Production of exopolysaccharides from a thermophilic microorganism isolated from a marine hot spring in flegrean areas

A thermophilic strain isolated from sea sand at Maronti, near Sant' Angelo (Ischia), is described. The organism grows well at an optimal temperature of 60 °C at pH 7.0. The thermophilic bacterium, named strain 4004, produces an exocellular polysaccharide (EPS) in yields of 90 mg/l. The EPS fraction was produced with all substrates tested, although a higher yield was obtained with sucrose or trehalose as sole carbon source. During growth, the EPS content was proportional to the biomass. Three fractions (EPS1, EPS2, EPS3) were obtained after purification. Quantitative monosaccharide analysis of the EPSs revealed the presence of mannose:glucose:galactose in a relative ratio of 0.5:1.0:0.3 in EPS1, mannose:glucose:galactose in a relative ratio of 1.0:0.3:trace in EPS2, and galactose:mannose:glucosamine:arabinose in a relative ratio of 1.0:0.8:0.4:0.2 in EPS3. The average molecular mass of EPS3 was determined to be 1×10⁶ Da. From comparison of the chemical shift values in ¹H and ¹³C spectra, we conclude that EPS3 presents a pentasaccharide repeating unit. Electronic Publication     

慢性前列腺炎患者前列腺液白细胞浓度与前列腺液尿酸 及锌含量的相关性研究

目的:探讨慢性前列腺炎患者前列腺液中白细胞(WBC)数量与前列腺液尿酸(UA)、锌(Zn)含量的关系。方法:选取慢性前列腺炎患者128例,健康对照组52例。分别进行EPS中白细胞(WBC)数量、尿酸(UA)和锌(Zn)含量测定。结果:慢性前列腺炎患者前列腺液UA含量显著高于健康对照组,Zn含量显著低于健康对照组,前列腺液中WBC数量与UA含量呈显著正相关,与Zn含量呈显著负相关(P<0.01)。2慢性前列腺炎患者治疗前后EPS中的UA和Zn对比有显著性差异。结论:EPS中的尿酸(U A)、锌(Zn)含量对慢性前列腺炎的诊断与评估疗效有一定价值。     

Isolation and characterization of exopolysaccharide produced by Vibrio harveyi strain VB23

AIMS: The aim of the study was to isolate and characterize exopolysaccharide (EPS) produced by Vibrio harveyi strain VB23. METHODS AND RESULTS: Growth and EPS production by V. harveyi strain VB23, was studied in mineral salts medium supplemented with NaCl (1.5%) and glucose (0.2%). The rate of EPS production in batch cultures was highest during the late log phase of growth when compared with stationary growth phase. The exopolymer was recovered from the culture supernatant by using a cold ethanol precipitation-dialysis procedure. Chemical analyses of EPS revealed that it is primarily composed of neutral sugars, uronic acids, proteins and sulfates. The purified EPS revealed prominent functional reactive groups, such as hydroxyl, carboxylic and amides, which correspond to a typical heteropolymeric polysaccharide and the EPS, also possessed good emulsification activity. The gas chromatographic analysis of an alditol acetate-derivatized sample of EPS revealed that it is composed primarily of galactose and glucose. Minor components found were rhamnose, fucose, ribose, arabinose, xylose and mannose. CONCLUSIONS: The EPS produced by V. harveyi strain VB23 is a heteropolysaccharide possessing good emulsification activity. EPS was readily isolated from culture supernatants, which suggests that the EPS was a slime-like EPS. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report of EPS characterization in luminous V. harveyi bacteria, which describes the isolation and characterization of an EPS expressed by V. harveyi. The results of the study contributes significantly towards an understanding of the chemical composition and applications of the EPS in environmental biotechnology and bioremediation.     

