scarcity with sustained growth of Rice by plant growth promoting bacteria.

Climate change augments the risk to food security by inducing drought stress and a drastic decline in global rice production. Plant growth-promoting bacteria (PGPB) have been known to improve plant growth under drought stress. Here in the present study, we isolated, identified, and well-characterized eight drought-tolerant bacteria from the rice rhizosphere that are tolerant to 20% PEG-8000. These strains exhibited multiple plant growth-promoting traits, i.e., 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity, exopolysaccharide production, phosphate (P)-solubilizing activity (51-356 µg ml-1), indole-3 acetic acid (IAA) production (14.3-46.2 µg ml-1), and production of organic acids (72-178 µg ml-1). Inoculation of bacterial consortium (Bacillus subtilis NM-2, Brucella haematophilum NM-4, and Bacillus cereus NM-6) significantly improved seedling growth and vigor index (1009.2-1100) as compared to non-inoculated stressed plants (630-957). Through rhizoscanning, efficiency of the consortium was validated by improved root parameters such as root length (17%), diameter, and surface area (18%) of all tested genotypes as compared with respective non-inoculated stressed treatments. Furthermore, the response of consortium inoculation on three rice genotypes was positively correlated with improved plant growth and drought stress ameliorating traits by the accumulation of osmoprotectant, i.e., proline (85.8%-122%), relative water content (51%), membrane stability index (64%), and production of antioxidant enzymes to reduce oxidative damage by reactive oxygen species. A decrease in temperature and improved chlorophyll content of inoculated plants were found using infrared thermal imaging and soil plant analyzer development (SPAD), respectively. The key supporting role of inoculation toward stress responses was validated using robust techniques like infrared thermal imaging and an infrared gas analyzer. Furthermore, principal component analysis depicts the contribution of inoculation on stress responses and yield of tested rice genotypes under water stress. The integration of drought-tolerant rice genotype (NIBGE-DT02) and potential bacterial strains, i.e., NM-2, NM-4, and NM-6, can serve as an effective bioinoculant to cope with water scarcity under current alarming issues related to food security in fluctuating climate.

Genome insights into the plant growth-promoting bacterium Saccharibacillus brassicae ATSA2T

Endophytes can facilitate the improvement of plant growth and health in agriculturally important crops, yet their genomes and secondary metabolites remain largely unexplored. We previously isolated Saccharibacillus brassicae strain ATSA2T from surface-sterilized seeds of kimchi cabbage and represented a novel species of the genus Saccharibacillus. In this study, we evaluated the plant growth-promoting (PGP) effect of strain ATSA2T in kimchi cabbage, bok choy, and pepper plants grown in soils. We found a significant effect on the shoot and root biomass, and chlorophyll contents following strain ATSA2T treatment. Strain ATSA2T displayed PGP traits such as indole acetic acid (IAA, 62.9 μg/mL) and siderophore production, and phosphate solubilization activity. Furthermore, genome analysis of this strain suggested the presence of gene clusters involved in iron acquisition (fhuABD, afuABC, fbpABC, and fepCDG) and phosphate solubilization (pstABCHS, phoABHLU, and phnCDEP) and other phytohormone biosynthesis genes, including indole-3-acetic acid (trpABCDEFG), in the genome. Interestingly, the secondary metabolites cerecidin, carotenoid, siderophore (staphylobactin), and bacillaene underlying plant growth promotion were found in the whole genome via antiSMASH analysis. Overall, physiological testing and genome analysis data provide comprehensive insights into plant growth-promoting mechanisms, suggesting the relevance of strain ATSA2T in agricultural biotechnology.

