Consolidated bioprocessing for production of polyhydroxyalkanotes from red algae Gelidium amansii.

Noncompetitive carbon sources such as algae are unconventional and promising raw material for sustainable biofuel production. The capability of one marine bacterium, Saccharophagus degradans 2-40 to degrade red seaweed Gelidium amansii for production of polyhydroxyalkanoates (PHA) was evaluated in this study. S. degradans can readily attach to algae, degrade algal carbohydrates, and utilize that material as main carbon source. Minimal media containing 8g/L G. amansii were used for the growth of S. degradans. The PHA content obtained was 17-27% of dry cell weight by pure culture of S. degradans and co-culture of S. degradans and Bacillus cereus, a contaminant found with S. degradans cultures. The PHA type was found to be poly(3-hydroxybutyrate) by gas chromatography and Fourier transform-infrared spectroscopy. This work demonstrates PHA production through consolidated bioprocessing of insoluble, untreated red algae by bacterial pure culture and co-culture.

Microorganisms as efficient biosystem for the synthesis of metal nanoparticles: current scenario and future possibilities.

Nanoparticles, the elementary structures of nanotechnology, are important materials for fundamental studies and variety of applications. The different sizes and shapes of these materials exhibit unique physical and chemical properties than their bulk materials. There is a great interest in obtaining well-dispersed, ultrafine, and uniform nanoparticles to delineate and utilize their distinct properties. Nanoparticle synthesis can be achieved through a wide range of materials utilizing a number of methods including physical, chemical, and biological processes with various precursors from liquids and solids. There is a growing need to prepare environmentally friendly nanoparticles that do not produce toxic wastes in their process synthesis protocol. This kind of synthesis can be achieved by green environment benign processes, which happen to be mostly of a biological nature. Microorganisms are one of the most attractive and simple sources for the synthesis of different types of nanoparticles. This review is an attempt to provide the up-to-date information on current status of nanoparticle synthesis by different types of microorganisms such as fungi, yeast, bacteria, cyanobacteria, actinomycete, and algae. The probable biosynthesis mechanism and conditions for size/shape control are described. Various applications of microbially synthesized nanoparticles are summarized. They include antibacterial, antifungal, anticancer, larvicidal, medical imaging, biosensor, and catalytic applications. Finally, limitations and future prospects for specific research are discussed.

Mosquito larvicidal and pupaecidal potential of prodigiosin from Serratia marcescens and understanding its mechanism of action.

Mosquitoes spread lethal diseases like malaria and dengue fever to humans. Considering mosquito vector control as one of the best alternatives to reduce new infections, here we have analyzed the effect of purified pigment prodigiosin extracted from Serratia marcescens (NMCC 75) against larval and pupal stages of Aedes aegypti and Anopheles stephensi mosquitoes. Mosquito larvicidal activities of purified prodigiosin revealed LC50 values of 14 ± 1.2, 15.6 ± 1.48, 18 ± 1.3, 21 ± 0.87 µg/ml against early IInd, IIIrd, IVth instar and pupal stages of Ae. aegypti, respectively. LC50 values for An. stephensi were found to be 19.7 ± 1.12, 24.7 ± 1.47, 26.6 ± 1.67, 32.2 ± 1.79 µg/ml against early IInd, IIIrd, IVth instar and pupae of An. stephensi, respectively. Further investigations toward understanding modes of action revealed variations in the activities of esterases, acetylcholine esterases, phosphatases, proteases and total proteins in the fourth instar larvae of Ae. aegypti indicating intrinsic difference in biochemical features due to prodigiosin treatment. Although there was no inhibition of enzymes like catalase and oxidase but may have profound inhibitory effect on carbonic anhydrase or H(+)-V-ATPase which is indicated by change in the pH of midgut and caeca of mosquito larvae. This reduced pH may be possibly due to the proton pump inhibitory activity of prodigiosin. Pure prodigiosin can prove to be an important molecule for mosquito control at larval and pupal stages of Ae. aegypti and An. stephensi. This is the first report on the mosquito pupaecidal activity of prodigiosin and its possible mechanism of action.

A rapid, sensitive, simple plate assay for detection of microbial alginate lyase activity.