Exopolysaccharide (EPS) biosynthesis by Lactobacillus sakei 0-1: production kinetics, enzyme activities and EPS yields

AIMS: To determine optimal exopolysaccharide (EPS) production conditions of the mesophilic lactic acid bacterium strain Lactobacillus sakei 0-1 and to detect possible links between EPS yields and the activity of relevant enzymes. METHODS AND RESULTS: Fermentation experiments at different temperatures using either glucose or lactose were carried out. EPS production took place during the exponential growth phase. Low temperatures, applying glucose as carbohydrate source, resulted in the best bacterial growth, the highest amounts of EPS and the highest specific EPS production. Activities of 10 important enzymes involved in the EPS biosynthesis and the energy formation of Lact. sakei 0-1 were measured. The obtained results revealed that there is a clear link for some enzymes with EPS biosynthesis. It was also demonstrated clearly that the presence of rhamnose in the EPS building blocks is due to high activities of the enzymes involved in the rhamnose synthetic branch. CONCLUSION: EPS production in Lact. sakei 0-1 is growth-associated and displays primary metabolite kinetics. Glucose as carbohydrate source and low temperatures enhance the EPS production. The enzymes involved in the biosynthesis of the activated sugar nucleotides play a major role in determining the monomeric composition of the synthesized EPS. SIGNIFICANCE AND IMPACT OF THE STUDY: The proposed results contribute to a better understanding of the physiological factors influencing EPS production and the key enzymes involved in EPS biosynthesis by Lact. sakei.     

Mutational analysis of the Lactococcus lactis NIZO B40 exopolysaccharide (EPS) gene cluster: EPS biosynthesis correlates with unphosphorylated EpsB

AIMS: To determine the role of the EpsA, EpsB, and EpsC proteins encoded at the 5'-end of the exopolysaccharide (EPS) gene cluster in regulation of EPS production in Lactococcus lactis. METHODS AND RESULTS: Deletion and paralog-replacement mutants of epsABCD were used to determine the function of EpsA, EpsB and EpsC in EPS production and polymer chain length determination in L. lactis. EpsA and EpsB appeared to be essential for EPS biosynthesis in L. lactis, while deletion of the phosphatase (EpsC) only had a minor effect on the EPS production level. Determination of the phosphorylation state of EpsB and analysis of a C-terminally truncated EpsB variant indicate that EPS biosynthesis in L. lactis is driven by a nonphosphorylated form of EpsB. CONCLUSIONS: The data presented here show that in L. lactis, EPS production is under control of a phosphoregulatory system and that EPS biosynthesis correlates with an unphosphorylated EpsB. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides molecular understanding of polysaccharide production in L. lactis that could eventually enable novel approaches to control EPS production by lactic acid bacteria during industrial fermentation processes.     

Growth and exopolysaccharide production by Lactobacillus helveticus ATCC 15807 in an adenine-supplemented chemically defined medium

AIMS: To analyse the exopolysaccharide (EPS) production by Lactobacillus helveticus ATCC 15807 in a chemically defined medium (CDM) and the effect of nutrients and stress culture conditions on cell growth and EPS formation. METHODS AND RESULTS: Cultures were conducted in CDM: (i) containing essential and nonessential bases and vitamins; (ii) without nonessential bases and vitamins [Simplified CDM (SCDM)]; (iii) SCDM supplemented individually with vitamins and bases. The influence of carbohydrates, pH and osmotic culture conditions on growth and polymer formation was analysed. Adenine and lactose stimulated both growth and EPS production. Constant pH fermentations (4.5 and 6.2) did not improve EPS synthesis while NaCl and glycerol were detrimental for growth and polymer formation. In all media the EPS monomer composition was glucose and galactose (2.5 : 1). CONCLUSIONS: A SCDM containing adenine and lactose was optimal for cell growth and EPS formation by Lact. helveticus ATCC 15807. Controlled pH (6.2 and 4.5) and osmotic stress culture conditions did not improve polymer production. The EPS characteristics were identical in all media. SIGNIFICANCE AND IMPACT OF THE STUDY: This work provides a better knowledge on EPS synthesis by Lact. helveticus. A CDM to perform regulation studies on EPS production by Lact. helveticus species is now available.     

Culture conditions for the production of an acidic exopolysaccharide by the nitrogen-fixing bacterium Burkholderia tropica

The endophytic diazotrophic bacterium Burkholderia tropica, strain Ppe8, produced copious amounts of exopolysaccharide (EPS) on batch growth in liquid synthetic media containing mannitol and glutamate as carbon and nitrogen sources. The effect of various aeration regimes and carbon source concentrations on EPS production was determined, as well as the effects of temperature and time of growth. The degree of aeration had a great influence on the yield of EPS, in contrast with the C:N ratio of the medium. Growth temperature also affected the EPS yield after the first 24 h of culture but seemed to be irrelevant after that. After isolation and purification, the EPS was analyzed by high-performance size exclusion chromatography and multiangle laser light scattering (HPSEC-MALLS), revealing a molecular mass of 300 kDa. The acid hydrolyzate of EPS was examined by HPLC and found to contain Glc, Rha, GlcA, and an aldobiouronic acid. The latter was found to have a GlcA and a Rha unit. Carboxy-reduced EPS contained Glc and Rha (3:2). The monosaccharide composition of the native acidic EPS was calculated as GlcA, Glc, and Rha in a molar ratio of 1:2:2.     

