Abstract:
A new antibiotic prepared from aerobic cultivation of Actinoplanes sarveparensis and a method for producing the same from a culture medium.

Description:
SUMMARY OF THE INVENTION 
     The present invention refers to a new antibiotic substance obtained by the fermentation of a strain belonging to the genus Actinoplanes, specifically Actinoplanes sarveparensis. The novel antibiotic substance, hereinafter referred to as antibiotic L 13365 is a light yellow crystalline compound having characteristic identifiable properties such as melting point, infrared and ultraviolet absorption maxima. 
     As stated above, antibiotic L 13365 is produced by cultivation of a fermenting strain named Actinoplanes sarveparensis. This strain, identified with out collection number A/13826, was isolated from a soil sample collected at Sarvepar Village, India. The strain has been deposited and made part of the stock culture collection of CBS (Centraal Bureau Voor Schimmelcultures -- Oosterstraat 1 -- Baarn -- The Netherlands) where it was assigned the number 305.76. 
     In the preparation of antibiotic L 13365, the microorganism is cultivated under aerobic conditions in an aqueous nutrient medium containing an assimilable source of carbon, an assimilable source of nitrogen and inorganic salts. 
     As used herein, the term &#34;assimilable source&#34; refers to a source of a substance required for the growth of the organism or for the production of the antibiotic supplied in a form which may be absorbed and used by the organism. 
     Ordinarily, the antibiotic producing strain is precultured in a shake flask until substantial antibiotic activity is present then the culture is used to inoculate jar fermentors containing a nutrient fermentative medium. 
     The culture is normally incubated at from about 25°-35° C under aerobic conditions for a time sufficient to produce a substantial antibiotic level. During this time, microbiological assays are carried out by the agar diffusion method to control the concentration of the antibiotic substance produced. 
     After eliminating the mycelium cake by filtration, the antibiotic substance is recovered from the filtered fermentation broth by conventional procedures known to the art, such as, for instance, by extraction with an organic solvent in which the antibiotic substance is soluble and which is immiscible with the aqueous medium. The extraction is carried out after adjustment of the pH of the filtrate between about 2 to about 4. Suitable organic solvents for the extraction are advantageously selected from alkanols containing from 1 to about 6 carbon atoms, (C 1  -C 4 )alkyl esters of lower aliphatic acids, or lower halogenated hydrocarbons. The solvent may then be separated from the fermentation broth by high-speed centrifugation, concentrated to about 1/200-1/400 of its original volume, cooled and allowed to stand until a precipitate forms which may be recovered by filtration. This precipitate consists of antibiotic L 13365 substantially free of major impurities. The mother liquors are collected and poured into an excess of an inert non-polar solvent such as light petroleum or the like giving a further amount of crude antibiotic L 13365. The crude product thus obtained is dissolved in a methanol-acetone mixture and is precipitated from the solution by addition of acidic water. 
     The two portions are gathered together and may be further purified by column chromatography using a chloroform-methanol mixture as the eluting system. 
     Antibiotic L 13365 is finally crystallized from methanol:ethyl acetate having a 1:1 ratio. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a typical ultraviolet spectrum of antibiotic L 13365 as recorded from a solution of methyl cellosolve. 
     FIG. 2 represents a typical infrared spectrum of antibiotic L 13365. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The antibiotic substance L 13365 shows a remarkable antibacterial in vitro and in vivo activity. More particularly, antibiotic L 13365 exhibits an outstanding in vitro antimicrobial action, especially against gram-positive bacteria, as shown in Table I below. 
     
                       TABLE I______________________________________                Minimal InhibitoryStrain               Concentration (μg/ml)______________________________________Staphylococcus aureus ATCC 6538                0.025Staphylococcus aureus Tour                0.025Streptococcus haemolyticus C 203                0.0062Diplococcus pneumoniae UC 41                0.00078Clostridium perfingens ISS 30543                0.012Mycoplasma gallisepticum H21 CZB                0.2______________________________________ 
    
     Furthermore, as stated above, antibiotic L 13365 also displays an excellent in vivo activity against experimental infections in mice. More particularly, the dose effective to protect 50 percent of the mice (ED 50 ) using antibiotic L 13365 against experimental infections provoked by Staphylococcus aureus, Streptococcus haemolyticus and Diplococcus pneumoniae are listed hereinbelow in Table II. 
     
