Biodegradation of chlorobenzene in a constructed wetland treating contaminated groundwater.

Monochlorobenzene (MCB) is an important groundwater contaminant world-wide. In this study, a horizontal subsurface flow constructed wetland with an integrated water compartment was fed with MCB contaminated groundwater originating from the local aquifer. Analysis of spatial concentration dynamics of MCB and oxygen was combined with isotope composition analysis of MCB for assessing in situ biodegradation. Removal of MCB was most effective in the upper layer of the soil filter, reaching up to 77.1%. Trace oxygen concentrations below 0.16 mg L(-1) were observed throughout the wetland transect, suggesting a considerable limitation of aerobic microbial MCB degradation. Enrichment of 13C in the residual MCB fraction at increasing distance from the inflow point indicated microbial MCB degradation in the wetland. The observed isotope shift was higher than expected for aerobic MCB degradation and thus pointed out a significant contribution of an anaerobic degradation pathway to the overall biodegradation.

Possibilities for controlling a PHB accumulation process using various analytical methods.

Poly-beta-hydroxybutyrate (PHB) and other polyesters can be produced by various species of bacteria. Of the possible carbon sources, methane could prove to be one of the most suitable substrates for the manufacture of PHB. The methanotrophic strain Methylocystis sp. GB 25 DSM 7674 was applied in order to accumulate PHB in a rapid, non-sterile process. Cultivation was performed in two stages: a continuous growth phase (dilution rate 0.17 h(-1)) and a PHB accumulation phase under deficiency conditions of an essential nutrient (e.g. phosphorus) in batch culture. The PHB content of the biomass was as high as 51%; efficiency was the highest during the first 5 h of the product formation process. The PHB produced is of very high quality, having a high molecular mass of up to 2.5 x 10(6) Da. In order to monitor and control the process, a rapid analysis method based upon turbidimetry in the visible range (438 nm) was applied. Moreover, the PHB content of the biomass was determined using an FT-IR-spectroscopic method with ATR sampling and multivariate calibration. We achieved a value of 1.4% as the best standard error of cross validation. The nitrogen content of the PHB final product (a product quality parameter) was estimated by spectroscopic method in the visible range.

[Effector influence of oxygen-containing C1 compounds in the cultivation of the methanotrophic bacterial strain GB 25]. / Effektorwirkung von sauerstoffhaltigen C1-Verbindungen bei der Kultivierung des methanotrophen Bakterienstammes GB 25.

Addition of oxygen-containing C1-compounds to chemostat cultures of GB 25 increases both the yield of biomass and the specific growth rate. At optimum concentrations the catalytic activity of these compounds increases with increasing growth rates. Their influence on maintenance coefficients and maximum yield coefficients decreases in the order CH3OH greater than CO2 greater than HCOOH greater than HCHO. This result together with spectrophotometric NADH determinations suggests that the NADH pool determines the balance between the assimilatory and oxidative utilization of formaldehyde.

[Effect of oxygen containing C1 compounds on the growth of methane-assimilating bacteria]. / Einfluss sauerstoffhaltiger C1-Verbindungen auf das Wachstum methanassimilierender Bakterien.

Added C1-compounds of the intermediates methanol, formaldehyde, formate and carbon dioxide show a catalytic effect on the growth rate and cell yield of CH4-assimilating bacteria GB 25 with serine pathway. Maximum stimulation is obtained by added amounts of about 20 mg C1-compound/g bacteria dry matter. The influence of C1-compounds decreases as follows: methanol greater than carbon dioxide greater than formate greater than formaldehyde.