Toward a novel membrane process for organic carbon removal-fate of slowly biodegradable substrate in super fast membrane bioreactor.

The study tested the performance of super fast membrane bioreactor (SFMBR) using starch as a slowly biodegradable substrate, exploring the fate of starch, and the response of the microbial community. SFMBR was operated at extremely low sludge ages of 0.5-2.0 days, with a hydraulic retention time of 1.0 h. Average values for permeate chemical oxygen demand (COD) always remained in the narrow range between 14 and 18 mg/L, regardless of the selected mode of MBR operation at different sludge ages. Soluble COD levels in the reactor were consistently higher than the corresponding permeate COD. Parameters defining process kinetics, determined by model calibration of oxygen uptake rate (OUR) profiles, varied as a function of sludge age. Model simulation of SFMBR performance indicated total removal of hydrolysis products so that permeate COD consisted of residual microbial products. PCR-DGGE experiments revealed significant shifts in the composition of the microbial community imposed by variations in the sludge age, reflecting on corresponding process kinetics.

Effect of high loading on substrate utilization kinetics and microbial community structure in super fast submerged membrane bioreactor.

The study investigated the effect of high substrate loading on substrate utilization kinetics, and changes inflicted on the composition of the microbial community in a superfast submerged membrane bioreactor. Submerged MBR was sequentially fed with a substrate mixture and acetate; its performance was monitored at steady-state, at extremely low sludge age values of 2.0, 1.0 and 0.5d, all adjusted to a single hydraulic retention time of 8.0 h. Each MBR run was repeated when substrate feeding was increased from 200 mg COD/L to 1000 mg COD/L. Substrate utilization kinetics was altered to significantly lower levels when the MBR was adjusted to higher substrate loadings. Molecular analysis of the biomass revealed that variable process kinetics could be correlated with parallel changes in the composition of the microbial community, mainly by a replacement mechanism, where newer species, better adapted to the new growth conditions, substituted others that are washed out from the system.

Cystic fibrosis patients from the Black Sea region: the 1677delTA mutation.

A 2 bp deletion in exon 10 of the CFTR gene, 1677delTA, which is very rare among CF chromosomes worldwide, was found to be a relatively common cause of cystic fibrosis in countries located in the region of the Black Sea. The frequency of the mutation was compared among cystic fibrosis patients from several populations, namely Bulgarians, Turks, Greek-Cypriots, Georgians, and Russians. The deletion is most common among Georgian CF patients and gradually declines in frequency in neighbouring populations. It is invariably related to a common polymorphic haplotype which is rare among normal chromosomes in Bulgaria but was found to be common in Turkey. The geographic gradient in the frequency of the mutation, along with findings on polymorphic haplotype distribution, suggest that the mutation is relatively young in evolutionary terms and spread as the result of west and south-bound migrations originating from Georgia. The 1677delTA mutation is related to a severe clinical phenotype with a high early mortality rate among homozygotes and possibly to an increased risk of meconium ileus.