                       TABLE II______________________________________Infection Strain      ED.sub.50 mg/kg* s.c.______________________________________Streptococcus haemolyticus                 0.2Staphylococcus aureus 10Diplococcus pnemoniae 0.4______________________________________ *median effective dose (ED.sub.50) 
    
     The new antibiotic substance is active also against microorganism strains which are resistant to other commonly used antibiotics. Representative examples of the minimum inhibiting concentrations (MIC) of antibiotic L 13365 against Staphylococcus aureus strains resistant to several antibiotics are reported in Table III. 
     
                                           TABLE III__________________________________________________________________________Strain         MIC of Other Antibiotics                        MIC of Antibiotic L 13365__________________________________________________________________________Staphylococcus aureus           penicillin &gt;100                        0.4ATCC 6538 resistant topenicillinStaphylococcus aureus Tour           streptomycin &gt;100                        0.078resistant to streptomycinStaphylococcus aureus           tetracycline &gt;100                        0.15ATCC 6538 resistant totetracyclineStaphylococcus aureus           rifampicin &gt;100                        0.01ATCC 6538 resistant torefampicinStaphylococcus aureus           neomycin &gt;100                        0.005ATCC 6538 resistant toneomycinStaphylococcus aureus           erythromycin &gt;100                        0.04ATCC 6538 resistant toerythromycinStaphylococcus aureus           chloramphenicol &gt;100                        0.02ATCC 6538 resistant tochloramphenicolStaphylococcus aureus           cephaloridine &gt;100                        0.078ATCC 6538 resistant tocephaloridineStaphylococcus aureus           kanamycin &gt;100                        0.04ATCC 6538 resistant tokanamycinStaphylococcus aureus           bacitracin &gt;100                        0.02ATCC 6538 resistant tobacitracinStaphylococcus aureus           lincomycin &gt;100                        0.15ATCC 6538 resistant tolincomycin__________________________________________________________________________ 
    
     The toxicity of antibiotic L 13365, administered either orally or intraperitoneally to mice is very low with the median lethal dose (LD 50 ) values higher than 1000 mg/kg. 
     Description of Actinoplanes sarveparensis A/13826 
     Macroscopic examination of colonies 
     The strain grows well on various nutrient agars. In oatmeal agar, the colonies are 3 to 4 mm in diameter, show irregular contours and a rough surface. Aerial mycelium is always absent. 
     Microscopic examination 
     Sporangia are produced in several agar media. They have a regular globose shape with a diameter ranging from 13 to 20 μ. The zoospores, highly motile, are spherical but occasionally are slightly elongated with a diameter of 1.5-2 μ. On the basis of these characteristics, the strain A/13826 is ascribed to the genus Actinoplanes and given the name Actinoplanes sarveparensis CBS 305.76. Table IV reports the cultural characteristics of Actinoplanes sarveparensis CBS 305.76 cultivated on various standard media suggested by Shirling and Gottlieb (Intern. J. Syst. Bact., 16, 313-340, 1966) and other media recommended by Waksman (The Actinomycetes, Vol. II, The Williams and Wilkins Co., 1961). The cultural characteristics were determined after 6-14 days of incubation at 30° C. 
     Table V reports the utilization of carbon sources examined according to the method of Pridham and Gottlieb (Intern. J. Syst. Bact. 56, 107, 1948). 
     Table VI reports the physiological characteristics of the strain. 
     
