Neil Cresswell

Characterization of activated carbon prepared from a single cultivar of Jordanian olive stones by chemical and physicochemical techniques

Abstract The yearly production of olives in Jordan is more than 100 kton of which a significant proportion is de-stoned prior to sale. In this work, olive stones from Jordan were used for the preparation of activated carbon with the aim of producing a water treatment product suitable for treatment of contaminated groundwater. The preparation conditions were varied to study their effects on the surface area, porosity, morphology, functionality and crystal structure. Variables studied included time of carbonization, time of activation, activating agent, particle size, sample pre-drying, hydrogen peroxide post treatment and the effect of the activation process itself. X-ray diffraction analysis showed that the prepared activated carbon is essentially amorphous and indicated the presence of traces of oxides of calcium and magnesium, while infrared spectroscopy showed peaks relating to hydroxyl, aliphatic, ether, aromatic and phenolic groups. These functional groups and crystals may have some effect(s), i.e. catalytic, if the products were to be used in any reaction for water treatment. Nitrogen adsorption was used for the determination of apparent surface area and pore size distribution. Results showed that the active carbon is of moderate surface area and micropore volume is over 80% of the total pore volume. Scanning electron microscopy showed the development of the pores during different treatments. The most noticeable effect on the texture was that when the sample was not pre-dried. The adsorption capacity and surface acidity/basicity of all the samples have been studied by methylene blue (MB) adsorption method and partial Boehm titrations, respectively. Results showed that the surface is mainly of basic nature, and also indicated that MB was adsorbed following the pore filling mechanism. Hydrogen peroxide post-treatment produced reduced surface area measurements.

Detection and quantification of Streptomyces violaceolatus plasmid DNA in soil

Two methods for the direct extraction of DNA from soil were investigated using soil inoculated with Streptomyces violaceolatus ISP5438 harbouring the multicopy plasmid pIJ673. Detection limits for plasmid DNA were determined by Southern blot technique. An SDS/heat lysis method gave approximately two orders of magnitude less sensitivity than lysis and extraction by bead‐beating soil inoculated with spores. The use of these two methods allowed differentiation between spore‐ and mycelial‐borne DNA. This was due to the resistance of the spores to lysis when subjected to SDS/heat lysis.

Gene transfer between Streptomycetes in soil

The growth and activity of Streptomyces violaceolatus and Streptomyces lividans was studied in soil under controlled conditions. The life cycle was followed under differing nutrient regimes and the fate of plasmid- and phage-borne genes determined by direct and indirect techniques. Methods were developed for the direct monitoring of plasmid DNA extracted from soil which allowed differentiation of the cellular location of plasmid DNA between mycelium and spores. In a dynamic, nutrient-fed soil microcosm, inoculants survived poorly, but a specific stage was defined by direct and indirect methods when the inoculants were most active and this correlated with the detection of gene transfer events. Plasmid transfer, phage infection and lysogeny only occurred to a significant extent within this stage at days 15-17 during a 60-day incubation. Estimates based on plasmid DNA recovery indicated that viable counts underestimated spore and mycelial propagules by a factor of greater than 100.

The fate of introduced streptomycetes, plasmid and phage populations in a dynamic soil system.

Summary: Populations of Streptomyces lividans and S. violaceolatus were monitored in natural soil amended with nutrients. The fates of a multicopy plasmid pIJ673, and an actinophage, KC301, were determined and the extent of gene transfer was estimated. The soil was incubated for 60 d during which time ‘spent’ soil was periodically removed followed by addition of fresh, uninoculated soil. Maximum numbers of bacteria and phage inoculants occurred at 15 d; this correlated with a peak in the amount of plasmid DNA detected and total numbers of transconjugants recovered. A KC301 lysogen of S. lividans was also recovered at this time. Plasmid DNA was monitored by two methods, bead-beating and SDS/heat lysis; the latter was specific for mycelium while the former released DNA from spores and mycelium. Southern blots of soil DNA only showed the presence of plasmid DNA in SDS/heat lysis extracts from 15 d and 17 d samples, whereas positive signals were obtained throughout the experiment from bead-beaten extracts. The results confirmed that a well-developed mycelium was necessary for conjugation, phage infection, multiplication and lysogeny in soil.