1. An engineering bacterium for directionally and highly producing gentamicin C2, which is a Micromonospora purpurea (Micromonospora purpurea) C21591 strain obtained by screening through a common pressure chamber temperature plasma mutagenesis technology, is registered and preserved in China general microbiological culture Collection center (CGMCC for short, with the address of No. 3 Siro 1 # in North Chen of the sunward area in Beijing) at 6-13 th 2021, and the preservation number is CGMCC No. 59450.

2. A method for preparing gentamicin C2 by fermentation of engineering bacteria of directionally and highly-yielding gentamicin C2 obtained by screening comprises the following steps: recovering the screened strain C21591, coating on a slant plate, culturing on the slant at 30-37 deg.C for 12-15 days, inoculating fresh spore to seed culture medium, culturing at 30-37 deg.C with shaking table rotation speed of 230r/min for 12-48 hr; transferring the strain to a fermentation medium according to the inoculum size of 5.0%, placing at 30-37 deg.C, and shaking table rotation speed of 230r/min, and culturing for 120-196 h.

3. The method for preparing gentamicin C2 by fermentation of the engineering bacteria of the directionally obtained and high-yield gentamicin C2 as claimed in claim 2, wherein the slant culture medium: 2.0 percent of soluble starch, 0.05 percent of L-asparagine and K₂HPO₄0.05％，MgSO₄ 0.05％，NaCl 0.05％，KNO₃ 0.1％，CaCO₃ 0.1％，FeSO₄0.001%, agar 2.0%, pH7.2-7.4.

Seed culture medium: soluble starch 1.5%, glucose 0.5%, peptone 0.5%, yeast powder 0.5%, (NH)₄)₂SO₄0.05％，K₂HPO₄·3H₂O 0.05％，NaCl 0.05％，MgSO₄·7H₂O 0.05％，CaCO₃ 0.1％，pH7.2。

Fermentation medium: fermentation medium: 2-6% of soluble starch, 0.5-2% of cane sugar, 1.0-4% of casein, 0.5-1% of corn steep liquor and MgSO₄·7H₂O 0.04-0.1％，FeSO₄·7H₂O 0.005-0.01％,CuSO₄·5H₂O 0.005-0.01％,CoCl₂·6H₂O 0.0005-0.001％，CaCO₃ 0.3-1％，pH7.2。

4. The method for preparing gentamicin C2 by fermentation of engineering bacteria of directionally and highly yielding gentamicin C2, which are obtained by screening, as claimed in claim 3, wherein the soluble starch is 3%, the sucrose is 0.7%, the casein is 1.5%, the corn steep liquor is 1%, and the MgSO is MgSO₄·7H₂O 0.04％，FeSO₄·7H₂O 0.007％,CuSO₄·5H₂O 0.007％,CoCl₂·6H₂O 0.0005％，CaCO₃0.5％，pH7.2。

5. The method for preparing gentamicin C2 by utilizing the screened engineering bacteria of the oriented high-yield gentamicin C2 through fermentation as claimed in claim 2, further comprising the steps of separating and purifying gentamicin C2, wherein the steps are as follows: centrifuging the fermentation liquid of the C21591 strain at 3000-₂SO₄Adjusting pH to about 2.0, adding NaOH to neutralize to pH6.8 to obtain neutralized solution, adding 732NH⁴⁺(Na⁺) Performing static adsorption for 5-6 hr under stirring for ion exchange, centrifuging saturated resin to remove foreign substances, and loading saturated resin into column with 7% HCl and NH₄Washing with Cl and deionized water until no Cl is formed^-Desorbing with 0.5N ammonia water, decolorizing with 711-OH type desorbed solution, film concentrating the decolorized solution to obtain concentrated solution, decolorizing with activated carbon, filtering, separating with adsorption macroporous resin, concentrating, gradient resolving with solvent to obtain main peak, and refining to obtain refined product with component content not lower than 95%.

6. A gentamicin C2 product when produced by the process of claims 2-5.

7. The application of the engineering bacterium of the directed high-yield gentamicin C2 as claimed in claim 1 in the synthesis of antibacterial drugs.

8. The use according to claim 7, wherein the antibacterial agent is gentamicin C2 or its sulfate.

Background

Gentamicin, which was first discovered by Weinstein in 1963, is a multicomponent aminoglycoside antibiotic produced by micromonospora, and includes C1, C2, C1a, C2a, and C2 b. Gentamicin is widely used clinically as its main components C1, C2 and C1a, of which the highest antibacterial activity is C1a, which is a precursor for the synthesis of etimicin, followed by C2b, also known as saxamycin. Such antibiotics are capable of binding to 16S rrna on the 30S subunit of the bacterial ribosome, causing misreading of the genetic code and thus blocking the synthesis of bacterial proteins, and are therefore used primarily for the treatment of bacterial infections, especially infections caused by gram-negative bacteria. However, their clinical use is limited due to high renal toxicity during practical use.

