Arbuscular mycorrhizal fungi (AMF) establish symbiotic associations with most terrestrial plants. These soil microorganisms enhance the plant’s nutrient uptake by extending the root absorbing area. In return, the symbiont receives plant carbohydrates for the completion of its life cycle. AMF also helps plants to cope with biotic and abiotic stresses such as salinity, drought, extreme temperature, heavy metal, diseases, and pathogens. For abiotic stresses, the mechanisms of adaptation of AMF to these stresses are generally linked to increased hydromineral nutrition, ion selectivity, gene regulation, production of osmolytes, and the synthesis of phytohormones and antioxidants. Regarding the biotic stresses, AMF are involved in pathogen resistance including competition for colonization sites and improvement of the plant’s defense system. Furthermore, AMF have a positive impact on ecosystems. They improve the quality of soil aggregation, drive the structure of plant and bacteria communities, and enhance ecosystem stability. Thus, a plant colonized by AMF will use more of these adaptation mechanisms compared to a plant without mycorrhizae. In this review, we present the contribution of AMF on plant growth and performance in stressed environments.

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Roles of Arbuscular Mycorrhizal Fungi on Plant Growth and Performance: Importance in Biotic and Abiotic Stressed Regulation

Much research and development effort is directed towards advances in municipal wastewater treatment aiming at reducing the effluent content of micro-pollutants and pathogens. The objective is to further reduce the eco-toxicity, hormone effects and pathogenic effects of the effluent. Such further polishing of the effluent, however, involves an environmental trade-off: the reduction in eco-toxicity, hormone effects, etc. will happen at the expense of increased resource- and energy consumption. Obviously, at some point of further advances, there must be an ‘environmental break-even’. This trade-off was investigated using Life Cycle Assessment (LCA) methodology and based on a literature review of advanced treatment performance. The LCA evaluation comprised sand filtration, ozonation and MBRs and assessed the effect of extending existing tertiary treatment with these technologies on a variety of micro-pollutants being: heavy metals (Cd, Pb, Ni), endocrine disruptors (E2 and EE2), PAH, DEHP, and detergents (LAS & NPE). It was found, in some of the studied scenarios, that more environmental impact may be induced than removed by the advanced treatment. The study showed that for the 3 technologies, sand filtration has the best balance between prevented and induced impacts, and sand filtration proved to have a net environmental benefit under the assumptions used in the study. But the outcome of the study suggests that this is not always the case for ozonation and MBR.

Weighing environmental advantages and disadvantages of advanced wastewater treatment of micro-pollutants using environmental life cycle assessment

Bioemulsifiers (BE) and biosurfactants (BS) are considered as multifunctional biomolecules of 21st century because of their functional abilities and eco-friendly properties. They are produced by various microorganisms under versatile and extreme environmental conditions. They have tremendous applications in various industries such as petroleum, food, medicine, pharmaceutical, chemical, paper & pulp, textile, and cosmetics. Currently, they are also considered as "green molecules" because of their wide applications in bioremediation of soil. Their importance has been increasing day by day in the global market as they are the natural resources with high-aggregate value. Although, there are numerous reports on BE and BS production by different bacteria, Acinetobacter spp. acquired special attention among all. This is because it is the earliest member known for the production of bioemulsifier. Emulsan and Alasan are the best examples of the commercially used BE produced by Acinetobacter spp. These BE are mainly used in microbial enhanced oil recovery and biodegradation of toxic compounds. This review is focused on BE and BS produced by Acinetobacter spp., their characterization and applications in different fields. This is the first review on genus Acinetobacter which defines independently about different types of BE and BS produced by it. It will also address the need of exploration of these molecules from various sources and their applications for the benefit of mankind and sustainable environment.

Production, characterization, and applications of bioemulsifiers (BE) and biosurfactants (BS) produced by Acinetobacter spp.: A review.

In the current scenario of changing climatic conditions and the rising global population, there is an urgent need to explore novel, efficient, and economical natural products for the benefit of humankind. Biosurfactants are one of the latest explored microbial synthesized biomolecules that have been used in numerous fields, including agriculture, pharmaceuticals, cosmetics, food processing, and environment-cleaning industries, as a source of raw materials, for the lubrication, wetting, foaming, emulsions formulations, and as stabilizing dispersions. The amphiphilic nature of biosurfactants have shown to be a great advantage, distributing themselves into two immiscible surfaces by reducing the interfacial surface tension and increasing the solubility of hydrophobic compounds. Furthermore, their eco-friendly nature, low or even no toxic nature, durability at higher temperatures, and ability to withstand a wide range of pH fluctuations make microbial surfactants preferable compared to their chemical counterparts. Additionally, biosurfactants can obviate the oxidation flow by eliciting antioxidant properties, antimicrobial and anticancer activities, and drug delivery systems, further broadening their applicability in the food and pharmaceutical industries. Nowadays, biosurfactants have been broadly utilized to improve the soil quality by improving the concentration of trace elements and have either been mixed with pesticides or applied singly on the plant surfaces for plant disease management. In the present review, we summarize the latest research on microbial synthesized biosurfactant compounds, the limiting factors of biosurfactant production, their application in improving soil quality and plant disease management, and their use as antioxidant or antimicrobial compounds in the pharmaceutical industries.

