Halophilic Strain Research Articles

HALOTOLERANCE AEROMONADS ISOLATED FROM WATER AND PERCH (SANDER LUCIOPERCA) IN THE DELTA OF THE VOLGA RIVER

The article presents the results of a study of halotolerance in aeromonads isolated from 447 specimens of perch (Sander lucioperca) and 375 water samples in areas of its habitat in the delta of the Volga River. They were subdominant in the microbial landscape of these biotopes. There were no significant differences inoculation aeromonads found in various parts of the delta. Their halotolerance was studied by means of inoculation of daily pure cultures of meat--peptone broth with 3, 7 and 10% of sodium chloride content and incubation at 37◦C. All the studied microflora of this spieces was established to have significant indices of halotolerance with a predominance in water isolates. Whereby in cases of 3.0 and 7.0% NaCl concentrations were 2.2 times more and in the 10.0% NaCl solution with water and fish strains had similar indices, showing them to be of “marine origin”. Among isolated aeromonads, shattering the water and fish most halophilic strains of A. hydrophila and A. sobria, and halophobic strains were presented by A. caviae. As a rule, water strains had stability indices above in the average of 1.3 times higher than fish ones. Epidemiologically important strains of A. sobria were isolated from water more frequently than from fish, whereas A. hydrophila was isolated as in water as in fish at the same level. Halotolerance of isolated aeromonads in hydroecosystems of the delta of the Volga River had seasonal specificity and dynamics. The gain in halotolerance in aquatic strains of aeromonads in spring and autumn was caused by natural and climatic processes and the elevation in the salinity of delta waters. Enhanced halophilic strains of fish in these seasons is determined by their migration with fish, because in seasons pike migrates from the sea to the river ecosystem.

Sketching a Suitable Immobilization Strategy for Ionic Liquid Removal in a Fixed-Bed Bioreactor

Generalization of the research on biocompatible ionic liquids is triggering great interest in cholinium-based solvents due to this cation being considered as biocompatible and biodegradable. However, the screening for choline degraders among different microbial sources from different extreme locations revealed the suitability of just one halophilic strain (Halomonas sp. LM1C) to efficiently remove high concentrations of choline cation from aqueous streams. An entrapment-based microbial immobilization technique in hydrogel spheres (agar, alginate, and alginate-polyvinyl) is evaluated in order to ease process scale up. The mass transfer resistance of the selected hydrogels during cholinium chloride (N1112OHCl) diffusion was evaluated by determining the external mass transfer (k) and diffusion coefficients (De). The results revealed the absence of significant diffusion problems for alginate and alginate-polyvinyl, while the agar-based matrix led to significant cell leakage. Given the superior mechanical perf...

Glycine betaine enhances biodegradation of phenol in high saline environments by the halophilic strain Oceanobacillus sp. PT-20.

The halophilic bacterial strain PT-20, isolated from saline alkali soil samples and identified as a member of the genus Oceanobacillus, exhibited a robust ability to degrade phenol under high salt conditions. It was determined that strain PT-20 was capable of degrading 1000 mg L−1 phenol completely in the presence of 10% NaCl within 120 h. Under the optimal degradation conditions, pH 8.0, 3% NaCl and 30 °C, 1000 mg L−1 phenol could be completely degraded in 48 h. Interestingly, the biodegradation rate of phenol was dramatically improved in the presence of glycine betaine. When glycine betaine was added, the time required to degrade 1000 mg L−1 phenol completely was significantly reduced from 120 h to 72 h, and the corresponding average degradation rate increased from 8.43 to 14.28 mg L−1 h−1 with 10% NaCl. Furthermore, transcriptome analysis was performed to investigate the effects of phenol and glycine betaine on the transcriptional levels of strain PT-20. The results indicated that the addition of glycine betaine enhanced the resistance of cells to phenol, increased the growth rate of strain PT-20 and upregulated the expression of related enzyme genes. In addition, the results of enzyme activity assays indicated that strain PT-20 degraded phenol mainly through a meta-fission pathway.

