Energetics of binary mixed culture of Pseudomonas aeruginosa and Pseudomonas fluorescence growth on phenol in aerobic chemostat culture

Bioenergetic analysis of the growth of the binary mixed culture (Pseudomonas aeruginosa and Pseudomonas fluorescence) on phenol chemostat culture was carried out. The data were checked for consistency using carbon and available electron balances. When more than the minimum number of variables are measured, and measurement errors are taken into account, the results of parameter estimation depend on which of the measured variables are chosen for this purpose. Similar parameter estimates were obtained using Pirt’s model based on the Monod equation approach and a modified model based on substrate consumption being rate limiting. Coupled with the covariate adjustmentestimation technique, the best estimates were the maximum likelihood estimates (MLE) based on when all the measured data were used. For the aerobic growth of the mixed culture on phenol, ηmax = 0.396 and me= −0.020 h-1. From the 95% confidence intervals, a maximum of about 38 – 41.3% of the energy contained in phenol is incorporated into the mixed culture biomass. The balance (58.7 – 62%) is evolved as heat with little or no energy needed for the maintenance of organisms.Keywords: Binary mixed culture, biomass energetic yield, chemostat culture, energetic analysis, maintenance coefficient, Pirt’s mode

Kinetics of batch microbial degradation of phenols by indigenous binary mixed culture of Pseudomonas aeruginosa and Pseudomonas fluorescence

The potential of various organisms to metabolize organic compounds has been observed to be a potentially effective means in disposing of hazardous and toxic wastes. Phenolic compounds have longbeen recognized as one of the most recalcitrant and persistent organic chemicals in the environment. The bioremediation potential of an indigenous binary mixed culture of Pseudomonas aeruginosa andPseudomonas fluorescence was studied in batch culture using synthetic phenol in water in the concentration range of 100 –500 mg/L as a model limiting substrate. The effect of initial phenol concentration on the degradation process was investigated. Phenol was completely degraded at different cultivation times for the different initial phenol concentrations. Increasing the initial phenol concentration from 100 to 500 mg/L increased the lag phase from 0 to 18 h and correspondinglyprolonged the degradation process from 24 to 96 h. There was decrease in biodegradation rate as initial phenol concentration increased. Fitting data into three different kinetic models (Monod, Haldane, andYano and Koga) showed that the difference in fit between the models was very small and thus statistically insignificant. Thus, the Yano and Koga model has been used to interpret the free cell dataon phenol biodegradation. The kinetic parameters have been estimated up to initial phenol concentration of 500 mg/L. The rsmax decreased, while Ks and Ki increased with higher concentration of phenol. The rsmaxhas been found to be a strong function of initial phenol concentration

Substrate inhibition kinetics of phenol degradation by binary mixed culture of Pseudomonas aeruginosa and Pseudomonas fluorescence from steady state and wash- out data

Steady states of a continuous culture with an inhibitory substrate were used to estimate kinetic parameters under substrate limitation (chemo stat operation). Mixed cultures of an indigenous Pseudomonas fluorescence and Pseudomonas aeruginosa were grown in continuous culture on phenol as the sole source of carbon and energy at dilution rates of 0.01 – 0.20 h-1. Using different dilution rates several steady states were investigated and the specific phenol consumption rates were calculated. In addition, phenol degradation was investigated by increasing the dilution rate above the critical dilution rate (washout cultivation). The results showed that the phenol degradation by mixed culture of P. fluorescence and P. aeruginosa can be described by simple substrate inhibition kinetics under substrate limitation but cannot be described by simple substrate inhibition kinetics under washoutcultivation. The phenol consumption rate (degradation rate) increased with increase in dilution rate. Fitting of the steady state data from continuous cultivation to six inhibition models resulted in the bestfit for Haldane, Yano and Koga, Aiba et al. and Teissier models, respectively. The rsmax value of 0.322 mg/mg/h obtained from these model equations was comparable to the experimentally calculated rsmax value of 0.342 mg/mg/h obtained under washout cultivation

