H. Sorkheh; A. Moezzi; N. Enayatizamir
Abstract
Introduction In Khuzestan province, Iran, huge amounts of organic waste is generated annually, leading to challenges for its safe disposal, with the waste being usually either burned or land filled.Agro-industrial wastes such as sugarcane pith, have been recognized as important renewable sources ...
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Introduction In Khuzestan province, Iran, huge amounts of organic waste is generated annually, leading to challenges for its safe disposal, with the waste being usually either burned or land filled.Agro-industrial wastes such as sugarcane pith, have been recognized as important renewable sources of value-added organic products such as compost.Compost is a mixture of decayed organic material decomposed by microorganisms in a warm, moist, and aerobic environment that release nutrients into readily available forms for plant use. Recycling of organic wastes by the process of composting in agriculture brings in the much needed organic matter to the soils and improves the overall soil fertility and soil productivity Thus, composting is a process for appropriate disposal of waste and is also beneficial from ecological and economic point of view. Lignocellulosic materials are not easily degraded due to the lignin, crystalline and structural complexity of cellulose matrix. Application of chemical and biological treatments may increases waste degradation and decrease composting process time. Bacteria and fungi are the two main microbes that help in decomposition of organic waste and forces of composting. In addition, efficient composting is dependent on the microbial activity. The objective of this research was to investigate the effect of chemical (gypsum) and microbial treatments (consortium of bacteria and fungi) on reduce C/N and shortening process of compost maturity which is used in agricultural fields. Materials and Methods In this research, an incubation experiment was carried out in laboratory condition as a factorial experiment based on a randomized complete design with two factors: 1) gypsum application in three levels including, 1%, 5% and 10% w/w, and 2) microbial inoculation in four levels including control (without microbial inoculation), inoculation of substrate with consortium of bacteria, consortium of fungi and consortium of bacteria + fungi, with three replications. The sugarcane pith for compost production was collected from Dehkhoda sugarcane Agro-industry, Ahvaz, SW Iran. The sugarcane pith was initially boiled for 2h, then air-dried. Sugarcane pith samples were sterilized in an autoclave and 1% w/w urea were added to each samples to reduce their C/N ratio. Then, sterilized gypsum and microbial treatments were added to samples in plastic jars. Samples were incubated for 90 days at constant temperature of 25 ± 2 °C. Samples moisture content was maintained at 80% of field capacity. The samples were weighted every day and the required amounts of distilled water were added. At the end of incubation period, sample properties such as organic matters loss percent (OM loss), ash content, carbon (C), nitrogen (N), hydrogen (H) and sulfur (S) content were measured. Also oxygen (O) content and atomic ratio including carbon to nitrogen (C/N), hydrogen to carbon (H/C), oxygen to carbon (O/C) and hydrogen to oxygen (H/O) ratio were determined. All statistical analyses were performed using SAS software. Means of different treatments were compared using the Duncan’s test at probability level of 5%. Results and Discussion The results of variance analysis showed that the gypsum levels and microbial treatments significantly affected the organic matters loss percent, carbon, nitrogen, hydrogen and sulfur content and O/C, H/O and H/O ratio. In addition interaction effect of gypsum and microbial treatments was significant on nitrogen, hydrogen content and C/N ratio. The results indicated that the gypsum addition and inoculation of bacteria and fungi consortium to sugarcane pith significantly (P < 0.05) decreased the carbon content and C/N, H/C and H/O ratio, while significantly (P < 0.05) increased nitrogen, oxygen and hydrogen content as well as O/C ratio. With increasing gypsum levels (from 1 to 10% w/w) the carbon content and C/N, H/C and H/O ratio significantly (P < 0.05) reduced, while nitrogen, oxygen and organic matter loss percent, hydrogen content and O/C ratio significantly (P < 0.05) increased. Comparison of microbial treatments showed that consortium of bacteria + fungi had higher effect on changes in organic matter loss percent, carbon and nitrogen content and C/N, H/C, H/O and O/C ratio. Maximum organic matter lost and nitrogen content as well as minimum and C/N, H/C and H/O ratio were recorded for co-inoculation of bacterial and fungi consortium combined with application of 10% gypsum treatments. Reduction of C/N, H/O and H/C as well as increasing O/C in the above mentioned treatment, indicating that maturation of sugarcane peat composting was completed three months after composting process. Conclusion From the results of this study, it can be concluded that inoculation of consortium of bacteria and fungi with 10% gypsum led to hasten the sugarcane pith degradation and shortening composting process duration.