Exopolysaccharide production by Streptococcus thermophilus SY: production and preliminary characterization of the polymer

AIMS: To evaluate the effect of yeast extract (YE) concentration, temperature and pH on growth and exopolysaccharide (EPS) production in a whey-based medium by Streptococcus thermophilus SY and to characterize the partially purified EPS. METHODS AND RESULTS: Factorial experiments and empirical model building were used to optimize fermentation conditions and the chemical composition, average molecular weight (MW) and rheological properties of aqueous dispersions of the EPS were determined. Exopolysaccharide production was growth associated and was higher (152 mg l(-1)) at pH 6.4 and 36 degrees C with 4 g l(-1) YE. High performance size exclusion chromatography of the partially purified EPS showed two peaks, with a weight average MW of 2 x 10(6) and 5 x 10(4), respectively. The EPS was a heteropolysaccharide, with a glucose : galactose : rhamnose ratio of 2 : 4.5 : 1. Its water dispersions had a pseudoplastic behaviour and showed a higher viscosity of xanthan solutions. SIGNIFICANCE AND IMPACT OF THE STUDY: The fermentation conditions and some properties of an EPS produced by Strep. thermophilus, a dairy starter organism, were described.     

一株红树林真菌抗单纯疱疹病毒Ⅱ型的研究

目的:对分离自海南红树林真菌菌株PH0016的胞外多糖(exopolysaccharide,EPS)抗单纯疱疹病毒Ⅱ型(Herpes simplex virus type 2,HSV-2)活性进行研究。方法:收集纯化菌株PH0016产生的EPS,体外采用细胞病变观察EPS的细胞毒性和抗HSV-2作用。为观察EPS对HSV-2体内感染的治疗效果,小鼠颅内注射0.02ml滴度为100LD50/0.1ml-1的HSV-2,24小时后以不同浓度EPS灌胃,持续7天,14天后计算小鼠存活率和存活时间。菌株分类采用形态学观察和ITS序列分析。结果:EPS可抑制HSV-2病毒活性,病毒感染的细胞病变的半抑制浓度(Inhibited concentration,IC50)为313μg/mL,SI为11.43。EPS 25mg.kg-1.d-1灌胃后,小鼠存活率为40.0%,存活时间为9.82±1.87天,相比模型组实验动物存活时间和存活率均有提高。菌株初步鉴定为淡紫色拟青霉。结论:从海南红树林分离一株淡紫色拟青霉,其产生的EPS具有抗HSV-2活性,值得进一步研究。     

UDP-galactose 4-epimerase: a key enzyme in exopolysaccharide formation by Lactobacillus casei CRL 87 in controlled pH batch cultures

AIMS: To evaluate the relationship between exopolysaccharide (EPS) production and the sugar nucleotide biosynthetic enzymes in Lactobacillus casei CRL 87 under optimum growth conditions for polymer formation: controlled pH on galactose or glucose. Studies with an EPS mutant were carried out to determine the key enzymes in EPS synthesis under the above culture conditions. METHODS AND RESULTS: EPS concentration was estimated by the phenol/sulphuric acid method, while the activities of the biosynthetic enzymes were determined spectrophotometrically by measuring the formation or disappearance of NAD(P)H at 340 nm. An environmental pH of 5.0, using galactose as carbon source, markedly improved not only polymer production and yield but also, cell growth and lactic acid production. Analysis of the activities of the EPS precursor-forming enzymes revealed that polysaccharide synthesis was correlated with uridine-diphosphate (UDP)-glucose pyrophosphorylase and UDP-galactose 4-epimerase under these growth conditions. CONCLUSIONS: EPS synthesis by Lact. casei CRL 87 was considerably improved at a controlled pH of 5.0 with galactose as carbon source, and was correlated with the activity of UDP-glucose pyrophosphorylase and UDP-galactose 4-epimerase. The results obtained with the wild-type and EPS- strains suggest that UDP-galactose 4-epimerase plays an essential role in EPS formation. SIGNIFICANCE AND IMPACT OF THE STUDY: Unravelling the key enzymes involved in EPS biosynthesis under optimum culture conditions for polymer production provides important information for the design of strategies, via genetic engineering, to enhance polysaccharide formation.     

