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A bioassay was developed and standardized for the rapid, specific, and quantitative assessment of naphthalene and salicylate bioavailability by use of bioluminescence monitoring of catabolic gene expression. The bioluminescent reporter strain Pseudomonas fluorescens HK44, which carries a transcriptional nahG-luxCDABE fusion for naphthalene and salicylate catabolism, was used. The physiological state of the reporter cultures as well as the intrinsic regulatory properties of the naphthalene degradation operon must be taken into account to obtain a high specificity at low target substrate concentrations. Experiments have shown that the use of exponentially growing reporter cultures has advantages over the use of carbon-starved, resting cultures. In aqueous solutions for both substrates, naphthalene and salicylate, linear relationships between initial substrate concentration and bioluminescence response were found over concentration ranges of 1 to 2 orders of magnitude. Naphthalene could be detected at a concentration of 45 ppb. Studies conducted under defined conditions with extracts and slurries of experimentally contaminated sterile soils and identical uncontaminated soil controls demonstrated that this method can be used for specific and quantitative estimations of target pollutant presence and bioavailability in soil extracts and for specific and qualitative estimations of napthalene in soil slurries.

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from 233 uranium compounds and ascribed to an ultraviolet gamma-ray emission from the metastable 229 thorium daughter is actually N 2 discharge emission induced in the air surrounding the sample by the sample radioactivity. The UV spectrum from high elemental and isotopic purity 233 UO 3 reported here also exhibits a line at 391.3 nm that does not appear to be due to electric discharge N 2 emission. [S0031-9007(99)

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The reporter bacterium, Pseudomonas fluorescens HK44 (HK44), was characterized in an immobilized state to investigate utility for deployment as a remote sensor in the subsurface. A packed‐bed reactor with alginate‐immobilized HK44 simulated hydrodynamic conditions such as might be found in a subsurface environment. The reporter bacterium, HK44, harbors a reporter plasmid, pUTK21, which contains a transcriptional fusion between the nahG gene in the lower pathway of the catabolic plasmic NAH7 and a luxCDABE gene cassette. The upper nah pathway and the lux pathway in pUTK21 are induced by salicylate. The lux enzymes catalyze the light reaction. HK44 demonstrated a quantitative relationship between salicylate concentration and degradation. Light intensity mimicked salicylate concentration, whereas degradation was first order in biomass and first order in salicylate concentration, with a degradation constant of 2.23 × 10−2 dm3 g−1 min−1. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 491–502, 1997.

The production of ethanol from starch was studied in a fluidized-bed reactor (FBR) using co-immobilized Zymomonas mobilis and glucoamylase. The FBR was a glass column of 2.54 cm in diameter and 120 cm in Iength. The 2. mobilis and glucoamylase were coimmobilized within small uniform beads (1.2 to 2.5 mm diameter) of K-carrageenan. The substrate for ethanol production was a soluble starch. Light steep water was used as the complex nutrient source. The experiments were performed at 35°C and pH range 4.0 to 5.5. The substrate concentrations ranged from 40 to 185 g/L, and the feed rates from 10 to 37 mL/min. Under relaxed sterility conditions, the FBR was successfully operated for a period of 22 days, during which no contamination or structural failure of the biocatalyst beads was observed. Maximum volumetric productivity of 38 g ethanol&-h, which was 76% of the theoretical value, was obtained. Typical ethanol volumetric productivity was in the range of 15 to 20 g/L-h. The average yield was 0.5 1 g ethanol/g substrate consumed, which was 90% of the theoretical yield. Vey low levels of glucose were observed in the reactor, indicating that starch hydrolysis was the rate-limiting step.

Use of genetic search algorithms for detection of subsurface biological activity zones (BAZ) is investigated through a series of hypothetical numerical biostimulation experiments. Continuous injection of dissolved oxygen (DO) and methane with periodically varying concentration stimulate the cometabolism of indigenous methanotropic bacteria. The observed breakthroughs of methane are used to deduce possible BAZ in the subsurface. The numerical experiments are implemented in a parallel computing environment to enable the large number of simultaneous transport simulations required by the algorithm. Our results show that genetic algorithms are very efficient in locating multiple activity zones provided the observed signals adequately sample the BAZ.