                       TABLE IV______________________________________Cultural Characteristics of Actinoplanes sarveparensisCBS 305.76Culture Medium     Cultural Characteristics______________________________________Medium No. 2     Abundant growth, wrinkled(yeast extract-malt agar)            surface, orange to brown; (cen-            tral part of colony is darker).Medium No. 3     Scant growth, thin, hyaline to(oatmeal agar)   light orange - production of            sporangia.Medium No. 4     Moderate growth, crusty surface,(inorganic salts-starch agar)            light orange (9/G/7).Medium No. 5     Abundant growth, crusty surface,(glycerol-asparagine agar)            brilliant orange (9/I/11).Medium No. 6     Scant growth, crusty suface,(peptone-yeast extract-            brown (13/C/7).iron agar)Medium No. 7     Moderate growth, crusty surface,(tyrosine agar)  orange (11/F/8).Oatmeal agar     Abundant growth, rough surface,(according to Waksman)            orange (9/H/12), (central part            of colony is darker).Hyckey and Tresner&#39;s agar            Moderate growth, wrinkled            surface brown (18/A/12).Czapek glucose agar            Abundant growth, wrinkled            surface orange (11/G/11).Glucose asparagine agar            Abundant growth, rough surface,            brilliant orange (9/I/11).Nutrient agar    Moderate growth, rough surface,            orange (11/F/8).Potato agar      Moderate growth, wrinkled            surface, orange to brown - pro-            duction of sporangia.Bennett&#39;s agar   Moderate growth, wrinkled            surface, light orange (9/D/5).Calcium malate agar            Scant growth, thin hyaline to            light orange - production of            sporangia.Skim milk agar   Abundant growth, wrinkled            surface, orange to light brown,            patch shadows.Czapek agar      Abundant growth, wrinkled            surface, orange (11/G/11).Egg agar         Scant growth, rough surface,            hyaline.Pept. glucose agar            Moderate growth, wrinkled            surface, deep orange (11/B/12).Agar             Very scant growth, thin, hyalineLoeffler Serum   Very scant growth, orangePotato           Scant growth, wrinkled, deep            orangeGelatin          Scant growth, light orangeCellulose        No growth______________________________________ 
    
     Color determination was made by the method of Maerz and Paul (Maerz, A. and M. Reg. Paul 1950. A dictionary of color, 2nd ed. M. Grow -- Hill Book Company, Inc., New York). 
     The numbers of some culture media refer to those given according to Shirling and Gottlieb (Intern. J. Syst. Bact., 16, 313-340, 1966). 
     
                       TABLE V______________________________________Utilization of Carbon CompoundsCarbon Sources       UtilizationC.sub.5 Arabinose    +Xylose               +C.sub.6 Glucose      +Fructose             +Mannose              +Mannitol             +Inositol             +Rhamnose             +(C.sub.6).sub.2 Sucrose                +Lactose              +(C.sub.6).sub.3 Raffinose                -(C.sub.6).sub.4 Cellulose                -Special Salicin      -______________________________________ + means utilization - means lack of utilization 
    
     
                       TABLE VI______________________________________Physiological Characteristics   Test            Results______________________________________Hydrolysis of starch    positiveH.sub.2 S formation     positiveMelanin production      negativeTyrosinase reaction     negativeCasein hydrolysis       positiveCalcium malate hydrolysis                   positiveNitrate reduction       positiveLitmus milk coagulation negativeLitmus milk peptonization                   positiveGelatin liquefaction    positive______________________________________ 
    
     Production and Isolation of the Antibiotic Substance 
     A preferred method for producing the antibiotic substance is by aerobically pre-culturing the Actinoplanes sarveparensis CBS 305.76 in a nutrient medium until substantial antibiotic activity is present at a pH value ranging from about 6 to about 10. The following shake flask culture was found satisfactory in the practice of the present invention. 
     
