School of Food and Agricultural Sciences
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Browsing School of Food and Agricultural Sciences by Subject "Food and Agricultural Science"
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Item Biodegradation of phenol by stenotrophomonas sp. And staphylococcus sp. Isolated from contaminated sites.(Applied Ecology and Enviromental Research, 2016) Nauman KhalidPhenol as environmental pollutant is detrimental to living organisms and needed to be eliminated for environmental safety. Among the various practiced approaches for its removal, bacterial utilization gets attraction due to its eco-friendly and cost effective nature. For this purpose, bacterial strains were isolated from bioremediation site and industrial waste through enrichment in phenol (250 mg L -1 ) for 3 days at 28oC. After enrichment, morphologically distinct colonies were purified on phenol (200 mg L-1 ) agar plates and the strains were identified through 16S rRNA gene sequence. Total of eight strains were identified, among them two strains, NCCP-310 and NCCP-405 had the best potential of phenol degradation which were identified as the members of the genera Stenotrophomonas and Staphylococcus. NCCP-310 and NCCP- 405 showed 98.85 and 98.9% sequence identity with Stenotrophomonas maltophilia and Staphylococcus equorum subsp. equorum, respectively. Both strains have ability to tolerate 1000 mg L-1 phenol. The isolated strains degraded 750 mg L-1 of phenol at pH 7 and 28+2oC. NCCP-310 and NCCP-405 showed degradation of such amount in 65 and 85 h with the average rate of 15.65 and 11.64 mg L-1 h -1 . Our work suggests that these strains are efficient in phenol removal and could be used for bioremediation.Item Controlled assembly of silver nano-fluid in heliotropium crispum extract: a potent anti-biofilm and bactericidal formulation.(applied surface science, Elsevier, 2016) Nauman KhalidThe study describes the optimized method for silver nanoparticle (AgNPs) synthesis using Heliotropium crispum (HC) plant extract. Optimization of physicochemical parameters resulted in stable and rapidly assembled AgNPs. FTIR results suggest presence of plant phytochemicals that helped in the reduction, stabilization and capping of AgNPs. The assembled Ag nano-composites displayed the peak surface plasmon resonance (SPR) around 428 nm. The presence of uniquely assembled Ag-biomolecule composites, cap and stabilize nanoparticles in aqueous plant suspension. Spherical, uniform-shaped AgNPs with low poly-dispersion and average particle size of 42 nm and was determined through dynamic light scattering (DLS) and scanning election microscopy (SEM) which present robust interaction with microbes. The study also evaluates the antimicrobial and anti-biofilm properties of biologically synthesized AgNPs on clinical isolates of MRSA, Pseudomonas aeruginosa and Acinetobacter baumannii. Minimum inhibitory concentration (0.5 mg mL−1) of nanoparticles that presented bactericidal effect was made through inhibition assays on bacterial strains. The concentration which presented potent bactericidal response was then evaluated through growth inhibition in liquid medium for anti-biofilm studies at 2.0 mg mL−1. HC-Ag nanoparticles mediated anti-biofilm effects on Pseudomonas aeruginosa was revealed through SEM. Complete breakdown of biofilm’s extracellular polymeric substances resulted after incubation with AgNPs. Peptidoglycan cell wall destruction was also revealed on planktonic bacterial images after 24 h of incubation.Item Flowering and fruiting responses of strawberry to growth hormone and chilling grown under tunnel conditions.(Pakistan Journal of Agricultural Sciences., 2016) Nauman KhalidStrawberry (Fragaria ananasa) is a berry fruit belonging to the family Rosaceae and requires certain amount of cold temperature to initiate flowering. Present study was conducted with the objective to study flowering and fruiting responses of strawberry to growth hormone and chilling under tunnel conditions. The study comprised of six different treatments as; control, GA3 (gibberellic acid) 200 ppm, GA3 400 ppm, chilling at 4°C, chilling at 4°C + GA3 200 ppm and chilling at 4°C + GA3 400 ppm. Treatments were applied at vegetative stage before flowering. It was inferred from the study that strawberry plants responded much better to application of GA3 at 400 ppm for their growth, flower stimulation, their number, quality features while chilling at 4°C proved better for maximum fruit production and better quality under tunnel condition.Item Formulation and characterization of esterified xylo-oligosaccharides-stabilized oil-in-water emulsions using microchannel emulsification.