Characterization and fouling properties of exopolysaccharide produced by Klebsiella oxytoca

Klebsiella oxytoca produced a type of exopolysaccharide (EPS) with the average molecular weight (Mw) of 116,018 Da and the average size of 260 nm. The EPS monosaccharide components contained rhamnose, fucose, arabinose, xylose, mannose, galactose and glucose and the molar ratio among them was 0.033:0.0411:0.0147:0.0051:0.2393:0.0986:0.1304. Typical EPS absorption peaks in FT-IR spectrum and pseudoplastic properties were also revealed. The polyvinylidenefluoride (PVDF) membrane showed a relatively larger flux decline resulted from the EPS fouling. The EPS filtration was dominated by more than one mechanism at the beginning phase and mainly by the cake formation at the later phase for both membranes. The pore blocking resistance had a predominant contribution to the filtration resistance and the cake resistance played a secondary role for both the membranes. The EPS adsorption resulted in a weak membrane fouling. The PVDF membrane exhibited a larger adsorption resistance than the polypropylene (PP) membrane.     

Physicochemical properties of the microbial exopolysaccharide ethapolan synthesized on a mixture of growth substrates

Some physicochemical properties of the microbial exopolysaccharide (EPS) ethapolan synthesized by Acinetobacter sp. 12S depended on whether the producer was grown on a mixture of ethanol and glucose or on single substrates. Irrespective of the carbon source in the nutrient medium, the contents of carbohydrates, pyruvic acid, uronic acids, and mineral components in the EPS remained unchanged. The EPS were also identical in their monosaccharide composition: the molar ratio of glucose, mannose, galactose, and rhamnose was 3:2:1:1. EPS with a higher proportion of fatty acids was synthesized during growth on the mixture of ethanol and glucose. Average molecular weight and the proportion of high-molecular (over two million) fractions were greater in ethapolan produced on the substrate mixture. In the presence of 0.1 M KCl, after transformation into the H+ form, and in the Cu(2+)-glycine system, solutions of these EPS showed higher viscosity than solutions of EPS synthesized on single substrates. The reasons for the improved rheological properties of the EPS produced on the substrate mixture are discussed.     

Culture conditions determine the balance between two different exopolysaccharides produced by Lactobacillus pentosus LPS26

Lactobacillus pentosus LPS26, isolated from a natural fermentation of green olives, produces a capsular polymer constituted of two exopolysaccharides (EPS): EPS A, a high-molecular-weight (high-Mw) polysaccharide (1.9x10(6) Da) composed of glucose and rhamnose (3:1), and EPS B, a low-Mw polysaccharide (3.3x10(4) Da) composed of glucose and mannose (3:1). Fermentation experiments in a chemically semidefined medium with different carbon sources (glucose, fructose, mannitol, and lactose) showed that all of them except fructose supported EPS A production rather than EPS B production. The influence of temperature and pH was further analyzed. As the temperature dropped, increased synthesis of both EPS was detected. The control of pH especially enhanced EPS B production. With regard to this, the maximum total EPS production (514 mg liter-1) was achieved at a suboptimal growth temperature (20 degrees C) and pH 6.0. Continuous cultures showed that EPS A, synthesized mainly at low dilution rates, is clearly dependent on the growth rate, whereas EPS B synthesis was hardly affected. EPS production was also detected in supplemented skimmed milk, but no increase on the viscosity of the fermented milk was recorded. This could be linked to the high proportion of the low-Mw polysaccharide produced in these conditions in contrast to that observed in culture media. Overall, the present study shows that culture conditions have a clear impact on the type and concentration of EPS produced by strain LPS26, and consequently, these conditions should be carefully selected for optimization and application studies. Finally, it should be noted that this is, to our knowledge, the first report on EPS production by L. pentosus.     

