Surfactants are surface-active compounds capable of reducing surface and interfacial tension at the interfaces between liquids, solids and gases, thereby allowing them to mix or disperse readily as emulsions in water or other liquids. The enormous market demand for surfactants is currently met by numerous synthetic, mainly petroleum-based, chemical surfactants. These compounds are usually toxic to the environment and non-biodegradable. They may bio-accumulate and their production, processes and by-products can be environmentally hazardous. Tightening environmental regulations and increasing awareness for the need to protect the ecosystem have effectively resulted in an increasing interest in biosurfactants as possible alternatives to chemical surfactants. Biosurfactants are amphiphilic compounds of microbial origin with considerable potential in commercial applications within various industries. They have advantages over their chemical counterparts in biodegradability and effectiveness at extreme temperature or pH and in having lower toxicity. Biosurfactants are beginning to acquire a status as potential performance-effective molecules in various fields. At present biosurfactants are mainly used in studies on enhanced oil recovery and hydrocarbon bioremediation. The solubilization and emulsification of toxic chemicals by biosurfactants have also been reported. Biosurfactants also have potential applications in agriculture, cosmetics, pharmaceuticals, detergents, personal care products, food processing, textile manufacturing, laundry supplies, metal treatment and processing, pulp and paper processing and paint industries. Their uses and potential commercial applications in these fields are reviewed.

Potential commercial applications of microbial surfactants.

Algal–bacterial processes for the treatment of hazardous contaminants: A review

http://dzumenvis.nic.in/microbes and metals interaction/pdf/metal bioremediation through growing cells.pdf

Metal bioremediation through growing cells.

Application of bacteria as self-healing agent for the development of sustainable concrete

Urban, industrial and agricultural wastewaters contain up to three magnitudes higher concentrations of total nitrogen and phosphorous, compared with natural water bodies.1 Normal primary and secondary treatment of these wastewaters eliminates the easily settled materials and oxidizes the organic material present, but does not remove the nutrients which will cause eutrophication of the rivers or lakes into which these wastewaters may be discharged. Tertiary treatment of the effluent is therefore required, and both chemical and physical methods which are used are very expensive. Oswald2 estimates that the relative cost of tertiary treatment to remove PO 4 3− , NH 4 + and NO 3 − is about 4 times the cost of primary treatment. Higher orders of treatment, such as quaternary treatment required to remove refractory organics and organic and inorganic toxicants and quinary treatment to remove inorganic salts and heavy metals, are 8 to 16 times as expensive as primary treatment. Algae can be used as a biological alternative tertiary treatment and also for the removal of heavy metals and possibly other toxic substances.3,4 The possibility exists that the algae produced in these systems can be used as animal feed supplements,5,6 or be composted. The use of waste-grown algae may ultimately also have application in closed cycle life-support systems,7,8 or may be used in conjunction with power stations, not only to treat wastewaters, but also to act as a CO2 sink for the amelioration of the impact of greenhouse gases.9–13

Limits to Growth

Chlorella stigmatophora LB 993 was grown in artificial seawater under controlled conditions. The production of cell wall polysaccharides attached to the cells and dissolved in the growth medium was monitored during algal growth. Preliminary characterization of the dissolved polysaccharides of C. stigmatophora and other Chlorella species is presented. The capacity of dissolved polysaccharides of C. stigmatophora to bind toxic heavy metals was also studied and compared with that of polysaccharides produced by other marine Chlorella species. The differences in metal-complexing capacity observed for dissolved polysaccharides obtained from various Chlorella species is attributable to differences in the composition of the polysaccharides, notably the uronic acids content.

Chelating Properties of Extracellular Polysaccharides from Chlorella spp.

