Biofertilizer Potential Research Articles

The Agronomic Potential of the Invasive Brown Seaweed Rugulopteryx okamurae: Optimisation of Alginate, Mannitol, and Phlorotannin Extraction

Rugulopteryx okamurae is an invasive brown macroalga that has recently proliferated in the western Mediterranean Sea, causing significant environmental challenges. This alga, however, contains valuable bioactive compounds—alginate, mannitol, and phlorotannins—that can serve as biofertilizers to promote plant growth and aid in bioremediation of degraded or contaminated soils. This study focused on optimizing the extraction of these compounds from R. okamurae, transforming an ecological issue into a beneficial resource. Algae samples collected from the Spanish Mediterranean coast were processed through a randomized factorial response surface design. Extraction conditions varied by time, temperature, algae-to-solvent ratio, and ethanol-to-water ratio to determine optimal yields. The highest yields achieved were 29.4, 11.9, and 0.35 g/100 g for alginate, mannitol, and phlorotannin’s under extraction conditions of 6, 6, and 3 h; 58.8, 60.0, and 60.0 °C; and an algae:solvent ratio of 1:50, 2:45, and 1.40 g/mL, respectively. Characterization of the extracted sodium alginate using 1H-NMR, FTIR, and high-resolution electron microscopy confirmed its high purity and typical morphological features. This study highlights a sustainable approach to mitigating the invasive spread of R. okamurae while supporting soil health and sustainable agriculture. Harnessing this invasive species’ biofertilizer potential provides a dual solution, aiding marine ecosystem conservation and developing eco-friendly agricultural practices.

Innovative Approach in Sustainable Agriculture: Harnessing Microalgae Potential via Subcritical Water Extraction

Microalgae can contribute to sustainable agriculture and wastewater treatment. This study investigated Tetradesmus obliquus, grown in piggery wastewater (To-PWW), as a biostimulant/biofertilizer compared to biomass grown in synthetic medium (To-B). Subcritical water extraction was tested for disruption/hydrolysis of wet biomass, at three temperatures (120, 170, and 220 ºC) and two biomass loads (1:10 and 1:80 (g dry biomass/mL water)). Extracts were evaluated for germination, and root formation/expansion. Residues were quantified for nutrient composition to assess their biofertilizer potential and tested for their affinity to oil compounds for bioremediation.The best germination was achieved by To-B extracts at 170 ºC (1:10: 148% at 0.2g/L, 1:80: 145% at 0.5g/L). Only To-PWW extracts at 0.2g/L had a significant germination effect (120 ºC: 120-123% for both loads; 170 ºC: 115% for 1:80). To-PWW extract at 120 ºC and 1:10 significantly affected cucumber and mung bean root formation (224 and 268%, respectively). Most extracts significantly enhanced root expansion, with all To-B extracts at 1:10 showing the best results (139-181%). The residues contained essential nutrients (NPK), indicating their biofertilizer potential, helping decrease synthetic fertilizers demands. To-B residues had high affinity to toluene and diesel but lower to used cooking and car oils. To-PWW showed very low affinity to all oil compounds. Finally, all residues were only able to form stable emulsions with the used car oil. This study fully exploits the use of microalgal biomass in sustainable agriculture, producing biostimulant extracts, and residues for biofertilizer and bioremediation, from a low-cost wastewater source.

Unveiling wheat growth promotion potential of phosphate solubilizing Pantoea agglomerans PS1 and PS2 through genomic, physiological, and metagenomic characterizations.

