Enhancement of dibenzothiophene desulfurization by Gordonia alkanivorans strain 1B using sugar beet molasses as alternative carbon source

There are several problems limiting an industrial application of fossil fuel biodesulfurization, and one of them is the cost of culture media used to grow the microorganisms involved in the process. In this context, the utilization of alternative carbon sources resulting from agro-industrial by-products could be a strategy to reduce the investment in the operating expenses of a future industrial application. Recently, Gordonia alkanivorans 1B was described as a fructophilic desulfurizing bacterium, and this characteristic opens a new interest in alternative carbon sources rich in fructose. Thus, the goal of this study was to evaluate the utilization of sugar beet molasses (SBM) in the dibenzothiophene (DBT) desulfurization process using strain 1B. SBM firstly treated with 0.25 % BaCl2 (w/v) was used after sucrose acidic hydrolysis or in a simultaneous saccharification and fermentation process with a Zygosaccharomyces bailii Talf1 invertase (1 %), showing promising results. In optimal conditions, strain 1B presented a ìmax of 0.0795 h.1, and all DBT was converted to 2-hydroxybiphenyl (250 ìM) within 48 h with a maximum production rate of 7.78 ìM h.1. Our results showed the high potential of SBM to be used in a future industrial fossil fuel biodesulfurization process using strain 1B

Acute toxicity evaluation of several compounds involved in fossil fuels biodesulphurisation studies

The increasing use of fossil fuels has led to increased emissions of sulphur oxides into the air, which is a major cause of acid rain. Legislation already adopted in 2009 stipulates that the maximum level of sulphur allowed in fuels is only 10 ppm. The process of hydrodesulphurization (HDS) used in refineries is based on very expensive physico-chemical techniques, and has limitations in the removal of organic sulphur. As for stricter legislation on the maximum levels of sulphur in fossil fuels, the most HDS recalcitrant compounds needs to be removed. This implies an increase in the intensity of the physical-chemical treatment and inherently its associated costs. As a result, the recalcitrant compounds to HDS represent a significant barrier to the achievement of very low levels of sulphur in some petroleum fractions. The alternative to the physical-chemical treatment could be the use of biological processes (biodesulphurisation) which is more effective for the desulphurization of fossil fuels, especially as the removal of sulphur covalently bound to organic matrices. The biodesulphurisation (BDS) occurs in more mild conditions of operation under conditions of atmospheric pressure and temperature, giving greater specificity of reaction due to the nature of the biocatalysts, not requiring molecular hydrogen. Thus, in the last 15 years there has been an increase of studies involving the use of microorganisms with the ability to specifically remove the HDS recalcitrant sulphur compounds. Several model compounds such as dibenzothiophene (DBT), DBT sulphone or benzothiophene (BT) are used in BDS studies to characterise organic sulphur in coal, coal tars and crude oils. The desulphurising microorganisms are able to remove the sulphur atom from these compounds and use it in their metabolism. However, such compounds are very toxic to the cells. The aim of this work was to evaluate the toxicity of several compounds used in BDS studies, such as DBT and its derivatives and organic solvents used to dissolve these hydrocarbons, to two typical desulphurising strains, namely: Gordonia alkanivorans strain 1B and Rhodococcus eritropolis strain D1. The toxicity bioassays evaluated the inhibitory effect of the studied compounds to the described bacteria by measuring the respiration rate (mg O2/l) under defined conditions in the presence of different concentrations of those compounds. The inhibitory or toxic effect of each chemical at a specific concentration is expressed as a percent of the baseline respiration rate. From these results the several IC50s were estimated and are described in Table 1. These toxicity values showed that strain 1B was less sensitive for almost all of the hydrocarbons, which is an important advantage considering the desulphurisation of fossil fuels process. On the other hand, strain 1B was more sensitive to dimethylformamide (DMF), a typical solvent used in BDS studies. However, a good correlation can be observed between IC50-1B versus IC50-D1 (IC50-D1 = 0.504 x IC50-1B + 2.84; r2 = 0.908, p < 0.05)

Production of carotenoids and biosurfactants by Gordonia Alkanivorans Strain 1B using food residues and derivatives [Poster]