Phosphate Solubilizing and Phytate Degrading Streptomyces Isolates Stimulate the Growth and P Accumulation of Maize (Zea mays) Fertilized with Different Phosphorus Sources

Actinobacteria are involved in many soil processes related to plant growth, including the secretion of various bioactive products and nutrient cycling. The aim of this study was to characterize the plant growth promoting traits (phosphate solubilizing activity, phytate degradation ability and indolic compounds production, and organic acids secretion) of seven actinobacteria isolates and evaluate the effect of two selected rhizospheric Streptomyces on growth and phosphorus content of maize in presence of different phosphorus (P) sources (tri-calcium phosphate, triple super phosphate and calcium phytate). Phylogenetic analysis of partial 16S rRNA sequences showed that the Streptomyces isolates were clustered in two distinct separated groups. All Streptomyces isolates produced 2-ketogluconic acid and oxalic acid in fermentation medium supplemented with inorganic P sources, while in the presence of phytate, all isolates secreted 2-ketogluconic acid and malic acid. All the isolates were able to release inorganic P from insoluble phosphate sources and this behavior was negatively correlated with pH reduction. Phytate degradation raged from 1.65% to 95.2%, and total indole compound production ranged from 6.3 to 27.8 µg ml−1. The shoot dry weight, root dry weight, plant height, chlorophyll content and tissue P concentration were significantly (p < 0.05) increased by both inoculations with Streptomyces isolates and by the addition of different phosphorus sources, compared to their appropriate controls. The inoculation of Streptomyces isolates resulted in a significant increase in plant phosphorus content from different phosphate sources. Streptomyces sp. UTMC 1478 (Streptomyces sp. 63) and Streptomyces sp. 47 were suitable inoculants for increasing maize growth and P from soil amended with different phosphorus sources, indicating their potential use as plant growth-promoting phospho-bacteria.

Screening and Characterization of Plant Growth Promoting Endophytic Microbes of Tomato (Solanum lycopersicum L.) combats Pythium aphanidermatum

About 45 bacteria, 9 fungi, 3 yeast, and 1 actinobacterium were isolated from plant tissues of tomato and screened for their plant growthpromoting traits and antagonistic activity against damping-off fungus Pythium aphanidermatum. The bacterial isolate, Bacillus pumilus TEB10 exhibited pathogen inhibition of about 55 and 79%, while yeast isolate Candida tropicalis TEY1 showed 30 and 68% in the dual plate and inverted plate assay, respectively. In addition, the Bacillus pumilus TB10 showed siderophore, HCN, cellulase, and phosphate solubilization activities. Similarly, yeast isolate Candida tropicalis TEY1 exhibited catalase, phosphate, and zinc solubilization activities. The sterol biosynthesis pathway end product ergosterol was profiled in secondary metabolites of P. aphanidermatum, suggesting the potentiality of this pathogenesis.

Plant growth-enhancing traits of rhizobacteria isolated from brinjal, okra, and leaf mustard

Exploring new plant-associated rhizobacteria and reintroducing them to the crop-soil environment is among the strategies to reverse the declining quality of the agricultural soil environment. A total of 340 isolates were recovered from the rhizospheres of okra (Abelmoschus esculentus), leaf mustard (Brassica juncea), and brinjal (Solanum melongena). From among the total, 155 isolates (45.59%) were diazotrophs, and 122 (35.88%) and 127 (37.35%) were isolates with the solubilising activity of phosphate and potassium, respectively. Thirteen of the most promising isolates were identified by gas chromatography for their cellular fatty acid methyl esters: Escherichia vulneris (TC19), Klebsiella pneumoniae (BA5, SA19, SB22), Pantoea ananatis (TC22), Pseudomonas aeruginosa (BA46), Pseudomonas putida (BA29, BA37, SC5, SC14), Salmonella bongori (BC17), Salmonella enterica (BB2), and Shigella dysenteriae (BA16). Three Pseudomonas strains viz. P. aeruginosa BA46 and P. putida BA37 and SC5 were selected after enhancing root elongation and vigour of lettuce seedlings. The American lettuce growth performance in the non-circulating hydroponic system was established. The inoculation with rhizobacteria strains, SC5 and BA46, stimulated shoot and root biomass over uninoculated control plants. The inoculation of lettuce plants with isolates BA37, BA46 and SC5, produced significantly longer roots compared to uninoculated control plants. This study indicates the potential use of the strains BA46 and SC5 as candidates for the formulation and production of hydroponic nutrient solution fortified with beneficial bacteria.