Soil Biology, Biochemistry and Biotechnology
Marzieh Mazraeh; Roya Zalaghi; Naiemeh Enayatizamir
Abstract
Introduction Growth-stimulating bacteria are now proposed as an alternative to chemical fertilizers in order to increase soil fertility in sustainable agriculture. Biofertilizers are also expressed as microbial inoculants that are capable of removing soil nutrients from an inaccessible state through ...
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Introduction Growth-stimulating bacteria are now proposed as an alternative to chemical fertilizers in order to increase soil fertility in sustainable agriculture. Biofertilizers are also expressed as microbial inoculants that are capable of removing soil nutrients from an inaccessible state through biological processes. Plant Growth Promoting Bacteria (PGPRs) refer to a broad group of susceptible bacteria, which grow alongside the plant as the host and stimulate plant growth. On the other hand, these microorganisms in the soil are able to stimulate and improve biological indicators, such as microbial carbon biomass, microbial respiration, and microbial yield, and may also affect different forms of carbon in the soil. Among the PGPRs, it is possible to refer to Enterobacter and Pseudomonas. Pseudomonas are bacteria present in all agro-soils and have different growth-promoting characteristics. Enterobacteriaceae family is a large group of bacteria that are naturally present in the water, soil, and materials that are corrupted and contaminated. To evaluate the biological changes of soil due to the activity of PGPRs, biochemical parameters (microbial respiration and microbial carbon biomass) are usually monitored in the plant's rhizosphere. The rhizobox is one of the tools used to study the changes in the rhizosphere, by limiting the roots in a certain volume of soil and facilitating the sampling of rhizosphere soil. The aim of this study was to investigate the effect of plant growth-promoting bacteria on some biological and chemical properties of the soil under Rhizobox conditions. Materials and Methods In order to study some of the chemical and biological properties of the soil cultivated with maize and wheat and inoculated with growth promoting rhizobacteria (PGPR), a completely randomized design, including two maize and wheat plants and three levels of inoculation, including non-inoculated, Pseudomonas sp. strain Rhizo_9 and Enterobacter cloacae strain Rhizo_33 in three replications in Rhizobox pots was done in greenhouse conditions. At the end of the period, the plants were harvested and the dry weight of roots and shoots was measured. Also, 3 soil samples were sampled from each rhizobox, as follows: rhizosphere 1 (soil clinging to the root), rhizosphere 2 (1 cm soil clinging to mesh), and non-rhizosphere (soil far from the mesh). Some soil characteristics, including basal respiration, substrate induced respiration, metabolic quotient, and soil carbon components (soil organic carbon, microbial carbon biomass, cold-water-soluble carbon, hot-water-soluble carbon, and permanganate oxidable carbon) were measured. Results and Discussion Results showed that the amount of each carbon component, as well as basal and substrate-induced respiration in treatments with bacteria, was higher than non-bacterial treatments and these biological properties in the soil cultivated with maize were higher than those under wheat cultivation. According to the results, the highest amounts of the basal respiration (0.31 mg CO2 g-1 day-1), the substrate-induced respiration (1.65 mg CO2 g-1 day-1), the permanganate oxidable carbon (213.1 mg kg-1), and the microbial carbon biomass (17.53 mg 100g-1) were related to rhizosphere 1 soil of maize inoculated with Pseudomonas. The highest amounts of the organic carbon (0.82%), the cold-water-soluble carbon (1727 mg kg -1), and the hot-water-soluble carbon (955 mg kg-1) were related to rhizosphere 1 soil in maize inoculated with Enterobacter. This could show the differences between two bacteria in affecting on different forms of carbon in the soil. Conclusion The results of this study showed that maize had a higher effect on carbon forms of soil that could be because of higher root biomass and probably higher root secretions of maize in comparison to wheat. Also, by increasing the distance from plant roots (from rhizosphere1 soil to bulk soil), different forms of carbon