Screening of microorganisms capable of producing alginate lyase enzyme is commonly carried out by investigating their abilities to grow on alginate-containing solid media plates and occurrence of a clearance zone after flooding the plates with agents such as 10% (w/v) cetyl pyridinium chloride (CPC), which can form complexes with alginate. Although the CPC method is good, advantageous, and routinely used, the agar in the media interferes with the action of CPC, which makes judgment about clearance zones very difficult. In addition, this method takes a minimum of 30 min to obtain the zone of hydrolysis after flooding and the hydrolyzed area is not sharply discernible. An improved plate assay is reported herein for the detection of extracellular alginate lyase production by microorganisms. In this method, alginate-containing agar plates are flooded with Gram's iodine instead of CPC. Gram's iodine forms a bluish black complex with alginate but not with hydrolyzed alginate, giving sharp, distinct zones around the alginate lyase producing microbial colonies within 2-3 min. Gram's iodine method was found to be more effective than the CPC method in terms of visualization and measurement of zone size. The alginate-lyase-activity area indicated using the Gram's iodine method was found to be larger than that indicated by the CPC method. Both methods (CPC and Gram's iodine) showed the largest alginate lyase activity area for Saccharophagus degradans (ATCC 43961) followed by Microbulbifer mangrovi (KCTC 23483), Bacillus cereus (KF801505) and Paracoccus sp. LL1 (KP288668) grown on minimal sea salt medium. The rate of growth and metabolite production in alginate-containing minimal sea salt liquid medium, followed trends similar to that of the zone activity areas for the four bacteria under study. These results suggested that the assay developed in this study of Gram's iodine could be useful to predict the potential of microorganisms to produce alginate lyase. The method also worked well for screening and identification of alginate lyase producers and non-producers from environmental samples on common laboratory media. They did this by clearly showing the presence or absence of clearance zones around the microbial colonies grown. This new method is rapid, efficient, and could easily be performed for screening a large number of microbial cultures. This is the first report on the use of Gram's iodine for the detection of alginate lyase production by microorganisms using plate assay.

Degradation of corn stover by fungal cellulase cocktail for production of polyhydroxyalkanoates by moderate halophile Paracoccus sp. LL1.

Bioprocessing of lignocellulose as a renewable resource for fuels, chemicals or value added products is a necessity to fulfil demands of petroleum products. This study aims to convert corn stover to polyhydroxyalkanoates (PHA). Corn stover was hydrolyzed to crude sugars by an on-site prepared cellulase cocktail from co-culture of Trichoderma reesei and Aspergillus niger. The potent PHA producer, Paracoccus sp. LL1, was isolated from Lonar Lake, India and could accumulate PHA up to 72.4% of its dry cell weight. PHA production reached 9.71 g/L from corn stover hydrolysate containing 40 g/L sugar mixture. The PHA synthase gene (phaC) sequence of the isolate showed 79% identity with the phaC gene of Paracoccus seriniphilus (E71) strain from the NCBI database. The nature/type of PHA was found to be poly(3-hydroxybutyrate) by Fourier transform infrared spectroscopy.

Biological synthesis of manganese dioxide nanoparticles by Kalopanax pictus plant extract.

Manganese dioxide (MnO2) nanoparticles were synthesised by the reduction of potassium permanganate (KMnO4) using Kalopanax pictus leaf extract at room temperature. A transparent dark-brown colour appeared after the addition of K. pictus leaf extract to the solution of permanganate. The time course of the reduction of KMnO4and synthesis of MnO2 nanoparticles was monitored by means of UV-Vis spectra. The reduction of KMnO4occurred after addition of plant extract with disappearance of KMnO4specific peaks and emergence of peak specific for MnO2nanoparticles. MnO2nanoparticles showed absorption maxima at 404 nm. The electron dispersive X-ray spectroscopy analyses confirmed the presence of Mn and O in the sample. X-ray photoelectron spectroscopy revealed characteristic binding energies for MnO2nanoparticles. Transmission electron microscopy micrographs revealed presence of uniformly dispersed spherical shaped particles with average size of 19.2 nm. The selected area electron diffraction patterns revealed the crystalline nature of MnO2nanoparticles. Fourier transform-infrared spectroscopy spectra of pure MnO2show the occurrence of O-Mn-O vibrational mode at around 518 cm⁻¹. The phyto-synthesised MnO2nanoparticles showed degradation ability of dyes (congo red and safranin O) similar to chemically synthesised MnO2nanoparticles. This study shows simple and eco-friendly synthesis of MnO2nanoparticles by plant extract and their utilisation for dye degradation for the first time.