         ______________________________________Meat extract         3.0 g/lTryptone             5.0 g/lYeast extract        5.0 g/lGlucose              1.0 g/lSoluble starch       24.0 g/lCalcium carbonate    4.0 g/lDistilled water      q.s. to 1000 ml______________________________________ 
    
     The flakes are shaken for about 24 hours at about 28°-30° C and the pre-cultures (one liter) are used to inoculate jar fermentors each containing 10 liters of the following nutrient medium: 
     
         ______________________________________Meat extract         40 gPeptone              40 gYeast extract        10 gSodium chloride      25 gSoybean meal         100 gGlucose              500 gCalcium carbonate    50 gTap water            q.s. to 10 liters______________________________________ 
    
     The fermentation batches are incubated aerobically under stirring at 28°-30° C. At intervals, the antibiotic activity is assayed microbiologically by the agar diffusion method using Staphylococcus aureus as the test organism. The maximum activity will be reached after about 72-96 hours of fermentation. 
     Isolation and Purification of Antibiotic L 13365 
     One method of isolating the enzyme found to be satisfactory was as follows: the fermentation broth (80 liters) was filtered using 1 percent clarcel (W/V) as a filter aid. The mycelium cake is discarded and the filtered solution, acidified to pH 2.5 with 10 percent HCl, is extracted twice with an amount of ethyl acetate corresponding to about 50 percent of its volume. 
     The organic phase was separated from the aqueous one by means of high-speed centrifugation, then dried over Na 2  SO 4 , concentrated at 45°-50° C under vacuum to about 1/300 of its orginal volume and finally cooled to about 0°-10° C. 
     A crude precipitate formed, which was collected on a filter, washed with a small quantity of ethyl acetate and dried at about 45° C under vacuum. 1.140 Grams of the antibiotic substance L 13365 were obtained with a purity degree of about 70 percent, determined spectrophotometrically. 
     The mother liquors deriving from the above filtration were poured into 20 volumes of light petroleum and an additional amount (2.550 g) of antibiotic substance with a purity degree of 20-25 percent (determined spectrotometrically) was obtained. This substance was suspended in a small amount of methanol:acetone 9:1 mixture, filtered from any insoluble impurities and diluted with water: the solution was brought to a pH value of about 2.5 by means of 10 percent HCl under stirring and the precipitate which formed was collected by centrifugation and redissolved in a minimum amount of butanol at about 45°-50° C. The solution was concentrated under vacuum to about 1/5 of the original volume and cooled to about 4° C. The resulting precipitate, after being collected and dried under vacuum, was the antibiotic substance L 13365 (0.450 g) having a purity degree of about 80 percent (determined spectrophotometrically). The obtained crops were then subjected to common purification operations known to the art. To this purpose, they were dissolved in a minimum amount of a chloroform:methanol 85:15 mixture and chromatographed through a silica-celite column (1:1 V/V), previously activated at 100° C, and washed with the above chloroform/methanol mixture. 
     Elution and thin layer chromatography control of the fractions are performed with the same mixture. The fractions collected according to t.l.c. analysis data were concentrated under vacuum to a small volume. Upon adding diethyl ether, a precipitate formed, consisting of antibiotic L 13365 with a purity degree of about 95 percent (determined spectrophotometrically). Said precipitate was dissolved in a methanol:ethyl acetate 1:1 mixture, heated to 45° C and filtered from any insolubles; upon cooling to 4° C and standing overnight at the same temperature substantially pure antibiotic L 13365 was obtained a light yellow needles. 
     Chemico-physical Properties of Antibiotic L 13365 
     Antibiotic L 13365 is a light yellow crystalline powder with acidic character. Analysis of an acid hydrolisate of antibiotic L 13365 in 6N hydrochloric acid in a sealed tube at 110° C revealed four amino acids, three of them have been identified in an amino acid autoanalyzer as aspartic acid, threonine and glycine. Furthermore, antibiotic L 13365 is characterized by the following properties: 
     (1) Melting point: -- 210° C 
     (2) Elemental analysis: -- C = 51.35, H = 5.05, N = 10.50, S = 11.05 and O (by difference) = 22.05. 
     (3) Ultraviolet and visible absorption spectrum 
     
