Ganesan Sathiyanarayanan

Synthesis of silver nanoparticles by polysaccharide bioflocculant produced from marine Bacillus subtilis MSBN17.

The polysaccharides are emerging as stabilizing and reducing agents for nanoparticles synthesis, however the commercial polysaccharides are not economically viable. Therefore, the exopolysaccharide from microbial origin such as bioflocculants are promising alternate for the synthesis and stabilization of nanoparticles. In this report, a bioflocculant (MSBF17) was produced from marine sponge-associated Bacillus subtilis MSBN17 under submerged fermentation using the economical substrates. The production was statistically optimized with most significant factors such as palm jaggery, NH(4)NO(2), K(2)HPO(4) and NaCl. The maximum bioflocculant production obtained with statistically optimized medium was 13.42 g/l. Based on the biochemical composition and FT-IR analysis, the flocculant compound was predicted as a polysaccharide derivative. The flocculating activity of the MSBF17 was invariably considerable at high salinity and temperature. It was found that the nano-scale silver can be synthesized in reverse micelles using the bioflocculant as stabilizer. The silver nanoparticles (AgNPs) were characterized by UV-spectroscopy, FT-IR and TEM analysis. The AgNPs were spherical shaped (60 nm) and stable for 5 months. Therefore, the bioflocculant-mediated synthesis of nanomaterials can be considered as environmental benign greener approach.

Optimization of polyhydroxybutyrate production by marine Bacillus megaterium MSBN04 under solid state culture

A marine sponge-associated bacterium Bacillus megaterium MSBN04 was used for the production of polyhydroxybutyrate (PHB) under solid state culture (SSC). A central composite design (CCD) was employed to optimize the production medium and to find out the interactive effects of four independent variables, viz. tapioca industry waste, palm jaggery, horse gram flour and trace element solution on PHB production. The maximum yield of PHB 8.637 mg g(-1) of substrate (tapioca industry waste) was achieved from biomass 15.203 mg g(-1) of substrate, using statistically optimized medium. The horse gram flour (nitrogen source) and trace element solution were found to be critical control factors for PHB synthesis. The (1)H NMR analysis revealed that the polymer was a PHB monomer. PHB obtained from this study having high molecular weight (6.7×10(5) Da) with low polydispersity index (PDI) value (1.71) and produced PHB was used to synthesize PHB polymeric nanoparticles using solvent displacement approach. Therefore, B. megaterium MSBN04 is an ideal candidate that can be exploited biotechnologically for the commercial production of PHB under solid state culture.

A statistical approach for optimization of polyhydroxybutyrate production by marine Bacillus subtilis MSBN17

The important biological macromolecule polyhydroxybutyrate (PHB) producing Bacillus subtilis was isolated from the marine sponge Callyspongia diffusa and identified by means of 16S rRNA analysis. The central composite design (CCD) was used to optimize the PHB production using cheap raw materials such as pulp industry waste (PIW), tamarind kernel powder (TKP), palm jaggery (PJ) and green gram flour (GGF). The extracted polymer was characterized by (1)H NMR analysis. The PIW was fed at three different intervals and the maximum production of PHB (19.08g/L) was attained after a period of 40h of incubation of B. subtilis. Dissolved oxygen, sodium chloride and nitrogen source were found to be the critical control factors that affected the PHB polymer production. The present investigation demonstrates an inexpensive model of producing PHB green thermoplastics in vitro for biomedical applications.

Synthesis of carbohydrate polymer encrusted gold nanoparticles using bacterial exopolysaccharide: a novel and greener approach

In the present study, a marine sponge-associated endosymbiotic bacterium Bacillus megaterium MSBN04 was evaluated for exopolysaccharide (EPS) production. The production process was optimized by central composite design (CCD). The productivity was increased up to 5.62 g L−1 with sucrose as sole carbon source. The secreted EPS was characterized by NMR analysis, confirming the presence of monosaccharide units such as α-D-glucose and α-D-galactose, which further confirms that the secreted EPS is a heteropolysaccharide. The purified EPS showed considerable flocculating activity (45.41%) with 4 mg L−1 of EPS. Using EPS as reducing and stabilizing agent, gold nanoparticles (AuNPs) were synthesized. The synthesized AuNPs (5–20 nm) were of spherical crystalline nature and capped with an EPS layer and were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. The synthesis of AuNPs was dependent on the concentration of EPS. The synthesized AuNPs showed significant antibacterial activity against clinical pathogenic bacteria. Hence, EPS-mediated synthesis of AuNPs is an alternative approach to chemical synthesis and thus it is an environmentally benign, greener and economical approach.