Comparative study of MnO2 nanoparticle synthesis by marine bacterium Saccharophagus degradans and yeast Saccharomyces cerevisiae.

Microorganisms are one of the most attractive and simple sources for the synthesis of different types of metal nanoparticles. The synthesis of manganese dioxide nanoparticles (MnO2 NPs) by microorganisms from reducing potassium permanganate was investigated for the first time in the present study. The microbial supernatants of the bacterium Saccharophagus degradans ATCC 43961 (Sde 2-40) and of the yeast Saccharomyces cerevisiae showed positive reactions to the synthesis of MnO2 NPs by displaying a change of color in the permanganate solution from purple to yellow. KMnO4-specific peaks also disappeared and MnO2-specific peaks emerged at an absorption maximum of 365 nm in UV-visible spectrophotometry. The washed Sde 2-40 cells did not show any ability to synthesize MnO2 NPs. The medium and medium constituents of Sde 2-40 showed similar positive reactions as supernatants, which indicate the role of the Sde 2-40 medium constituents in the synthesis of MnO2 NPs. This suggests that microorganisms without nanoparticle synthesis ability can be misreported for their abilities to synthesize nanoparticles. S. cerevisiae washed cells showed an ability to synthesize MnO2 NPs. The strategies of keeping yeast cells in tea bags and dialysis membranes showed positive tests for the synthesis of MnO2 NPs. A Fourier transform-infrared spectroscopy study suggested roles for the proteins, alcoholic compounds, and cell walls of S. cerevisiae cells in the synthesis of MnO2 NPs. Electron-dispersive X-ray spectroscopy analyses confirmed the presence of Mn and O in the sample. X-ray photoelectron spectroscopy revealed characteristic binding energies for MnO2 NPs. Transmission electron microscopy micrographs revealed the presence of uniformly dispersed hexagonal- and spherical-shaped particles with an average size of 34.4 nm. The synthesis approach using yeast is possible by a simple reaction at low temperature without any need for catalysts, templates, or expensive and precise equipment. Therefore, this study will be useful for the easy, cost-effective, reliable, and eco-friendly production of nanomaterials.

Innovative approach for urease inhibition by Ficus carica extract-fabricated silver nanoparticles: An in vitro study.

In the present study, a rapid, low-cost, and ecofriendly method of stable silver nanoparticles (AgNPs) synthesis using leaves extract of Ficus carica (F. carica), a plant with diverse metabolic consortium, is reported for the first time. An absorption peak at 422 nm in UV-Vis spectroscopy, a spherical shape with an average size of 21 nm in transmission electron microscopy, and crystalline nature in X-ray powder diffraction studies were observed for the synthesized AgNPs. Fourier transform infrared analysis indicated that proteins of F. carica might have a vital role in AgNP synthesis and stabilization. AgNPs were found to inhibit urease, a key enzyme responsible for the survival and pathogenesis of the bacterium, Helicobacter pylori. Inhibition of urease by AgNPs was monitored spectrophotometrically by the evaluation of ammonia release. The urease inhibition potential of AgNPs can be explored in the treatment of H. pylori by preparing novel combinations of standard drugs with AgNPs- or AgNPs-encapsulated drug molecules.

Biofunctionalized silver nanoparticles as a novel colorimetric probe for melamine detection in raw milk.