Harvest of the Oleaginous Microalgae Scenedesmus obtusiusculus by Flocculation From Culture Based on Natural Water Sources.

Harvest and dewatering poses a significant economical burden for industrial algae biomass production. To mitigate these effects, energy efficient techniques for these process steps have to be developed. Flocculation of the microalgae Scenedesmus obtusiusculus in salt based medium was induced by pH-shift and alternatively by addition of two biological flocculants, chitosan, and the commercial tannin CFL-PT. This is the first time that CFL-PT is used as an algae flocculant particularly focusing on harvesting of halophilic strains. The method was characterized and subsequently optimized. In comparison to biological flocculants, induction by pH shift is far cheaper, but due to buffering effects of the brackish cultivation medium infeasible amounts of base are required to raise the pH-value. tannin appears to be superior compared to chitosan not only in the absence of algae organic matter (AOM), but tannin-based harvest is also more robust regarding culture pH in presence of AOM. A higher flocculant-demand for modified tannin compared to chitosan is offset by the lower price. Given the employed strain and cultivation conditions, cultivation time had no pronounced effect on flocculation efficiencies (FE) while algae zeta-potential and bacterial communities also remained stable.

Production and Characterization of Polyhydroxybutarate from Halophilic Bacteria

Halophilic microorganisms thrive at elevated concentrations of sodium chloride up to saturation and are capable of growing on a wide variety of carbon sources. Hence, the biotechnological application of these microorganisms can cover many aspects one of these is bioplastic production. Biodegradable plastics are plastics that are decomposed by the action of living organisms using bacteria. Biodegradable plastic is a renewable biopolymers synthesized in bacteria having similar characteristics of plastics produced from petroleum character. In the following work preisolated halophilic strains were screened for PHB production. The positive strains were subjected to PHB production. Estimation of PHB was done by using UV spectrophotometer and FTIR. Highest PHB producing strain was further used for optimization of different parameters for PHB production.

Production of nanocalcite crystal by a urease producing halophilic strain of Staphylococcus saprophyticus and analysis of its properties by XRD and SEM.

Cementation of salt-containing soils can be achieved by salt-tolerant or halophilic calcite precipitation bacteria. Therefore, the isolation of calcite-producing bacteria in the presence of salt is the first step in the microbial cementation of saline soils. Urease producing bacteria can cause calcite nano-crystals to precipitate by producing urease in the presence of urea and calcium. The purpose of this study was to isolate urease producing halophilic bacteria in order to make calcite precipitate in saline soil. The calcite and the properties of the strains were further analyzed by X-ray diffraction (XRD) and scanning electron microscope equipped with an energy dispersive X-ray detector. In this study, a total of 110 halophilic strains were isolated, from which 58 isolates proved to have the ability of urease production. Four strains were identified to produce nano-calcite using urease activity in the precipitation medium. The XRD studies showed that the size of these particles was in the range of 40-60nm. Strain H3 revealed that calcite is mostly produced in the precipitation medium containing 5% salt in comparison with other strains. This strain also produced calcite precipitates in the precipitation medium containing 15% salt. Phylogenetic analysis indicated that these isolates are about 99-100% similar to Staphylococcus saprophyticus.

Biodegradation of crude oil by Halomonas elongata strain KWPA-12: a moderately halophilic strain detected in oil spills around Garo sulfidic springs, MIS Oilfield, Iran

The oil spills in the vicinity of the Garo sulfidic springs in Golgir region, MIS oilfield, Iran, were investigated for halotolerant/halophilic microorganisms capable of crude oil biodegradation. Screenings resulted in an isolate capable of growth on crude oil of the local Asmari reservoir in media containing 30–100 g/L NaCl at 28 °C. The isolate, designed as KWPA-12, was an aerobic, motile, oxidase and catalase positive, Gram-negative rod. It was shown that strain KWPA-12 can utilize crude oil as the carbon and sulfur sources with a significant efficiency. The Asmari crude oil biodegradation in 90 g/L NaCl containing media was investigated by turbidity measurement, GC-FID and TPH analyses. The results showed that the aliphatic hydrocarbons including: small C11–C12 and long chains: C31–C33, are mostly favored by strain KWPA-12. Anthracene: a tri-ring and one of the most dominant poly-aromatic compounds of Asmari crude oil, was reduced down to about 1.1% of the starting moiety. Phylogenetic investigations performed on the partial 16S rRNA gene sequence indicated that the strain belongs to the genus Halomonas and it fell into the Halomonas elongata clade.