Diversity of duckweed (&lt;i&gt;Lemnaceae&lt;/i&gt;) associated yeasts and their plant growth promoting characteristics

&lt;abstract&gt; &lt;p&gt;The diversity of duckweed (&lt;italic&gt;Lemnaceae&lt;/italic&gt;) associated yeasts was studied using a culture-dependent method. A total of 252 yeast strains were isolated from 53 duckweed samples out of the 72 samples collected from 16 provinces in Thailand. Yeast identification was conducted based on the D1/D2 region of the large subunit (LSU) rRNA gene sequence analysis. It revealed that 55.2% and 44.8% yeast species were Ascomycota and Basidiomycota duckweed associated yeasts, respectively. Among all, &lt;italic&gt;Papiliotrema laurentii&lt;/italic&gt;, a basidiomycetous yeast, was found as the most prevalent species showing a relative of frequency and frequency of occurrence of 21.8% and 25%, respectively. In this study, high diversity index values were shown, indicated by the Shannon-Wiener index (&lt;italic&gt;H′&lt;/italic&gt;), Shannon equitability index (&lt;italic&gt;E&lt;sub&gt;H&lt;/sub&gt;&lt;/italic&gt;) and Simpson diversity index (&lt;italic&gt;1-D&lt;/italic&gt;) values of 3.48, 0.86 and 0.96, respectively. The present results revealed that the yeast community on duckweed had increased species diversity, with evenness among species. Principal coordinate analysis (PCoA) revealed no marked differences in yeast communities among duckweed genera. The species accumulation curve showed that the observed species richness was lower than expected. Investigation of the plant growth promoting traits of the isolated yeast on duckweed revealed that 178 yeast strains produced indole-3-acetic acid (IAA) at levels ranging from 0.08–688.93 mg/L. Moreover, siderophore production and phosphate solubilization were also studied. One hundred and seventy-three yeast strains produced siderophores and exhibited siderophores that showed 0.94–2.55 activity units (AU). One hundred six yeast strains showed phosphate solubilization activity, expressed as solubilization efficiency (SE) units, in the range of 0.32–2.13 SE. This work indicates that duckweed associated yeast is a potential microbial resource that can be used for plant growth promotion.&lt;/p&gt; &lt;/abstract&gt;

Phytobeneficial traits of Rhizobacteria isolated from degraded soil and evaluate their effect in augmentation of Acacia (Acacia abyssinica Hochst. Ex Benth) seeds germination

Microbes are an integral component of the soil ecosystem but degraded soil has few native beneficial microbes. This necessitates the characterization of phytobeneficial bacteria having numerous features. The study was initiated to evaluate rhizobacteria enhancing Acacia (Acacia abyssinica) seed germination. Isolates were selected based primarily on phosphate solubilization activity and other traits hydrogen cyanide (hcn), phytohormone, hydrolytic enzyme, siderophore, ammonia. Among isolates, 45% each was categorized as high and medium phosphate solubilizers and the amount was found to range from 195 to 373 µg/mL. The highest solubilization index (SI) 7 was recorded for Acinetobacter BS-27 and 6 for Pantoea BS-38. The maximum P and iaa were produced by Pseudomonas FB-49 (373 and 659.07µg/mL), respectively. Isolates with multiple traits were chosen for seed germination. Accordingly, Agrobacterium RS-79 and Pseudomonas BS-26 showed 100% activity. A 100% seed germination and vigor index (343.33 and 306.67) were observed in Pseudomonas BS-26 and FB-49. Degraded soil is considered a source for phosphate solubilizing and other beneficial bacteria with many traits to be used for seed germination assay.

