1‑Ethyl-3-methylimidazolium Diethylphosphate Based Extraction of Bioplastic “Polyhydroxyalkanoates” from Bacteria: Green and Sustainable Approach

An eco-friendly approach toward downstream processing of bacterial biomass for extraction of an intracellular potential bioplastic material polyhydroxyalkanoates replacing chlorinated organic solvents is reported using ionic liquid (IL) 1-ethyl-3-methylimidazolium diethylphosphate ([C₂mim]­[(C₂)₂OPO₃]) as an extractant. [C₂mim]­[(C₂)₂OPO₃] dissolved wet bacterial biomass of <i>Halomonas hydrothermalis</i> (MTCC accession no. 5445; NCBI Genbank accession no. GU938192), with ease on account of its high hydrogen bond basicity (β = 1.07). The recovered polymer with a yield of 60% ± 2% was characterized using ¹H NMR, FT-IR, and TGA techniques and confirmed to be polyhydroxybutyrate (PHB). The properties of PHB were found to be in close proximity to the standard PHB. The [C₂mim]­[(C₂)₂OPO₃] was recovered with 60% yield and retention of chemical structure after two consecutive dissolution cycles, which minimized the cost of developed process. The recovered PHB was used to prepare a bioplastic film, which showed good thermal and mechanical stability, as characterized by FT-IR, DSC, TGA, and DMA techniques

Biofabricated Silver Nanoparticles Act as a Strong Fungicide against <i>Bipolaris sorokiniana</i> Causing Spot Blotch Disease in Wheat

<div><p>The present study is focused on the extracellular synthesis of silver nanoparticles (AgNPs) using culture supernatant of an agriculturally important bacterium, <i>Serratia</i> sp. BHU-S4 and demonstrates its effective application for the management of spot blotch disease in wheat. The biosynthesis of AgNPs by <i>Serratia</i> sp. BHU-S4 (denoted as bsAgNPs) was monitored by UV–visible spectrum that showed the surface plasmon resonance (SPR) peak at 410 nm, an important characteristic of AgNPs. Furthermore, the structural, morphological, elemental, functional and thermal characterization of bsAgNPs was carried out using the X-ray diffraction (XRD), electron and atomic microscopies, energy dispersive X-ray (EDAX) spectrometer, FTIR spectroscopy and thermogravimetric analyzer (TGA), respectively. The bsAgNPs were spherical in shape with size range of ∼10 to 20 nm. The XRD and EDAX analysis confirmed successful biosynthesis and crystalline nature of AgNPs. The bsAgNPs exhibited strong antifungal activity against <i>Bipolaris sorokiniana</i>, the spot blotch pathogen of wheat. Interestingly, 2, 4 and 10 µg/ml concentrations of bsAgNPs accounted for complete inhibition of conidial germination, whereas in the absence of bsAgNPs, conidial germination was 100%. A detached leaf bioassay revealed prominent conidial germination on wheat leaves infected with <i>B. sorokiniana</i> conidial suspension alone, while the germination of conidia was totally inhibited when the leaves were treated with bsAgNPs. The results were further authenticated under green house conditions, where application of bsAgNPs significantly reduced <i>B. sorokiniana</i> infection in wheat plants. Histochemical staining revealed a significant role of bsAgNPs treatment in inducing lignin deposition in vascular bundles. In summary, our findings represent the efficient application of bsAgNPs in plant disease management, indicating the exciting possibilities of nanofungicide employing agriculturally important bacteria.</p></div

EDAX spectrum (A), FTIR spectrum (B) and TGA graph (C) of bsAgNPs by <i>Serratia</i> sp. BHU-S4.

<p>EDAX spectrum (A), FTIR spectrum (B) and TGA graph (C) of bsAgNPs by <i>Serratia</i> sp. BHU-S4.</p

Effect of different treatments on lignification in wheat stem by histochemical staining.

<p>Control (C), <i>Bipolaris</i> control (BC); <i>Bipolaris</i> + bsAgNPs by <i>Serratia</i> sp. BHU-S4 (B4).</p

Efficacy of bsAgNPs in controlling pathogen attack under greenhouse conditions (A).

<p>Arrow indicates lesion developed as a result of <i>B. sorokiniana</i> infection. (B) Symptoms developed on leaves of <i>B. sorokiniana</i> infected plants (<i>Bipolaris</i> control). (C) SDS-PAGE profile of wheat leaf protein in different treatments. (D) Effect of different treatments on plant parameters are shown by bar graph. Control (C), <i>Bipolaris</i> control (BC); <i>Bipolaris</i> + bsAgNPs by <i>Serratia</i> sp. BHU-S4 (B4). Root length, shoot length (cm); root dry wt., shoot dry wt. (mg).</p

Biosynthesis of AgNPs by supernatant of <i>Serratia</i> sp. BHU-S4 (A).

<p>Culture supernatant without 1₃ showed no color change (C) and after adding 1 mM AgNO₃ showed visual color change from yellow to dark brown. (B) UV-visible absorption spectrum of bsAgNPs and 1 mM aqueous solution of AgNO₃.</p

Inhibitory effects of bsAgNPs by <i>Serratia</i> sp. BHU-S4 on conidial germination of <i>B. sorokiniana</i> after 24 h as determined by cavity slide experiment.

<p>Conidial germination in control set (without bsAgNPs) was prominent as indicated by arrow (A). Detached leaf assay showing conidial germination over leaf surface in pathogen treated leaf (BC), while in presence of bsAgNPs (B4) conidial germination was totally inhibited (B).</p

The phylogenetic tree of <i>Serratia</i> sp. BHU-S4 based on 16S rDNA sequence.

<p>The partial 16S rDNA sequence has been deposited in NCBI GenBank, nucleotide sequence database under the accession number KF863906. <i>Bar</i> 0.002 substitutions per site.</p

X-ray diffraction pattern (A), SEM (B) and TEM (C) micrographic images of bsAgNPs by <i>Serratia</i> sp. BHU-S4.

<p>AFM micrographs 2D (D) and 3D (E) illustrating the nanostructure of bsAgNPs.</p

Physiological and biochemical characteristics of <i>Serratia</i> sp. BHU-S4.

<p>Physiological and biochemical characteristics of <i>Serratia</i> sp. BHU-S4.</p