Polyacrylamide (PAM) is a water-soluble polymer that is widely used as a flocculant in sewage treatment. The accumulation of PAM affects the formation of dewatered sludge and potentially produces hazardous monomers. In the present study, the bacterial strain HI47 was isolated from dewatered sludge. This strain could metabolize PAM as its sole nutrient source and was subsequently identified as Pseudomonas putida. The efficiency of PAM degradation was 31.1% in 7 days and exceeded 45% under optimum culture condition (pH 7.2, 39 °C and 100 rpm). The addition of yeast extract and glucose improved the bacterial growth and PAM degradation. The degraded PAM samples were analyzed by gel-filtration chromatography, Fourier transform infrared and high-performance liquid chromatography. The results showed that high-molecular-weight PAM was partly cleaved to small molecular oligomer derivatives and part of the amide groups of PAM had been converted to carboxyl groups. The biodegradation did not accumulate acrylamide monomers. Based on the SDS-PAGE and N-terminal sequencing results, the PAM amide groups were converted into carboxyl groups by a PAM-induced extracellular enzyme from the aliphatic amidase family.

A new material, activated carbon monolith, can be used as an adsorbent to remove volatile organic compounds (VOCs). Vapor-solid adsorption isotherms of three VOCs (toluene, 1-butanol, and ethyl acetate) on an activated carbon monolith were measured at: 20 °C, 60 °C, 100 °C, and 140 °C using a microbalance. The experimental data were correlated with the following adsorption isotherm models: Langmuir, Freundlich, Langmuir-Freundlich, and Toth equations. The Langmuir-Freundlich and Toth equations provided good fits to the experimental data.

No abstract

No abstract

Rice bran oil was acetone fractionated at low temperature. Two methods, independent fractionation (−8, −14 and −35C) and sequential fractionation (0, −8 and −14C), were compared for the preparation of triacylglycerol (TG) fraction‐enriched unsaturated fatty acids (UFAs). Among all fractions obtained from both methods, the liquid fraction from independent fractionation at −35C referred to as −35L was the best (89.6%) compared to other procedures used for enrichment of UFAs. However, when weight yield was considered, the largest amount of UFAs was obtained from the liquid fraction at 0C (0L) from sequential fractionation. After sequential fractionation at 0C, 87.5 wt % was recovered in the liquid fraction that contained 71.5% total UFAs. In addition, as the fractionation temperature was lowered, the content (%) of γ‐oryzanol in the liquid fractions was increased gradually. Reversed‐phase high‐performance liquid chromatography showed four regions based on the partition number of TG molecules of the separated peaks.

Pseudomonas putida strain BNF1 was isolated to degrade aromatic hydrocarbons efficiently and use phenol as a main carbon and energy source to support its growth. Catechol 2,3-dioxygenase was found to be the responsible key enzyme for the biodegradation of aromatic hydrocarbons. Catechol 2,3-dioxygenase gene was cloned from plasmid DNA of P. putida strain BNF1. The nucleotide base sequence of a 924 bp segment encoding the catechol 2,3-dioxygenase (C23O) was determined. This segment showed an open reading frame, which encoded a polypeptide of 307 amino acids. C23O gene was inserted into NotI-cut transposon vector pUT/mini-Tn5 (Km r ) to get a novel transposon vector pUT/mini-Tn5-C23O. With the helper plasmid PRK2013, the transposon vector pUT/miniTn5-C23O was introduced into one alkanes degrading strain Acinetobacter sp. BS3 by triparental conjugation, and then the C23O gene was integrated into the chromosome of Acinetobacter sp. BS3. And the recombinant BS3-C23O, which could express catechol 2,3-dioxygenase protein, was obtained. The recombinant BS3-C23O was able to degrade various aromatic hydrocarbons and n-alkanes. Broad substrate specificity, high enzyme activity, and the favorable stability suggest that the BS3-C23O was a potential candidate used for the biodegradation of crude oil.

No abstract

Parameter estimation is needed for process management, design, and reactor scaling when values from the literature vary tremendously or are unavailable. A Bayesian approach, implemented via Markov chain Monte Carlo (MCMC) simulations using SAS software, was used to estimate the kinetic parameters of toluene and trichloroethylene (TCE) biodegradation by the microorganism Pseudomonas putida F1 in batch cultures. The prediction capabilities of Bayesian estimation were illustrated by comparing predicted and observed data and reported in goodnessof-fit statistics. The sensitivity analysis showed that the parameters obtained using this approach were consistent under the designated toluene and TCE concentration range. Moreover, the impact of TCE on toluene degradation kinetics was numerically exhibited, verifying the fact that TCE was able to stimulate toluene degradation; hence, TCE's presence increased the apparent maximum toluene-specific rate. Various kinetic models were explored at different degrees of complexity. At a low TCE concentration range (e.g., <2 mg L −1 ), a simplified Michaelis-Menten model (i.e., substrate half-saturation parameters approximated the inhibition parameters) was adequate to describe the reaction kinetics. However, at a higher TCE range (e.g., 5 mg L −1 ), a full-scale Michaelis-Menten model was needed to discriminate among the inhibition parameters in the model. The results demonstrated that a Bayesian estimation method is particularly useful for determining complex bioreaction kinetic parameters in the presence of a small volume of experimental data.Abbreviations: DIC, deviance information criterion; MAE, mean absolute error; MCMC, Markov chain Monte Carlo; MSE, mean squared error; ODE, ordinary differential equation; TCE, trichloroethylene.