Microbacterium oxydans Regulates Physio-Hormonal and Molecular Attributes of Solanum lycopersicum under Drought Stress

Among the types of abiotic stresses, drought is one of the most serious growth limiting factors for crop plants. In recent years, various strategies have been employed to alleviate the adverse effects of drought stress in crops, but the use of plant growth-promoting rhizobacteria (PGPR) is among the standout techniques. Currently, we have isolated 55 strains of bacteria from the rhizosphere of Achyranthes aspera L. and Calotropis procera (Aiton). However, AGH3, AGH5, and AGH9 produced significant (p = 0.05) amounts of plant hormones and exhibited siderophore and phosphate solubilization activities. Bioassay experiments on Waito-C rice demonstrated an enhanced growth in the presence of the isolate AGH3. Moreover, the isolate AGH3 promoted the growth of Solynum lycopersicum L. under drought stress. The results revealed that AGH3-associated S. lycopersicum plants showed significantly (p = 0.05) reduced production of abscisic acid (ABA) and jasmonic acid (JA) as compared with the AGH3-free plants under polyethylene glycol (PEG) stress. In addition, high expressions of SlmiR 159 (from 6- to 10-fold), SlHsfA1a (from 1- to 4-fold), and SlHAKT1 (from 0.26- to 1-fold) genes were noticed in AGH3-associated S. lycopersicum plants under drought stress. From the results, it is concluded that rhizobacteria (AGH3) can be used as a pragmatic biofertilizer to ensure organic farming under normal as well as drought conditions.

Characterization of Plant Growth Promoting Endophytic Bacteria from Castor Plants [Ricinus communis (L.)

The present study was carried out in June–Janauary (2021–2022) at the Laboratory of the Department of Microbiology, Chimanbhai Patel College of Agriculture, Sardarkrushinagar Dantiwada Agricultural University (SDAU), Sardarkrushinagar, Gujarat, India. 15 promising endophytic bacterial isolates from castor plants showing higher dry matter accumulation in seedlings of wheat were subjected to detailed characterization for their molecular and plant growth promoting abilities. The bacterial isolate Erc7 performed best for plant growth promoting activities viz., ammonia and IAA production, phosphate solubilization, nitrogen fixation, HCN production and antagonistic activity against Fusarium oxysporum f. sp. ricini in-vitro which cause wilt in castor plant. Pot trials involving wheat seed inoculation (rabi 2021–22) with bacterial isolates showed that the treatment with endophytic bacterial isolate Erc7 showed maximum shoot and root length (47.65 cm, 10.50 cm), shoot fresh and dry weight (824.90 mg, 308.83 mg), root fresh and dry weight (122.37 mg, 36.20 mg), spike length (09.76 cm) and number of seeds in central tiller plant-1 (15.33). PCR amplification of 16S rRNA genes and ARDRA profiling using restriction enzymes AluI, TaqI and HpaII grouped the 15 isolates in 2 clusters (A and B) at a Jaccard’s similarity co-efficient of 0.54. The best PGPR isolate Erc7 was gene sequenced for 16S rRNA gene. The sequence was submitted to the NCBI Genbank (Accession number ON514555). Upon BlastN It showed maximum similarity to Bacillus cereus. The isolates Erc7 showed presence of diplobacillus endospores which is a typical characteristic of Bacillus cereus.