Medium engineering for enhanced production of undecylprodigiosin antibiotic in Streptomyces coelicolor using oil palm biomass hydrolysate as a carbon source.

In this study, a biosugar obtained from empty fruit bunch (EFB) of oil palm by hot water treatment and subsequent enzymatic saccharification was used for undecylprodigiosin production, using Streptomyces coelicolor. Furfural is a major inhibitor present in EFB hydrolysate (EFBH), having a minimum inhibitory concentration (MIC) of 1.9mM, and it reduces utilization of glucose (27%), xylose (59%), inhibits mycelium formation, and affects antibiotic production. Interestingly, furfural was found to be a good activator of undecylprodigiosin production in S. coelicolor, which enhanced undecylprodigiosin production by up to 52%. Optimization by mixture analysis resulted in a synthetic medium containing glucose:furfural:ACN:DMSO (1%, 2mM, 0.2% and 0.3%, respectively). Finally, S. coelicolor was cultured in a fermenter in minimal medium with EFBH as a carbon source and addition of the components described above. This yielded 4.2μg/mgdcw undecylprodigiosin, which was 3.2-fold higher compared to that in un-optimized medium.

Microbial biodiesel production from oil palm biomass hydrolysate using marine Rhodococcus sp. YHY01

The effect of various biomass derived inhibitors (i.e. furfural, hydroxymethylfurfural (HMF), vanillin, 4-hydroxy benzaldehyde (4-HB) and acetate) was investigated for fatty acid accumulation in Rhodococcus sp. YHY 01. Rhodococcus sp. YHY01 was able to utilize acetate, vanillin, and 4-HB for biomass production and fatty acid accumulation. The IC50 value for furfural (3.1mM), HMF (3.2mM), vanillin (2.0mM), 4-HB (2.7mM) and acetate (3.7mM) was calculated. HMF and vanillin affect fatty acid composition and increase saturated fatty acid content. Rhodococcus sp. YHY 01 cultured with empty fruit bunch hydrolysate (EFBH) as the main carbon source resulted in enhanced biomass (20%) and fatty acid productivity (37%), in compression to glucose as a carbon source. Overall, this study showed the beneficial effects of inhibitory molecules on growth and fatty acid production, and support the idea of biomass hydrolysate utilization for biodiesel production by avoiding complex efforts to remove inhibitory compounds.

Formulation of iron oxide nanoparticles using exopolysaccharide: evaluation of their antibacterial and anticancer activities

