Engineered acetaldehyde dehydrogenase for the efficient degradation of acetaldehyde

New insight in the biotreatment of produced water: Pre-oxidation paves a rapid pathway for substrate selection in microbial community

The deep treatment of produced water (PW) had emerged as a formidable challenge due to the coexistence of hydrocarbons, surfactants, ammonium nitrogen, and other refractory organics. On the basis of the pre-oxidation coupled heterotrophic ammonia assimilation (PHAA) system constructed in previous research, this work refined the catalyst selection and reduced the hydraulic retention time. The stable running PHAA system removed 96.2 % of total organic carbon (TOC). The study simulated the effects of organic loading fluctuations on the system and dissected the mechanism of pre-oxidation process and its contribution to microbial community. Pre-oxidation significantly improved the ability of microbial community to handle loading shocks and improved organic degradation efficiency in PW during long-term reactor operation. The PHAA process effectively removed medium to long chain alkanes above C24 in PW and proposed potential degradation pathways and direction. The determination of hydrocarbon enzymes activity showed that pre-oxidation changed the substrate selection, making more aldehydes available as auxiliary carbon sources for microorganisms. Pre-oxidation also enriched and preserved microbial diversity, facilitating the accumulation of functional microorganisms in the PHAA process.

Efficient bioremediation of multiple steroid hormones by halotolerant 17β-hydroxysteroid dehydrogenase derived from moderately halophilic Pontibacillus chungwhensis HN14

Steroid hormones exhibit potent endocrine disrupting activity and have been shown to disrupt the equilibrium of aquatic ecosystems and pose a threat to public health through their persistent and carcinogenic effects. Pontibacillus chungwhensis HN14, a moderately halophilic bacterium with the capacity to effectively degrade various polycyclic aromatic hydrocarbons and other organic pollutants, was previously isolated. Additionally, the strain HN14 showed strong environmental adaptability under various environmental stress conditions. In this study, the steroid degradation by strain HN14 was studied for the first time. We demonstrated that strain HN14 could degrade estradiol (E2) to maintain the growth of the strain and could convert E2 to estrone. Additionally, the efficient substrate degradation efficiency of P. chungwhensis HN14 under high salinity and high substrate concentration conditions was demonstrated. Furthermore, a 17β-hydroxysteroid dehydrogenase, 17β-HSD(HN14), was identified in strain HN14. Comparative analysis reveals that 17β-HSD(HN14) shares approximately 38% sequence identity with 17β-HSDx from Rhodococcus sp. P14. In addition, 100 µg of purified 17β-HSD(HN14) could effectively convert about 40% of 0.25 mM of E2 within 1 h period, with an enzyme activity of 17.5 U/mg, and catalyze the dehydrogenation of E2 and testosterone at the C-17 position. The characterization of purified enzyme properties reveals that 17β-HSD(HN14) exhibits exceptional structural robustness and enzymatic efficacy even under high salinity conditions of up to 20%. Overall, this study enhances our comprehension of steroid biodegradation in strain HN14 and contributes novel ideas and theoretical underpinnings for advancing bioremediation technologies targeting steroid pollution in high-saline environments.

Genome analysis of a newly isolated Bacillus velezensis-YW01 for biodegrading acetaldehyde

Acetaldehyde (AL), a primary carcinogen, not only pollutes the environment, but also endangers human health after drinking alcohol. Here a promising bacterial strain was successfully isolated from a white wine cellar pool in the province of Shandong, China, and identified as Bacillus velezensis-YW01 with 16 S rDNA sequence. Using AL as sole carbon source, initial AL of 1 g/L could be completely biodegraded by YW01 within 84 h and the cell-free extracts of YW01 has also been detected to biodegrade the AL, which indicate that YW01 is a high-potential strain for the biodegradation of AL. The optimal culture conditions and the biodegradation of AL of YW01 are at pH 7.0 and 38 °C, respectively. To further analyze the biodegradation mechanism of AL, the whole genome of YW01 was sequenced. Genes ORF1040, ORF1814 and ORF0127 were revealed in KEGG, which encode for acetaldehyde dehydrogenase. Furthermore, ORF0881 and ORF052 encode for ethanol dehydrogenase. This work provides valuable information for exploring metabolic pathway of converting ethanol to AL and subsequently converting AL to carboxylic acid compounds, which opened up potential pathways for the development of microbial catalyst against AL.