BIOELECTRICITY PRODUCTION FROM CASSAVA MILL EFFLUENTS USING MICROBIAL FUEL CELL TECHNOLOGY

A Microbial Fuel Cell (MFC) is a biochemical-catalyzed system that generates electricity by oxidation of biodegradable organic substance in the presence of microorganisms or enzymes. Microbial fuel cell technology is a new form of renewable and sustainable technology for electricity generation as it recovers energy from renewable materials such as organic wastes and wastewaters that can constitute environmental pollution if not disposed without proper treatment. This work therefore investigated the possibility of electricity generation from cassava mill effluent using MFC. The cassava mill effluent was found to generate voltage and current to the maximum of 275 mV and 2.75 mA, respectively, corresponding to a maximum power density of 189 mW/m2. The voltage and current generation was respectively and significantly influenced with change in temperature, pH, concentration (strength) of effluent and addition of nutrient. Thus, it can be concluded that bioelectricity can directly be generated from cassava mill effluent using the MFC technology. http://dx.doi.org/10.4314/njt.v35i2.1

Vigorous star formation hidden by dust in a galaxy at z=1.4z=1.4

Near-infrared surveys have revealed a substantial population of enigmatic faint galaxies with extremely red optical-to-near-infrared colours and with a sky surface density comparable to that of faint quasars. There are two scenarios for these extreme colours: (i) these distant galaxies have formed virtually all their stars at very high redshifts and, due to the absence of recently formed stars, the colours are extremely red and (ii) these distant galaxies contain large amounts of dust, severely reddening the rest-frame UV--optical spectrum. HR10 ($z = 1.44$) is considered the archetype of the extremely red galaxies. Here we report the detection of the continuum emission from HR10 at 850$\mu$m and at 1250$\mu$m, demonstrating that HR10 is a very dusty galaxy undergoing a major episode of star formation. Our result provides a clear example of a high-redshift galaxy where the star formation rate inferred from the ultraviolet luminosity would be underestimated by a factor up to 1000, and shows that great caution should be used to infer the global star formation history of the Universe from optical observations only.Comment: 12 pages, 1 figure, Nature, in press (30 April 1998

The Diagnostic Value of Endoprobe for Small Esophageal Leiomyomas Derived from the Muscularis Mucosae

Esophageal leiomyoma derived from the muscularis mucosae (MM) is a rare condition, and the optimal modality for diagnosis and treatment is controversial. Endoscopic ultrasonography can provide an accurate image of esophageal layer structure, providing information on lesion suitability for potential endoscopic therapy. We attempted to investigate the diagnostic value of a transendoscopic balloon-tipped miniature ultrasonic endoprobe for small esophageal leiomyomas derived from MM. We resected 7 small esophageal leiomyomas derived from MM by endoscopic mucosal resection (EMR), all of which were diagnosed by a balloon-tipped endoprobe. The endosonographic and pathologic features of 7 cases of small esophageal leiomyomas derived from MM were compared. The balloon-tipped endoprobe clearly showed all 7 small esophageal leiomyomas derived from MM, even those under 5 mm in size (smallest lesion, 3.0 mm). The endosonographic characteristics of small esophageal leiomyomas derived from MM were a hypoechoic mass with smooth, regular, and a well-defined outer margin and homogenous inner echogram arising from the second hypoechoic layer. Complete resections were possible in all 7 cases by EMR without any complications. Tumor size was 3.0 - 13.5 mm (mean 7.8 mm) in maximum diameter. In all cases, endosonographic findings by endoprobe were exactly concordant with pathologic finding in determining the tumors depth in the esophageal wall, tissue origin and characteristics, growth pattern, and size. We detail the balloon-tipped endoprobe is a simple, convenient, and very useful in making accurate diagnosis of small esophageal leiomyomas derived from the MM and the appropriate applications of EMR

A glycoconjugate of Haemophilus influenzae Type b capsular polysaccharide with tetanus toxoid protein: hydrodynamic properties mainly influenced by the carbohydrate

