Solubilization of inorganic phosphates by fungi isolated from agriculture soil

Most agricultural soils contain large reserves of phosphorus (P), a considerable part of which accumulates as a consequence of regular applications of P fertilizers. However, a greater part of soilphosphorus, approximately 95–99% is present in the form of insoluble phosphates and hence cannot be utilized by the plants. In the present study fungal strains isolated from agriculture soil, havingpotential to solubilize insoluble inorganic phosphates were characterized. Two fungal isolates were tested for their tricalcium phosphate (TCP) solubilization efficiency in both solid and liquid medium.Isolates were identified as Aspergillus sp. and Penicillium sp. depending upon their colony morphology and microscopic studies. Phosphate solubilization was related to pH decrease caused by growth of fungus in medium containing glucose as carbon source. Aspergillus sp. solubilized 480 g/ml of phosphorus, while Penicillium sp. solubilized 275 g/ml of phosphorus from 0.5% tricalcium phosphate after 4 and 3 days of growth respectively. Both the strains show diverse levels of phosphate solubilization activity in liquid broth culture in presence of various carbon and nitrogen sources. Drop in pH during growth was more prominent in absence of TCP in the liquid medium. This indicates that absence of soluble P in media induces the acid production. Phosphate solubilizing microorganisms convert insoluble phosphates into soluble forms generally through the process of acidification, chelation and exchange reactions. Thus such microorganisms may not only compensate for higher cost of manufacturing fertilizers in industry but also mobilizes the fertilizers added to soil

Dissolution of heavy metals from electrostatic precipitator (ESP) dust of a coal based sponge iron plant by fungal leaching

Coal based sponge iron industries in India generate considerable quantity of solid waste, 40% of which is flue dust produced from the electrostatic precipitator (ESP) connected to rotary kiln. This paper reports the dissolution of Zn, Cu, Pb, Mn and Fe from the ESP dust using three fungal species, Aspergillus niger, Aspergillus fumigatus and Aspergillus flavus at 5 and 10% pulp densities over a period of 28 days. Highest metal leaching was achieved with A. niger followed by A. flavus. The least metal leaching was achieved with A. fumigatus. The pH of the medium declined consistently over the incubation period. Maximum leaching for Zn, Cu, Pb, Mn and Fe were 81, 76, 74, 72 and 52% respectively.Key words: Fungal leaching, sponge iron, electrostatic precipitator (ESP) dust, metal dissolution

Potential therapeutic applications of microbial surface-activecompounds

Numerous investigations of microbial surface-active compounds or biosurfactants over the past two decades have led to the discovery of many interesting physicochemical and biological properties including antimicrobial, anti-biofilm and therapeutic among many other pharmaceutical and medical applications. Microbial control and inhibition strategies involving the use of antibiotics are becoming continually challenged due to the emergence of resistant strains mostly embedded within biofilm formations that are difficult to eradicate. Different aspects of antimicrobial and anti-biofilm control are becoming issues of increasing importance in clinical, hygiene, therapeutic and other applications. Biosurfactants research has resulted in increasing interest into their ability to inhibit microbial activity and disperse microbial biofilms in addition to being mostly nontoxic and stable at extremes conditions. Some biosurfactants are now in use in clinical, food and environmental fields, whilst others remain under investigation and development. The dispersal properties of biosurfactants have been shown to rival that of conventional inhibitory agents against bacterial, fungal and yeast biofilms as well as viral membrane structures. This presents them as potential candidates for future uses in new generations of antimicrobial agents or as adjuvants to other antibiotics and use as preservatives for microbial suppression and eradication strategies

Bioleaching of low-grade copper ore using indigenous microorganisms

588-592Investigations have been carried out on the iron oxidation rate of Acidithiobacillus ferrooxidans, the bacteria used in bioleaching process. It was observed that the regeneration time of the bacteria is reduced from 168 to 16 h by repeated sub-culturing, which in turn gave rise to higher iron oxidation rate thus increasing the kinetics of the process. This active strain was utilized for bioleaching of low-grade copper ore by varying two parameters namely, pH and pulp density. It was observed that around 30% of copper could be leached at an initial pH and pulp density of 2 and 20% (m/v) respectively