Microbial Syntrophy-mediated Eco-enterprising

Microbial Syntrophy-Mediated Eco-enterprising summarizes and reviews possible microbial applications for eco-industrial sustainability. The book emphasizes a wide spectrum of experimental and theoretical contributions from eminent researchers in the field. In 13 chapters, there is a focus on the microbial intrusions for remediating sites by accumulated pesticides, heavy metals, polyaromatic hydrocarbons, and other industrial effluents. Moreover, the potentiality and key mechanisms used by microorganisms for sustainable environmental management and their prospects are also considered in this new release.

The term syntrophy for nutritional interdependence is often used in microbiology to describe the symbiotic relationship between bacterial species. Understanding such interactions can be of considerable interest when we come to manipulate microbes to our own benefit, such as by disrupting pathogenic communities with antibiotics or by promoting efficiency in communities that produce energy or break down waste.

• Summarizes and reviews possible microbial applications for eco-industrial sustainability
• Includes a wide spectrum of experimental and theoretical contributions from eminent researchers in the field
• Focuses on microbial intrusions for remediating sites and other industrial effluents

• Language: English
• Publisher: Academic Press
• Release date: Feb 9, 2022
• ISBN: 9780323913966

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Chapter 1: Anabaena-azollae, significance and agriculture application: A case study for symbiotic cyanobacterium

Azza A.M. Abd El-Aal    Soil Microbiology Department, Soils, Water and Environment Research Institute, Agricultural Research Center, Giza, Egypt

Abstract

Anabaena azollae is a heterocystous filamentous nitrogen-fixing cyanobacterium that is naturally growing symbiotically in specialized leaf cavities of a small eukaryotic water fern Azolla pinnata. It is well documented that Anabaena azollae has been successfully grown and propagated freely in synthetic media like BG-110 with pleasant biomass.

A. azollae is considered a promising natural biosource for agricultural, medicinal, and industrial applications. Where the cyanobacterium biomass and/or extract greatly enhanced the physical and chemical properties of soil texture. It is also well-known to produce several biologically active substances against a wide array of plant-infecting pathogens. Moreover, it is considered a good phycoremediator of industrial wastewater.

To the best of our knowledge, this is the first review of A. azollae, a case study for its characteristics, significance with a special focus on its agricultural applications.

The commercial production and exploitation of A. azollae-derived materials with interesting properties such as fungicides, bactericides, nematicides, insecticides, biofertilizers, as well as its phycoremediation ability were highlighted in detail in this review.

Numerous growths promoting substances like indole acetic acid (IAA), gibberellic acid (GA), bioactives such as fatty acids, polysaccharides, phenolic compounds were extracted from A. azollae, and reported to have in vitro and in vivo microbicidal effects. Additionally, the high nitrogenase activity of A. azollae has been accepted as a pioneer indicator for its biofertilization ability. Strikingly, the induced dehydrogenase activity and its polysaccharides excretions were reported to increase soil fertility by increasing the soil microbial communities. Thus, A. azollae could provide multiple benefits to the agricultural sector and can be considered as a promising and safe bio-inoculant in recent trends of organic farming.

Keywords

Anabaena-azollae; Azolla pinnata; Bio-fertilizer; Antifungal activity; Antinematode activity; Bioinsecticidal activity; Bioremediation

Acknowledgments

The authors wish to thank Soils, Water and Environment Research Institute (SWERI), Agriculture Research Center, Giza, Egypt for the facilities provided to conduct this research work.

1: Introduction

Bio-fertilizer was recognized as an option in sustainable agriculture to increase soil fertility and crop manufacturing. Because of their potential role in food safety and sustainable crop production, the exploitation of beneficial microbes as biofertilizers has become of paramount importance in the agricultural sector (Itelima et al., 2018). Furthermore, biofertilizers such as nitrogen fixers, cyanobacteria, bacteria, and aquatic Azolla fern are becoming increasingly important in sustainable agriculture, where different complementary combinations of microbial inoculants are required for the management of significant nutrients such as nitrogen and phosphorus (Brahmaprakash and Sahu, 2012).

