Interplay between Sulfur Assimilation and Biodesulfurization Activity in Rhodococcus qingshengii IGTS8: Insights into a Regulatory Role of the Reverse Transsulfuration Pathway

Abstract

Precise genome editing of the model biocatalyst Rhodococcus qingshengii IGTS8 was performed for the first time, more than 3 decades after its initial discovery. We thus gained insight into the regulation of dsz gene expression and biocatalyst activity, depending on the presence of two reverse transsulfuration enzymes, CβS and MetB.

Deciphering the biodesulfurization potential of two novel <i>Rhodococcus</i> isolates from a unique Greek environment

“…Having in mind that in Gordonia alkanivorans [48] glucose can induce a lag-phase of more than 72 h, the glucose cultures were incubated for more than a week without achieving any substantial growth level, similarly to those depicted in Figure 3 . A more scrutinous look on the relevant studies reveals that glucose had been used as carbon source in the past, but until recently, never in a minimal salt medium in combination with DMSO as the sole sulfur source [27] . Even in R. qingshengii IGTS8 studies where glucose (at 20 g/L) and DMSO are claimed to be the best combination of carbon and sulfur sources, respectively, with respect to growth and BDS activity, the basal medium employed contained an additional 20 g/L of glycerol [29] , [40] .…”

“…To examine the effect of different media on growth and desulfurization activity, the wild-type strain R. qingshengii IGTS8 and the isolated strains R. qingshengii ATHUBA4003 and ATHUBA4006 were grown in CDM pH = 7.0, under different carbon, nitrogen, and sulfur sources of a predefined concentration. Growth took place in 96-well cell culture plates (F-bottom; Greiner Bio-One, Fischer Scientific, US) in thermostated plate shakers at 30 °C and 600 rpm as previously described [27] . An initial biomass concentration of 0.045–0.055 g/L (dry cell weight) was universally applied, while 60 identical well-cultures were used per condition (150 µL culture per cell).…”

“…A tube with equivalent amounts of cells and acetonitrile without incubation (t = 0) was used as blank. The supernatant was assayed for 2-HBP determination by HPLC with fluorescence detection [27] . BDS activity was expressed as Units per mg DCW, with 1 U corresponding to the release of 1 nmole 2-HBP per h under the above-described conditions.…”

A new impetus for biodesulfurization: bypassing sulfate inhibition in biocatalyst production

“…, easy-access S-sources), such as sulfate (SO 4 2− ). 15 The presence of SO 4 2− in the culture medium used to grow the biocatalysts, or as supplementation for the BDS process, leads to the repression of the dsz operon. Even concentrations as low as a few mg L −1 can cause severe inhibition of BDS activity.…”

Medium composition overturns the widely accepted sulfate‐dependent repression of desulfurization phenotype in Rhodococcus qingshengii IGTS8

“…The process is realized using resting cells of the microorganism (biocatalyst) in well‐aerated biphasic bioreactors, following biocatalyst production in a medium where the 4S‐related pathway is induced. Although the influence of media composition in the induction of the 4S phenotype has been explored (Abo‐State et al, 2014; del Olmo et al, 2005a; Yan et al, 2000), certain limitations impede the process such as the problem of sulfate‐, methionine‐, or cysteine‐mediated repression of catalytic activity (Li et al, 1996; Martzoukou et al, 2022). Moreover, the true influence of carbon source on growth and BDS activity of R. qingshengii IGTS8 remained understudied, partly due to the practice of dual carbon source supplementation employed in several studies (del Olmo et al, 2005a; 2005b; Li et al, 1996; Piddington et al, 1995).…”