Polyhydroxyalkanoate (PHA), produced by mixed microbial cultures (MMCs), is a biodegradable biopolyester that alleviates the global plastic crisis in the nearest future. Even PHA has become a research hotspot, reviews on PHA composition determining thermodynamic and processing properties of PHA products are rare. The primary focus of the evaluation relies on the factors affecting the PHA monomer composition of MMC-PHA production. Besides, since the volatile fatty acids (VFAs) composition of the substrates strongly influences the PHA monomer composition, regulating the ratio of even-carbon to odd-carbon VFAs, PHA, vary properties could be obtained predictably. So oriented acid production process, the first stage process in three-stage MMC-PHA production that can regulate the VFAs composition, is also comprehensively introduced to help understand PHA monomer regulation.
The microbial characteristics of water treated by tea polyphenols after the ultrafiltration process were studied based on the continuous disinfection performance of tea polyphenols. Metagenomics was carried out to investigate the microbial community distribution, functional characteristics, and variations after disinfection, to reveal the disinfection principle of tea polyphenols, and to provide the theoretical basis for using tea polyphenols as a disinfectant to better control the growth of microorganisms. The analysis of microbial diversity and community structure showed that the microbial diversity in water was significantly reduced after disinfection with tea polyphenols. The results of hierarchical clustering analysis showed that microbial metabolism, environmental information processing, and functional modules in genetic information processing were significantly inhibited after disinfection treatment using tea polyphenols. The tea polyphenols inhibit the growth and reproduction of microorganisms by selection on the microorganisms in the water, thus achieving the effect of bacterial inhibition.
To reduce the risk of by-products from traditional disinfection technology and to ensure safe water quality, tea polyphenols (TP) were used as disinfectants after the ultrafiltration (UF) process. The disinfectant effect of TP was tested on the total number of bacteria and changes in bacterial community structure, and pathogen virulence factors were detected by Illumina’s high-throughput sequencing technology. The results showed that the recommended dosage of TP for water treatment after UF was 5 mg/L, which can effectively inhibit bacterial growth and maintain the disinfectant effect for up to 48 h later. In the disinfection process, the degradation of the tea polyphenols concentration was fitted to the equation of the second order reaction kinetics. The lower the initial concentration and the higher the reaction temperature, the faster the TP decay. The metagenomic analysis of the microorganisms indicated that disinfection with tea polyphenols reduced the diversity of microorganisms in the water and altered the structure of the bacterial community. The existence of tea polyphenols also significantly inhibited the growth of potential common Gram-negative pathogens, especially Mycobacterium. TP disinfectant can also reduce the diversity and abundance of pathogenic bacterial virulence factors and improve biological safety in drinking water.
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