Identification of two alkane hydroxylases involved in long-chain n-alkane degradation by Dietzia sp. DQ12-45-1b北大核心CSCD

The aim of this study was to identify genes involved in long-chain alkane degradation in Dietzia sp. DQ12-45-1b. Functional genes were annotated by genome analysis. Induction of alkane hydroxylase genes by C28 n-alkane was analyzed by using quantitative real-time PCR in wild-type Dietzia sp. DQ12-45-1b and its alkW1 gene knockout mutant strain M 5-5. From the genome of Dietzia sp. DQ12-45-1b, two homologues, G1 and G2 genes were annotated, which showed 50% amino acid sequence similarity with AlmA from Acinetobacter sp. DSM17874, and 48% amino acid sequence similarity with LadA from Geobacillus thermodenitrificans NG80-2, respectively. In addition, G1 showed 71% amino acid sequence similarity with G1a, and G2 showed 34% and 87% amino acid sequence similarities with G2a and G2ß, respectively, which were annotated from Dietzia sp. E1 genome. In addition, the alkW1 gene knockout strain M 5-5 could grow with C28 n-alkane as the sole carbon source, indicating the presence of potential long-chain alkane hydroxylase gene(s) other than alkW1 in Diezia sp. DQ12-45-1b. Accordingly, induction of G1 and G2 genes was observed when Dietzia ap. DQ12-45-1b and alkW1 knockout mutant strain M 5-5 grew with C28 n-alkane as sole carbon source. The results indicated that G1 and G2 genes are mostly responsible for the degradation of long-chain alkanes in Dietzia sp. DQ12-45-1b, which has unique multiple alkane hydroxylase systems.     

The oligopeptides production by the feather-degrading bacterium Bacillus methylotrophicus H0北大核心CSCD

Due to the high nutritive value of oligopeptides and the waste of feather resources, this study aimed at screening efficient strains of bacteria able to rapidly degrade feathers and produce large quantities of value-added oligopeptides. In order to assess the potential yield of oligopeptides, the promising strain H0 was selected from 16 feather-degrading microorganisms. To identify the strain, we analyzed the morphological and physiological characteristics of different strains, and carried out a gene sequence analysis of their 16S rRNAs. A single factor experiment was used to promote feather degradation and oligopeptide production, and the characteristics of the oligopeptides produced were also analyzed by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS). The strain was identified as Bacillus methylotrophicus. The optimal initial pH and temperature for oligopeptide production were 11 and 40 °C, respectively. After 72 h of fermentation under these optimal conditions, the feathers were almost completely degraded, with a 38.19% of oligopeptides (accounting for 67.53% of the total soluble peptides) and a 11.11% of free amino acids produced. LC-MS/MS analysis indicated that the oligopeptides were mainly short peptides containing 5-10 amino acids, with a molecular mass (Mr) of less than 1 300. Moreover, the peptides were abundant in branched-chain amino acids, that might be responsible for the antioxidant property of the feather hydrolysate. Our results demonstrate the great capability of B. methylotrophicus H0 in feather degradation and oligopeptide production. This research provides a high-quality microorganism resource, and the scientific basis for the development of feather-derived oligopeptide products. © 2018 Science Press. All rights reserved.     

Removal of sulfamethoxazole and trimethoprim from reclaimed water and the biodegradation mechanism

Sulfamethoxazole (SMX) and trimethoprim (TMP) are two critical sulfonamide antibiotics with enhanced persistency that are commonly found in wastewater treatment plants. Recently, more scholars have showed interests in how SMX and TMP antibiotics are biodegraded, which is seldom reported previously. Novel artificial composite soil treatment systems were designed to allow biodegradation to effectively remove adsorbed SMX and TMP from the surface of clay ceramsites. A synergy between sorption and biodegradation improves the removal of SMX and TMP. One highly efficient SMX and TMP degrading bacteria strain, Bacillus subtilis, was isolated from column reactors. In the removal process, this bacteria degrade SMX and TMP to NH ₄ ⁺ , and then further convert NH ₄ ⁺ to NO ₃ ^– in a continuous process. Microbial adaptation time was longer for SMX degradation than for TMP, and SMX was also able to be degraded in aerobic conditions. Importantly, the artificial composite soil treatment system is suitable for application in practical engineering.

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Screening and degradation characteristics of a tetracycline-degrading bacterial strain北大核心CSCD

Tetracycline is widely used in livestock and poultry breeding industry, which can cause serious problems to the environment. Antibiotic pollution has become an important environmental issue. This study aimed to isolate and identify a well-functioning tetracycline-degrading bacteria strain from activated sludge and to investigate its optimum degradation conditions. The strain was identified through morphological features, Gram staining, and the sequence analysis of 16S rRNA. Furthermore, the temperature, initial pH of the medium, inoculation amount, and type of metallic salt were analyzed to investigate the tetracycline degradation performance of the isolated strain. Based on the single factor test, the method of response surface analysis was adopted to optimize the degradation condition. The strain was named TTC-1 and identified as Klebsiella pneumoniae. The optimum condition for tetracycline degradation was determined as follows: temperature of 34.4 °C, pH of 7.22, and MnSO4 concentration of 0.32 g/L. Under this optimum condition, the predicted tetracycline degradation rate was 93.77%, whereas the observed value was 94.26%. The experimental results showed that the proposed model had high accuracy. TTC-1 showed a good performance in degrading tetracycline, which can provide reference for the bacteria during the biological treatment of tetracycline containing wastewater. © 2018 Science Press. All rights reserved.