Fusarium is a complex genus of ascomycete fungi that consists of plant pathogens of agricultural relevance. Controlling Fusarium infection in crops that leads to substantial yield losses is challenging. These economic losses along with environmental and human health concerns over the usage of chemicals in attaining disease control are shifting focus toward the use of biocontrol agents for effective control of phytopathogenic Fusarium spp. In the present study, an analysis of the plant-growth promoting (PGP) and biocontrol attributes of four bacilli (Bacillus simplex 30N-5, B. simplex 11, B. simplex 237, and B. subtilis 30VD-1) has been conducted. The production of cellulase, xylanase, pectinase, and chitinase in functional assays was studied, followed by in silico gene analysis of the PGP-related and biocontrol-associated genes. Of all the bacilli included in this study, B. subtilis 30VD-1 (30VD-1) demonstrated the most effective antagonism against Fusarium spp. under in vitro conditions. Additionally, 100 μg/ml of the crude 1-butanol extract of 30VD-1's cell-free culture filtrate caused about 40% inhibition in radial growth of Fusarium spp. Pea seed bacterization with 30VD-1 led to considerable reduction in wilt severity in plants with about 35% increase in dry plant biomass over uninoculated plants growing in Fusarium-infested soil. Phase contrast microscopy demonstrated distortions and abnormal swellings in F. oxysporum hyphae on co-culturing with 30VD-1. The results suggest a multivariate mode of antagonism of 30VD-1 against phytopathogenic Fusarium spp., by producing chitinase, volatiles, and other antifungal molecules, the characterization of which is underway.

/pdf/antifungal-activity-of-bacillus-species-against-fusarium-and-2m5f58l4nv.pdf

Antifungal Activity of Bacillus Species Against Fusarium and Analysis of the Potential Mechanisms Used in Biocontrol.

Removal of chemical and microbiological contaminants from domestic greywater using a recycled vertical flow bioreactor (RVFB)

Heavy metals are released into waterways due to various anthropogenic activities. Their treatment is of special importance, since heavy metals are nonbiodegradable and persist in the environment posing a threat to the biota due to their toxic nature. In this chapter, the current methods that have been used to remove and/or detoxify heavy metals in aquatic environments are reviewed with specific emphasis on microalgae. A literature survey indicates microalgae have developed a wide spectrum of absorption (extracellular) and adsorption (intracellular) mechanisms for coping with heavy metal toxicity. The potential of prokaryotic and eukaryotic microalgae living cells or their dead cell biomass in comparison to currently available physicochemical processes aimed at removing toxic heavy metals is discussed. Also addressed are the mandatory requirements to bring this heavy metal removal potential to an applicable, commercial stage.

32 Absorption and Adsorption of Heavy Metals by Microalgae

 Premise of the study: Plant roots comprise more than 50% of the plant’s biomass. Part of that biomass includes the root microbiome, the assemblage of bacteria and fungi living in the 1–3 mm region adjacent to the external surface of the root, the rhizosphere. We hypothesized that the microorganisms living in the rhizosphere and in bulk soils of the harsh environment of the Negev Desert of Israel had potential for use as plant-growth-promoting bacteria (PGPB) to improve plant productivity in nutrient-poor, arid soils that are likely to become more common as the climate changes.  Methods: We used cultivation-dependent methods including trap experiments with legumes to finitrogen-fi xing rhizobia, specialized culture media to determine iron chelation via siderophores and phosphate-solubilizing and cellulase activities; cultivation-independent methods, namely 16S rDNA cloning and sequencing; and also community-level physiological profi ling to discover soil microbes associated with the Negev desert perennials Zygophyllum dumosum and Atriplex halimus during the years 2009–2010.  Key results: We identifi ed a number of PGPB, both epiphytes and endophytes, which fi x nitrogen, chelate iron, solubilize phosphate, and secrete cellulase, as well as many other bacteria and some fungi, thereby providing a profi le of the microbiomes that support the growth of two desert perennials.  Conclusion: We generated a snapshot of the microbial communities in the Negev Desert, giving us an insight in its natural state. This desert, like many arid environments, is vulnerable to exploitation for other purposes, including solar energy production and dry land farming.

/pdf/a-survey-of-the-microbial-community-in-the-rhizosphere-of-1kza2r207o.pdf

A survey of the microbial community in the rhizosphere of two dominant shrubs of the Negev Desert highlands, Zygophyllum dumosum (Zygophyllaceae) and Atriplex halimus (Amaranthaceae), using cultivation-dependent and cultivation-independent methods

Drora Kaplan

Papers

Chelating Properties of Extracellular Polysaccharides from Chlorella spp.

Antifungal Activity of Bacillus Species Against Fusarium and Analysis of the Potential Mechanisms Used in Biocontrol.

Removal of chemical and microbiological contaminants from domestic greywater using a recycled vertical flow bioreactor (RVFB)

32 Absorption and Adsorption of Heavy Metals by Microalgae

A survey of the microbial community in the rhizosphere of two dominant shrubs of the Negev Desert highlands, Zygophyllum dumosum (Zygophyllaceae) and Atriplex halimus (Amaranthaceae), using cultivation-dependent and cultivation-independent methods