ABSTRACT: Through different bioprocesses, microorganisms, such as yeasts and bacteria, ferment and transform residue streams into high added value products, such as carotenoids and biosurfactants. Gordonia alkanivorans strain 1B is one of such bacteria, capable of consuming and transforming many types of residues. It is mostly known for its biodesulfurizing ability and it was recently described as a producer of both carotenoids and biosurfactants. In previous works, strain 1B has been cultivated on different sugar rich alternative carbon sources. However, it was shown, that in order to promote surfactant production, the microorganisms should be exposed to inducing factors, such as lipids and alcohols. This work focusses on valorisation of residues from the restaurant and food industry, and derivatives from their processing, by using them as carbon sources to grow the bacterium and produce carotenoids and surfactants.N/

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

Aims: Through biodesulphurization (BDS) is possible to remove the sulphur present in fossil fuels to carry out the very strict legislation. However, this biological process is limited by the cost of the culture medium, and thus, it is important to explore cheaper alternative carbon sources, such as Jerusalem artichoke (JA). These carbon sources usually contain sulphates which interfere with the BDS process. The goal of this work was to remove the sulphates from Jerusalem artichoke juice (JAJ) through BaCl2 precipitation viewing the optimization of dibenzothiophene (DBT) desulphurization by Gordonia alkanivorans strain 1B. Methods and Results: Using a statistical design (Doehlert distribution), the effect of BaCl2 concentration (0·125–0·625%) and pH (5–9) was studied on sulphate concentration in hydrolysed JAJ. A validated surface response derived from data indicated that zero sulphates can be achieved with 0·5–0·55% (w/v) BaCl2 at pH 7; however, parallel BDS assays showed that the highest desulphurization was obtained with the juice treated with 0·5% (w/v) BaCl2 at pH 8·73. Further assays demonstrated that enhanced DBT desulphurization was achieved using hydrolysed JAJ treated in these optimal conditions. A total conversion of 400 µmol l-1 DBT into 2-hydroxybiphenyl (2-HBP) in <90 h was observed, attaining a 2-HBP maximum production rate of 28·2 µmol l-1 h-1 and a specific production rate of 5·06 µmol-1 g-1(DCW) h-1. Conclusions: These results highlight the efficacy of the treatment applied to JAJ in making this agromaterial a promising low-cost renewable feedstock for improved BDS by the fructophilic strain 1B. Significance and Impact of the Study: This study is a fundamental step viewing BDS application at the industrial level as it accounts a cost-effective production of the biocatalysts, one of the main drawbacks for BDS scale-up

Evaluation of Jerusalem artichoke as a sustainable energy crop to bioethanol: energy and CO(2)eq emissions modeling for an industrial scenario

ABSTRACT: An alternative to the sugar/starch-based crops bioethanol is lignocellulosic biomass, but its utilization to biofuels is still not economically viable. In this context, an increasing interest has arising on the search for specific energy crops that do not require arable lands and are not water intensive, such as Jerusalem artichoke (JA). So, this work consisted on the cultivation of JA on those agricultural conditions and its further evaluation as a sustainable feedstock towards bioethanol. Two strategies of producing bioethanol were evaluated pointing out for the consolidated bioprocessing with the Zygosaccharomyces bailii Talf1 yeast as the best approach for further scale-up, based on energy data analysis and ethanol productivity. Different industrial scenarios were outlined and compared for overall CO(2)eq emissions and energy consumption per liter of ethanol (L-EtOH), using adequate criteria on a cradle-to-gate approach. With no land-use change, no biogenic and no co-products credits, the comparison of the overall energy consumption and CO(2)eq emissions (100% process) from JA ethanol (9 MJ/L-EtOH; 679 g CO2/L-EtOH) with sugarcane/sugar beet ethanol (42/29 MJ/L-EtOH; 731/735 g CO2/L-EtOH) and with gasoline refinery (15 MJ/L-EtOH eq; 1154 g CO2/L-EtOH eq), highlights the JA as an alternative feedstock to be a focus of ethanol research for gasoline blends.info:eu-repo/semantics/publishedVersio