Bio-fertilizer inoculation is now regarded to restrict and minimize the use of mineral fertilizers and is an efficient instrument for soil development in less polluted settings, Reduction of agricultural expenses, maximization of crop yields owing to the availability of nutrients, and development of substances (Al-Erwy et al., 2016). Azolla, a free-floating aquatic fern with a dichotomous branch, is naturally accessible in India’s tropical belt. The exposed dorsal lobe has a particular cavity comprising its symbiotic partner, Anabaena azollae, a blue-green alga.

Azolla’s abundant development not only makes the combined nitrogen added to the ecosystem helpful but can also provide green manure (Rkyadav et al., 2014).

Biofertilizers maintain a rich soil environment with all sorts of micro- and macro-nutrients via nitrogen fixation, phosphate, and potassium solubilization or mineralization. The release of plant growth regulating biologically active substances including phytohormones, such as auxin, Gibberellins, and cytokinin’s, antibiotic production, and organic soil biodegradation (Divya and Ram, 2018).

Azolla also produces many other components that enhance the overall soil fertility by enhancing the amount of nutrients available to plants, as the organic matter in the soil increases, and the soil structure improves (Nevine and El-Shahat, 2018).

Purushottam and Jiban (2015) was noted that the soil’s biological health owing to the implementation of Azolla resulted in improved mineralization and a consequent boost in the soil’s microbial status.

The use of Azolla fern and cyanobacteria as a bio-fertilizer is advocated to minimize the dependency on chemical fertilizer. Azolla supplements rice nitrogen by setting atmospheric nitrogen in the soil for plant growth, crop manufacturing, and soil fertility improvements (Bharati et al., 2016).

The impacts of the use of magnetite, diatoms, and some biofertilizers (azolla and cyanobacteria) on the development yield and quality of Valencia orange cultivated under saline soil circumstances in El Bustan County, Egypt, was the best combination for achieving the highest total yield (Hoda et al., 2013).

The effect on the development of cyanobacteria, Azolla, bacteria with biostraw as biofertilizers or coupled with urea, rice output showed several advantages over chemical fertilizers and enhanced saline soil fertility (Abd El-Aal et al., 2013).

Arafa and Abd El-Aal (2013) additionally, the organic fertilizer humic acid gave the highest outcomes for all soil characteristics using the combination of Spirulina platensis and Azolla pinnata. It also saves on using bio-organic fertilizers for colored cotton without influencing the characteristics of the colored fiber.

Algae are a big and varied group of microorganisms that can perform photosynthesis as they capture sunlight energy. Anabaena azalea plays a significant role in farming where it is used as a biofertilizer and soil stabilizer. Anabaena azallea is a symbiotically related photoautotrophic cyanobacterium with the tiny eukaryotic water fern Azolla pinnata, in specialized leaf cavities of the fern under natural conditions. It is a multicellular organism with two separate, interdependent kinds of cells. Which are vegetative cells and heterocyst’s; to fix atmospheric nitrogen. Cyanobacteria Anabaena azallea from the symbiosis has also been separated and cultivated as a bioagent suppressor against Fusarium oxysporum and Alternaria alternata separately of the fern. This antifungal activity may be attributed to the presence of bioactive compounds identified Filters such as phenolic compounds, saponins, and alkaloids that act as natural defense mechanisms against pathogenic fungi in cyanobacterial culture (Abd El-Aal, 2013). Mohamed et al. (2015) discovered that Anabaena azollae played a major role in enhancing the pelarogonium potential and antibiotic studies have shown promising control results; Fusarium oxysporum and Rhizoctonia solani by various microorganisms, such as Pseudomonas fluorescens and/or extracts of either single or combined Pleurotus columbinus or Anabaena azollae. The combination of Anabaena azollae extract, Spirulina platensis and Pleurotus columbinus was the best therapy to achieve high output in the manufacturing of herbal and oil.

In addition, the 25% reduction in the recommended bioagent treatment dose was higher than the recommended N fertilizer dose in plant yield and oil quality and quantity production (Mohsen et al., 2015).

Therefore, this review is regarded as the first of its kind to highlight and summarize the potential for using Anabaena azollae as the biological control of certain agricultural diseases; Integrated pest management, and plant growth improvement to promote sustainable agricultural technology.

