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

Streamlining the biodesulfurization process: development of an integrated continuous system prototype using Gordonia alkanivorans strain 1B

Biodesulfurization is a biotechnological process that uses microorganisms as biocatalysts to actively remove sulfur from fuels. It has the potential to be cleaner and more efficient than the current industrial process, however several bottlenecks have prevented its implementation. Additionally, most works propose models based on direct cultivation on fuel, or batch production of biocatalysts followed by a processing step before application to batch biodesulfurization, which are difficult to replicate at a larger scale. Thus, there is a need for a model that can be adapted to a refining process, where fuel is being continuously produced to meet consumer needs. The main goal of this work was to develop the first bench-scale continuous biodesulfurization system that integrates biocatalyst production, biodesulfurization and fuel separation, into a single continuous process, taking advantage of the method for the continuous production of the biodesulfurization biocatalysts previously established. This system eliminates the need to process the biocatalysts and facilitates fuel separation, while mitigating some of the process bottlenecks. First, using the bacterium Gordonia alkanivorans strain 1B, continuous culture conditions were optimized to double biocatalyst production, and the produced biocatalysts were applied in batch biphasic biodesulfurization assays for a better understanding of the influence of different factors. Then, the novel integrated system was developed and evaluated using a model fuel (n-heptane + dibenzothiophene) in continuous biodesulfurization assays. With this system strain 1B surpassed its highest biodesulfurization rate, reaching 21 μmol h-1 g-1. Furthermore, by testing a recalcitrant model fuel, composed of n-heptane with dibenzothiophene and three alkylated derivatives (with 109 ppm of sulfur), 72% biodesulfurization was achieved by repeatedly passing the same fuel through the system, maintaining a constant response throughout sequential biodesulfurization cycles. Lastly, the system was also tested with real fuels (used tire/plastic pyrolysis oil; sweet and sour crude oils), revealing increased desulfurization activity. These results highlight the potential of the continuous biodesulfurization system to accelerate the transition from bench to commercial scale, contributing to the development of biodesulfurization biorefineries, centered on the valorization of sulfur-rich residues/biomasses for energy production.

A New Biosurfactant/Bioemulsifier from Gordonia alkanivorans Strain 1B: Production and Characterization

Biosurfactants and bioemulsifiers (BS/BE) are naturally synthesized molecules, which can be used as alternatives to traditional detergents. These molecules are commonly produced by microorganisms isolated from hydrocarbon-rich environments. Gordonia alkanivorans strain 1B was originally found in such an environment, however little was known about its abilities as a BS/BE producer. The goal of this work was to access the potential of strain 1B as a BS/BE producer and perform the initial characterization of the produced compounds. It was demonstrated that strain 1B was able to synthesize lipoglycoprotein compounds with BS/BE properties, both extracellularly and adhered to the cells, without the need for a hydrophobic inducer, producing emulsion in several different hydrophobic phases. Using a crude BS/BE powder, the critical micelle concentration was determined (CMC = 16.94 mg/L), and its capacity to reduce the surface tension to a minimum of 35.63 mN/m was demonstrated, surpassing many commercial surfactants. Moreover, after dialysis, emulsification assays revealed an activity similar to that of Triton X-100 in almond and sunflower oils. In benzene, the E24 value attained was 83.45%, which is 30% greater than that of the commercial alternative. The results obtained highlight for the presence of promising novel BS/BE produced by strain 1B.