Phosphorus is an abundant element in the earth's crust and is generally found as complex insoluble conjugates. Plants cannot assimilate insoluble phosphorus and require external supplementation as chemical fertilizers to achieve a good yield. Continuous use of fertilizers has impacted soil ecology, and a sustainable solution is needed to meet plant elemental requirements. Phosphate solubilizing microbes could enhance phosphorus bioavailability for better crop production and can be employed to attain sustainable agriculture practices. The current study unveils the biofertilizer potential of wheat rhizospheric bacteria through physiological, taxonomic, genomic, and microbiomics experimentations. Culture-dependent exploration identified phosphate-solubilizing PS1 and PS2 strains from the wheat rhizosphere. These isolates were rod-shaped, gram-negative, facultative anaerobic bacteria, having optimum growth at 37°C and pH 7. Phylogenetic and phylogenomic characterization revealed their taxonomic affiliation as Pantoea agglomerans subspecies PS1 & PS2. Both isolates exhibited good tolerance against saline (>10% NaCl (w/v), >11.0% KCl (w/v), and >6.0% LiCl (w/v)), oxidizing (>5.9% H2O2 (v/v)) conditions. PS1 and PS2 genomes harbor gene clusters for biofertilization features, root colonization, and stress tolerance. PS1 and PS2 showed nitrate reduction, phosphate solubilization, auxin production, and carbohydrate utilization properties. Treatment of seeds with PS1 and PS2 significantly enhanced seed germination percentage (p = 0.028 and p = 0.008, respectively), number of tillers (p = 0.0018), number of leaves (p = 0.0001), number of spikes (p = 0.0001) and grain production (p = 0.0001). Wheat rhizosphere microbiota characterizations indicated stable colonization of PS1 and PS2 strains in treated seeds at different feek stages. Pretreatment of seeds with both strains engineered the wheat rhizosphere microbiota by recruiting plant growth-promoting microbial groups. In vitro, In vivo, and microbiota characterization studies indicated the biofertilizer potential of Pantoea sp. PS1 & PS2 to enhance wheat crop production. The employment of these strains could fulfill plant nutrient requirements and be a substitute for chemical fertilizers for sustainable agriculture.

Isolation and molecular characterization of microorganisms with biofertilizer potential

Biofertilizers are microbial-agro products containing mixed culture of microorganisms that promote plant growth, yield, soil quality and disease control. This study aimed to isolate, identify and screen microorganisms with biofertilizer potentials for application in farms. Soil samples were collected from farmland and waste-dump soils around University of Port Harcourt. The various microorganisms were isolated and estimated using nutrient agar, potato dextrose agar, cetrimide agar and Ashby’s agar. The microorganisms were screened for biofertilizer potentials based on nitrogen fixation, potassium and phosphate solubilization using Pikovskaya media. The results obtained from this study showed that thefarmland soil sample had a total heterotrophic bacterial and fungal counts of 5.045±0.02 and 4.220±0.02 Log10Cfu/gwhile the corresponding values in the waste-dump soil was 4.890±0.30 and 3.505±0.30 Log10Cfu/g respectively. After screening, the microorganisms with biofertilizer potentials were identified as Aspergillus niger, Penicillium chrysogenum, Bacillus cereus, Bacillus licheniformis, Pseudomonas fluorescens and Azotobacter chroococcum. Findings from this study have demonstrated that the microorganisms isolated from the farmland soil were more adept at nitrogen fixation and solubilizing insoluble potassium and phosphate compounds than their counterparts in waste-dump soil. These microorganisms have shown potentials to improve soil fertility and crop productivity in a sustainable way.

Enhanced extracellular ammonium release in the plant endophyte Gluconacetobacter diazotrophicus through genome editing.

Our results demonstrate increased extracellular ammonium release in the endophyte plant growth-promoting bacterium Gluconacetobacter diazotrophicus. Strains were constructed in a manner that leaves no antibiotic markers behind, such that these strains contain no transgenes. Levels of ammonium achieved by cultures of modified G. diazotrophicus strains reached concentrations of approximately 18 mM ammonium, while wild-type G. diazotrophicus remained much lower (below 50 µM). These findings demonstrate a strong potential for further improving the biofertilizer potential of this important microbe.

Experimental evaluation of fresh human feces biogas and compost potential: Evidence for circular economy from waste streams in Ethiopia

Biogas toilets are one of the most resource-efficient sanitation technologies. The technology has dual purposes of generating energy and stabilizing waste-producing biofertilizers. In Ethiopia, knowledge of human feces' energy potential is limited to optimize the development of biogas toilet facilities. Therefore, this study was aimed to evaluate the biogas and biofertilizer potential of human feces in Jimma City, Ethiopia, which may contribute to the development of sustainable sanitation technologies. The study was lab-based experimental design. In the lab-scale batch experiment, fresh human excreta samples were collected using a urine diversion raised toilet. Using ultimate and proximate laboratory analyses, the theoretical yield of biogas was predicted. Then a series of anaerobic digestion batch experiments were conducted to determine the practical energy yield. The bio-fertilizer potential of human feces was determined by analyzing the nutrient contents of human feces. The findings of this study showed that the bio-methane yield from the experimental results has a mean of 0.393 m3 kg−1, which is 14.16 MJ kg−1. The bio-methane meter cube per capita per head per year were 28.71 (28.03–29.27) from the experimental result and 45.26 for the theoretical yield of methane. In this study, the bio-fertilizer potential of human feces was evaluated using nutrient analysis, specifically the NPK (nitrogen, phosphorus, and potassium). Accordingly, human feces contain potassium (2.29 mg kg−1), phosphorus (1.12 mg kg−1), and nitrogen (3.71 mg kg−1). This finding suggests the bio-methane potential of human feces can be used for energy recovery and alternative sanitation options, providing a positive remedy for the sanitation crisis in urban settings.