2: Anabaena azollae description isolated from Azolla pinnata

The Azolla cyanobiont is classified taxonomically in phylum Cyanophyta, Order-Nostocales, Family-Nostocaceae. It was first named Nostoc and then renamed Anabaena azollae.

Abd El-Aal (2013) revealed the morphological characteristics of Anabaena azollae isolated from Azolla pinnata and demonstrated that it can be cultured free in BG11 medium (Figs. 1–4).

Fig. 1

Fig. 1 Azolla pinnata .

Fig. 2

Fig. 2 Anabaena azollae colonies isolated from Azolla pinnata .

Fig. 3

Fig. 3 Growth of Anabaena azollae free in BG11 medium.

Fig. 4

Fig. 4 Cells in Anabaena azollae grown in BG11 medium.

3: Use of Anabaena azollae in the farming sector

3.1: Professional biostimulation on plant growth

Biostimulants are products that reduce the need for fertilizers and increase plant growth, resistance to water and abiotic stresses. In small concentrations, these substances are efficient, favoring the good performance of the plant’s vital processes, and allowing high yields and good quality products. In addition, biostimulants applied to plants enhance nutrition efficiency, abiotic stress tolerance, and/or plant quality traits, regardless of its nutrient contents. Several researches have been developed in order to evaluate the biostimulants in improving plant development subjected to stresses, saline environment, and development of seedlings, among others. Furthermore, various raw materials have been used in biostimulant compositions, such as humic acids, hormones, algae extract, and plant growth-promoting bacteria (Yakhin et al., 2017).

Cyanobacteria excrete a great number of substances that influence plant growth and development. These microorganisms have been reported to benefit plants by producing growth-promoting regulators (the nature of which is said to resemble gibberellin and auxin), vitamins, amino acids, polypeptides, antibacterial and antifungal substances that exert phytopathogen biocontrol and polymers, especially exopolysaccharides, that improve soil structure and exoenzyme activity (Oluwaseyi et al., 2017). In three cyanobacterial strains, plant growth promoters are estimated (Anabaena azollae Strasburger, Spirulina platensis Geitler, and Nostoc muscorum C. Agardh in the presence of potassium nitrate, sodium chloride, and tryptophan, with different concentrations. The highest concentrations of IAA and GA3 were determined and applied to maize that was planted in soil with EC (5.4). During the maize cultivation period, three times cyanobacterial therapies are applied. Mineral fertilization has been implemented in compliance with the Egyptian Ministry of Agriculture guidelines, with 100% to control, and 75% to all other treatments. Final results showed that the highest yield was obtained through the treatment of maize (Spirulina platensis with tryptophan, Anabaena azollae with both potassium nitrate and tryptophan).

These results were nearly three times greater than the yield of the control. For yield improvement, it is recommended to use the selected strains, especially in sandy and saline soils. Applying different cyanobacterial strains to maize grown in a soil affected by relatively high EC, treated with different additives, such stress was found to be overcome if cyanobacteria were applied during the optimum period of IAA and GA3 production (Al Awamri et al., 2018).

3.2: Anabaena azollae as biofertilizer

Azolla biofertilizer may be a promising approach to achieve better N use efficiency (NUE) in paddy rice fields due to its great potential for biological N fixation (BNF) (Bharati et al., 2016). One of the Hopeful biofertilizers for a variety of crops, including rice (Joshi et al., 2012), wheat (Babu et al., 2015), taro (Petruccelli et al., 2015), and soybean (Sholkamy et al., 2015) is Azolla anabaena. When used in a rotating rice-wheat cropping method, Azolla is useful for wheat (Gaind and Singh, 2015).