Physicochemical Properties of the Microbial Exopolysaccharide Ethapolan Synthesized on a Mixture of Growth Substrates

Some physicochemical properties of the microbial exopolysaccharide (EPS) ethapolan synthesized by Acinetobacter sp. 12S depended on whether the producer was grown on a mixture of ethanol and glucose or on a single substrate. Irrespective of the carbon source in the nutrient medium, the contents of carbohydrates, pyruvic acid, uronic acids, and mineral components in the EPS remained unchanged. The EPS were also identical in their monosaccharide composition: the molar ratio of glucose, mannose, galactose, and rhamnose was 3 : 2 : 1 : 1. EPS with a higher content of fatty acids was synthesized during growth on the mixture of ethanol and glucose. The average molecular mass and the content of high-molecular (M > 2 MDa) fractions were greater in ethapolan produced on the substrate mixture. In the presence of 0.1 M KCl, after transformation into the H⁺ form, and in the Cu²⁺–glycine system, solutions of these EPS showed higher viscosity than solutions of EPS synthesized on single substrates. The reasons for the improved rheological properties of the EPS produced on the substrate mixture are discussed.     

Fermentation conditions affecting the bacterial growth and exopolysaccharide production by Streptococcus thermophilus ST 111 in milk-based medium

AIMS: To study the effect of different fermentation conditions and to model the effect of temperature and pH on different biokinetic parameters of bacterial growth and exopolysaccharides (EPS) production of Streptococcus thermophilus ST 111 in milk-based medium. METHODS AND RESULTS: The influence of temperature and pH was studied through fermentation and modelling. Fermentations under non-pH controlled conditions with S. thermophilus ST 111 indicated that the EPS production was low in milk medium, even if additional nitrogen sources were supplemented. Under pH-controlled conditions, addition of whey protein hydrolysate to the milk medium resulted in a fivefold increase of the EPS production. This medium did not contain polysaccharides interfering with EPS isolation. Primary and secondary modelling of different fermentations revealed an optimum temperature and pH of 40 degrees C and constant pH 6.2, respectively, for growth in milk medium supplemented with whey protein hydrolysate. Maximum EPS production was observed in the range of 32-42 degrees C and constant pH 5.5-6.6. Whereas growth and maximum EPS production were clearly influenced by temperature and pH, the specific EPS production was only affected by stress conditions (T = 49 degrees C). CONCLUSIONS: Addition of whey protein hydrolysate to milk medium resulted in an increased growth and EPS production of S. thermophilus ST 111 under pH-controlled conditions. A modelling approach allowed studying the influence of temperature and pH on the kinetics of both growth and EPS production. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of an appropriate milk-based medium and a combined model of temperature and pH can be of practical importance for the production of yoghurt or other fermented milks as well as for process optimization of the large-scale production of starter strains to be used for their EPS production.     

Physicochemical properties and membrane biofouling of extra-cellular polysaccharide produced by a Micrococcus luteus strain

The physicochemical properties of the extra-cellular polysaccharide (EPS) produced by a Micrococcus luteus strain, a dominating strain isolated from membrane biofouling layer, were determined in this study. The EPS isolated from this strain was measured to have an average molecular weight of 63,540 Da and some typical polysaccharide absorption peaks in Fourier transform infrared spectrum. Monosaccharide components of the EPS contained rhamnose, fucose, arabinose, xylose, mannose, galactose and glucose in a molar ratio of 0.2074:0.0454:0.0262:0.0446:1.7942:1.2086:0.4578. Pseudo plastic properties were also observed for the EPS through the rheological measurement. The EPS was further characterized for its behavior to cause membrane flux decline. The results showed that both flux declines for polyvinylidenefluoride (PVDF) and polypropylene membranes became more severe as EPS feed concentration increased. A higher irreversible fouling for the PVDF membrane suggested that the EPS had the larger fouling potential to this microfiltration membrane.     

Production of exopolysaccharides by Antarctic marine bacterial isolates

AIMS: This study was undertaken to examine and characterize Antarctic marine bacterial isolates and the exopolysaccharides (EPS) they produce in laboratory culture. METHODS AND RESULTS: Two EPS-producing bacterial strains CAM025 and CAM036 were isolated from particulate material sampled from seawater and sea ice in the southern ocean. Analyses of 16S rDNA sequences placed these isolates in the genus Pseudoalteromonas. In batch culture, both strains produced EPS. The yield of EPS produced by CAM025 was 30-fold higher at -2 and 10 degrees C than at 20 degrees C. Crude chemical analyses showed that these EPS were composed primarily of neutral sugars and uronic acids with sulphates. Gas chromatographic analysis of monosaccharides confirmed these gross compositional findings and molar ratios of monosaccharides revealed differences between the two EPS. CONCLUSIONS: The EPS produced by Antarctic bacterial isolates examined in this study appeared to be polyanionic and, therefore, 'sticky' with respect to cations such as trace metals. SIGNIFICANCE AND IMPACT OF THE STUDY: As the availability of iron as a trace metal is of critical importance in the southern ocean where it is know to limit primary production, the role of these bacterial EPS in the Antarctic marine environment has important ecological implications.     