Biopesticide and biofertilizer potential of tropical earthworm vermicast tea

The adverse effects of chemical pesticides have continued to drive the search for safe, biological alternatives. Studies on biopesticide potential of earthworm casts have remained largely limited to those of temperate earthworms. We evaluated the insect pest repellency and growth-promoting potential of tropical earthworm-derived vermicast tea on the seedlings of Arachis hypogaea (groundnut), Zea mays (maize) and Phaseolus vulgaris (bean). Field-sourced earthworm casts were soaked in water for 48 hours, routinely stirred every 6 hours, and filtered through a fine mesh cloth. The filtrate was the vermicast tea. Seedlings grown in garden soil were sprayed with vermicast tea every four days. The seedlings were monitored for insect pest-induced leaf damage and growth performance for 5 weeks. Vermicast tea exhibited insect pest repellency effect on groundnut and bean seedlings, as evidenced by the significantly lower (p<0.01) insect pest attack on the treated seedlings, as against the untreated that recorded high pest infestations. However, leaf damage was relatively low in maize seedlings, and the differences in percentage leaf damage among the treated and untreated were not significant (p>0.05). The effect of vermicast tea on the physical growth of seedlings was positive, but marginal. This result calls for increased research on tropical earthworms.

A study of microbial diversity in a biofertilizer consortium.

Biofertilizers supply living microorganisms to help plants grow and keep their health. This study examines the microbiome composition of a commercial biofertilizer known for its plant growth-promoting activity. Using ITS and 16S rRNA gene sequence analyses, we describe the microbial communities of a biofertilizer, with 163 fungal species and 485 bacterial genera found. The biofertilizer contains a variety of microorganisms previously reported to enhance nutrient uptake, phytohormone production, stress tolerance, and pathogen resistance in plants. Plant roots created a microenvironment that boosted bacterial diversity but filtered fungal communities. Notably, preserving the fungal-inoculated substrate proves critical for keeping fungal diversity in the root fraction. We described that bacteria were more diverse in the rhizosphere than in the substrate. In contrast, root-associated fungi were less diverse than the substrate ones. We propose using plant roots as bioreactors to sustain dynamic environments that promote the proliferation of microorganisms with biofertilizer potential. The study suggests that bacteria grow close to plant roots, while root-associated fungi may be a subset of the substrate fungi. These findings show that the composition of the biofertilizer may be influenced by the selection of microorganisms associated with plant roots, which could have implications for the effectiveness of the biofertilizer in promoting plant growth. In conclusion, our study sheds light on the intricate interplay between plant roots and the biofertilizer's microbial communities. Understanding this relationship can aid in optimizing biofertilizer production and application, contributing to sustainable agricultural practices and improved crop yields.

Isolation and characterization of indigenous bacterial consortium for augmentation of biofertilizer potential for biogas plant waste (Jabalpur, M.P., India)

The integrated approach to determine the most favourable plant-microorganism interaction is critical for improving and maintaining agricultural land production. The present trend of using low-input chemicals and waste as biofertilizer in sustainable agriculture systems will help to achieve this aim. Biogas plant waste efficiency may be improved by employing indigenous microorganisms to fix NPK in soil. We successfully demonstrated the utilisation of isolated bacterial inoculums for improving the biofertilizer potential of biogas plant waste in Jabalpur, M.P., India for several leguminous crops. The inoculum creation technology employed in this work is capable of creating enough effective inoculum with a reasonable shelf life for economical usage in various agricultural systems. Farmers would be able to grasp the impacts of biofertilizers produced from biogas plant waste and would be eager to utilise them because of their increased viability and high NPK value. This contributes to the achievement of an environmentally benign and cost-effective solution for increased plant growth from healthy soil.