Manipulation of some cyanobacteria like Anabaena azollae or Spirulina platensis or white rot fungi like Pleurotus columbinus under 50%, 75%, and 100% of N fertilizer on Pelargonium graveolens L. were tested to study the growth, herb yield, essential oil % and essential oil yield, and its components. Geranium seedlings were soaking with these bio-agents then plants were sprayed with the bio-agent suspension five times after sowing. Results indicated that inoculation with these bio-agents caused a significant increase in plant height, a number of branches/plant, herb fresh and dry weights per plant (g) and per fed (ton), essential oil percentage in the herb, and essential oil yield per plant (cc) and per fad (L) as well as Total carbohydrates (%). The highest increase in these parameters was obtained when plants were treated with Anabaena azollae(A) + Spirulina platensis(B) + Pleurotus columbinus (C) in the presence of 75% of N fertilizer. The lowest mean of all parameters in two cuts for both seasons was obtained in the plants which fertilized by 50% of N. The highest percentages of Geranyl formate, linalool, citronellol, and geraniol in essential oil were recorded with the same treatment. In addition, the highest total carbohydrates percentages and phenol content were recorded in herb of treated plants with this treatment.

There is no doubt that the use of different bio-agent treatment of Anabeana Azollae, spirulina platensis, and pleurotus columinus in different combinations and application of 75% N- fertilizer on Pelargonium plant led to an increase in plant growth as: plant height, a number of branches/plant and herb fresh and dry weights per plant and per fed. As well as essential oil yield per plant and per fed (Mohsen et al., 2015).

The role of Azolla pinnata, Anabaena azolla, Pleurotus columbinus, and Azotobacter sp. in the presence of urea (46.5% N) as a source of nitrogen fertilizer on the growth and yield of wheat on sandy soil. It was found that the total count of bacteria, fungi, azotobacter, and algae at different treatments were higher than those of other treatments especially with the treatment of Mix only which gave the highest values of total bacteria count. Also, for different microbes such as fungal, algae and N2-fixing bacteria count it was noticed that treatment (Mix of biofertilizer  +  75% of the recommended dose of nitrogen) gave the more optimum results for different types of microbes count. The results have showed that the highest values for IAA production were at (mix + urea 50%) and (mix + urea 75%), while (mix only) and (mix + urea 75%) gave mostly higher N2-ase activity at 120 days of incubation compared to other treatments. Also, straw and grain yields were significantly increased with (mix + 75%) of the recommended dose of nitrogen fertilizer. Also it was noticed that treatments of the mix of biofertilizer have a pivotal role in increasing N, P, and K uptake in straw and grain yields.

The use of microorganisms in plant production especially in cereal crops can improve growth and yield components, lower use of mineral fertilizers, and higher microbiological activity of soil.

So, the application of different kinds of biofertilizers enriched soil fertility and so it is helpful to improve the soil properties such as organic matter content,

As well as, macronutrients uptake (N, P, and K) in the wheat cropping system, which is reflected on the yield and its components. Hence, it is imperative to popularize the use of biofertilizers, which is a low-cost input technology.

to reduce the dependence on inorganic fertilizers and contribute to a pollution-free atmosphere, which is the need of the day (Taha et al., 2017).

3.3: Anabaena azollae biological control

3.3.1: Antifungal activity

Anabaena azollae can be used as a bioagent suppressor for Fusarium oxysporum (Fig. 5) and Alternaria alternates (Fig. 6) pathogenic fungal members.

Fig. 5

Fig. 5 Antibiosis among Anabaena azollae and Fusarium oxysporum. (A) Anabaena azollae + Fusarium oxysporum. (B) (Control) Fusarium oxysporum. (C) (Control) Anabaena azollae.

Fig. 6

Fig. 6 Antagonistic activity of A. azollae toward (A) Anabaena azollae  +  Alternaria alternat . (B) (Control) Alternaria alternat . (C) (Control) Anabaena azollae .

In this respect, Different cyanobacterial strains are known to produce intracellular and extracellular metabolites with various biological activities, including antibacterial and antifungal effects (Mohamed et al., 2011). It has been reported that several attempts to recombine isolated Anabaena azollae with cyanobacterium-free Azolla are unsuccessful (John and Jeff, 2002).

Some fungal diseases may attack geranium plants (Pelargonium graveolens L. Herit.) causing a drop in harvested crop and deterioration in oil yield, as root rot and wilt syndromes. Antibiosis studies showed promising results in control of; Fusarium oxysporum and Rhizoctonia solani, by different microorganisms such as Pseudomonas fluorescens and/or the extracts of either Pleurotus columbinus or A. azollae individually or in combination at the second cut of the second season.