Paixão S, S. Fernandes A, C. Roseiro J, Alves L. New Insights on Carotenoid Production by Gordonia alkanivorans Strain 1B

Gordonia alkanivorans strain 1B is a desulfurizing bacterium and a hyper-pigment producer. Most carotenoid optimization studies have been performed with light, but little is still known on how carbon/sulfur-source concentrations influence carotenoid production under darkness. In this work, a surface response methodology based on a two-factor Doehlert distribution (% glucose in a glucose/fructose 10 g/L mixture; sulfate concentration) was used to study carotenoid and biomass production without light. These responses were then compared to those previously obtained under light. Moreover, carbon consumption was also monitored, and different metabolic parameters were further calculated. The results indicate that both light and glucose promote slower growth rates, but stimulate carotenoid production and carbon conversion to carotenoids and biomass. Fructose induces higher growth rates, and greater biomass production at 72 h; however, its presence seems to inhibit carotenoid production. Moreover, although at a much lower yield than under light, results demonstrate that under darkness the highest carotenoid production can be achieved with 100% glucose (10 g/L), ≥27 mg/L sulfate, and high growth time (>216 h). These results give a novel insight into the metabolism of strain 1B, highlighting the importance of culture conditions optimization to increase the process efficiency for carotenoid and/or biomass production.

Metabolite Analysis of Jerusalem Artichoke (Helianthus tuberosus L.) Seedlings in Response to Polyethylene Glycol-Simulated Drought Stress

Jerusalem artichokes are a perennial crop with high drought tolerance and high value as a raw material to produce biofuels, functional feed, and food. However, there are few comprehensive metabolomic studies on Jerusalem artichokes under drought conditions. Methods: Ultra-performance liquid chromatography and tandem mass spectrometry were used to identify differential metabolites in Jerusalem artichoke seedling leaves under polyethylene glycol (PEG) 6000-simulated drought stress at 0, 18, 24, and 36 h. Results: A total of 661 metabolites and 236 differential metabolites were identified at 0 vs. 18, 18 vs. 24, and 24 vs. 36 h. 146 differential metabolites and 56 common were identified and at 0 vs. 18, 24, and 36 h. Kyoto Encyclopedia of Genes and Genomes enrichment identified 236 differential metabolites involved in the biosynthesis of secondary metabolites and amino acids. Metabolites involved in glycolysis, phenolic metabolism, tricarboxylic cycle, glutamate-mediated proline biosynthesis, urea cycle, amino acid metabolism, unsaturated fatty acid biosynthesis, and the met salvage pathway responded to drought stress. Conclusion: A metabolic network in the leaves of Jerusalem artichokes under drought stress is proposed. These results will improve understanding of the metabolite response to drought stress in Jerusalem artichokes and develop a foundation for breeding drought-resistant varieties.

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

Biodesulfurization (BDS) is an ecofriendly process that uses microorganisms to efficiently remove sulfur from fossil fuels. To make the BDS process economically competitive with the deep hydrodesulfurization process, which is currently used in the oil industry, it is necessary to improve several factors. One crucial limitation to be overcome, common within many other biotechnological processes, is the cost of the culture medium. Therefore, an important line of work to make BDS scale-up less costly is the optimization of the culture medium composition aiming to reduce operating expenses and maximize biocatalyst production. In this context, the main goal of this study was on the minimization of inorganic key components of sulfur-free mineral (SFM) medium in order to get the maximal production of efficient desulfurizing biocatalysts. Hence, a set of assays was carried out to develop an optimal culture medium containing minimal amounts of nitrogen (N) and magnesium (Mg) sources and trace elements solution (TES). These assays allowed the design of a SFMM (SFM minimum) medium containing 85% N-source, 25% Mg-source and 25% TES. Further validation consisted of testing this minimized medium using two carbon sources: the commercial C-source (glucose + fructose) versus Jerusalem artichoke juice (JAJ) as a cheaper alternative. SFMM medium allowed microbial cells to almost duplicate their specific desulfurization rate (q_2-HBP) for both tested C-sources, namely from 2.15 to 3.39 μmoL g⁻¹ (DCW) h⁻¹ for Fru + Glu and from 1.91 to 3.58 μmoL g⁻¹ (DCW) h⁻¹ for JAJ, achieving a similar net 2-hydroxybiphenyl produced per g of consumed sugar (∼17 μmoL g⁻¹). These results point out the great advantage of using cheaper culture medium that in addition enhances the bioprocess effectiveness, paving the way to a sustainable scale-up for fossil fuel BDS.