Biogas production potential from animal farm waste in Bangladesh: Case studies of two selected farms

AbstractIncreasing prices of conventional energy sources and ongoing environmental pollution have encouraged policymakers to search for sustainable energy resources. In developing countries, livestock waste is often mismanaged and negatively impacts the environment. Bioenergy production from agricultural and animal wastes can be a viable solution. This study conducted a month‐wise survey on a multipurpose farm and a dairy farm in Chattogram, Bangladesh, to estimate the bioenergy potential from farm livestock waste. Based on the survey, mathematical modeling was applied to estimate the selected farm's theoretical bioelectricity, biogas and biofertilizer production potential. The analysis shows that the multipurpose and dairy farm have an annual biogas production potential of 209,660.2 and 1,205,035.5 m3, generating 3.77E+05 and 2.17E+06 kWhyr−1 of bioelectricity, respectively. The multipurpose farm and the dairy farm could generate 982.03 and 16092.49 tons of bio manure yearly and had an annual biofertilizer potential of 64.36 and 2090.91 tons. Both environmental and economic analyses show that both farms have good greenhouse gas mitigation potential and can earn significant revenue by selling electricity and biofertilizer in the market. The outcome can provide valuable guidelines for policymakers to invest in bioenergy production from farm animal waste.

Isolation of Pesticide Resistant Bacteria with Biofertilizer Potential from Agricultural Soil of Erutheyampathy, Palakkad, Kerala

Abstract: Soil loaded with millions of microorganisms forms the most important medium for the survival, growth and multiplication of microorganisms along with plant growth promotion. Understanding the importance of soil micro flora will enable us to learn deeply about soil ecosystem which could be effectively utilized in agricultural practices. The quantity of production is increased gradually by treating large variety of chemical pesticides, which also inhibits the useful microorganisms present in the soil. Chemical pesticides kills the useful bacteria, nematodes, earthworms also causing health effects to people. In this study the soil samples were collected from tomato farms of Erutheympathy where chemical pesticides is used. Total heterotopic population were determined and predominant bacteria were identified as genus Bacillus, Pseudomonas, Serratia, Micrococcus and Enterococcus. After studying pesticide resistance property Pseudomonas found to be resistant to pesticide followed by Serratia. After analysing the bio fertilizer potential for NPK of isolated bacteria Bacillus and Pseudomonas found to solubilize Phosphorus and Potassium. Bacillus, Serratia, Micrococcus and Enterococcus found to have role in conversion of nitrogen which can be absorbed by plants. Unique combination of the soil bacteria with pesticide resistance and bio fertilizer property is a boon to farmers since soil fertility can be retained even after application of chemical pesticide. Key Words: Tomato, Pesticides, Bio fertilizers

Estimation of renewable biogas energy potential from livestock manure: A case study of India

The rationale of the case study is to estimate biomass resources potential in rural Haryana, India from animal manure and mitigate greenhouse gas emissions. The state has the potential of 52.29 million tons of livestock dung which generates a biogas of 5464.11 million m3 and electrical energy of 9835.4 GWh annually. Assessment of biogas equivalence of traditional fuels is also carried out. The state has a biofertilizer potential of 6.78 million tons/year. The biomass resource distribution, power density, and electricity per-capita potential of livestock manure are projected to be 27.41 kton/km2, 0.59 W/m2, and 387.96 kWh/capita respectively. Biomass power generation leads to an estimated saving of 1707.08 to 3583.73 million kg/year, with a baseline headline of 2560.32 million kg/year CO2equivalent emissions, from transition to local livestock biomass in place of diesel for power. These findings can assist policy planners in decentralized bioenergy generation and map emission profiles with bioenergy.

Antalya Bölgesinden Soğuğa Dayanıklı Bakteri İzolasyonu ve Büyüme Hızlarının Analizi

Only a portion of chemical fertilizers applied to soil can be used by plants, because nutrients can become insoluble in soil. Application of biofertilizers can make the nutrients bio-available for plants. This practice would be beneficial for both plant productivity and the environment. Aim of this study was to isolate and compare growth rates of bacterial strains isolated from low altitude and high altitude regions of Antalya. Our results showed that, bacterial strains isolated from high alitudes have higher growth rates at room temperature (15-25 C) and temperatures as low as 2 C, compared to strains isolated from low altitudes. This suggests that strains that can grow at 2 C also would have higher enzymatic activities at low temperatures which makes them better candidates for development of biofertilizers. Using cold adapted biofertilizer would have a positive effect on plant productivity in agricultural areas located in cold regions of Türkiye. Therefore, isolation of these organisms and testing of their biofertilizer potential is important for our agricultural applications.