Roseovarius tibetensis sp. nov., a halophilic bacterium isolated from Lake LongmuCo on Tibetan Plateau

Two Gram-stain negative halophilic strains, designated as LM2T and LM4, were isolated from Lake LongmuCo on Tibetan Plateau. These two strains were aerobic, catalaseand oxidase-positive, nonmotile and rod-shaped organisms. Phylogenetic analysis based on 16S rRNA gene sequences indicated that LM2T and LM4 belong to the genus Roseovarius, with Roseovarius tolerans EL-172T (97.3% and 97.4% 16S rRNA gene sequence similarity, respectively) and Roseovarius azorensis SSW084T (95.5% and 95.6% 16S rRNA gene sequence similarity, respectively) as their closest neighbors. Q-10 was the sole respiratory quinone of these two strains. The major fatty acids were C18:1ω7c/C18:1ω6c, C16:0, C19:0 cyclo ω8c, and 11-methyl C18:1ω7c. The polar lipids included phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, phospholipid of unknown structure containing glucosamine, and unidentified aminolipid. The DNA G + C content was between 64.2 and 64.5 mol%. DNA-DNA hybridization showed 96.7% relatedness between LM2T and LM4, 24.9% relatedness between LM2T and R. tolerans EL-172T, and 36.3% relatedness between LM4 and R. tolerans EL-172T. Based on phylogenetic analysis, DNA-DNA hybridization, a range of physiological and biochemical characteristics, LM2T and LM4 belong to the same species and were clearly distinguished from the type strains of the genus Roseovarius. It was evident that LM2T and LM4 could be classified as a novel species of the genus Roseovarius, for which the name Roseovarius tibetensis sp. nov. is proposed. The type strain is LM2T (= CGMCC 1.16230T = KCTC 62028T).

Isolation and characterization of halophilic bacteria producing exopolymers with emulsifying and antioxidant activities

Abstract Halophilic bacteria are considered a great source of new strains producing novel exopolymers with functional properties. In this work we isolated ten halophilic strains producing exopolymers from different hypersaline environments in Morocco. Phenotypic characterization showed that the strains were moderately halophilic, mesophilic and neutrophilic with the ability to produce some hydrolytic enzymes. Strains identification based on 16S rRNA gene sequences comparison showed that nine strains, designed as N1, N2, N5, N7, N8, N9, N10, N11 and N12 belong to Halomonas genus and one strain, designed as N4, to Marinobacter genus. The majority of the strains showed high levels of exopolymer production. The study of emulsifying and antioxidant activities revealed that all the polymers have an interesting emulsifying and antioxidant activities with the polymer from Marinobacter sp. N4 forming the highest and most stable emulsions and exhibiting the best antioxidant activity in comparison with other exopolymers produced by Halomonas strains. The obtained results demonstrate the great potential of exopolymers from halophilic bacteria to be applied as emulsifying and antioxidant agents in food, cosmetics and oil industries.

Biosecretion of higher halophilic lipase by a novel Bacillus amyloliquefaciens AIKK2 using agro-waste as supporting substrate

Abstract Lipase secretion by halophilic strains under solid state fermentation has been relatively understudied, especially when utilizing agro-industrial substrates. Eleven halophilic bacterial strains were locally isolated and screened for lipase secretion. All the strains were subsequently subjected to the screening on various agro-industrial substrates for the lipase production, and to assess the best supporting substrate. The halophilic strain with the maximum lipase secretion (0.264 U/g) potential was selected and identified as Bacillus amyloliquefaciens AIKK2. Coconut fibre was found the best supporting substrate for halophilic lipase secretion and influence of nutritional and environmental parameters on halophilic lipase secretion was determined using One-Factor-At-A-Time. The optimized experiment was conducted at 6% glucose, 9% NaCl, 40 °C, and 200 rpm agitation speed resulted in the enhanced lipase secretion (0.29 U/g). Further, halophilic lipase characterization studies revealed that the enzyme was thermally stable at 50 °C, showed the improved activity at moderate NaCl and rare tolerance in hydrophilic solvents.