Microbial Biosurfactant: A New Frontier for Sustainable Agriculture and Pharmaceutical Industries.

Improving bioremediation process of petroleum wastewater using biosurfactants producing Stenotrophomonas sp. S1VKR-26 and assessment of phytotoxicity.

In the present study, a combined treatment strategy involving the addition of rhamnolipid, rhamnolipid-producing bacteria (Shewanella sp. BS4) and a native soil microbial community for the remediation of hydrocarbon-contaminated soil under pilot-scale conditions was adopted. The isolate BS4 (rhl+), demonstrating the highest emulsification activity and surface tension reduction efficiency, was identified based on 16 S rDNA sequencing as Shewanella sp. strain. Growth conditions for rhamnolipid production were optimized based on Central Composite Design (CCD) as 2.9% crude oil, a 54 × 106 CFU g−1 inoculation load of soil, a temperature of 30.5 °C, and a pH of 6.7. In situ bioremediation experiments, conducted using hydrocarbon-contaminated soil treated with the combination of rhamnolipid and rhamnolipid-producing bacteria, showed that the inoculated Shewanella sp. BS4, along with the indigenous soil microbial community, supported the highest hydrocarbon-degrading bacterial population and soil respiration activity, and this treatment resulted in 75.8% hydrocarbon removal efficiency, which was higher compared to contaminated soil devoid of any treatment.

https://www.mdpi.com/2076-3417/9/18/3773/pdf

Simultaneous Application of Biosurfactant and Bioaugmentation with Rhamnolipid-Producing Shewanella for Enhanced Bioremediation of Oil-Polluted Soil

Soil extract calcium phosphate media for screening of phosphate-solubilizing bacteria

Acinetobacter sp. ACMS25, which showed inhibitory effect on Xanthomonas oryzae pv. oryzae XAV24 was tested for biosurfactant production. Preliminary characterization showed that this strain was positive for hemolytic and oil spreading activity and was able to reduce the surface tension of water from 71.9 to 37.6 mN/m. The biosurfactant produced by this strain was characterized as a ‘glycolipid-type’ based on thin layer chromatography (TLC), fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1HNMR) analysis. Inhibition studies showed that this biosurfactant was able to reduce the specific growth rate of X. oryzae by 38.4% and spermosphere population by 43.5%. Glycolipid biosurfactant treatment improved the germination and vigour index, when challenge inoculated with X. oryzae and this treatment was able to offer 76.9% disease protection efficiency against the rice blight disease in rice.

Isolation, characterization of glycolipid type biosurfactant from endophytic Acinetobacter sp. ACMS25 and evaluation of its biocontrol efficiency against Xanthomonas oryzae

Plants during the process of growth and development are subjected to numerous biotic and abiotic stresses. These stresses they encounter play a major role in effecting the productivity in agriculture. Interestingly, 70 % of plant species are harbored by AM fungi and this interaction plays a major role in influencing plant growth, nutrient absorption, and protection against pathogenic microbes. In addition to their interaction with plants, they are also known to interact with microorganisms in the rhizosphere. These types of interactions include interactions with phosphate-solubilizing bacteria (PSB), nitrogen-fixing bacteria, and biocontrol agents. Additional interactions are reported to happen in the fungal spores and hyphae. These interactions between AM fungi and microorganisms may play a major role in regulating plant growth, development, and resistance to different stresses they encounter. However, despite numerous studies, these interactions are only partially understood; this chapter tries to bring out the merits of tripartite interactions, i.e., interactions between AM fungi–Microorganisms–plants. In this chapter, we try to bring some important aspects on the AM fungi–Microorganisms based interactions.

Interaction of Rhizobacteria with Arbuscular Mycorrhizal Fungi (AMF) and Their Role in Stress Abetment in Agriculture

In the present study the antibacterial activity of spent green tea (SGT) was evaluated against Pectobacterium spp causing soft rot incidence Gas chromatography and mass spectroscopy (GC-MS) analysis reveal the presence of caffeine in the SGT extracts Time kill assay revealed that SGT was able to kill Pectobacterium spp at 18 h at 10 × MIC and at 24 h at 1 × MIC concentration SGT led to the significant decrease in pectin lyase (PL), polygalcturonase (PG) and pectin methyl esterase activity in carrots challenge inoculated with Pectobacterium spp SGT treated carrots recorded low degree of maceration, and relative electrolyte leakage (REL) values and also maintained high β carotene content, phenolic content and total antioxidant percentage Based on the results of this study it could be concluded that SGT was able to offer protection to carrot against soft rot causing Pectobacterium spp under post-harvest storage conditions

Allen John Henry

Papers

Simultaneous Application of Biosurfactant and Bioaugmentation with Rhamnolipid-Producing Shewanella for Enhanced Bioremediation of Oil-Polluted Soil

Soil extract calcium phosphate media for screening of phosphate-solubilizing bacteria

Isolation, characterization of glycolipid type biosurfactant from endophytic Acinetobacter sp. ACMS25 and evaluation of its biocontrol efficiency against Xanthomonas oryzae

Interaction of Rhizobacteria with Arbuscular Mycorrhizal Fungi (AMF) and Their Role in Stress Abetment in Agriculture

Treatment of carrots with spent green tea extract reduces the soft rot of Pectobacterium spp.