The first use of morphologically isolated arbuscular mycorrhizal fungi single-species from Moroccan ecosystems to improve growth, nutrients uptake and photosynthesis in Ceratonia siliqua seedlings under nursery conditions.

The carob tree (Ceratonia siliqua L.) is an important component in semi-arid Mediterranean ecosystems, particularly in Morocco where it plays a considerable socio-economic role. This species is widely used in the reforestation programmes and in the rehabilitation of degraded soils serving both environmental and socio-economic objectives. In spite of these assets, this species is suffering the particular climatic conditions, rare and irregular rains, long hot and dry summers, generally, leading to desertification processes. To withstand these contrasting conditions, selected arbuscular mycorrhizal fungi (AMF) were tested for their contribution to the growth, nutrient uptake and photosynthesis improvement of the carob tree C. siliqua under nursery conditions.The objective of this study was, to evaluate the effects of some arbuscular mycorrhizal fungi complexes isolated in different Mediterranean ecosystems compared to single-species isolates selected using morphological tools on the growth, mineral nutrition, and chlorophyll content of C. siliqua seedlings.The results indicate that all the used AMF inocula stimulated significantly the height of C. siliqua seedlings after eight months under nursery conditions. An increase in plant height between 33% and 70% compared to a control without inoculation was recorded. Similarly, the aerial dry weight recorded an increase of 62% to 124% comparing inoculated and non-inoculated seedlings. The root dry weight has shown an increase rate of 24% to 86% compared to the control. The analysis of mineral contents in plant tissues, showed a highly significant increase in P. N. K. Ca and Mg levels of the aerial parts compared to the control. A significant increase in chlorophyll contents was noticed when inoculated seedlings were compared to non-inoculated ones. This study had confirmed the importance of AMF improving the growth of C. siliqua seedlings; the AMF complexes remain to have the important growth and mineral nutrition responses. However some single- species have shown similar magnitude to the complexes for all analysed parameters. A large biofertilizer potential of the single-species isolates in the inoculation of C. siliqua is demonstrated for the first time.

Exploring biofertilizer potential of plant growth-promoting rhizobacteria Bacillus clausii strain B8 (MT305787) on Brassica napus and Medicago sativa

Plant Growth Promoting Rhizobacteria (PGPR) are soil bacteria that can stimulate plant growth by supplying substances that are usually in limited quantities in the soil especially phosphorous, nitrogen and growth hormone such as indole acetic acid (AIA). These bacteria can also slow the growth of plant pathogens through the production of several antimicrobial metabolites. To investigate the role of rhizobacteria as a biostimulant agent a novel bacterium B8, isolated from the rhizospheric soil of medlar (Mespilus germanica L.- Family Rosaceae), was evaluated on Brassica napus and Medicago sativa. In addition to the classical methods of identification (physiological and biochemical tests), B8 was identified by 16S rRNA gene sequencing as Bacillus clausii. The ability of the strain to produce lytic enzymes such as cellulases, chitinases, pectinases, and phospholipases was studied. Furthermore, the strain B8 was tested for the capability to produce plant growth metabolites like phosphatases and phytases in order to solubilize inorganic phosphate and production of siderophores, cyanhydric acid (HCN) and indole-3-acetic acid. The strain was able to produce lytic enzymes, with an intense production of siderophores and to solubilize inorganic phosphate. Result of in vivo experiments indicated that the application of B8 at 107 CFU/mL, improved markedly the germination rate of rapeseed, whereas alfalfa seeds treated with the same strain showed a lower germination rate than the controls. The vegetative growth parameters; Roots length, lateral roots number, stem length, number of leaves, diameters of stems and plant weight were significantly improved. We also noted capacity of bacteria to colonize root systems of both plants B. napus and M. sativa in one week of inoculation. The overall results of this study showed that B clausii B8 has a great potential to be commercialized as a biostimulant agent and provide promising new option for sustainable agriculture.

