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Carbaryl wastewater treatment and the resource recycling of biomass as sludge by Rhodopseudomonas sphaeroides (R. sphaeroides) with the assistance of starch processing wastewater (SPW) was investigated in this research. It was observed that carbaryl was not degraded under the 100, 500 mg/L COD groups. The addition of SPW assisted R. sphaeroides to degrade carbaryl efficiently. Carbaryl removal reached 100% after 5 days under the optimal group (3500 mg/L). Interestingly, carbaryl in the mixed wastewater began to be degraded after day 1. Further research indicated that cehA gene was expressed after day 1. Subsequently, carbaryl hydrolase was synthesized under gene regulation. Analysis revealed that cehA and carbaryl hydrolase were adaptive gene expressions and enzymes. Carbaryl as stimulus signal started cehA gene expression through signal transduction pathway. This process took one day for R. sphaeroides. However, organics in 100, 500 mg/L COD groups were deficient, which could not maintain R. sphaeroides growth for over one day. Organics in SPW provided sufficient carbon sources for R. sphaeroides under other groups. The method could complete the mixed (SPW and carbaryl) wastewater treatment, carbaryl removal, the resource recycling of R. sphaeroides biomass as sludge simultaneously. • Carbaryl wastewater treatment under the assistance of SPW was investigated. • Carbaryl removal and biomass recovery using R. sphaeroides and SPW was feasible. • Carbaryl hydrolase, cehA gene were found after inoculation day 1. • COD in SPW provided carbon sources for R. sphaeroides growth to exceed day 1. [ABSTRACT FROM AUTHOR]

Enhancing the biodegradation efficiency of atrazine, a kind of commonly applied herbicide, has been attracted much more concern. Here, Zn 2+ which has long been considered essential in adjusting cell physiological status was selected to investigate its role on the biodegradation of atrazine by Arthrobacter sp. DNS10 as well as the transmembrane transport of atrazine during the biodegradation period. The results of gas chromatography showed that the atrazine removal percentages (initial concentration was 100 mg L -1 ) in 0.05 mM Zn 2+ and 1.0 mM Zn 2+ treatments were 94.42% and 86.02% respectively at 48 h, while there was also 66.43% of atrazine left in the treatment without exogenous Zn 2+ existence. The expression of atrazine chlorohydrolase gene trzN in the strain DNS10 cultured with 0.05 mM and 1.0 mM Zn 2+ was 7.30- and 4.67- times respectively compared with that of the non-zinc treatment. In addition, the flow cytometry test suggests that 0.05 mM of Zn 2+ could better adjust the membrane permeability of strain DNS10, meanwhile, the amount of atrazine accumulation in the strain DNS10 co-cultured with this level Zn 2+ was 2.21 times of that of the strain without Zn 2+ . This study may facilitate a better understanding of the mechanisms that exogenous Zn 2+ enhances the biodegradation of atrazine by Arthrobacter sp. DNS10., (Copyright © 2019 Elsevier Ltd. All rights reserved.)