Influence of culture conditions towards optimal carotenoid production by Gordonia alkanivorans strain 1B

Differentiation of different dibenzothiophene (DBT) desulfurizing bacteria via surface-enhanced Raman spectroscopy (SERS)

Fossil fuels are considered vital natural energy resources on the Earth, and sulfur is a natural component present in them. The combustion of fossil fuels releases a large amount of sulfur in the form of SO x in the atmosphere. SO x is the major cause of environmental problems, mainly air pollution. The demand for fuels with ultra-low sulfur is growing rapidly. In this aspect, microorganisms are proven extremely effective in removing sulfur through a process known as biodesulfurization. A major part of sulfur in fossil fuels (coal and oil) is present in thiophenic structures such as dibenzothiophene (DBT) and substituted DBTs. In this study, the identification and characterization of DBT desulfurizing bacteria (Chryseobacterium sp. IS, Gordonia sp. 4N, Mycolicibacterium sp. J2, and Rhodococcus sp. J16) based on their specific biochemical constituents were conducted using surface-enhanced Raman spectroscopy (SERS). By differentiating DBT desulfurizing bacteria, researchers can gain insights into their unique characteristics, thus leading to improved biodesulfurization strategies. SERS was used to differentiate all these species based on their biochemical differences and different SERS vibrational bands, thus emerging as a potential technique. Moreover, multivariate data analysis techniques such as principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were employed to differentiate these DBT desulfurizing bacteria on the basis of their characteristic SERS spectral signals. For all these isolates, the accuracy, sensitivity, and specificity are above 90%, and an AUC (area under the curve) value of close to 1 was achieved for all PLS-DA models.

Optimized carotenoid production and antioxidant capacity of Gordonia hongkongensis

The current emphasis within the cosmetic market on sustainable ingredients has heightened the exploration of new sources for natural, active components. Actinomycetota, recognized for producing pigments with bioactive potential, offer promising functional cosmetic ingredients. This study aimed to optimize pigment and antioxidant metabolite production from the Gordonia hongkongensis strain EUFUS-Z928 by implementing the Plackett-Burman experimental design and response surface methodology. Extracts derived from this strain exhibited no cytotoxic activity against human primary dermal fibroblast (HDFa, ATCC® PCS-201-012™, Primary Dermal Fibroblast; Normal, Human, Adult). Eight variables, including inoculum concentration, carbon and nitrogen source concentration, NaCl concentration, pH, incubation time, temperature, and stirring speed, were analyzed using the Plackett-Burman experimental design. Subsequently, factors significantly influencing pigment and antioxidant metabolite production, such as temperature, inoculum concentration, and agitation speed, were further optimized using response surface methodology and Box-Behnken design. The results demonstrated a substantial increase in absorbance (from 0.091 to 0.32), DPPH radical scavenging capacity (from 27.60% to 84.61%), and ABTS radical scavenging capacity (from 17.39% to 79.77%) compared to responses obtained in the isolation medium. The validation of the mathematical model accuracy exceeded 90% for all cases. Furthermore, liquid chromatography coupled with mass spectrometry (LC-MS) facilitated the identification of compounds potentially responsible for enhanced pigment production and antioxidant capacity in extracts derived from G. hongkongensis. Specifically, six carotenoids, red-orange pigments with inherent antioxidant capacity, were identified as the main enhanced compounds. This comprehensive approach effectively optimized the culture conditions and medium of a G. hongkongensis strain, resulting in enhanced carotenoid production and antioxidant capacity. Beyond identifying bioactive compounds and their potential cosmetic applications, this study offers insights into the broader industrial applicability of these extracts. It underscores the potential of G. hongkongensis and hints at the future utilization of other untapped sources of rare actinomycetes within the industry.

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.

Methods of Identifying Gordonia Strains in Clinical Samples

Gordonia spp. are members of the family Gordoniacea in the suborder Corynebacteriales; their habitat, in most cases, is soil. Many representatives of this genus are human or veterinary pathogens. The main cause of the lack of a standardized approach to dealing with infections caused by Gordonia is their erroneous identification and little information regarding their susceptibility to antimicrobial drugs. This review presents the most common methods for identifying Gordonia strains, including modern approaches for identifying a species. The main prospects and future directions of this field of knowledge are briefly presented.