Exploring biofertilizer potential of plant growth-promoting rhizobacteria candidates from different plant ecosystems

Abstract. Agustiyani D, Dewi TK, Laili N, Nditasari A, Antonius S. 2021. Exploring biofertilizer potential of plant growth-promoting rhizobacteria candidates from different plant ecosystems. Biodiversitas 22: 2691-2698. Plant growth-promoting rhizobacteria (PGPR) have been widely used as inoculants to increase the growth of crops. This study aims to evaluate the effective PGPR strains according to their capability in various plant growth-promoting activities in vitro. Ten rhizosphere soil samples were obtained from several plant ecosystems in Bangkinang, Kampar, Sumatra Island, Indonesia. A total of 42 bacteria were isolated and tested for three plant growth–promoting activities i.e., phosphate solubilization, indole-3-acetic acid (IAA) production, and N fixation. Out of 42 isolates, 26 were positive for phosphate solubilization, 11 were positive for IAA production, and five were positive for N fixation. The qualitative and quantitative analysis of plant growth–promoting activities revealed that the highest phosphate solubilizing isolate was PK.4.2 (SI 4.33); the highest IAA-producing isolate was I.4.2 (73.1 ppm); while the highest N-fixing ability was NFB.1.1. According to the seed bioassay results, the shoot and root length of bok choy (Brassica rapa) seedlings were significantly enhanced with the PGPR isolates treatment. The highest shoot length (2.53 cm) was observed among seeds treated with I.4.2 isolate, followed by PK.6.1 (2.45 cm) and I.5.3 (2.07 cm). The NFB.1.1 isolate promoted the longest root length (6.4 cm), although this was similar with I.5.3 isolate (6.11 cm). Two isolates that showed significant plant growth–promoting activities were analyzed using 16S rDNA sequences. The two isolates had a close evolutionary relationship with genus Sinomonas strain Cw 108 (I.4.2) and Arthrobacter (I.5.3.).

Microbial Diversity of Nigerian Sludge and Its Potential for Use as Biofertilizer

Sludge samples were collected from a wastewater treatment plant in Nigeria for characterization and evaluation for agricultural applications. Conventional and Molecular techniques were adopted for the isolation and identification of indigenous microorganisms and resulting isolates were characterized and identified by consulting Bergey’s manual of determinative bacteriology and subjected to further screenings to assess their biofertilizer potential using standard microbiological techniques. The viable cells obtained were enumerated and were found to be in the range of 1.03 ± 0.09 x103 cfu/g to 7.45 ± 0.78 x103 cfu/g for heterotrophic Bacteria and 1.63 ± 0.74 x103 cfu/g for fungal community. The Molecular analysis carried out revealed a rich assemblage of diverse species of microorganisms with Bacteria (99.40%) being the most dominant group, followed by Fungi (0.39%) and others (0.21%). Thirty (30) isolates belonging to four (4) Phyla was recovered culturally and identified with Firmicutes 9(30%) being the most dominant group, followed by Proteobacteria 8(26.7%) and Zygomycota 1(3.33%) was the least dominant. The phosphate solubilization index range from 0.86 to 6.3 for bacterial and 2.5 to 3.8 for fungal isolates respectively. The molecular analysis also revealed microbes adept at improving soil fertility to include those in the order Rhizobiales and Actinomycetales. Although pathogens are of a concern in the land application of sludge, our findings have revealed rich microbial consortia of heterotrophic microorganisms whose beneficial attributes can be harnessed to produce nutrient rich biofertilizer and soil amendment.

Profiling of Metabolites of Bacillus spp. and Their Application in Sustainable Plant Growth Promotion and Biocontrol