The mixture of Pseudomonas and the extract of both Pleurotus and Anabaena increased geranium plant length. Due to either Fusarium or Rhizoctonia disease(s), the fresh and dry weights of plants increased in the second cut in the second season. A. azollae extract treatment was the superior management of diseases of either Fusarium or Rhizoctonia as demonstrated by fresh geranium crop yield.

And the yield of second season pelargonium oil, in the second cut. Highly significant rises in fresh yields of A. azollae, Pseudomonas sp. interaction therapy. And then pleurotus sp. Compared to the control.

The influence of bio-agents on pelargonium productivity caused by stress from Fusarium or Rhizoctonia. Treatments with bio-agents played a major role in avoiding the disease and increasing fresh and dry weights. Any of the three used microbes raised the fresh weight about four times compared to control, while being doubled in the case of dry weight for the second cut (Mohamed et al., 2015).

3.3.2: Antinematode activity

Root-knot nematodes, Meloidogyne spp., are among the most dangerous nematodes in agriculture, causing a worldwide total loss of US$ 100 billion (Entsar, 2018).

Symptoms of nematode infection are root gall formation, resulting in reduced growth, nutrients, and water absorption, wilting increase, and mineral deficiency, resulting in weak and low-yielding plants (Ping et al., 2014).

Chemical nematicides have been found to be an effective measure for controlling nematodes but have a toxic residual effect on the environment, especially on non-target organisms and human health. Moreover, the use of chemical nematicides in organic farming is banned. Therefore, the creation of alternative, healthy environmental strategies for controlling nematodes is urgent (Anastasiadis et al., 2008). Research on nematode control over the last decades has concentrated on suggesting strategies to inhibit egg hatch, degradation of hatching factor or metabolite production (Fereidoun and Abolfazl, 2020). One of the biological control practices recently attempted is the study of the nematocidal capacity of cyanobacterial culture filtrates, which parasitize plant-parasitic nematodes (Nikoletta et al., 2020).

Cyanobacteria that excrete a large number of substances have been reported to benefit plants by producing growth-promoting regulators (PGPRs), vitamins, amino acids, polypeptides, phytopathogenic antibacterial and antifungal substances, and polymers, in particular exopolysaccharides, that improve soil structure and exoenzyme activity (Zaccaro et al., 2001).

In the productivity greenhouse experiment, the combination of mixing five algal culture filtrates of Spirulina platensis, Oscillatoria sp., Anabaena oryzae, Nostoc muscorum, and Phormedium fragile, with A. pinnata aqueous extract filtrate and compost extract achieved the highest reduction in the number of the 2nd stage juveniles in soil, the numbers of galls, developmental stages, females, egg masses, Egg numbers/egg mass in roots of cucumber plants comparing with the individual treatment and the non-treated control. In addition, all combinations significantly improved the fresh weight of roots and shoots and increased the plant yield (Shawky et al., 2009).

Two algal cultures, Spirulina platensis, Anabaena azollae, Azolla pinnata and Pleurotus columbinus were also used in the control of root-knot nematode in addition to olive mill waste, Meloidogyne javanica in banana was monitored under both laboratory and commercial greenhouse conditions. Laboratory experiment revealed that high juvenile mortality percentage occurred during all the exposure periods of all treatments, the best results were after 72 h exposure. Spirulina platensis followed by Anabaena azollae, Azolla pinnata, Pleurotus columbinus, and olive watery extract significantly increased juveniles mortality up to 70% after 72 h at the highest concentration of 1:10 (85.2, 81.4, 79.9, 73.5 and 71.7%, respectively).

In the productivity greenhouse experiment, the combination of culture filtrates of Spirulina platensis, Anabaena azollae, Azolla pinnata, Pleurotus columbinus, and olive mill wastewater achieved the highest reduction in the number of total nematodes in both soil and roots, also in numbers of galls. In addition, all combinations significantly increased the crop yield of banana plants comparing with the individual treatment and the control.

Combined treatments significantly increased the regulation activities of CO2, dehydrogenase, and nitrogenase. It may be advised that the use of biological control agents in bananas against root-knot nematode is preferred in order to reduce the inputs of chemical nematicides (Shawky et al., 2014).

