Fructophilic behaviour of Gordonia alkanivorans strain 1B during dibenzothiophene desulfurization process

Abstract

Biodesulfurization (BDS) aims at the removal of recalcitrant sulfur from fossil fuels at mild operating conditions with the aid of microorganisms. These microorganisms can remove sulfur from dibenzothiphene (DBT), a model compound, or other polycyclic aromatic used as sulfur source, making BDS an easy and environmental friendly process. Gordonia alkanivorans strain 1B has been described as a desulfurizing bacterium, able to desulfurize DBT to 2-hydroxybiphenyl (2-HBP), the final product of the 4S pathway, using d-glucose as carbon source. However, both cell growth and desulfurization can be largely affected by the nutrient composition of the growth medium, due to cofactor requirements of many enzymes involved in the BDS biochemical pathway. In this study, the main goal was to investigate the influence of several sugars, as carbon source, on the growth and DBT desulfurization ability of G. alkanivorans strain 1B. The results of desulfurization tests showed that the lowest values for the growth rate (0.025 hour(-1)) and for the overall 2-HBP production rate (1.80 μm/hour) by the strain 1B were obtained in glucose grown cultures. When using sucrose, the growth rate increase exhibited by strain 1B led to a higher biomass productivity, which induced a slightly increase in the 2-HBP production rate (1.91 μm/hour), conversely in terms of 2-HBP specific production rate (q2-HBP) the value obtained was markedly lower (0.718 μmol/g/hour in sucrose versus 1.22 μmol/g/hour in glucose). When a mixture of glucose and fructose was used as carbon source, strain 1B reached a value of q2-HBP=1.90 μmol/g/hour, close to that in fructose (q2-HBP=2.12 μmol/g/hour). The highest values for both cell growth (μ=0.091 hour(-1)) and 2-HPB production (9.29μm/hour) were obtained when strain 1B was desulfurizing DBT in the presence of fructose as the only carbon source, indicating a fructophilic behaviour by this bacterium. This fact is in agreement with the highest value of biomass productivity by strain 1B be in fructose, which resulted in a higher amount cells fulfilling the DBT-desulfurization. The greater number of functional cells conducted to a more effectiveness BDS process by strain 1B, as they attained a q2-HBP about 74% higher than in glucose grown cultures. Moreover, this significant BDS enhancement can better be observed in terms of the overall 2-HBP production rate, which increased over 5-fold, from 1.80 μm/hour (in glucose) to 9.29 μm/hour (in fructose).

On the road to cost-effective fossil fuel desulfurization byGordonia alkanivoransstrain 1B

“…Trace element solution (TES). For the SFM medium used to grow G. alkanivorans strain 1B, a sulfur-free TES stock solution 9 is usually added in a concentration of 0.5 mL L À1 . Therefore, as in prior assays performed for N and Mg sources minimization, different formulations with decreasing concentrations of TES (F#8 to F#13, described in Table 1) were tested and compared with control (100% TES, F#1) in order to evaluate the minimum concentration of the TES needed by the bacterium to grow and desulfurize DBT.…”

“…Moreover, if a suitable cheaper alternative C-source is also addressed this may turn the overall bioprocess more sustainable and cost-effective, since the C-source is usually one of the most important and expensive nutrients into the culture medium. 16 Several alternative C-sources were already tested for BDS studies with strain 1B, but JAJ was the one with the most promising results, [9][10][11][12]17 and for that reason JAJ (>80% fructose) should be better exploited as the optimal alternative C-source for the fructophilic bacterium, specially using an SSF approach. 26 In addition to the cost reduction within the biocatalysts production step, high added-value byproducts, such as the carotenoids from strain 1B, 19,27 may be also exploited for their potential benets to turn BDS process economically viable.…”

“…In the last decade, several works have demonstrated the great potential of G. alkanivorans strain 1B towards fossil fuel BDS. 3,[7][8][9][10][11][12] However, this bioprocess still has a few limitations, such as the cost of the culture medium for the biocatalysts production. [12][13][14][15][16] In order to reduce the production costs, it is important to search for cheaper carbon sources which can contribute to produce less expensive microbial biomass.…”

“…25412 | RSC Adv., 2019, 9,[25405][25406][25407][25408][25409][25410][25411][25412][25413] This journal is © The Royal Society of Chemistry 2019…”

Jerusalem artichoke as low-cost fructose-rich feedstock for fossil fuels desulphurization by a fructophilic bacterium

“…These characteristics make this plant a natural source of fructose for the industry and an attractive alternative carbon source for microbial growth and further application to bioprocesses that use fructophilic microorganisms, such as BDS (Paixão et al . ; Alves and Paixão ).…”