Novel bionanocatalysts for green chemistry applications

Desulfovibrio desulfuricans have been known to synthesize good catalysts in a number of industrially and environmentally relevant reactions but the underlying reasons and/or mechanisms for such catalysis have largely remained elusive. This study has shown that in addition to nanoparticle (NP) size, the catalytic properties of D. desulfuricans is hinged on several factors such as the textural surface of the bacterial support, binding mechanism to surface functional groups (amine, carboxyl, phosphoryl and sulfuryl groups) and the crystal structure of the resulting catalyst NPs. In this study, various characterization techniques: AFM, EDX, SEM, HAADF-STEM, HRTEM, XRD and XPS and catalytic hydrogenation of soybean oil. The concept of intracellular trafficking of palladium into the cells of both Gram-negative (Desulfovibrio desulfuricans) and Gram-positive (Bacillus benzeovorans) bacteria was pioneered against previously known extracellular NP deposition. The membrane integrity and membrane potentials of “palladized” cells (‘bio-Pd’) were found to be retained through flow cytometry analysis. Bio-supported bimetallic (bio-Pd/Pt) catalyst from D. desulfuricans and B. benzeovorans demonstrated comparable catalytic properties to a commercial catalyst (Ni-Mo/Al$_2$O$_3$) as a potential ‘green’ alternative. Generally, the extent of viscosity reduction was: 98.7% (thermal), 99.2% (bio-NPs) and 99.6% (Ni-Mo/Al$_2$O$_3$) below 1031 mPa.s of the feed heavy oil. Also the bimetallic bio-NPs produced an increment of ~2$^o$ in API (American petroleum institute) gravity (~9.1$^o$) than monometallic (~7.6$^o$) on average while the API gravity using thermal was lower (6.3$^o$) while that of a commercial catalyst was 11.1$^o$. Finally, the concept of tandem (one-pot) catalysis was pioneered as a potential platform for the remediation of chlorinated benzenes

Phytoconstituents, proximate and nutrient investigations of Saba florida (Benth.) from Ibaji forest

Quantitative determination of chemical and nutritional composition of the leaf, fruit pulp, pericarp and seed of Saba florida (Apocynaceae), an underexploited medicinal and food plant in Nigeria, was carried out using standard methods. The plant parts contain levels of alkaloids, tannins, saponins, flavonoids and other phytochemical. Proximate analysis (total protein, fats, carbohydrate, ash, and moisture contents) were carried out following methods of Association of official Analytical chemists. The order of increasing concentration of the proximate composition is protein -> moisture->ash->crude fibre->fats ->carbohydrate in all plant parts. Elemental nutrients Ca, K, Na, Mg, Pb, Fe, Cu, Zn, Ni and Cd were analyzed using atomic absorption spectrometry. Results revealed higher concentration of macronutrients in all plant parts except K. In conclusion S. florida has high nutritional and medicinal value

In-situ catalytic upgrading of heavy oil using dispersed bionanoparticles supported on gram-positive and gram-negative bacteria

AbstractWith the continuous depletion of global oil reserves, unconventional alternative oil resources like heavy oil and bitumen have become increasingly attractive. This study investigates the use of bimetallic bio-nanoparticles (bio-NPs), a potential alternative to commercial catalysts in heavy oil upgrading. The bio-NPs were made by sequential reduction of precious metal (Pd and Pt) ions with hydrogen as the electron donor at 5wt% and 20wt% metal loading using bacterial (Desulfovibrio desulfuricans and Bacillus benzeovorans) cells as support. The bio-NPs were characterized using transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Results of the catalytic upgrading of a feed heavy oil show that the bimetallic bio-NPs produced an increment of ∼2° in API (American Petroleum Institute) gravity (i.e. ∼9.1°) better than monometallic bio-NPs (∼7.6°) on average while the API gravity using thermal upgrading was lower (6.3°). The API gravity of a commercial Ni-Mo/Al2O3 catalyst was 11.1°. However, more coking was produced using the commercial catalyst than with the bio-NPs. The extent of viscosity reduction was: 98.7% (thermal), 99.2% (bio-NPs) and 99.6% (Ni-Mo/Al2O3) below 1031mPas for the feed heavy oil reference (baseline). The potential advantage of using bio-NPs is that the precious metals can be sourced cheaply from waste streams, which could serve as a potential platform for the green synthesis of catalytically active materials using bacteria for in-situ catalytic upgrading of heavy oils

Characterization of intracellular palladium nanoparticles synthesized by Desulfovibrio desulfuricans and Bacillus benzeovorans

Early studies have focused on the synthesis of palladium nanoparticles within the periplasmic layer or on the outer membrane of Desulfovibrio desulfuricans and on the S-layer protein of Bacillus sphaericus. However, it has remained unclear whether the synthesis of palladium nanoparticles also takes place in the bacterial cell cytoplasm. This study reports the use of high-resolution scanning transmission electron microscopy with a high angle annular dark field detector and energy dispersive X-ray spectrometry attachment to investigate the intracellular synthesis of palladium nanoparticles (Pd NPs). We show the intracellular synthesis of PdNPs within cells of two anaerobic strains of D. desulfuricans and an aerobic strain of B. benzeovorans using hydrogen and formate as electron donors. The Pd nanoparticles were small and largely monodispersed, between 0.2 and 8 nm, occasionally from 9 to 12 nm with occasional larger nanoparticles. With D. desulfuricans NCIMB 8307 (but not D. desulfuricans NCIMB 8326) and with B. benzeovorans NCIMB 12555, the NPs were larger when made at the expense of formate, co-localizing with phosphate in the latter, and were crystalline, but were amorphous when made with H2, with no phosphorus association. The intracellular Pd nanoparticles weremainly icosahedrons with surfaces comprising {111} facets and about 5 % distortion when compared with that of bulk palladium. The particles were more concentrated in the cell cytoplasm than the cell wall, outer membrane, or periplasm. We provide new evidence for synthesis of palladium nanoparticles within the cytoplasm of bacteria, which were confirmed to maintain cellular integrity during this synthesis

Selective hydrogenation catalyst made via heat-processing of biogenic Pd nanoparticles and novel ‘green’ catalyst for Heck coupling using waste sulfidogenic bacteria

A heterogeneous Pd catalyst, biologically-mineralized palladium nanoparticles (bio-Pd), was synthesized using sulfidogenic bacteria which reduced soluble Pd(II) to catalytically-active Pd-nanoparticles (NPs). Heat treatment (processing) of bio-Pd (5 or 20 wt% on the cells) made by Desulfovibrio desulfuricans evolved supported Pd-catalyst comprising Pd-NPs held on large spherical hollow structures. The rate of hydrogenation of 2-butyne-1,4-diol was ~5-fold slower than for a commercial catalyst (~twice that of native bio-Pd), but with high selectivity to the alkene, fulfilling a key industrial criterion. In the Heck reaction, while bio-Pd showed a comparable reaction rate in ethyl cinnamate synthesis to that achieved by commercial Pd/C, heat-treated bio-Pd had negligible activity. D. desulfuricans bio-Pd was replaced by bio-Pd made using a consortium of waste acidophilic sulfidogenic bacteria (CAS) supplied from an unrelated primary remediation process. This gave comparable activity to commercial 5 wt% Pd/C in ethyl cinnamate synthesis, signposting an economic, scalable route to catalyst manufacture