Olive Mill wastewater bioremediation by Bjerkandera paranensis: a sustainability and technological evaluation

Remediation of olive mill wastewater (OMW) is an important issue associated with olive-oil manufacturing, a widespread activity in the Mediterranean area. This high organic loading effluent contains water, organic acids, high-molecular-weight polyphenols such as tannins, antocyanins and catechins, which are considered to be responsible for its brownish black colour and toxic properties. The composition of OMWs is highly variable with respect to each individual component, depending on the process conditions and on the agricultural specificities. In this work, the ability of a “white-rot” fungus, Bjerkandera paranensis, to use undiluted OMW from a two phase process mill (COD = 11.1 gl-1; Phenol Content = 3.9 gl-1; ColourAbs395nm = 7.8) as a substrate was studied. The biodegradation potential of B. paranensis was assessed monitoring several physico-chemical parameters. A chronic ecotoxicity test (Vibrio fisheri growth inhibition test) was carried out to follow the detoxification ability of this fungus. In work, the results demonstrate that OMW was a suitable medium for cultivation of B. paranensis, with corresponding changes in the physico-chemical properties of the OMW. The results showed that B. paranensis removed 93% phenols and 54% COD from the culture medium within 21 days of treatment. In addition, the IC50s values obtained for the different treated samples showed a significant decrease in the effluent chronic toxicity to V. fischeri when the OMW pH was adjusted to 6.0 prior to the treatment (71.8 %), highlighting the OMW detoxification capacity of B. paranensi

Influence of the carbon source on Gordonia alkanivorans strain 1B resistance to 2-hydroxybiphenyl toxicity

The viability of bacteria plays a critical role in the enhancement of fossil fuels biodesulfurization efficiency since cells are exposed to toxic compounds such as 2-hydroxybiphenyl (2-HBP), the end product of dibenzothiophene (DBT) biodesulfurization. The goal of this work was to study the influence of the carbon source on the resistance of Gordonia alkanivorans strain 1B to 2-HBP. The physiological response of this bacterium, pregrown in glucose or fructose, to 2-HBP was evaluated using two approaches: a growth inhibition toxicity test and flow cytometry. The results obtained from the growth inhibition bioassays showed that the carbon source has an influence on the sensitivity of strain 1B growing cells to 2-HBP. The highest IC50 value was obtained for the assay using fructose as carbon source in both inoculum growth and test medium (IC50-48 h=0.464 mM). Relatively to the evaluation of 2-HBP effect on the physiological state of resting cells by flow cytometry, the results showed that concentrations of 2-HBP >1 mM generated significant loss of cell viability. The higher the 2-HBP concentration, the higher the toxicity effect on cells and the faster the loss of cell viability. In overall, the flow cytometry results highlighted that strain 1B resting cells grown in glucose-SO4 or glucose-DBT are physiologically less resistant to 2-HBP than resting cells grown in fructose-SO4 or fructose-DBT, respectively

Fructose rich alternative carbon sources for enhanced fossil fuels biodesulfurization

Biodesulfurization allows the removal of recalcitrant sulfur from fossil fuels at mild operating conditions with the aid of microorganisms. However the production of biocatalysts still has elevated costs which hinder its industrial application. So the use of agro-industrial by-products and wastes, as alternative carbon sources could present an opportunity to cheapen the process. In previous works we showed that Gordonia alkanivorans strain 1B has the ability to use materials such as recycled paper sludge hydrolysate and carob pulp liquor to grow and desulfurize after some optimization. Since this is a fructophilic bacterium it is important to compare the use of carbon sources progressively richer in fructose

Zygosaccharomyces bailii strain talf1 inulinases: a versatile tool for bioprocesses

Fructans are one of the most abundant non-structural polysaccharides found in a wide range of plants. Inulin is a polydisperse fructan polymer composed by linear chains of b-2, 1-linked D-fructofuranose molecules terminated by a glucose residue through a sucrose-type linkage at the reducing end. Inulin or inulin-rich materials can be actively hydrolyzed into fermentable sugars (glucose and fructose) using inulinases and then further used within bioprocesses