         ______________________________________Solvent        λ.sub.max (nm)                       E.sup.1%.sub.1cm______________________________________Hydrochloric acid 0.1N          360          103          290 (shoulder)          237          326Buffer 0.15 M  408 (shoulder)pH 7.5         378          67          290 (shoulder)          237          326Buffer 0.15 M  408          99pH 8.8         290 (shoulder)          238          336______________________________________ 
    
     Ultraviolet absorption spectra were determined with a UNICAM Sp 800 ultraviolet spectrophotometer using solutions of L 13365 in methylcellosolve (MCS)-buffers at different pH in one to one proportion. The complete ultraviolet spectrum is shown in FIG. 1. 
     (4) Fluorescence spectrum: -- The antibiotic contains a strongly fluorescent chromophore and a solution of the product in 0.1 N sodium hydroxide excited at 240 nm shows an emission spectrum with maxima at 355 and 490 nm. Fluorescense spectrum was determined with a Perkin Elmer Mod. MPF - 44 fluorescence spectrophotometer. 
     (59 Infrared spectrum: -- Characteristic absorption bands in nujol have been observed at the following frequencies (cm -1 ): 3400 (shoulder), 3350 (sharp), 3200 (shoulder), 3100 (sharp), 2930 and 2870 (nujol), 2800-2400, 2380 (atmospheric carbon dioxide), 1750 (sharp), 1670 (sharp), 1620 (sharp), 1540 (sharp), 1480 (sharp), 1460 and 1380 (nujol), 1420 (sharp), 1340 (sharp), 1320 (sharp), 1280 (sharp), 1240 (sharp), 1195 (sharp), 1170 (sharp), 1145 (sharp), 1120 (sharp), 1075 (broad), 1015 (sharp), 990 (sharp), 935 (sharp), 920 (broad), 900 (sharp), 865 (sharp), 840 (sharp), 800 (sharp), 770 (sharp), 755 (sharp), 740 (sharp), 720 (nujol). The infrared spectrum was determined with a Perkin Elmer Mod. 157 spectrophotometer. The complete infrared spectrum is shown in FIG. 2. 
     (6) Specific rotation: -- [α] 436 .sup. 25 = + 125° (C = 0.8 percent in methanol:chloroform 1:1) 
     (7) Solubility: -- The compound is soluble in dimethylsulfoxide, dimethylformamide and in chloroform/-methanol mixtures; slightly soluble in chloroform, methanol, methanol/ethyl acetate mixtures, sodium bicarbonate solutions and glacial acetic acid; insoluble in water and in the other common organic solvents. 
     (8) Characteristic reactions 
     
         ______________________________________Fehling             positiveTollens             positiveKMnO.sub.4          positiveH.sub.2 SO.sub.4 conc.               dark brown colorNinhydrin           negativeFeCl.sub.3          positiveMillon              negativeSchiff              negativeAnthrone            positiveFolin Ciocalteau    negativeElson Morgan        negative______________________________________ 
    
     (9) Acidity: An ionizable function with pK a  7.8 is evidenced by potentiometric titration with 0.1 N sodium hydroxide of antibiotic L 13365 in a 2-methoxyethanol:water 4:1 solution. The equivalent weight determined accordingly is 1400. 
     (10) Chromatographic behavior 
     
         ______________________________________Solvent System            Rf*______________________________________Buffer pH 6.0 saturated n-butanol                     0.75Water saturated n-butanol + 2%                     0.80p-toluenesulfonic acidWater saturated n-butanol + 2%                     0.70conc. ammoniaButanol saturated buffer pH 6.0                     0.0Ammonium chloride (20% W/V in water)                     0.0n-butaniol:methanol:water 40:10:20                     0.90containing 0.75 g methyl orangen-butaol:methanol:water 40:10:30                     0.90water:acetone 1:1         0.35water saturated ethyl acetate                     0.0-0.31chloroform:methanol 85:15 (**)                     0.51______________________________________ (*) = Paper chromatography on Whatman paper no. 1. Antibiotic visualized on agar plates seeded with S. aureus. (**) = Tlc on silica gel plates HF/UV.sub.254. Fluorescent spot under ultra-violet light.