3.3.3: Bioinsecticidal activity

Pesticides kill beneficial predators, parasites, and pathogens as well as pests, and can result in secondary pest outbreaks or rapid resurgence of pests that were previously suppressed. Biological control is the use of non-chemical and environmentally friendly methods of controlling insect pests and diseases through the action of natural control agents. Biological pest control is the use of pathogens, predators, and parasitoids to kill pests by reducing their populations or eliminating them entirely from our farms, gardens, and forests, thereby increasing productivity and safety. Microbial antagonists have been used to control pests and diseases in recent years. A common example is Bacillus thuringiensis, which is toxic to many insect species. Furthermore, Entomopathogenic nematodes from the families Steinernematidae and Heterorhabditidae have been used to suppress pest insect populations in a variety of agroecosystems, and in several cases, their positive effects on crop yield have been demonstrated (Nafiu and Mustapha, 2014).

With a wide variety of host plants and world distribution, the two-spotted spider mite, Tetranychus urticae Koch, is one of the most common mite pest species (Rabie et al., 2018). T. urticae is an important one in global distribution. Its phytophagous nature, high reproductive potential, and short life cycle rapid resistance development too many acaricides often after a few applications.

On the other hand, the great reliance on Chemical pesticides had its serious drawbacks, manifested in resistance problems and high residue levels in food products (fruits, vegetables, grains, and seeds) that may hinder its marketing (Adekunle et al., 2019). Phytoseiid mites are important biological control agents because of their well-known capacity to suppress pest mite populations, mainly tetranychids in diverse cropping system (James et al., 2013). Two mite predators of the family Phytoseiidae have been found in association with the two-spotted spider mite on cucumber and pepper fields in Egypt. Neoseiulus barkeri (Hughes) (Acari: Phytoseiidae) is an oligophagous predatory mite. T. negevi Swirski and Amitai (Acari: Phytoseiidae) is the agriculturally important predator of spider and eriophyid mites (Momen, 2010).

Significant biocontrol agents are many species of predatory mites and the species Phyto seiulus macropilis and Neoseiulus californicus are used to monitor the two-spotted spider mite Tetranychuschus Urticae, a major worldwide agricultural pest (Morgana et al., 2020).

For optimal biological mite management, it is important to know if the tested compounds have adverse undesirable effects on the predatory mite. The toxicity effects of some saves compounds (Manure Tea (M.Tea), Manure neem Tea (M.N.Tea) and Boric acid) or some microorganisms (Spirulina platensis, A. azollae, Paenibacillus polymyxa, Pleurotus columbinus) comparing with recommended compound Abamectin were tested against the adult females of two-spotted spider mite, Tetranychus urticae Koch and adult females of its predatory mite, T. negevi Swirski and Amitai under laboratory conditions. The mortality percentages of T. urticae and toxicity of T. negevi Swirski and Amitai were recorded after 24, 48, and 72 h from treatment, which were increased gradually with increasing the exposure time of the tested compounds. Abamectin gave highly percent reduction and toxicity against the adult females of T.urticae and its predatory mite, T. negevi so came in the first category. M.Tea, M.N.Tea, and Boric acid came in the second category with moderate mortality percentages against T. urticae and toxicity of T. negevi. The microorganisms "Paenibacillus polymyxa, Anabaena azollae, Pleurotus columbinus, and Spirulina platensis" came in the last category. Generally, the adult female of T. negevi was more tolerant comparing with adult females of T. urticae.

Laboratory observations reported that no adult females of T. negevi deposited eggs due to the effectiveness of Abamectin and M.Tea. The gross fecundity (the number of eggs laid per female) of the adult females of T. negevi reached 31.8, 22.3, 12.5, 14.2, 7.8 and 5.1 eggs when treated with Anabaena azollae, Spirulina platensis, Boric acid, Pleurotus columbinus, Paenibacillus polymyxa and M.N.Tea, respectively. Comparing with control which the fecundity reached 58.2 eggs (Nour El-Deen et al., 2015).