Optimization of Medium Components for Fed-Batch Fermentation Using Central Composite Design to Enhance Lichenysin Production by Bacillus licheniformis Ali5

Lichenysin, an amphiphilic biosurfactant with structural and physicochemical properties similar to surfactin, is produced by Bacillus licheniformis. Its low toxicity, good environmental compatibility, solubilization, foaming, emulsification and detergent activities have led to a wide range of applications in agricultural biocontrol, enhanced oil recovery, foaming agents for cosmetics and detergents for household cleaning products. However, despite the extraordinary surface-active properties and potential applications of lichenysin, the number of wild bacteria found so far is relatively low. Low titers and high costs are the main limiting factors for widespread industrial applications. In this study, a factorial design was used to optimize the composition of the medium for the production of lichenysin by Bacillus licheniformis Ali5. Firstly, the solutions of carbon, nitrogen, amino acids, inorganic salts and trace elements in the medium were evaluated in flasks using a single-factor optimization method. Meanwhile, the operating conditions were optimized in the same way. Afterwards, a partial factorial design was used to investigate the effect of six variables (five medium compositions and inoculum size) on lichenysin production. Based on the results obtained, the concentrations of sucrose and ammonium nitrate and the inoculum size were considered to be important for lichenysin production. Subsequently, a full factorial design was used to optimize these three variables. The optimized medium composition were sucrose 19.8 g/L, NH4NO3 3.9 g/L, K2HPO4·3H2O 4.0 g/L, MgSO4·7H2O 0.6 g/L, FeSO4·7H2O 0.1 g/L, CaCl2 0.01 g/L, NaCl 3.0, trace elements 1.2 mL/L. Finally, the titer of lichenysin after fed-batch fermentation reached 1425.85 mg/L, which was approximately 5.5 times higher than the titer of lichenysin from the original medium. Consequently, the method was further demonstrated to be suitable for lichenysin production.

Diversity, mechanisms and beneficial features of phosphate-solubilizing Streptomyces in sustainable agriculture: A review.

Currently, the use of phosphate (P) biofertilizers among many bioformulations has attracted a large amount of interest for sustainable agriculture. By acting as growth promoters, members of the Streptomyces genus can positively interact with plants. Several studies have shown the great potential of this bacterial group in supplementing P in a soluble, plant-available form by several mechanisms. Furthermore, some P-solubilizing Streptomyces (PSS) species are known as plant growth-promoting rhizobacteria that are able to promote plant growth through other means, such as increasing the availability of soil nutrients and producing a wide range of antibiotics, phytohormones, bioactive compounds, and secondary metabolites other than antimicrobial compounds. Therefore, the use of PSS with multiple plant growth-promoting activities as an alternative strategy appears to limit the negative impacts of chemical fertilizers in agricultural practices on environmental and human health, and the potential effects of these PSS on enhancing plant fitness and crop yields have been explored. However, compared with studies on the use of other gram-positive bacteria, studies on the use of Streptomyces as P solubilizers are still lacking, and their results are unclear. Although PSS have been reported as potential bioinoculants in both greenhouse and field experiments, no PSS-based biofertilizers have been commercialized to date. In this regard, this review provides an overview mainly of the P solubilization activity of Streptomyces species, including their use as P biofertilizers in competitive agronomic practices and the mechanisms through which they release P by solubilization/mineralization, for both increasing P use efficiency in the soil and plant growth. This review further highlights and discusses the beneficial association of PSS with plants in detail with the latest developments and research to expand the knowledge concerning the use of PSS as P biofertilizers for field applications by exploiting their numerous advantages in improving crop production to meet global food demands.

Genomic Landscape Highlights Molecular Mechanisms Involved in Silicate Solubilization, Stress Tolerance, and Potential Growth-Promoting Activity of Bacterium Enterobacter sp. LR6.

Silicon (Si) is gaining widespread attention due to its prophylactic activity to protect plants under stress conditions. Despite Si's abundance in the earth's crust, most soils do not have enough soluble Si for plants to absorb. In the present study, a silicate-solubilizing bacterium, Enterobacter sp. LR6, was isolated from the rhizospheric soil of rice and subsequently characterized through whole-genome sequencing. The size of the LR6 genome is 5.2 Mb with a GC content of 54.9% and 5182 protein-coding genes. In taxogenomic terms, it is similar to E. hormaechei subsp. xiangfangensis based on average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH). LR6 genomic data provided insight into potential genes involved in stress response, secondary metabolite production, and growth promotion. The LR6 genome contains two aquaporins, of which the aquaglyceroporin (GlpF) is responsible for the uptake of metalloids including arsenic (As) and antimony (Sb). The yeast survivability assay confirmed the metalloid transport activity of GlpF. As a biofertilizer, LR6 isolate has a great deal of tolerance to high temperatures (45 °C), salinity (7%), and acidic environments (pH 9). Most importantly, the present study provides an understanding of plant-growth-promoting activity of the silicate-solubilizing bacterium, its adaptation to various stresses, and its uptake of different metalloids including As, Ge, and Si.