In the present study, we report the formulation, characterization, and in vitro antibacterial and cytotoxicity effects of exopolysaccharide (EPS) stabilized iron oxide nanoparticles (FeONPs) against the human epidermoid carcinoma cell line (A431). EPS is extracted from a spore-forming strain of Bacillus subtilis, VT03, isolated from the gut microbiome of the freshwater fish Oreochromis mossambicus (Tilapia). FTIR, 1H NMR and 13C NMR spectroscopic studies show the presence of sugar moieties, confirming that EPS might be a glucan. Later, EPS is used as an eco-friendly reducing and stabilizing agent for the formulation of iron oxide nanoparticles (FeONPs). Initially, the generation of nanoscale FeO was confirmed through the formation of a black-coloured precipitate with an absorbance maxima at 250–300 nm in a UV-visible spectrometer. X-ray diffraction (XRD) planes clearly confirm that the synthesized FeONPs are in the cubic spinel phase. The morphometric features of the synthesized FeONPs are exclusively studied using electron microscopy (FESEM and HRTEM) which shows spherical FeONPs in sizes ranging between 75–120 nm; the mean size was found to be 106 ± 12 nm. Additionally, energy dispersive X-ray analysis (EDAX), selected area emission diffraction (SAED) and dynamic light scattering (DLS) confirms the purity and homogeneity of the synthesized FeONPs. The vibrating sample magnetometer (VSM) technique reveals the presence of both ferro- and antiferromagnetic phases in the EPS-stabilized FeONPs. Further, the inhibitory activity of EPS-stabilized FeONPs against human and fish pathogenic strains such as Aeromonas hydrophila (ATCC 49140), Aeromonas hydrophila (MTCC 1739), Aeromonas sobria (MTCC 3613) and Aeromonas hydrophila (obtained from OIE Reference Laboratory, C. Abdul Hakeem College, Melvisharam) was assessed. The in vitro cytotoxicity effects of free EPS and EPS-stabilized FeONPs were probed in the human epidermoid carcinoma cell line A431. The IC50 values of EPS and EPS-stabilized FeONPs were found to be 350.18 and 62.946 μg ml−1 respectively. Further, acridine orange/ethidium bromide (AO/EtBr) staining of A431 cells at different time intervals clearly distinguishes the live cells and the cells that have undergone apoptotic cell death. In conclusion, our research paves the way for a facile and greener route to synthesize FeONPs at room temperature. On the other hand, this study also proves that the formulated multifunctional hybrid FeONPs have remarkable qualities such as enhanced bioavailability and magnetic properties. This can be developed into a successful theragnostic platform for cancer treatment.

Overexpression of succinyl‐CoA synthase for poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) production in engineered Escherichia coli BL21(DE3)

This study aims to increase the 3‐hydroxyvalerate (3HV) fraction in poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) [P(HB‐co‐HV)] using succinyl‐CoA synthase.

Exopolysaccharide from psychrotrophic Arctic glacier soil bacterium Flavobacterium sp. ASB 3-3 and its potential applications

A novel exopolysaccharide (EPS) producing psychrotrophic bacterium Flavobacterium sp. ASB 3-3 was isolated from Arctic glacier soil and identified. The optimum fermentation conditions for EPS production were an initial medium pH of 7.2 and an initial inoculum size of 5% (v/v). The maximum yield of EPS (7.25 ± 0.26 g L−1) was obtained after cultivation at 25 °C for 120 h with glycerol as the sole carbon source. The EPS was purified and its structural characteristics were analyzed by 1H and 13C NMR. The predominant repeating units of this EPS are (α, β) D-glucose and D-galactose and it is different from the structure of EPSs produced by other Arctic and Antarctic bacteria, which have mannose units. In addition, EPS has demonstrated a comparable emulsifying property than SDS and flocculating properties with kaolinite, suggesting their potential applications in various industries. The EPS also significantly improved the tolerance of Flavobacterium sp. and Escherichia coli from freeze–thaw cycles, suggesting that it might be used to survive in polar regions and it can have possible usage as microbial cryoprotectants.

Microbial exopolysaccharide-mediated synthesis and stabilization of metal nanoparticles

Abstract Exopolysaccharides (EPSs) are structurally and functionally valuable biopolymer secreted by different prokaryotic and eukaryotic microorganisms in response to biotic/abiotic stresses and to survive in extreme environments. Microbial EPSs are fascinating in various industrial sectors due to their excellent material properties and less toxic, highly biodegradable, and biocompatible nature. Recently, microbial EPSs have been used as a potential template for the rapid synthesis of metallic nanoparticles and EPS-mediated metal reduction processes are emerging as simple, harmless, and environmentally benign green chemistry approaches. EPS-mediated synthesis of metal nanoparticles is a distinctive metabolism-independent bio-reduction process due to the formation of interfaces between metal cations and the polyanionic functional groups (i.e. hydroxyl, carboxyl and amino groups) of the EPS. In addition, the range of physicochemical features which facilitates the EPS as an efficient stabilizing or capping agents to protect the primary structure of the metal nanoparticles with an encapsulation film in order to separate the nanoparticle core from the mixture of composites. The EPS-capping also enables the further modification of metal nanoparticles with expected material properties for multifarious applications. The present review discusses the microbial EPS-mediated green synthesis/stabilization of metal nanoparticles, possible mechanisms involved in EPS-mediated metal reduction, and application prospects of EPS-based metal nanoparticles.