(Colloids and Surfaces B-Biointerfaces, Elsevier, 2016) Nauman KhalidAseries of amphiphilically esterified xylo-oligosaccharides (xylo esters) with differentfatty acids residues – decanoic acid (C-10), lauric acid (C-12) and palmitic acid (C-16) – were enzymatically modified at 60 ◦C for 4 h. These xylo esters were used as emulsifiers to formulate oil-in-water (O/W) emulsions by microchannel emulsification (MCE). Grooved and straight-through MCE was used to investigate the droplet generation and/or emulsion stability. Xylo ester-stabilized oil droplets were generated smoothly from microchannels arranged linearly or two dimensionally, while xylo ester-stabilized emulsions were less monodispersed owing to low surface activity of the xylo esters. The combined use of xylo esters (2.5% (w/w)) and Tween series (0.1% (w/w)) in the continuous phase can improve the monodispersity of the resultant oil. Successful droplet generation was achieved with the straight-through MCE using 2.5% (w/w) xylo laurate and 0.1% (w/w) Tween 20. The optimized combination of xylo laurate and Tween 20 inhibited coalescence and oiling off more efficiently than the droplets solely stabilized by Tween 20 during 30 days of storage.Item Formulation and stability assessment of ergocalciferol loaded oil-in-water nanoemulsions: insights of emulsifiers effect on stabilization mechanism.(Food Research International, Elvsevier, 2016) Nauman KhalidIn the study, we investigated the effect of emulsifiers with different stabilizing mechanisms on the formulation and stability of ergocalciferol loaded oil-in-water (O/W) emulsions. O/W emulsion stabilized by modified lecithin (ML; electrostatic stabilization), sodium caseinate (SC; electrosteric stabilization) or decaglycerol monooleate (MO-7S; steric stabilization) were formulated using high-pressure homogenization. The Sauter mean diameter (d3,2) of emulsions produced by ML, SC and MO-7S were 126 ± 1, 127 ± 4 and 138 ± 3 nm, respectively. The stability of resulting emulsions was evaluated when they exposed to different environmental stresses and during 30 days of storage at 25 and 55 °C. Results showed that the emulsions prepared by MO-7S or ML were stable against a wide range of pH (2–8), while SC-stabilized emulsions showed instability with extensive droplet aggregation at pH 4 or and 5. Only ML-stabilized emulsions showed droplet growth due to coalescence when treated at high NaCl concentration (300–500 mM). In the absence of glucose, SC-stabilized O/W emulsions showed better freeze-thaw stability, in comparison to those formed with ML or MO-7S emulsifiers. The emulsion produced by ML was found to be stable to droplet aggregation at heating temperatures (80–120 °C) for 1 h. All the O/W emulsions stored at 25 °C showed good physical and chemical stability. However, the chemical stability of ergocalciferol in emulsion system decreased in order of ML > MO-7S ≫ SC during storage at 55 °C for a period of 30 days. These findings provide valuable information for the development of nanoemulsion-based delivery system applied in food and beverage products.Item Microchannel emulsification study on formulation and stability characterization of monodisperse oil-in-water emulsions encapsulating quercetin.(Food Chemistry, Elsevier, 2016) Nauman KhalidThe study used microchannel emulsification (MCE) to encapsulate quercetin in food grade oil-in-water (O/W) emulsions. A silicon microchannel plate (Model WMS 1-2) comprised of 10,300 discrete 10 × 104 μm microslots was connected to a circular microhole with an inner diameter of 10 μm. 1% (w/w) Tween 20 was used as optimized emulsifier in Milli-Q water, while 0.4 mg ml−1 quercetin in different oils served as a dispersed phase. The MCE was carried by injecting the dispersed phase at 2 ml h−1. Successful emulsification was conducted below the critical dispersed phase flux, with a Sauter mean diameter of 29 μm and relative span factor below 0.25. The O/W emulsions remained stable in terms of droplet coalescence at 4 and 25 °C for 30 days. The encapsulation efficiency of quercetin in the O/W emulsions was 80% at 4 °C and 70% at 25 °C during the evaluated storage period.