Bacillus spp. are well-characterized as efficient bioinoculants for sustainable plant growth promotion and biocontrol of phytopathogens. Members of this spp. exhibit the multifaceted beneficial traits that are involved in plant nutrition and antimicrobial activities against phytopathogens. Keeping in view their diverse potential, this study targeted the detailed characterization of three root-colonizing Bacillus strains namely B. amyloliquefaciens, B. subtilis, and B. tequilensis, characterized based on 16S rRNA sequencing homology. The strains exhibited better plant growth promotion and potent broad-spectrum antifungal activities and exerted 43–86% in-vitro inhibition of growth of eight fungal pathogens. All strains produced indole acetic acid (IAA) in the range of 0.067–0.147 μM and were positive for the production of extracellular enzymes such as cellulase, lipase, and protease. Ultra-performance Liquid Chromatography-Electrospray Ionization-Mass Spectrometry (UPLC-ESI-MS/MS) analysis revealed the production of antifungal metabolites (AFMs) such as surfactins, iturins, fengycins, macrolactins, bacillomycin-D, and catechol-based siderophore bacillibactin which were further confirmed by amplifying the genes involved in the biosynthesis of these antimicrobial lipopeptides. When compared for the amounts of different cyclic-peptides produced by three Bacillus strains, B. amyloliquefaciens SB-1 showed the most noticeable amounts of all the antifungal compounds. Plant experiment results revealed that inoculation with phytohormone producing Bacillus spp. strains demonstrated substantial growth improvement of wheat biomass, number of spikes, and dry weight of shoots and roots. Results of this study indicate the biocontrol and biofertilizer potential of Bacillus spp. for sustainable plant nutrient management, growth promotion, and effective biocontrol of crop plants, particularly cultivated in the South Asian region.

Biofertilizer potential of digestates from small-scale biogas plants in the Cuban context

The residual sludge from anaerobic digestion known as digestate has been used as a valuable biofertilizer, but the effect of the substrate, the configuration of the reactor and the operating parameter changes the quality and amounts of nutrients in it. Therefore, it is necessary to know its potential characteristic of fertilizer to apply it correctly in crops of national interest. The aim of this work was to characterize the digestate generated from three biodigester technologies (fixed dome, floating drum and tubular) and three substrates: swine manure, cow manure, and co-digestion of swine and cow manure obtained in the province of Sancti Spíritus, Cuba, in terms of nutrient and matter content. For this purpose, stratified statistical sampling was carried out to ensure representative samples and descriptive statistical techniques were used to process the analyses. The digestate was divided into liquid and solid fractions according to the dry matter content (15%). The content of organic matter and ash represented around 50% for both fractions, which enhances its value as a soil conditioner. The nutrient content of both fractions showed good fertilizing properties, having a nutrient ratio (NH4+:PO43-:K+:SO42-:Mg2+:Ca2+) in the liquid (0.002:0.80:0.10:1.00:0.89:0.93) and solid (0.0003:0.96:0.002:1.00:0.52:0.50) fractions, that would contribute to the return nutrients to the soil. The quality of the liquid fraction as irrigation water was assessed as good, according to the relationship between the concentration of the nutrients (Ca, Mg, Na and K) and hardness. Further research is needed on the appropriate dosage for the different crops, and its contribution to sustainable agriculture in the Cuban context.

The 2,2’ Dipyridyl-Induced Iron Starvation and its Effects on Growth and Photosynthesis in Cyanobacterium Nostoc punctiforme ATCC 29133

Iron is essential for growth of most organisms, including cyanobacteria, a ubiquitous and ecologically important group of microorganisms in nature. The present study was initiated to investigate the effects of iron starvation on the growth, frequency of heterocysts (the sites for nitrogen-fixation), photosynthetic pigments and photosynthesis in the filamentous, nitrogen-fixing cyanobacterium Nostoc punctiforme ATCC 29133. Iron starvation was achieved in cyanobacterial cultures by growing them in medium free of combined nitrogen containing 2,2’dipyridyl (a high affinity iron-chelator) without any addition of iron source. Compared to iron-sufficient control cultures, the iron-starved cultures showed decrease in growth determined for 15 days. The reduction in growth was coupled with a decreased heterocyst (N2-fixation sites) frequency and the number of cells per filament measured after 2 and 4 days of iron-starvation. Similarly, a considerable drop in the concentration of photosynthetic pigments such as, phycocyanin and chlorophyll a were also noticed in iron-starved cultures. Carotenoid level, however, was higher in iron-starved cultures compared to control. The maximum quantum efficiency of photosystem II photochemistry indicating the photosynthetic efficiency was severely affected in iron-starved Nostoc punctiforme ATCC 29133. Overall, the results presented in this study suggest that deficiency of iron negatively impacts growth, photosynthesis and perhaps nitrogen-fixation in the cyanobacterium N. punctiforme ATCC 29133. Given the role of cyanobacteria in biofertilizer technology, it is suggested that iron bio-availability in agricultural fields may strongly impact the biofertilizer potential of diazotrophic cyanobacteria. Therefore, efforts to improve biofertilizer potential of cyanobacteria may be directed towards identifying strains which can better adapt to iron deficiency.