Phosphate solubilization by Antarctic yeasts isolated from lichens.

Antarctica has a great diversity of microorganisms with biotechnological potential but is not very well Known about yeasts with phosphate solubilization activity. Thus, the aim of this study was to evaluate the ability of yeasts from Antarctica lichens to solubilize phosphate in vitro. In the screening, 147 yeasts were tested and 43 (29%) showed P solubilization in solid NBRIP medium at 15.0°C, with a higher prevalence of positive genera Vishniacozyma, followed by Cystobasidium. Most of the positive yeasts were isolated from Usnea auratiacoatra, followed by Polycauliona regalis and Lecania brialmontii. Two strains with better activity after screening were selected for the solubilization in the liquid medium, Vishniacozyma victoriae 2.L15 and A.L6 (unidentified). Vishniacozyma victoriae 2.L15 exhibiting activities at 25.0°C (29.91mg/L of phosphate and pH 6.85) and at 30.0°C (619.04mg/L of phosphate and pH 3.73) and A.L6 strain at 25.0°C (25.05mg/L of phosphate and pH 6.69) and at 30.0°C (31.25mg/L of phosphate and pH 6.47). Of eight organic acids tested by HPLC, tartaric and acetic acids were detected during phosphate solubilization, with greater release in the period of 144 (2.13mg/L) and 72 (13.72mg/L) hours, respectively. Future studies to elucidate the presence of functional genes for P metabolism in lichens, as well as studies in the field of proteomics for the discovery of yeast proteins related to P solubilization are needed. Thus, the high prevalence of lichen-associated yeast communities probably contributed to the high frequency of phosphate-solubilizing isolates in this study.

Isolation, immobilization of salt-tolerant and inorganic phosphate solubilizing bacteria for producing controlled-release inorganic fertilizer in combination with microorganisms

Salt tolerance is one of the characteristics to ensure the viability of microorganisms when combined with chemical fertilizers. This research aimed to isolate bacteria that had both phosphate-solubilizing and salt-tolerant abilities for production of controlled-release inorganic fertilizer-incorporated microorganisms. Of twenty-five phosphate solubilizing bacteria strains isolated from soil samples collected from Ho Chi Minh City, Dong Nai, and Long An provinces on Pikovskaya medium (PVK), there were three strains of bacteria that had both phosphate solubilizing activity and salt tolerance. The analysis results on PVK medium supplemented with 3% and 4% NaCl showed that only PSM54 strain had phosphorusdegrading ring. Species identification based on 16S-rRNA sequence showed that PSM54 was 99.9% similar to Bacillus velezensis. The controlled-release fertilizer was made by coating biodegradable polymers incorporated with PSM54 bacteria that met standards for slow dissolution according to The Association of American Plant Food Control Officials. After 60 days of being immobilized in the membrane of controlled release, the PSM54 bacteria remained at 88.3% compared to the initial density.

