Search

Abstract Background Aquaponics are food production systems advocated for food security and health. Their sustainability from a nutritional and plant health perspective is, however, a significant challenge. Recirculated aquaculture systems (RAS) form a major part of aquaponic systems, but knowledge about their microbial potential to benefit plant growth and plant health is limited. The current study tested if the diversity and function of microbial communities in two commercial RAS were specific to the fish species used (Tilapia or Clarias) and sampling site (fish tanks and wastewaters), and whether they confer benefits to plants and have in vitro antagonistic potential towards plant pathogens. Results Microbial diversity and composition was found to be dependent on fish species and sample site. The Tilapia RAS hosted higher bacterial diversity than the Clarias RAS; but the later hosted higher fungal diversity. Both Tilapia and Clarias RAS hosted bacterial and fungal communities that promoted plant growth, inhibited plant pathogens and encouraged biodegradation. The production of extracellular enzymes, related to nutrient availability and pathogen control, by bacterial strains isolated from the Tilapia and Clarias systems, makes them a promising tool in aquaponics and in their system design. Conclusions This study explored the microbial diversity and potential of the commercial RAS with either Tilapia or Clarias as a tool to benefit the aquaponic system with respect to plant growth promotion and control of plant diseases.

Background: Aquaponics are food production systems advocated for food security and health. Their sustainability from a nutritional and plant health perspective is, however, a significant challenge. Recirculated aquaculture systems (RAS) form a major part of aquaponic systems, but knowledge about their microbial potential to benefit plant growth and plant health is limited. The current study tested if the diversity and function of microbial communities in two commercial RAS were specific to the fish species used (Tilapia or Clarias) and sampling site (fish tanks and wastewaters), and whether they confer benefits to plants and have in vitro antagonistic potential towards plant pathogens. Results: Microbial diversity and composition was found to be dependent on fish species and sample site. The Tilapia RAS hosted higher bacterial diversity than the Clarias RAS; but the later hosted higher fungal diversity. Both Tilapia and Clarias RAS hosted bacterial and fungal communities that promoted plant growth, inhibited plant pathogens and encouraged biodegradation. The production of extracellular enzymes, related to nutrient availability and pathogen control, by bacterial strains isolated from the Tilapia and Clarias systems, makes them a promising tool in aquaponics and in their system design. Conclusions: This study explored the microbial diversity and potential of the commercial RAS with either Tilapia or Clarias as a tool to benefit the aquaponic system with respect to plant growth promotion and control of plant diseases. [ABSTRACT FROM AUTHOR]

Biosurfactant with efficient emulsification properties could be produced by Pseudomonas flourescens using cassava flour wastewater (manipueira) as media. The ability of P. flourescens to produce biosurfactant could suggest potential use in industrial and environmental applications. Media containing a mixture of natural manipueira and nutrient broth with 48 h fermentation was the optimum condition for the biosurfactant production. Based on UV-Vis and FT-IR spectra, the biosurfactant was indicated as rhamnolipids containing hydroxyl, ester, carboxylic and aliphatic carbon chain functional groups. Biosurfactant exhibited critical micelle concentration (CMC) value of 715 mg/L and reduced the surface tension of the water from 80 mN/m to 59 mN/m. The biosurfactant was able to decrease the interfacial tension about 51-70% when benzyl chloride, palm oil and kerosene were used as water-immiscible compounds. The biosurfactant was able to form stable emulsion until 30 days when paraffin, soybean oil, lubricant oil and kerosene were used as water-immiscible compounds.

Brown spot of paddy is prevalent in all the rice growing countries of the world and most of the cultivars grown are susceptible to this pathogen. Though the disease is considered to be minor one, it is increasingly posing a serious emerging threat. A field experiment on management of brown spot of paddy was carried out in two consecutive Kharif seasons (2012,2013) on two aromatic rice varieties Pusa Sugandh-4 and Pusa Sugandh-5 in hot spot area for brown spot disease at IARI Regional Station Pusa (Bihar). Eleven different treatment combinations involving combination of fungicides and bioagent were used in this experiment. The approach of seed treatment, seedling dip and foliar spray alone and in combination was tried against brown spot of paddy. The disease data was recorded in three stages for disease rating using SES of IRRI. T8, Seed treatment with Carboxin 37.5% and Thiram 37.5% WS @2.5 gm kg-1 seed and Seedling dip in suspension of Pseudomonas flourescens @ 10gm/ litre followed by two sprays of Propiconazole 25% EC @0.1% at 45 days and 60 days after transplanting gave best result. Minimum disease severity and maximum yield was observed under this treatment combination. As far as only seed treatment is concerned a fungicidal combination of Carboxin 37.5% and Thiram 37.5% WS @2.5 gm kg-1 seed was found superior than other seed treated plots. An yield advantage of 13.6 q/ha in Pusa sugandh-4 and 22 q/ha in Pusa Sugandh-5 has been observed over control. The increased incidence of this disease in recent years and lack of information about suitable management strategies based on field observations are the key drivers in formulation of this experiment. [ABSTRACT FROM AUTHOR]

Many industrial processes are susceptible to biofouling. The thickness and structure of such biofilms are key factors in the design of effective cleaning strategies. A novel method based on fluid dynamic gauging has been developed for measuring the thickness and the shear stress needed for removal of the biofilms formed on cylindrical surfaces. The device operates with the test cylinder immersed in liquid: liquid is withdrawn or ejected from a nozzle located near the biofilm surface. There is no net change of liquid volume, making it ideal for sterile and aseptic operation and for studies using valuable liquids. Biofilm removal may also be tested by using appropriate hydrodynamic conditions. Calibration tests using ejection and suction flows in the laminar regime (Reynolds number around 100) indicated a measurement accuracy of ±19 μm and showed good agreement with computational fluid dynamics simulations. The device was commissioned in tests on Pseudomonas fluorescens biofilms formed on high density polyethylene (HDPE) and stainless steel (SS) cylinders of diameter 25 mm under conditions of mild shear stress (around 2 Pa in these tests). The biofilm thickness was not uniform to the eye and measurements made over the surface of the test cylinders confirmed this: layer thicknesses ranged from effectively 0–300 μm. The biofilms formed on HDPE were thicker than those formed on SS. [ABSTRACT FROM AUTHOR]