A fixed-film bioscrubber of Microbacterium esteraromaticum SBS1-7 for toluene/styrene biodegradation.

In the present study, a fixed-film bioscrubber (FFBS) of BTEX-degrading bacterium Microbacterium esteraromaticum SBS1-7 with 'AQUAPOROUSGEL® or APG' supporting material was continuously fed with toluene- or styrene-contaminated gas stream for 172 days. Response Surface Methodology (RSM) was used to optimize the biofilm formation on APG as well as the toluene biodegradation in mineral salt medium (MM). The results suggested that 1000 ppm of yeast extract (YE) was necessary for biofilm formation of SBS1-7. The optimized combination of YE and toluene concentration exhibiting the highest biofilm formation and toluene removal was further employed in an up-scale FFBS operation. The maximum Elimination Capacity (ECmax) of 203 g·m-3·h-1 was obtained at the toluene Inlet Loading Rate (ILR) of 295 g·m-3·h-1. FFBS of SBS1-7 was able to withstand a 5-day shutdown and required only 24 h to recover. Moreover, when the inlet Volatile Organic Compound was shifted to styrene, FFBS required only 24 h for adaptation and the system was able to efficiently remove ~95% of styrene after that. Finally, the performance of the bioscrubber when operated in 2 different modes of operation (FFBS vs Biotricking Filter or BTF) were compared. This study evidently demonstrated the robustness and stability of FFBS with M. esteraromaticum SBS1-7.

Colorimetric reverse transcription loop-mediated isothermal amplification (RT-LAMP) as a visual diagnostic platform for the detection of the emerging coronavirus SARS-CoV-2.

COVID-19, caused by the infection of SARS-CoV-2, has emerged as a rapidly spreading infection. The disease has now reached the level of a global pandemic and as a result a more rapid and simple detection method is imperative to curb the spread of the virus. We aimed to develop a visual diagnostic platform for SARS-CoV-2 based on colorimetric RT-LAMP with levels of sensitivity and specificity comparable to that of commercial qRT-PCR assays. In this work, the primers were designed to target a conserved region of the RNA-dependent RNA polymerase gene (RdRp). The assay was characterized for its sensitivity and specificity, and validated with clinical specimens collected in Thailand. The developed colorimetric RT-LAMP assay could amplify the target gene and enabled visual interpretation in 60 min at 65 °C. No cross-reactivity with six other common human respiratory viruses (influenza A virus subtypes H1 and H3, influenza B virus, respiratory syncytial virus types A and B, and human metapneumovirus) and five other human coronaviruses (MERS-CoV, HKU-1, OC43, 229E and NL63) was observed. The limit of detection was 25 copies per reaction when evaluated with contrived specimens. However, the detection rate at this concentration fell to 95.8% when the incubation time was reduced from 60 to 30 min. The diagnostic performance of the developed RT-LAMP assay was evaluated in 2120 clinical specimens and compared with the commercial qRT-PCR. The results revealed high sensitivity and specificity of 95.74% and 99.95%, respectively. The overall accuracy of the RT-LAMP assay was determined to be 99.86%. In summary, our results indicate that the developed colorimetric RT-LAMP provides a simple, sensitive and reliable approach for the detection of SARS-CoV-2 in clinical samples, implying its beneficial use as a diagnostic platform for COVID-19 screening.

BTEX biodegradation by Bacillus amyloliquefaciens subsp. plantarum W1 and its proposed BTEX biodegradation pathways.

Benzene, toluene, ethylbenzene and (p-, m- and o-) xylene (BTEX) are classified as main pollutants by several environmental protection agencies. In this study, a non-pathogenic, Gram-positive rod-shape bacterium with an ability to degrade all six BTEX compounds, employed as an individual substrate or as a mixture, was isolated. The bacterial isolate was identified as Bacillus amyloliquefaciens subsp. plantarum strain W1. An overall BTEX biodegradation (as individual substrates) by strain W1 could be ranked as: toluene > benzene, ethylbenzene, p-xylene > m-xylene > o-xylene. When presented in a BTEX mixture, m-xylene and o-xylene biodegradation was slightly improved suggesting an induction effect by other BTEX components. BTEX biodegradation pathways of strain W1 were proposed based on analyses of its metabolic intermediates identified by LC-MS/MS. Detected activity of several putative monooxygenases and dioxygenases suggested the versatility of strain W1. Thus far, this is the first report of biodegradation pathways for all of the six BTEX compounds by a unique bacterium of the genus Bacillus. Moreover, B. amyloliquefaciens subsp. plantarum W1 could be a good candidate for an in situ bioremediation considering its Generally Recognized as Safe (GRAS) status and a possibility to serve as a plant growth-promoting rhizobacterium (PGPR).

BTEX- and naphthalene-degrading bacterium Microbacterium esteraromaticum strain SBS1-7 isolated from estuarine sediment.

In this study, a non-pathogenic, BTEX-degrading Microbacterium esteraromaticum SBS1-7 was isolated from estuarine sediment in Thailand via an enrichment technique. M. esteraromaticum SBS1-7 was able to degrade all six BTEX components, in both liquid medium and soil slurry system, when BTEX was supplied as an individual component or a mixture. It exhibited a high level of tolerance towards a wide range of hydrocarbons and also utilized alkanes and naphthalene. Detection of metabolites produced during BTEX and naphthalene degradation revealed highly extensive biodegradation pathways used by M. esteraromaticum SBS1-7. Toluene was metabolized via activities of both monooxygenase (toluene 4-monooxygenase or T4MO) and dioxygenases (toluene dioxygenase or TDO and naphthalene 1,2-dioxygenase or NDO). Benzene was metabolized via phenol, possibly by an activity of T4MO. Ethylbenzene was converted into styrene and 1-phenethyl alcohol by a well-documented activity of NDO. Dioxidation of ethylbenzene, possibly by ethylbenzene dioxygenase or EBDO, was also found. All xylene isomers were converted into their corresponding alcohols via an activity of NDO while naphthalene was metabolized via dioxidation reaction by the same enzyme. This study is, by far, the first direct evidence of BTEX biodegradation by a non-pathogenic, rhizosphere bacterium M. esteraromaticum.