Characterization and Bioactive Potential of Carotenoid Lutein from Gordonia rubripertncta GH-1 Isolated from Traditional Pixian Douban

The characterization and bioactive properties of carotenoid produced by Gordonia rubripertincta GH-1 originating from Pixian Douban (PXDB), the Chinese traditional condiment, was investigated. The produced and purified yellow pigment was characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier transformed infrared (FTIR), nuclear magnetic resonance (NMR), and high-resolution mass spectrometry (HRMS), and was identified as carotenoid lutein. Additionally, the bioactive activity of lutein from G. rubripertincta GH-1 was evaluated by measuring the free radical scavenging capacity in vitro and feeding zebrafish lutein through aqueous solution. The results showed that the carotenoid lutein had strong antioxidant capacity and a protective effect on zebrafish eye cells, which could inhibit the apoptosis of eye cells in a concentration dependent manner. The results suggested that carotenoid lutein from G. rubripertincta GH-1 could be utilized as a potential source of natural antioxidants or functional additives for food/pharmaceutical industries.

Bacterial pigments: A colorful palette reservoir for biotechnological applications

Synthetic derivatives are currently used instead of pigments in many applicative fields, from food to feed, from pharmaceutical to diagnostic, from agronomy to industry. Progress in organic chemistry allowed to obtain rather cheap compounds covering the whole color spectrum. However, several concerns arise from this chemical approach, as it is mainly based on nonrenewable resources such as fossil oil, and the toxicity or carcinogenic properties of products and/or precursors may be harmful for personnel involved in the productive processes. In this scenario, microorganisms and their pigments represent a colorful world to discover and reconsider. Each living bacterial strain may be a source of secondary metabolites with peculiar functions. The aim of this review is to link the physiological role of bacterial pigments with their potential use in different biotechnological fields. This enormous potential supports the big challenge for the development of strategies useful to identify, produce, and purify the right pigment for the desired application. At the end of this ideal journey through the world of bacterial pigments, the attention will be focused on melanin compounds, whose production relies upon different techniques ranging from natural producers, heterologous hosts, or isolated enzymes. In a green workflow, the microorganisms represent the starting and final point of pigment 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.

Design and validation of an expeditious analytical method to quantify the emulsifying activity during biosurfactants/bioemulsifiers production

Biosurfactants (BS) and bioemulsifiers (BE) are amphiphilic molecules that are produced by a wide range of microorganisms. Although the chemical composition of BS and BE is different, both BS/BE have recognized emulsifying properties, which are the focus of this study. Herein, a rapid and simple analytical method to quantify the emulsifying activity (EA) of a product produced by the actinomycete Gordonia alkanivorans strain 1B (BS/BE), which exhibits emulsifying properties, was developed. The analytical approach was based on the ability of a BS/BE solution to form a stable emulsion when mixed with n-heptane. So, using 4 mL screw cap glass tubes (10 × 75 mm, ND10 caps with PTFE septum), the EA was assessed by adding 1 mL of n-heptane to 1 mL of an aqueous solution containing the test product, mix by vortexing at high speed (2 min) and place the tube in an upright stable position for 10 _min before analyzing. A set of emulsification tests with increasing volumes of test product solutions was carried out until 100% emulsion was obtained in the organic phase. One emulsification unit was defined as the minimum volume of product (Vol_min of emulsifier/surfactant, up to 1 mL) needed to form and maintain 100% emulsion in the organic phase. The corresponding emulsifying activity value is presented in U/mL, and it is calculated as: EA (product) = 1 U/Vol_min (mL). Further validation by testing several synthetic surfactants and industrial/domestic dishwashing detergents, in parallel with the bacterial crude BS/BE, towards emulsifying activity determination (U/mL) was performed demonstrating the wide range of the method applicability. Moreover, the specific emulsifying activity for each product tested was estimated though correlation analysis (linear regression) between volumetric emulsifying activity (U/mL) and product concentration (g/L). Indeed, this new analytical approach to quantify the emulsifying activity is accurate and reproducible, and consequently it can be a promising tool to apply in screening/monitorization studies on BS/BE production enabling reliable comparisons.