Preliminary characterization of exopolysaccharides produced by a marine biofilm-forming bacterium Pseudoalteromonas ruthenica (SBT 033)

AIM: The major objective of the present study was the partial characterization of the exopolysaccharides (EPS) produced by a marine biofilm-forming bacterium Pseudoalteromonas ruthenica under shake culture conditions. METHODS AND RESULTS: EPS-producing bacterial cultures were isolated from the sea water collected from the vicinity of coastal electric power station. Zobell marine broth medium was used for growth of the cultures and the EPS produced was quantified using phenol sulfuric acid method. Chemical characterization of the EPS was carried out using Fourier transform infrared spectroscopy (FTIR), and capillary gas chromatography (GC). Further, viscosity and rheological properties of the purified EPS were studied. The FTIR spectrum revealed prominent peaks of various groups of OH and CH(3) bending. GC analysis showed the presence of eight individual sugars. Rheological studies of the aqueous EPS showed good shearing property. CONCLUSIONS: Pseudoalteromonas ruthenica isolated from marine environment produced copious amount of EPS under shake culture conditions. GC analysis of the EPS revealed the presence of eight individual sugars and the EPS had good shearing property. SIGNIFICANCE AND IMPACT OF THE STUDY: The EPS produced by P. ruthenica is pseudoplastic in nature and is stable at higher pH levels. These properties suggest that the EPS may have potential applications in the oil, textiles and food industries.     

Culture conditions affect the chemical composition of the exopolysaccharide synthesized by the fungus Aureobasidium pullulans

Aims:  To identify if culture conditions affect the chemical composition of exopolysaccharide (EPS) produced by Aureobasidium pullulans .
Methods and Results:  In batch airlift and continuously stirred tank (CSTR) reactors the EPS produced with low (0·13 g l⁻¹ N) initial NaNO₃ or (NH₄)₂SO₄ levels contained pullulan, with maltotriose as its major component, similar to that synthesized in the airlift reactor with high (0·78 g l⁻¹ N) initial NaNO₃ levels. EPS produced by CSTR grown cultures with high (NH₄)₂SO₄ levels contained little pullulan, possibly because of a population shift from unicells to mycelium. This chemical difference may explain why total EPS yields did not fall as they did with cultures grown under identical conditions with high NaNO₃ levels, where the pullulan component of the EPS disappeared. EPS synthesized in N-limiting chemostat cultures of A. pullulans changed little with growth rate or N source, being predominantly pullulan consisting of maltotriose units.
Conclusions:  While the EPS chemical composition changed little under N-limiting conditions, high initial medium N levels determined maltotriose content and/or pullulan content possibly by dictating culture morphology.
Significance and Impact of the Study:  These results emphasize the requirement of all studies to determine EPS chemical composition when examining the influence of culture conditions on EPS yields.     

Disruption of ste23 gene affects composition profile and bioactivity of exopolysaccharide produced by Streptomyces sp. 139

AIMS: To study the function of the gene ste23 involved in the biosynthesis of Ebosin. METHODS AND RESULTS: In search of databases, the deduced product of the gene ste23 showed high homology to dTDP-4-dehydrorhamnose 3,5-epimerases. ste23 was replaced by a kanamycin resistance gene through double crossover. Compared with Ebosin, an exopolysaccharide (EPS) produced by wild-type Streptomyces sp. 139, the EPS produced by the ste23 mutant (designated EPS1) had a remarkably different monosaccharide composition and significantly diminished rhamnose content, though the molecular mass of EPS1 was similar to that of Ebosin. In addition, EPS1 lost the interleukin 1 (IL-1) antagonist activity in vitro. CONCLUSIONS: ste23 may be involved in the Ebosin biosynthesis in S. sp. 139. and its bioactivity. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first genetic work investigating functions of genes involved in EPS production in streptomyces by gene replacement of the pathway genes.