Biocatalytic hydrogenation of the C=C bond in the enone unit of hydroxylated chalcones\u2014process arising from cyanobacterial adaptations

To verify the hypothesis that cyanobacteria naturally biosynthesising polyphenolic compounds possess an active enzymatic system that enables them to transform these substances, such an ability of the biocatalytic systems of whole cells of these biota was assessed for the first time. One halophilic strain and seven freshwater strains of cyanobacteria representing four of the five taxonomic orders of Cyanophyta were examined to determine the following: (i) whether they contain polyphenols, including flavonoids; (ii) the resistance of their cultures when suppressed by the presence of exogenous hydroxychalcones—precursors of flavonoid biosynthesis and (iii) whether these photoautotrophs can transform hydroxylated chalcones. All examined strains were found to contain polyphenols and flavonoids, and the growth of their cultures was inhibited in the presence of 2′-hydroxychalcone, 2″-hydroxychalcone and 4″-hydroxychalcone. We also confirmed that the examined cyanobacteria transformed hydroxychalcones via hydrogenative bio-reduction and formed the corresponding hydroxydihydro derivatives with yields above 90% whenever the substrates were bioavailable for such a conversion. Moreover, we observed that the routes and efficiency of biohydrogenation (and hydroxylation) of chalcones were dependent on the location of the hydroxyl substituent. The final products obtained as the results of biotransformations were extracted from the media and identified by mass spectrometry (LC-MS/MS) and nuclear magnetic resonance (1H NMR, 13C NMR, COSY, HSQC). Based on those results, we believe that the very efficient biohydrogenation of hydroxychalcones, which may easy be scaled up for biotechnological purposes, reflects the natural activity of the cyanobacterial defence system, because hydroxydihydrochalcones were less active inhibitors of the growth of cyanobacterial cultures than the corresponding substrates.

Isolation and identification of two extremely halophilic archaea from sebkhas in the Algerian Sahara

In Algeria, many salt lakes are to be found spread from southern Tunisia up to the Atlas Mountains in northern Algeria. Oum Eraneb and Ain El beida sebkhas (salt lakes), are located in the Algerian Sahara. The aim of this study was to explore the diversity of the halobacteria in this type of habitats. The physicochemical properties of these shallow saline environments were examined and compared with other hypersaline and marine ecosystems. Both sites were relatively alkaline with a pH around 8.57- 8.74 and rich in salt at13% and16% (w/v) salinity for Oum Eraneb and Ain El beida, respectively, with dominant ions of sodium and chloride. The microbial approach revealed the presence of two halophilic archaea, strains JCM13561 and A33T in both explored sebkhas. Growth occurred between 10 and 25% (w/v) NaCl and the isolates grow optimally at 20% (w/v) NaCl. The pH range for growth was 6 to 9.5 with an optimum at pH 7.5 for the first strain and 7 to 9.5 with an optimum pH at 8.5-9 for the second strain. On the basis of 16S rRNA gene sequence analysis, strains JCM13561 and A33T were most closely related to Halorubrum litoreum and Natronorubrum bangense (99% and 96% similarity, respectively).

Emended description of Salinivibrio proteolyticus, including Salinivibrio costicola subsp. vallismortis and five new isolates.