Nanoparticles have emerged as a promising analytical tool for monitoring food adulteration and safety. In the present study, silver nanoparticles (AgNPs) were synthesized using leaves' extract of Jatropha gossypifolia. AgNPs revealed a characteristic surface plasmon resonance (SPR) peak at 419 nm and have spherical and grain shape with size range between 18 and 30 nm. A selective and rapid method of melamine detection in raw milk was developed with the use of these biofunctionalized AgNPs. The color change, deviation in SPR spectra, and change in the absorption ratio (A500 /A419 ) of AgNPs occurred after an AgNPs-melamine interaction. The detection limit for melamine up to 2 µM (252 ppb) was attained with this method, which is quite lower than safety level recommendations of regulatory bodies demonstrating sensitivity of the method. Dynamicx light scattering and transmission electron microscopy analyses exhibited an increase in hydrodynamic diameter and size of AgNPs after melamine interaction. Melamine sensing by AgNPs was investigated by different physicochemical and thermal analyses.

A laboratory case study of efficient polyhydoxyalkonates production by Bacillus cereus, a contaminant in Saccharophagus degradans ATCC 43961 in minimal sea salt media.

A contaminating bacterium growing along with the stock culture of Saccharophagus degradans ATCC 43961 (Sde 2-40) on marine agar plate was isolated and investigated for its ability to produce polyhydoxyalkonates (PHA). Preliminary screening by Sudan black B and Nile blue A staining indicated positive characteristic of the isolate to produce PHA. The isolate was able to grow and produce PHA in minimal sea salt medium broth. PHA quantification studies with gas chromatographic analyses of the dry cells derived from culture broths revealed accumulation of PHA in bacterial cells. PHA production started after 20 h and increased with cell growth and attained maximum values of 61 % of dry cell weight at 70 h of cultivation. After 70 h, a slight decrease in the level of PHA content was observed. The nature/type of PHA was found to be poly(3-hydroxybutyraye) by Fourier transform-infrared spectroscopy. Microbiological and 16S rRNA gene sequencing analyses suggested that the PHA producing bacterial isolate belongs to Bacillus genera and shows 100 % nucleotide sequence similarity with Bacillus cereus species in GenBank. This study is a first report for ability of Bacillus species to grow in marine sea salt media and produce PHA. The media used for the polymer production was novel in the context of the genus Bacillus and the production of PHA was three-fold higher than Sde 2-40 using same growth medium. This study shows that the contaminant bacteria once properly investigated can be used for advantageous characteristic of metabolites production in place of original cultures.

Potential of Kalopanax septemlobus leaf extract in synthesis of silver nanoparticles for selective inhibition of specific bacterial strain in mixed culture.

Silver nanoparticles (AgNPs) were synthesised using Kalopanax septemlobus plant leaf extracts. UV-visible spectrophotometric, Fourier-transform infrared, electron dispersive X-ray spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses confirmed synthesis of AgNPs. TEM micrographs revealed presence of well-dispersed AgNPs predominantly of small size and different shapes with an average particle size of 30.8 nm. Antimicrobial susceptibility tests of AgNP treatments revealed variability in sensitivity of bacteria Bacillus cereus and Saccharophagus degradans under study. Minimum inhibitory concentration (MIC) values of the AgNPs for B. cereus and S. degradans were found to be 30 and 10 µg/mL, respectively. The mixed culture of B. cereus and S. degradans treated with AgNPs at 10 µg/mL showed increase in growth with time, suggesting survival of bacteria in liquid media. The plating of mixed culture before AgNP treatment showed presence of both bacteria, but 24-h-old mixed culture treated with AgNPs at the concentration of 10 µg/mL showed presence of B. cereus colonies. SEM micrographs revealed damage to S. degradans cells but no effect on B. cereus cells after AgNP treatment. Confocal microscopic observations of AgNP-treated mixed cultures by Nile blue A staining indicated intact polyhydroxyalkanoates producing flourescent cells of B. cereus but damage and deformities in S. degradans cells. This study suggests that AgNPs can selectively inhibit growth of S. degradans and retain B. cereus at MIC of S. degradans. This report is a case study for selective inhibition of one bacteria and growth of the other in a culture using plant-synthesized silver nanoparticles.

Mercury sensing and toxicity studies of novel latex fabricated silver nanoparticles.