Phenotypic and Biochemical Characterization of Rhizobia Associated with Medicagopolymorpha Growing in Rajasthan

In present study, a total of 15rhizobial isolates were isolated from the root nodules of Medicagopolymorphagrowing in Jaipur and were characterized for their phenotypic, biochemical and plant growth promoting activities. The root nodules of M. polymorpha were elongated, branched and indeterminate. All isolated rhizobia were highly diverse in their physiological traits. Based on colony morphology, all isolates were categorized into six groups. Major group containing 6 isolates (MP1, MP3, MP9, MP10, MP11 and MP13) showed white, opaque, raised, smooth edges, non-gummy, and mucilaginous characteristics. Four rhizobia strains MP3, MP4, MP9, and MP15 showed salt-tolerance up to 3% and were well adapted to high alkaline conditions and exhibited growth in extremely alkaline media (pH 10). Majority of strains showed positive result for IAA production, nitrate reductase and catalase activity. In addition, citrate utilization, ammonia production, phosphate solubilization and cellulase activity were observed in few isolates. In present study, some rhizobia isolates like MP3, and MP15 were very versatile rhizobia that showed high plant growth promoting activities (IAA production and phosphate solubilization) and were also tolerant to high pH and salt concentration. Such type of superior rhizobia can be part of biofertilizers to enhance legume crop productivity in an ecofriendly manner without application of chemical fertilizers. Our study suggested that rhizobia isolates associated with Medicagopolymorpha were significantly diverse in their physiological and biochemical parameters

Effects of ultrasound-assisted H2O2 on the solubilization and antioxidant activity of yeast β-glucan

Yeast β-glucan (YG) possess an extensive range of biological activities, such as the inhibition of oxidation, but the poor water solubility of macromolecular YG limits its application. In this study, through the combined degradation of ultrasonic waves and H2O2, and the optimization of the main process parameters for solubilizing YG by response surface methodology (RSM), a new product of YGUH was generated. The molecular weight, structural characteristics and degradation kinetics before and after solubilization were evaluated. The results showed that the optimal solubilization conditions were reaction time: 4 h, ultrasonic power: 3 W/mL, H2O2 concentration: 24 %. Under these conditions, ultrasound-assisted H2O2 increased the solubility (from 13.60 % to 70.00 %) and reduced molecular weight (from 6.73 × 106 Da to 1.22 × 106 Da). Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), Congo red (CR), scanning electron microscopy (SEM) revealed that ultrasound-assisted H2O2 increased the conformation's flexibility greatly, without changing the main structure of YG. More importantly, solubilization of YG improved free radical scavenging activity with YGUH exhibiting the highest levels of DPPH and ABTS+ free radical scavenging activity. These results revealed that ultrasound-assisted H2O2 degradation could be a suitable way to increase the solubility of YG for producing value-added YG.

Bacterial diversity of a floating vegetation (Phumdi) of Loktak Lake and its extracellular enzymes and bacterial antagonistic property.

134 bacterial strains were isolated from phumdis of Loktak Lake. Through 16S rRNA sequencing, Bacillus sp. (23, 17.1%), Staphylococcus sp. (14, 10.4%), Pseudomonas sp. (11, 8.2%) and Acinetobacter sp. (8, 5.9%) were identified as the predominant bacterial taxa of Loktak Lake. B. pumulis (12, 8.9%), S. arlettae (4, 2.9%), P. knackmussii (6, 4.4%) are the leading species of Bacillus, Staphylococcus and Pseudomonas, respectively. Similarly, A. seifertii (2, 1.4%) and A. calcoaceticus (2, 1.4%) are the common species of Acinetobacter. 75 (55.9%) bacterial strains showed the ability to hydrolyze one or more extracellular enzymes tested. Among the extracellular enzymes produced by the bacterial isolates, the presence of elastase activity cannot be underestimated, since the enzyme is involved in the process of bacterial lung infection. Phosphate solubilizing activity could be seen in 11.1% of the bacterial isolates. 27 (20.1%) of the strains shown to have antagonistic activity against one or more tested pathogens. An isolate, MRC 52 showed antagonistic activity against eleven different pathogens including carbapenem resistant E. coli which was further subjected to extraction and identification of the biomolecule exerting the antimicrobial property. Based on GC-MS analysis, the bioactive compound was identified as phenyl ethyl alcohol.