We carried out a comparative taxonomic study of Salinivibrio proteolyticus and Salinivibrio costicola subsp. vallismortis, as well as of five halophilic strains (IB574, IB872, PR5, PR919 and PR932), isolated from salterns in Spain and Puerto Rico that were closely related to these bacteria. Multilocus sequence analysis of concatenated gyrB, recA, rpoA and rpoD housekeeping genes showed that they constituted a single cluster separate from the other species and subspecies of Salinivibrio. Experimental and in silico DNA-DNA hybridization studies indicated that they are members of the same species, with relatedness of 100-74 % and 97.8-70.0 %, respectively. The average nucleotide identity (ANI) determined for these strains was 99.7-95.6 % for ANIb and 99.7-95.7 % for OrthoANI. However, the ANI values for S. costicolasubsp.vallismortis DSM 8285T with respect to S. costicolasubsp.costicola DSM 11403T and S. costicolasubsp.alcaliphilus DSM 16359T were 78.7 and 78.9 % (ANIb) and 79.4 and 79.4 % (OrthoANI), respectively. The phylogenomic tree based on 1072 concatenated orthologous single-copy core genes confirmed that S. proteolyticus, S. costicolasubsp.vallismortis and the five new isolates constitute a coherent single phylogroup, separated from the other species and subspecies of Salinivibrio. All these data indicate that S. costicolasubsp.vallismortis is a heterotypic synonym of S. proteolyticus and we propose an emended description of this species.

Comparison of Extremely Halophilic Archaea Isolated from Three Salt Lakes in China

There’re many kinds of extremely halophilic archaea living in salt lakes all over the world and the ecological environment of lakes can affect their archaeal species. To illustrate the relationships between archaeal species and salt lake environment, we isolated and cultured 25 extremely halophilic archaeal strains from three salt lakes in China (Gou Salt Lake, Huama Salt Lake and Yuncheng Salt Lake). According to the 16S rRNA gene sequence analysis and the construction of Neighbor-Joining phylogenetic trees, the isolates were closely related to each other. The most dominant archaea was genus halorubrum (88.0%), followed by genus haloarcula (8.0%) and a small amount of genus halovivax (4.0%). Yuncheng salt lake (YC) had the most abundant number of species. Through the study of the basic information of the three sampling sites, we considered the species of extremely halophilic archaea were related to their living natural conditions of brine. Warm weather and high mineralization degree are likely to be functional components to enrich the species diversity.

Isolation and characterization from solar salterns of North Algeria of a haloarchaeon producing a new halocin.

Halophilic archaea, thriving in hypersaline environments, synthesize antimicrobial substances with an unknown role, called halocins. It has been suggested that halocin production gives transient competitive advantages to the producer strains and represents one of the environmental factors influencing the microbial community composition. Herein, we report on the antibacterial activity of a new haloarchaeon selected from solar salterns of the northern coast of Algeria. A total of 81 halophilic strains, isolated from the microbial consortia, were screened for the production of antimicrobial compounds by interspecies competition test and against a collection of commercial haloarchaea. On the basis of the partial 16S rRNA sequencing, the most efficient halocin producer was recognized as belonging to Haloferax (Hfx) sp., while the best indicator microorganism, showing high sensitivity toward halocin, was related to Haloarcula genus. The main morphological, physiological and biochemical properties of Hfx were investigated and a partial purification of the produced halocin was allowed to identify it as a surface membrane protein with a molecular mass between 30 and 40kDa. Therefore, in this study, we isolated a new strain belonging to Haloferax genus and producing a promising antimicrobial compound useful for applications in health and food industries.

Use of a mixed culture strategy to isolate halophilic bacteria with antibacterial and cytotoxic activity from the Manaure solar saltern in Colombia