Safe and eco-friendly alternatives to currently used hazardous chemico-physical methods of silver nanoparticles (AgNPs) synthesis are need of time. Rapid, low cost, selective detection of toxic metals in environmental sample is important to take safety action. Toxicity assessment of engineered AgNPs is essential to avoid its side effects on human and non-target organisms. In the present study, biologically active latex from Euphorbia heterophylla (Poinsettia) was utilized for synthesis of AgNPs. AgNPs was of spherical shape and narrow size range (20-50 nm). Occurrence of elemental silver and crystalline nature of AgNPs was analyzed. Role of latex metabolites in reduction and stabilization of AgNPs was analyzed by FT-IR, protein coagulation test and phytochemical analysis. Latex-synthesized AgNPs showed potential in selective and sensitive detection of toxic mercury ions (Hg(2+)) with limit of detection around 100 ppb. Addition of Hg(2+) showed marked deviation in color and surface plasmon resonance spectra of AgNPs. Toxicity studies on aquatic non-target species Daphnia magna showed that latex-synthesized AgNPs (20.66 ± 1.52% immobilization) were comparatively very less toxic than chemically synthesized AgNPs (51.66 ± 1.52% immobilization). Similarly, comparative toxicity study on human red blood cells showed lower hemolysis (4.46 ± 0.01%) by latex-synthesized AgNPs as compared to chemically synthesized AgNPs causing 6.14 ± 0.01% hemolysis.

Studies on production and biological potential of prodigiosin by Serratia marcescens.

Efficacy of Serratia marcescens for pigment production and biological activity was investigated. Natural substrates like sweet potato, mahua flower extract (Madhuca latifolia L.), and sesam at different concentrations were taken. As a carbon source microorganism favored potato powder was followed by sesam and mannitol, and as nitrogen source casein hydrolysate was followed by yeast and malt extract. The effect of inorganic salts on pigment production was also studied. At final optimized composition of suitable carbon, nitrogen source, and trace materials and at suitable physiological conditions, prodigiosin production was 4.8 g L(-1). The isolated pigment showed antimicrobial activity against different pathogenic bacteria and fungi. Extracted pigment was characterized by spectroscopy, Fourier transform infrared (FTIR), and thin layer chromatography (TLC) which confirm production of biological compound prodigiosin. This study suggests that use of sweet potato powder and casein can be a potential alternative bioresource for commercial production of pigment prodigiosin.

Plant extract: a promising biomatrix for ecofriendly, controlled synthesis of silver nanoparticles.

Uses of plants extracts are found to be more advantageous over chemical, physical and microbial (bacterial, fungal, algal) methods for silver nanoparticles (AgNPs) synthesis. In phytonanosynthesis, biochemical diversity of plant extract, non-pathogenicity, low cost and flexibility in reaction parameters are accounted for high rate of AgNPs production with different shape, size and applications. At the same time, care has to be taken to select suitable phytofactory for AgNPs synthesis based on certain parameters such as easy availability, large-scale nanosynthesis potential and non-toxic nature of plant extract. This review focuses on synthesis of AgNPs with particular emphasis on biological synthesis using plant extracts. Some points have been given on selection of plant extract for AgNPs synthesis and case studies on AgNPs synthesis using different plant extracts. Reaction parameters contributing to higher yield of nanoparticles are presented here. Synthesis mechanisms and overview of present and future applications of plant-extract-synthesized AgNPs are also discussed here. Limitations associated with use of AgNPs are summarised in the present review.

Transformation of aromatic dyes using green synthesized silver nanoparticles.

Nowadays, increasing use of nanoproducts in area of human and environmental applications raises concern about safety aspects of nanoparticles synthesized using traditional physicochemical methods. Silver nanoparticles (AgNPs) synthesis at ambient parameters using latex of medicinally important plant Jatropha gossypifolia (J. gossypifolia) is reported in the present study. Potential of AgNPs in degradation of methylene blue and eosin B was also evaluated. Rapid formation of stable AgNPs was analyzed by visual color change from colorless to yellow-red after addition of latex in AgNO3 solution and by characteristic surface plasmon resonance (SPR) peak at 430 nm in UV-Vis spectroscopy. FT-IR analysis, protein coagulation test showed capping of proteins, flavonoids, terpenoids and polyphenols of latex on surface of AgNPs. FE-SEM, HR-TEM analysis revealed spherical shape of AgNPs. Narrow size range of AgNPs (5-40 nm) observed in HR-TEM analysis. EDS analysis confirms the presence of elemental silver while XRD revealed crystalline nature of AgNPs. Zeta potential of -21.4 mV indicates high stability of AgNPs. Effects of different parameters (pH, temperature, incubation time) on nanosynthesis were studied in the present study. Dye reduction studies were performed using UV-Vis spectroscopy, TLC, FT-IR and HPLC analysis showing decreased absorbance maxima of both dyes with respect to time, change in R f values, changes in wave number, transmittance, and retention time of dyes after AgNPs addition. The rate constant for methylene blue and eosin B reduction by AgNPs was found to be 0.062 and 0.022 min(-1).