The utilization of desulfurizing microorganisms that can grow in low nutrient culture media without vitamins and other growth promoters (e.g. yeast extract, peptone) is an advantage for BDS upgrade since it may reduce the biocatalyst production costs significantly

Simultaneously saccharification and fermentation approach as a tool for enhanced fossil fuels biodesulfurization

Biodesulfurization can be a complementary technology to the hydrodesulfurization, the commonly physical-chemical process used for sulfur removal from crude oil. The desulfurizing bacterium Gordonia alkanivorans strain 1B as a fructophilic microorganism requires fructose as C-source. In this context, the main goal of this work was the optimization of a simultaneous saccharification and fermentation (SSF) approach using the Zygosaccharomyces bailii strain Talf1 crude enzymes with invertase activity and sucrose as a cheaper fructose-rich commercial C-source (50% fructose) towards dibenzothiophene (DBT) desulfurization by strain 1B. The determination of optimal conditions, for both sucrose hydrolysis and DBT desulfurization was carried out through two sequential experimental uniform designs according to the Doehlert distribution for two factors: pH (5.5-7.5) and temperature (28-38 °C), with the enzyme load of 1.16 U/g/L; and enzyme load (0-4 U/g/L) and temperature (28-38 °C), with pH at 7.5. Based on 2-hydroxybiphenyl production, the analysis of the response surfaces obtained pointed out for pH 7.5, 32 °C and 1.8 U/g/L as optimal conditions. Further optimized SSF of sucrose during the DBT desulfurization process permitted to attain a 4-fold enhanced biodesulfurization. This study opens a new focus of research through the exploitation of sustainable low cost sucrose-rich feedstocks towards a more economical viable bioprocess scale-up.

Ability of Gordonia alkanivorans strain 1B for high added value carotenoids production

Currently, carotenoids are valuable bioactive molecules for several industries, such as chemical, pharmaceutical, food and cosmetics, due to their multiple benefits as natural colorants, antioxidants and vitamin precursors.

Transcriptional analysis of Kluyveromyces marxianus for ethanol production from inulin using consolidated bioprocessing technology

BACKGROUND

Ethanol production from non-crop materials, such as Jerusalem artichokes, would make a great contribution to the energy industry. The non-conventional yeast, Kluyveromyces marxianus, is able to carry out ethanol fermentation of sugar molecules obtained from inulin-containing materials by consolidated bioprocessing. Lower inulin concentrations and micro-aeration can lead to a relatively fast and ideal fermentation process; however, it is unclear what causes the inhibition of higher concentrations of inulin and the promotion effect of aeration.

RESULTS

Next-generation sequencing technology was used to study the global transcriptional response of K. marxianus Y179 under three fermentation conditions, including 120 g/L inulin without aeration (120-N), 230 g/L inulin without aeration (230-N), 230 g/L inulin with aeration by ORP controlling at -130 mV (230-130mV). A total of 35.55 million clean reads were generated from three samples, of which 4,820 predicted that open reading frames were annotated. For differential expression analysis, 950 and 1,452 differentially expressed genes were discovered under the conditions of 230-130mV and 120-N, respectively, and the sample 230-N was used as the control. These genes are mainly associated with the pathways of central carbon metabolism and ethanol formation. Increased expression of inulinase and the low activity of the autophagy-related gene, ATG8, ensured fast and ideal fermentation processes.

CONCLUSIONS

Despite being reported as the "crabtree-negative" species, K. marxianus Y179 could achieve favorable ethanol fermentation profiles under micro-aeration and high inulin concentrations. K. marxianus Y179 cells responded to inulin concentrations and micro-aeration that is involved in the whole ethanol metabolism network. These results will serve as an important foundation for further exploration of the regulatory mechanisms involved in ethanol fermentation from inulin by consolidated bioprocessing and also provide a valuable reference for future studies on optimization and reconstruction of the metabolism network in K. marxianus.