Valorisation of wheat bran to produce natural pigments using selected microorganisms

Pigments are compounds with highly diverse structures and wide uses, which production is increasing worldwide. An eco-friendly method of bioproduction is to use the ability of some microorganisms to ferment on renewable carbon sources. Wheat bran (WB) is a cheap and abundant lignocellulosic co-product of low recalcitrance to biological conversion. Microbial candidates with theoretical ability to degrade WB were first preselected using specific databases. The microorganisms were Ashbya gossypii (producing riboflavin), Chitinophaga pinensis (producing flexirubin), Chromobacterium vaccinii (violacein) and Gordonia alkanivorans (carotenoids). Growth was shown for each on minimal salt medium supplemented with WB at 5 g.L^-1. Activities of the main enzymes consuming WB were measured, showing leucine amino-peptidase (up to 8.45 IU. mL^-1) and β-glucosidase activities (none to 6.44 IU. mL^-1). This was coupled to a FTIR (Fourier Transform Infra-Red) study of the WB residues that showed main degradation of the WB protein fraction for C. pinensis, C. vaccinii and G. alkanivorans. Production of the pigments on WB was assessed for all the strains except Ashbya, with values of production reaching up to 1.47 mg.L^-1. The polyphasic approach used in this study led to a proof of concept of pigment production from WB as a cheap carbon source.

Effect of dibenzothiophene and its alkylated derivatives on coupled desulfurization and carotenoid production by Gordonia alkanivorans strain 1B

Nowadays, the production of green transportation fuels is essential for a healthy life and environment. Effective and complete removal of organosulfur recalcitrant compounds from fuel oils is crucial to meet the stringent requirements of sulfur standards. However, the industry's solution (Hydrodesulfurization, HDS) is not effective in the removal of complex sulfur heterocyclic hydrocarbons. Thus, the development of more efficient and ecofriendly/sustainable desulfurization methods is critical, as either an alternative or a complement to HDS, foreseeing the production of ultra-low sulfur fuels (ULSF). Among the desulfurization techniques available, microbial desulfurization of organosulfur hydrocarbons (biodesulfurization, BDS) is attracting great attention. BDS is carried out at mild operation conditions, making it energetically cheaper and more ecofriendly, since it does not require hydrogen and produces far less greenhouse gases emission than HDS. In this context, the behavior of Gordonia alkanivorans strain 1B, a desulfurizing bacterium and hyper-pigment producer, was evaluated in the presence of four sulfur sources common in fuel oils: dibenzothiophene (DBT); 4-mDBT; 4,6-dmDBT and 4,6-deDBT (single/mixed), in terms of both desulfurization rate and overall carotenoid production. Simultaneously, the influence of the carbon source used (fructose vs glucose) on the overall effectiveness of the coupled bioprocesses was also assessed. The results obtained highlight the potential of strain 1B to desulfurize all the tested recalcitrant compounds and simultaneously produce carotenoids. However, the highest BDS values were observed for 4,6-deDBT (5.75 μmol/g (DCW)/h) and for the mix of DBTs (5.20 μmol/g (DCW)/h), when fructose was used as carbon source. Indeed, when the mixture of DBTs ("model oil surrogate") was desulfurized by cells growing in fructose both desulfurization rate and total pigments amount were higher than those observed for glucose growing cells. Moreover, under these conditions, the strain 1B was able to produce high added-value carotenoids, namely astaxanthin, lutein and canthaxanthin. Hence, these results are promising when aiming to achieve a scale-up scenario. In fact, the inclusion of the production of high added-value products within a BDS process targeting ULSF may be a sustainable way to turn its scale-up economically viable.

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