Catalytic and synergistic antibacterial potential of green synthesized silver nanoparticles: Their ecotoxicological evaluation on Poecillia reticulata.

In the present study, stable silver nanoparticles (AgNPs) were fabricated at a rapid rate from leaf extract of medicinally important plant Alstonia macrophylla. Biosynthesized AgNPs are of spherical shape and narrow size (70 nm), exhibiting a surface plasmon resonance peak at 435 nm, and a zeta potential of -30.8 mV and have a crystalline nature. A diverse biochemical consortium of protein, terpenoids, phenolics, and flavonoids in leaf extract of A. macrophylla was found to be responsible for AgNP synthesis as evidenced from qualitative-quantitative chemical analysis and Fourier transform infrared spectroscopy studies. Nitroaromatic compounds are anthropogenic pollutants with long-lasting environmental persistence and are needed to transform into less toxic derivatives. 4-Nitrophenol and p-nitroaniline were reduced to less hazardous and commercially useful 4-aminophenol and p-phenylenediamine by phytosynthesized AgNPs. Rate constants of 0.052 and 0.040 Min(-1) were calculated for 4-nitrophenol and p-nitroaniline reduction, respectively. Thin-layer chromatography also confirms the reduction of these nitroaromatic compounds. Combinational studies could be one of the strategies to overcome microbial resistance to antibiotics. In synergistic antibacterial assay, the highest increase in a fold area of 3.84 was reported against Staphylococcus aureus using a combination of AgNPs with penicillin. Biosynthesized AgNPs were found to be less toxic (LC50 = 9.13 ppm) than chemically synthesized AgNPs having a LC50 value of 2.86 ppm against nontarget fish Poecillia reticulata. Our green nanosynthesis method offers a faster rate of formation of stable AgNPs having antibacterial and catalytic potential with lower environmental toxicity.

Mosquito Larvicidal Potential of Gossypium hirsutum (Bt cotton) Leaves Extracts against Aedes aegypti and Anopheles stephensi larvae.

BACKGROUND: We aimed to extract the ingredients from leaves of Gossypium hirsutum (Bt cotton) using different solvents and evaluate for potential use to control different larval stages of mosquito species, Aedes aegypti and Anopheles stephensi. METHODS: Qualitative and quantitative estimation of ingredients from Go. hirsutum (Bt) plant extract was carried out and their inhibitory action against mosquito larvae was determined using mosquito larvicidal assay. RESULTS: LC50 values of water, ethanol, ethyl acetate and hexane extracts for Ae. aegypti were 211.73±21.49, 241.64±19.92, 358.07±32.43, 401.03±36.19 and 232.56±26.00, 298.54±21.78, 366.50±30.59, 387.19±31.82 for 4(th) instar of An. stephensi, respectively. The water extract displayed lowest LC50 value followed by ethanol, ethyl acetate and hexane. Owing to the comparatively better activity of water extract, its efficacy was further evaluated for mosquito larvicidal activity, which exhibited LC50 values of 133.95±12.79, 167.65±11.34 against 2(nd) and 3(rd) instars of Ae. aegypti and 145.48±11.76, 188.10±12.92 against 2(nd) and 3(rd) instars of An. stephensi, respectively. Crude protein from the water extract was precipitated using acetone and tested against 2(nd), 3(rd) and 4(th) instars of Ae. aegypti and An. stephensi. It revealed further decrease in LC50 values as 105.72±25.84, 138.23±23.18, 126.19±25.65, 134.04±04 and 137.88±17.59, 154.25±16.98 for 2(nd), 3(rd) and 4(th) instars of Ae. aegypti and An. stephensi, respectively. CONCLUSION: Leaves extracts of Go. hirsutum (Bt) is potential mosquito larvicide and can be used as a potent alternative to chemical insecticides in integrated pest management.