BackgroundWater evaporation in solar salterns creates salinity gradients that promote the adaptation of microbial species to different salinities. This competitive habitat challenges the metabolic capabilities of microorganisms and promotes alterations in their production of secondary metabolites. Thus, solar salterns are a potentially important source of new natural products. In Colombia, the most important and representative solar saltern is located in Manaure (La Guajira) in the north of Colombia. The aim of this study was to develop an alternative screening strategy to select halophilic bacteria as producers of bioactive compounds from mixed microbial cultures rather than individual environmental isolates. Brine and sediment samples from different ponds (across a salinity gradient) were inoculated in seven different culture media to grow bacteria and archaea, allowing for a total of 40 different mixed cultures. An organic extract from each mixed culture was obtained and tested against multidrug resistant pathogens, including Klebsiella pneumoniae, vancomycin-resistant Enterococcus faecium, methicillin-resistant Staphylococcus aureus and Bacillus subtilis. In addition, the extracts were tested against two human cancer cell lines, cervical adenocarcinoma (SiHa) and lung carcinoma (A-549).ResultsTwenty-four of the forty extracts from mixed cultures obtained from brine and sediment samples from the Manaure solar saltern showed antibacterial activity against Bacillus subtilis. Two extracts, referred to as A1SM3–29 and A1SM3–36, were also active against a methicillin-resistant Staphylococcus aureus, with the latter extract also showing slight cytotoxic activity against the assayed human lung cancer cell line. From this mixed culture, nine isolates were cultivated, and their extracts were tested against the same pathogens, resulting in the identification of a Vibrio sp. strain (A1SM3–36-8) with antimicrobial activity that was similar to that observed for the mixed culture extract. The extract of this strain was subjected to a bioautography assay, and 3 different fractions exhibited antibacterial activity against methicillin-resistant Staphylococcus aureus. Based on the amount obtained for each fraction, F3 was selected to isolate and identify its metabolites. The major compound was identified by NMR and HRMS as 13-cis-docosenamide, an amide that has been previously reported to be an antimicrobial and cytotoxic compound.ConclusionsOur results shows the utility of our strategy in detecting bioactive molecules in initial mixed cultures by biological assays, resulting in the isolation and characterization of Vibrio sp. A1SM3–36-8, a halophilic strain with great antibacterial and cytotoxic potential.

Phenol biodegradation by isolated Citrobacter strain under hypersaline conditions.

Phenol is a toxic pollutant in many kinds of hypersaline industrial effluents that should be treated properly before discharged into water bodies. In this work, a halophilic strain which could utilize phenol as the sole source of carbon and energy was isolated. Based on 16S rRNA results, it was identified as a member of Citrobacter. The phenol biodegradation ability and cell growth of the strain was evaluated with the variation of initial phenol concentration and salinity. The effect of temperature and pH on phenol removal was also investigated. The results showed that the strain was capable of withstanding high phenol (up to 1,100 mg L-1) environment with varying salinity conditions (0-10% of NaCl). The optimal initial phenol concentration was 400 mg L-1, at which the average removal rates of phenol peaked at 10.8 mg L-1 h-1. The higher initial concentration of phenol could inhibit the microbial metabolism. The optimal temperature, pH, and salinity were 35 °C, 6.0, and 0%, respectively. Under these conditions, 400 mg L-1 of phenol could be completely degraded within 20 h. The high removal rates of phenol by the strain might provide an alternative for treating phenolic wastewaters containing high salinity.

Desulfovibrio senegalensis sp. nov., a mesophilic sulfate reducer isolated from marine sediment.

Several strains of sulfate-reducing bacteria were isolated from marine sediments recovered from Hann Bay (Senegal). All were related to members of the genus Desulfovibrio. A strictly anaerobic, mesophilic and moderately halophilic strain designated BLaC1T was further characterized. Cells of strain BLaC1T stained Gram-negative and were 0.5 µm wide and 2-4 µm long, motile, rod-shaped and non-spore-forming. The four major fatty acids were anteiso-C15 : 0, iso-C15 : 0, iso-C17 : 0 and anteiso-C17 : 0. Growth was observed from 15 to 45 °C (optimum 40 °C) and at pH 5.5-8 (optimum pH 7.5). The salinity range for growth was 5-65 g NaCl l-1 (optimum 30 g l-1). Yeast extract was required for growth. Strain BLaC1T was able to grow on lactate and acetate in the presence of sulfate as an electron acceptor. Sulfate, thiosulfate and sulfite could serve as terminal electron acceptors, but not fumarate, nitrate or elemental sulfur. The DNA G+C content was 55.8 mol%. 16S rRNA gene sequence analysis assigned strain BLaC1T to the family Desulfovibrionaceae; its closest relative was Desulfovibrio oxyclinae DSM 19275T (93.7 % similarity). On the basis of 16S rRNA gene sequence comparisons and physiological characteristics, strain BLaC1T is proposed as representing a novel species of Desulfovibrio, with the name Desulfovibrio senegalensis sp. nov. The type strain is BLaC1T (=DSM 101509T=JCM 31063T).

