Optimization of fed-batch fermentation and direct spray drying in the preparation of microbial inoculant of acetochlor-degrading strain Sphingomonas sp. DC-6

Abstract

Microbial inoculant preparation is a prerequisite for its application in large-scale bioremediation. In the present study, sp. DC-6, an efficient acetochlor-degrading strain, was used to investigate the process of preparing the inoculant. Optimization of submerged fermentation (SmF) by response surface methodology (RSM) resulted in a first 22% increase in biomass of liquid inoculant. Then, a biomass increase of 2.18 times with 14.58% shortened incubation period was further obtained in optimized medium using a 7.5-l bioreactor. However, less than 0.4% viable cells in liquid inoculant survived after 180-days storage. Thus, optimized spray drying conditions were subsequently employed for the production of high viability powder (2.11 × 10 cfu g powder) without additive and its survival ratio (SR) after 180-days storage was still maintained at 90.5%. Both the 180-days stored powder and the original powder showed the same degradation performance, being able to completely degrade 200 mg l acetochlor within 48 h. This study demonstrated that strain DC-6 was suitable for industrial production of bacteria powder and provided a potential approach for the preparation of pesticide-degrading microbial inoculant.

Degradation of acetochlor and beneficial effect of phosphate-solubilizing Bacillus sp. ACD-9 on maize seedlings

“…The degradation rate of acetochlor was highest at 42 °C and exceeded 60% at 37-46 °C. Several reported strains exhibit optimum acetochlor degradation effects at pH 7.0 and temperatures of approximately 30 and 37 °C (Xu et al 2013;Luo et al 2015;Chen et al 2015;Wang et al 2018a). Hence, in the present study, good tolerance to a high temperature range (40-46 °C) and neutral to partially acid conditions (pH 5.0-7.0) is a major advantage of strain ACD-9.…”

“…Other acetochlor-degrading strains, such as Sphingomonas sp. DC-6 (Li 2016;Wang et al 2018a), can also significantly reduce the harmful effects of acetochlor on maize. The degradation rate of acetochlor (1 mg/kg soil) by it could reach 89.29% within 15 days, but no significant growth-promoting effect on maize growth was observed.…”

Microbial Blends: Terminology Overview and Introduction of the Neologism “Skopobiota”

“…According to this analysis and in light of the fact that they are often used interchangeably, we conclude that the terms microbial consortium, synthetic microbial community, microbial cocktail, and synthetic microbiome Del Frari et al, 2019;El Hage et al, 2019;Colpa et al, 2020;Pereira et al, 2020;Dai et al, 2021 Chen et al, 2018;Wang et al, 2018;Rafique et al, 2019;Rékási et al, 2019;Dong et al, 2020;Singh et al, 2020 Synthetic microbial community Shahab et al, 2018;Carrión et al, 2019;Christiaens et al, 2019;Honjo et al, 2019;Wang et al, 2020;Krieger et al, 2021 Microbial cocktail Moreira et al, 2017;Qu et al, 2018;Pasaribu et al, 2019;Pires et al, 2019;Tobin et al, 2020;Zheng et al, 2020 Synthetic microbiome Venturelli et al, 2018;Timmis et al, 2019;Vandeplassche et al, 2019;Voges et al, 2019;Koskella, 2020;Mabwi et al, 2021 The symbol "+" indicates the presence of the specific key characteristic, while the symbol "-" indicates its absence, in association with each term (refer to the text for the definition of the concepts of each key characteristic).…”