decreased that showed the impact of rhizosphere (plant roots and rhizospheric microorganisms) on physicochemical and biological characteristics.Inoculation of PGPR bacteria caused an increase in soil respiration and soil different carbon forms but the two bacteria were different in increasing various forms of soil carbon that seems to be related to different secretions or different effects of bacteria or plant-bacteria associate on soil carbon forms. Although inoculation of Pseudomonas resulted in a higher amount of microbial carbon biomass, inoculation of Enterobacter resulted in higher amounts of cold-water-soluble carbon, hot-water-soluble carbon, and soil organic carbon. Also, the application of two PGPR bacteria (Enterobacter was more effective) increased root and shoot dry weights of maize and wheat compared to non-bacterial treatments.
Plant Nutrition, Soil Fertility and Fertilizers
banafsheh rezaee niko; Naeimeh Enayatizamir; mojtaba norozi masir
Abstract
Introduction Zinc is one of the imperative micronutrients required relatively in small concentrations in tissues for healthy growth and reproduction of plants. Zinc deficiency in plants leads to reduced membrane integrity and synthesis of carbohydrates, auxins, nucleotides, cytochromes, and chlorophyll ...
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Introduction Zinc is one of the imperative micronutrients required relatively in small concentrations in tissues for healthy growth and reproduction of plants. Zinc deficiency in plants leads to reduced membrane integrity and synthesis of carbohydrates, auxins, nucleotides, cytochromes, and chlorophyll and develops susceptibility to heat stress. The solubility of Zn is highly dependent upon soil pH and moisture and hence arid and semiarid areas are often zinc-deficient. The use of microorganisms with the aim of improving nutrients availability for plants is an important practice and necessary for agriculture. Zinc-solubilizing microorganisms can solubilize zinc from inorganic and organic pools of total soil zinc and can be utilized to increase zinc availability to plants. Therefore, the present study was carried out to isolate and characterize native zinc-solubilizing bacteria from Zea mays rhizosphere and evaluate their zinc-solubilizing potential and the effect of zinc solubilizing isolate on Zea mays growth.Materials and Methods: In vitro zinc solubilization assay of isolates was done using 0.1% zinc from zinc oxide in both plate and broth assays. Actively growing cultures of each isolates were spot-inoculated (7 µL) onto the agar and plates were incubated at 28°C for 48 h. The clearing zone around colony was recorded. Quantitative study of zinc solubilization was studied in 150 mL conical flasks containing 50 mL of liquid mineral salt medium. The broth was inoculated with 10 µL of overnight grown bacterial inoculum and incubated for 72 h at 160 rpm in an incubator shaker at 28°C. After incubation, the culture broth was centrifuged and the concentration of Zn in the supernatant was estimated in atomic absorption spectrophotometer. Among these isolates, 18 isolates with a solubility index of 1 and higher were selected based on morphological, biochemical and physiological characteristics for further studies. An isolate with more ability to dissolve zinc, phosphorus, potassium and auxin production were selected for investigation the effect of isolate on Zea mays growth. Maize seeds of cultivable variety were surface sterilized with 1% sodium hypochlorite for 5 min and washed several times with sterile distilled water. Seeds were treated with inoculum containing 108 cfu•g−1 of isolate. A factorial experiment in a completely randomized design with five replications was conducted. The treatments included two levels of bacteria B1 (control), B2 (Stenotrophomonas) and zinc sulfate fertilizer at three levels of Zn0 (control), Zn20 (20 kg/ha) and Zn40 (40 kg/ha). After 60 days of sowing, plants were removed from the tubes carefully and biometric parameters like root length, shoot length and dry mass of plants were recorded as the indicative of plant growth. Results and Discussion: A total of 50 bacterial isolates were isolated from corn rhizosphere. Of all, sixteen isolates showed solubilization halo on plate agar medium. Among the cultures, Z1, Z3, Z16 and Z12 showed the highest solubilisation zone in ZnO amended medium with