4: Anabaena azollae bioremediation

Rapid growth in population and industrialization has resulted in disposing of various harmful compounds into the environment. The major sources of environmental contamination include industries, agrochemicals, mining activities, and waste disposals (Navarro and Vincenzo, 2019). Treating industrial effluent is very important as it may contain heavy metals, for instance, arsenic, cadmium, mercury, chromium, cobalt, nickel, zinc, lead, and copper, which are major pollutants of freshwater reservoirs Due to their non-biodegradable, poisonous and persistent nature (Arezoo et al., 2017). These contaminants affect the human health and surroundings (Florence et al., 2015).

Biological treatment has given preference over chemical treatment because the chemical materials only react with a small number of waste materials and heavy metals, and large portions of waste material remain unaffected.

However, chemical materials are very costly and produce a large quantity of chemical sludge. Thus, biological methods are appropriate to treat wastewater by producing dense biomass produced from organic matter, which is easily removed by sedimentation. Microbes also feed on dissolved organic matter resulting in small sludge production as compared to the chemical treatment (Samer, 2015).

Olive oil extraction is a process that is conducted by mechanical procedures in olive mills. During this process, large amounts of liquid effluents and solid residues are produced, with a high organic load, the nature of which depends on the technology of the extraction process and the system employed (Adnan and Ghaida, 2020).

Seven strains of algal species including Anabaena azollae were tested for degradation of phenolic compounds, a decrease of COD, decolorization of olive mill wastewater (OMWW), and biomass produced. In addition to recording the change in pH, E.C, Carbohydrate, Indole acetic acid, and gibberellins.

Degradation of phenolic compounds in 20 and 10% olive mill wastewater (OMWW) treated by Anabaena azollae was 19.02, 28.37% respectively after 30 days and reduction of COD in 20 and 10% (OMWW) treated by Anabaena azollae was 25.0, 30.54% respectively after 30 days decolorization of (OMWW) of 20 and 10% concentrations treated with Anabaena azollae was 9.9 and 21.5% after 30 days increased the carbohydrate content from o.56 g/L to 1.11 g/L by Anabaena azollae after 10 days of incubation but after 20 days, the value of carbohydrates began to decrease reached to 0.99 after 30 days in the concentration of 20% (OMWW). While in the concentration of 10% decrease total carbohydrate from 1.16 g/L to 0.51 g/L after 10 days of incubation by Anabaena azollae and decrease to 0.44 g/L after 30 days of incubation (Rokia, 2017).

5: Conclusion

In conclusion, this review indicated the morphological characteristics of Anabaena azollae isolated from Azolla pinnata and it can be free cultured in BG11 medium, as well as, it can be used, as a bioagent suppressor for the pathogenic fungal members’ Fusarium oxysporum and Alternaria alternate. The results also showed that the extract of Anabaena azollae was the best. Played an important role in increased yielding potentials and disease control in pelargonium plantations.

It could be recommended that application of Anabaena azollae as bio-control agents and plant growth-promoting substances to increase plant nutrients availability and has a nematicidal effect to control root-knot nematode. And Its toxicity effects on the two-spotted spider mite, T. urticae Koch, and its predatory mite, T. negevi Swirski and Amitai. Also the reduction of 25% of N recommended dose with bio-agent treatment was more superior to a recommended dose of N fertilizer in the yield of Pelargonium plant and in quality and quantity of oil production. The beneficial effect is to reduce the use of chemical fertilizers, as well as to improve macronutrients uptake (N, P, and K) in wheat crop, which is reflected on the yield and its components and enhanced microbiological activity, and produce various biologically active substances like growth-promoting substances as Indol Acetic Acid (IAA), Gibberellic acid (GA), (Nitrogenase, dehydrogenase) enzymes and carbohydrate excretion which help soil aggregation and again may result in soil fertility for sustainable crop production. Also, it recommended that using treatments (Anabaena azollae with KNO3) and (Anabaena azollae with tryptophan), each separately; can improve the yield of Maize three times more than control, while treatment (Anabaena azollae with NaCl) could improve the yield of Maize two times more than control. And the possibility of the transformation of the components of the olive mill wastewater from high toxicity components to less toxic taking advantage of the wastewater in fertilization and plant irrigation for the containing of elements and nutrients to the plant.

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