Alteration in Bacillus thuringiensis toxicity by curing gut flora: novel approach for mosquito resistance management.

Mosquitoes are known for acquiring resistance against insecticides in many ways, namely target side mutation, enzyme modification, sequestration, quick elimination, etc. But, the role of microflora present in abundance in the larval midgut is less explored with respect to their role in insecticide resistance. During the course of their development, mosquitoes are continuously exposed to microbes and have naturally acquired midgut microbial flora. This midgut flora can modulate the mosquito's susceptibility to Bacillus thuringiensis (Bt) infection by degrading toxic Bt protein forms through an unknown mechanism. In this study, we show that microbe-free aseptic mosquito larvae displayed an increased susceptibility to Bt toxicity compared to larvae harboring natural microbial flora. Fourth instar larvae of Anopheles stephensi were treated separately with penicillin, streptomycin, erythromycin (100 µg/ml), and mixtures of all three antibiotics and then analyzed for Bt toxicity. We have also examined the influence of the mosquito's midgut microbial flora under microaerophilic condition on the Bt protein degradation through plate, broth, TLC, and UV-vis spectrophotometric assay. A better understanding of the roles of microbiota in preventing Bt toxicity to mosquitoes could potentially lead to the development of new sustainable mosquito control strategies.

Enhanced production of bacterial cellulose by using Gluconacetobacter hansenii NCIM 2529 strain under shaking conditions.

Bacterial cellulose (BC), a biopolymer, due to its unique properties is valuable for production of vital products in food, textile, medicine, and agriculture. In the present study, the optimal fermentation conditions for enhanced BC production by Gluconacetobacter hansenii NCIM 2529 were investigated under shaking conditions. The investigation on media components and culture parameters revealed that 2 % (w/v) sucrose as carbon source, 0.5 % (w/v) potassium nitrate as nitrogen source, 0.4 % (w/v) disodium phosphate as phosphate source, 0.04 % (w/v) magnesium sulfate, and 0.8 % (w/v) calcium chloride as trace elements, pH5.0, temperature 25 °C, and agitation speed 170 rpm with 6 days of fermentation period are optimal for maximum BC production. Production of BC using optimized media components and culture parameters was 1.66 times higher (5.0 g/l) than initial non optimized media (3.0 g/l). Fourier transform infrared spectroscopy spectrum and comparison with the available literature suggests that the produced component by G. hansenii in the present study is pure bacterial cellulose. The specific action of cellulase out of the investigated hydrolytic enzymes (cellulase, amylase, and protease) further confirmed purity of the produced BC. These findings give insight into conditions necessary for enhanced production of bacterial cellulose, which can be used for a variety of applications.

Biosynthesis of silver nanoparticles using latex from few Euphorbian plants and their antimicrobial potential.

The synthesis of well-dispersed and ultrafine metal nanoparticles has great interest due to their distinctive physicochemical properties and biomedical applications. This study is the first report of one-step solvent-free synthesis of AgNPs using Euphorbiaceae plant latex. Among evaluated eight latex-producing plants, four (Jatropha curcas, Jatropha gossypifolia, Pedilanthus tithymaloides, and Euphorbia milii) showed high potential to produce physicochemically distinct, small-sized and bactericidal AgNPs. Phytochemical screening showed presence of rich amount of biochemicals in these plants. J. gossypifolia showed uniformly dispersed comparatively small-sized AgNPs. Dose-dependent growth inhibition of bacterial pathogens Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermis, and Micrococcus luteus was observed for J. gossypifolia latex-synthesized AgNPs with minimum inhibitory concentration values 30, 40, 70, 60, and 60 ppm, respectively, after 24 h. Possible mode of action of AgNPs against pathogens was confirmed by analyzing enzymes and cell leakage.