maximum solubility index (1.3). Quantitative assay for zinc solubilisation revealed that Z14 were able to dissolve 44.8 ppm from ZnO in liquid medium. While solubility index of this isolate was lower that above mentioned isolates (1). Of all, the isolate Z14 with highest zinc solubilisation by broth assay was characterized and identified as Stenotrophomonasspecies based on Gram-negtive reaction and other biochemical and physiological properties. This isolate was able to produce auxin and dissolve insoluble phosphorus and potassium from the source tricalcium phosphate and vermiculte, respectively. One of these strains (Z14), Stenotrophomonas was used as inoculum in corn culture. Seed bacterization of maize with zinc solubilising Stenotrophomonas enhanced the plant growth significantly after 15 days. Results indicated a significant interaction effect of bacterium and fertilizer on shoot dry weight and chlorophyll content (p < 0.01). The maximum spad index and wet weight of aerial part obtained at present of bacterium and without using of zinc sulfate. The main effect of bacterium on wet and dry weight of root and wet weight of aerial part, root length and shoot height was significant (p < 0.01). َApplication of bacterium in all treatments caused to increased all measured parameters in th eperesence of zinc fertilizer or absence of zinc fertilizer.Conclusion: PGPR is known as a group of useful rhizospheric bacteria that increase plant growth. Today, the increasing use of PGPRs in agriculture as an alternative to chemical fertilizers to prevent environmental contamination.
Soil Biology, Biochemistry and Biotechnology
Naeimeh Enayatizamir; A Moezzi; Shila Khajavi
Abstract
Introduction Biosurfactants or microbial surfactants are surface active molecules that are produced from a variety of microorganisms. Due to its amphiphilic nature, these biomolecules are capable of lowering the surface tension, interfacial tension and forming micro-emulsion to enable mixing of two immiscible ...
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Introduction Biosurfactants or microbial surfactants are surface active molecules that are produced from a variety of microorganisms. Due to its amphiphilic nature, these biomolecules are capable of lowering the surface tension, interfacial tension and forming micro-emulsion to enable mixing of two immiscible solutions. Such properties exhibit excellent detergency, emulsifying, foaming and dispersing traits, which can be applied in various industries. The features that make them commercially promising alternatives to chemically synthesized surfactants are their lower toxicity, higher biodegradability, better foaming properties, and greater stability towards temperature and pH. Limited full scale production has been realized for many biosurfactants due to expensive raw material, low production yield and high purification cost. In order to alleviate these problems, many studies have been carried out using cost-free or low-cost feed stocks or agricultural byproducts as substrates for biosurfactant production. Oil pollution and remediation technology has become a global phenomenon of increasing importance. Materials and Methods In this study, Potential strains of microorganism were isolated from various hydrocarbon polluted area on nutrient agar medium using sterile saline (0.85% NaCl) method and different bacterial isolates were selected based on the colony morphology on nutrient agar. The selected isolates were screened for the production of biosurfactants using following screening methods. Pure culture of bacterial isolates were streaked on the freshly prepared blood agar and incubated at 37°C for 48-72 h. Results were recorded based on the type of clear zone observed i.e. α-hemolysis when the colony was surrounded by greenish zone, β-hemolysis when the colony was surrounded by a clear white zone and γ-hemolysis when there was no change in the medium surrounding the colony. Surface tension reduction and emulsification index of isolates was determined by culturing the isolates in minimal mineral salt solution containing glucose as carbon source. Based on the screening test results, the positive isolates were inoculated into the mineral salt medium for the biosurfactant production and then identified by its microscopic appearance, biochemical tests based on Bergey’s manual of determinative bacteriology and molecular