Three important physical properties which may affect the performance of glycoconjugate vaccines against serious disease are molar mass (molecular weight), heterogeneity (polydispersity), and conformational flexibility in solution. The dilute solution behaviour of native and activated capsular polyribosylribitol (PRP) polysaccharides extracted from Haemophilus influenzae type b (Hib), and the corresponding glycoconjugate made by conjugating this with the tetanus toxoid (TT) protein have been characterized and compared using a combination of sedimentation equilibrium and sedimentation velocity in the analytical ultracentrifuge with viscometry. The weight average molar mass of the activated material was considerably reduced (Mw ~ 0.24 × 106 g.mol−1) compared to the native (Mw ~ 1.2 × 106 g.mol−1). Conjugation with the TT protein yielded large polydisperse structures (of Mw ~ 7.4 × 106 g.mol−1), but which retained the high degree of flexibility of the native and activated polysaccharide, with frictional ratio, intrinsic viscosity, sedimentation conformation zoning behaviour and persistence length all commensurate with highly flexible coil behaviour and unlike the previously characterised tetanus toxoid protein (slightly extended and hydrodynamically compact structure with an aspect ratio of ~3). This non-protein like behaviour clearly indicates that it is the carbohydrate component which mainly influences the physical behaviour of the glycoconjugate in solution

Variable strength of forest stand attributes and weather conditions on the questing activity of Ixodes ricinus ticks over years in managed forests

Given the ever-increasing human impact through land use and climate change on the environment, we crucially need to achieve a better understanding of those factors that influence the questing activity of ixodid ticks, a major disease-transmitting vector in temperate forests. We investigated variation in the relative questing nymph densities of Ixodes ricinus in differently managed forest types for three years (2008–2010) in SW Germany by drag sampling. We used a hierarchical Bayesian modeling approach to examine the relative effects of habitat and weather and to consider possible nested structures of habitat and climate forces. The questing activity of nymphs was considerably larger in young forest successional stages of thicket compared with pole wood and timber stages. Questing nymph density increased markedly with milder winter temperatures. Generally, the relative strength of the various environmental forces on questing nymph density differed across years. In particular, winter temperature had a negative effect on tick activity across sites in 2008 in contrast to the overall effect of temperature across years. Our results suggest that forest management practices have important impacts on questing nymph density. Variable weather conditions, however, might override the effects of forest management practices on the fluctuations and dynamics of tick populations and activity over years, in particular, the preceding winter temperatures. Therefore, robust predictions and the detection of possible interactions and nested structures of habitat and climate forces can only be quantified through the collection of long-term data. Such data are particularly important with regard to future scenarios of forest management and climate warming

Solution conformation and flexibility of capsular polysaccharides from Neisseria meningitidis and glycoconjugates with the tetanus toxoid protein

The structural integrity of meningococcal native, micro-fluidized and activated capsular polysaccharides and their glycoconjugates – in the form most relevant to their potential use as vaccines (dilute solution) - have been investigated with respect to their homogeneity, conformation and flexibility. Sedimentation velocity analysis showed that the polysaccharide size distributions were generally bimodal with some evidence for higher molar mass forms at higher concentration. Weight average molar masses Mw where lower for activated polysaccharides. Conjugation with tetanus toxoid protein however greatly increased the molar mass and polydispersity of the final conjugates. Glycoconjugates had an approximately unimodal log-normal but broad and large molar mass profiles, confirmed by sedimentation equilibrium “SEDFIT MSTAR” analysis. Conformation analysis using HYDFIT (which globally combines sedimentation and viscosity data), “Conformation Zoning” and Wales-van Holde approaches showed a high degree of flexibility – at least as great as the unconjugated polysaccharides, and very different from the tetanus toxoid (TT) protein used for the conjugation. As with the recently published finding for Hib-TT complexes, it is the carbohydrate component that dictates the solution behaviour of these glycoconjugates, although the lower intrinsic viscosities suggest some degree of compaction of the carbohydrate chains around the protein