Bacillus kiskunsagensis sp. nov., a novel alkaliphilic and moderately halophilic bacterium isolated from soda soil

An alkaliphilic and moderately halophilic strain characterized by optimal growth at pH 9.0-10.0 and 7 % (w/v) NaCl, and designated B16-24T, was isolated from the rhizosphere soil of the bayonet grass Bolboschoenus maritimus at a soda pond in the Kiskunság National Park, Hungary. Cells of the strain were Gram-staining-positive, non-motile, straight rods, and formed central, ellipsoidal endospores with slightly swollen sporangia. The isolate was facultative anaerobic, catalase positive, oxidase negative, and contained a peptidoglycan of type A1γ based on meso-diaminopimelic acid. Menaquinone-7 (MK-7) was the predominant isoprenoid quinone, and anteiso-C15 : 0 the major cellular fatty acid. The DNA G+C content of strain B16-24T was 36.6 mol%. The 16S rRNA gene-based phylogenetic analysis revealed that the novel isolate had the greatest similarities to the type strains of Bacillus okhensis Kh10-101T (97.8 %), B. akibai 1139T (97.4 %), B. alkalisediminis K1-25T (97.3 %) and B. wakoensis N-1T (97.1 %). The DNA-DNA relatedness of strain B16-24T and the closely related Bacillus species ranged between 24±6 % and 35±3 %. The distinctive phenotypic and genetic results of this study confirmed that strain B16-24T represents a novel species within the genus Bacillus, for which the name Bacillus kiskunsagensis sp. nov. is proposed. The type strain is B16-24T (=DSM 29791T=NCAIM B.02610T).

Highly effective, regiospecific reduction of chalcone by cyanobacteria leads to the formation of dihydrochalcone: two steps towards natural sweetness

BackgroundChalcones are the biogenetic precursors of all known flavonoids, which play an essential role in various metabolic processes in photosynthesizing organisms. The use of whole cyanobacteria cells in a two-step, light-catalysed regioselective bio-reduction of chalcone, leading to the formation of the corresponding dihydrochalcone, is reported. The prokaryotic microalgae cyanobacteria are known to produce phenolic compounds, including flavonoids, as natural components of cells. It seems logical that organisms producing such compounds possess a suitable “enzymatic apparatus” to carry out their biotransformation. Therefore, determination of the ability of whole cells of selected cyanobacteria to carry out biocatalytic transformations of chalcone, the biogenetic precursor of all known flavonoids, was the aim of our study.ResultsChalcone was found to be converted to dihydrochalcone by all examined cyanobacterial strains; however, the effectiveness of this process depends on the strain with biotransformation yields ranging from 3% to >99%. The most effective biocatalysts are Anabaena laxa, Aphanizomenon klebahnii, Nodularia moravica, Synechocystis aquatilis (>99% yield) and Merismopedia glauca (92% yield). The strains Anabaena sp. and Chroococcus minutus transformed chalcone in more than one way, forming a few products; however, dihydrochalcone was the dominant product. The course of biotransformation shed light on the pathway of chalcone conversion, indicating that the process proceeds through the intermediate cis-chalcone. The scaled-up process, conducted on a preparative scale and by using a mini-pilot photobioreactor, fully confirmed the high effectiveness of this bioconversion. Moreover, in the case of the mini-pilot photobioreactor batch cultures, the optimization of culturing conditions allowed the shortening of the process conducted by A. klebahnii by 50% (from 8 to 4 days), maintaining its >99% yield.ConclusionsThis is the first report related to the use of whole cells of halophilic and freshwater cyanobacteria strains in a two-step, light-catalysed regioselective bio-reduction of chalcone, leading to the formation of the corresponding dihydrochalcone. The total bioconversion of chalcone in analytical, preparative, and mini-pilot scales of this process creates the possibility of its use in the food industry for the production of natural sweeteners.