method. Bio-surfactant production by superior isolate was evaluated in minimal mineral salt medium containing different carbon sources (kerosene, sugar cane molasses, phenanthrane and glucose) at 30 and 37 °C within the incubation periods of 48 and 156 hours. Emulsification activity, oil spreading, drop collapse, cell hydrophobicity and surface tension activity of isolate were used to detect biosurfactant production. Results and Discussion Out of 13 isolates of microorganism, strain S10 showed positive response to biosurfactant tests (hemolytic activity, surface tension reduction and emulsification index) and was select for identification and considering the effect of different carbon sources on its biosurfactant production. The biochemical and molecular identification results showed isolate S10 belongs to Bacillus pumilus. Results showed that Bacillus pumilus was able to grow in all carbon sources. Based on bio-surfactant production, this strain had a positive or β hemolysis on blood agar medium. Results showed that this bacterium was able to grow in all carbon sources. The compound produced by this strain in each of carbon sources at both temperatures (30 and 37 °C) and incubation periods (48 and 156 hours) collapsed down. The maximum surface tension reduction was recorded in the samples containing molasses as carbon source incubated at 30 ° C for 48 hours, in which bacterium reduced surface tension to 20.33 mNm-1. The highest bacterial growth with a higher surface tension reduction selected this isolate as a potential biosurfactant producing microorganism. The maximum emulsifying and cell hydrophobicity were also recorded in molasses (28%) and kerosene (70%) respectively. Conclusion In conclusion, the study represented surfactant activity of the bacterial strain isolated from oil contaminated soils. This confirms that environment has an influence on the metabolism of the tested microbes. This study suggests that, Bacillus pumilus isolated from oil contaminated soil showed biosurfactant producing ability. Further study on the utilization of agro industrial wastes as substrates for the large-scale production of biosurfactants is recommended.
P Khaji; N Enayatizamir; A Moezzi
M. Varnaseri Ghand Ali; A. Moezzi; N. Enayatizamir
Safoura Jafari; Mostafa Chorom; Naeimeh Enayatizamir; Hossein Motamedi
Volume 35, Issue 2 , March 2013, , Pages 55-70
Abstract
Soil salinity induces a stressful environment for soil micro-organisms and reduces their number and activity. The objective of this research is investigating the effect of different levels of salinity on some of soil biological indicators and also assessing the effect of two types of halotolerant rhizospheric ...
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Soil salinity induces a stressful environment for soil micro-organisms and reduces their number and activity. The objective of this research is investigating the effect of different levels of salinity on some of soil biological indicators and also assessing the effect of two types of halotolerant rhizospheric bacteria on the value of these indexes in soil. 35 strains were isolated from saline rhizospheric soils and their ability to grow in concentrations of 0 to 600 mM salt was evaluated. Among them, two isolates were identified as salt tolerant bacteria that were recognized as genera of Bacillus subtilis and Corynebacterium glutamicum. The factorial experiment, as the completely randomized design, was performed with two factors including salinity in four levels (2, 4, 8 and 12 dS/m) and bacteria in three levels (none inoculated, inoculated with Bacillus subtilis and inoculated with Corynebacterium glutamicum) in the greenhouse. The cultivated plant was barley. Different levels of salinity in soil were created by adding the mixture of salts including NaCl, CaCl2 and MgCl2. After 8 weeks, the amount of soil respiration, microbial biomass carbon and qCO2 were measured in the soil. The results of the statistical analysis showed that the effect of salinity levels on these indicators were significant (P<0.001). Bacterial inoculation in different levels of salinity, significantly, increased the soil respiration (P<0.05) and microbial biomass carbon (P<0.001) and reduced qCO2 (P<0.001) in soil. The results of this research showed that the halotolerant rhizospheric bacteria reduced the negative effects of salinity on soil microbial indicators.