For better research on biological fermentation of gentamicin, gentamicin biosynthetic gene clusters in 3 strains have been sequenced and published, wherein one strain is micromonospora purpurea (GenBank Accession No. AJ575934) and the other two strains are micromonospora echinospora (GenBank Accession No. AY524043 and AJ 628149). Comparing the 3 reported gentamicin gene clusters, the sizes and the sequences of the biosynthesis core genes are completely consistent, and the tissue structures are completely the same, which indicates that the gene cluster exists in different strains through horizontal gene transfer. Gentamicin belongs to 4, 6-disubstituted aminoglycoside antibiotics, and the core structure of gentamicin is 2-deoxystreptomycin. The biosynthetic pathway was first suggested by Testa and Tilley in studying a Micromonospora purpurea mutant producing Bararomycylamine, and it was found that gentamicin C1 could not be converted to other species, whereas C2 could be converted to C1, while C1a could be converted to C2 b. The biosynthetic pathway of gentamicin can be roughly divided into two main stages: firstly, synthesizing a gentamicin precursor A2; ② the synthesis of gentamicin C group compound. During the second step, one of the predicted routes is that gentamicin A2 forms G418 under the action of C-methyltransferase, then JI-20B under the action of dehydrogenase and aminotransferase, and then the C-3' and C-4' undergo reductive deoxygenation reaction under the action of dehydratase to form gentamicin C2, wherein a portion of C-6' of C2 undergoes N-methylation to form gentamicin C1, and another portion of C2 forms C2a through epimerization, wherein C2a and C2 are a pair of epimers. Therefore, the two substances are generated at all times in the microbial fermentation production, and cannot be effectively distinguished.

The two epimer drugs have similar chemical structures and similar physicochemical properties, and the separation of a single component of gentamicin C2 from the epimer drugs is very difficult, so that the supply of gentamicin C2 is short, the production cost is high, the chromatographic separation period is long, the yield is low, the material consumption is high, the pollution is serious, the extraction and refining processes are complex, the product quality is unstable, and the by-product gentamicin C2a which is similar to the gentamicin C2 in structure interferes at any time, so that the product quality control is greatly uncertain, and the stability, safety and effectiveness of the drug are seriously influenced, thereby being a scientific problem which needs to be solved urgently.

Disclosure of Invention

The invention aims to provide an engineering bacterium for directionally producing high-yield gentamicin C2, which is a Micromonospora purpurea (Micromonospora purpurea) C21591 strain obtained by screening through a constant pressure chamber temperature plasma mutagenesis technology, is registered and preserved in China general microbiological culture Collection center (CGMCC for short, No. 3 of West Lu 1 institute of China center for culture Collection management) at 13 th 2021, 6 th and 13 th days, and has the preservation number of CGMCC No. 59450.

Further, the invention provides an operation step of normal pressure room temperature plasma mutagenesis for screening engineering bacteria of oriented high yield gentamicin C2, which comprises the following steps: (1) culturing strains; (2) carrying out plasma mutagenesis at normal pressure and room temperature; (3) screening a high-flux deep hole plate; (4) re-screening; (5) verifying the genetic stability of the strain; (6) and (5) seed production and preservation.

Further, the invention provides a method for preparing gentamicin C2 by fermentation of engineering bacteria of directionally and highly-yielding gentamicin C2 obtained by screening, which comprises the following steps: recovering the screened strain C21591, coating on a slant plate, culturing on the slant at 30-37 deg.C for 12-15 days, inoculating fresh spore to seed culture medium, culturing at 30-37 deg.C with shaking table rotation speed of 230r/min for 12-48 hr; transferring the strain to a fermentation medium according to the inoculum size of 5.0%, placing at 30-37 deg.C, and shaking table rotation speed of 230r/min, and culturing for 120-196 h.

Wherein, slant culture medium: 2.0 percent of soluble starch, 0.05 percent of L-asparagine and K₂HPO₄ 0.05％，MgSO₄0.05％，NaCl 0.05％，KNO₃ 0.1％，CaCO₃ 0.1％，FeSO₄0.001%, agar 2.0%, pH7.2-7.4.

Seed culture medium: soluble starch 1.5%, glucose 0.5%, peptone 0.5%, yeast powder 0.5%, (NH)₄)₂SO₄ 0.05％， K₂HPO₄·3H₂O 0.05％，NaCl 0.05％，MgSO₄·7H₂O 0.05％，CaCO₃ 0.1％，pH7.2。

Fermentation medium: 2% of soluble starch, 0.5% of cane sugar, 1.0% of casein, 0.5% of corn steep liquor and MgSO₄·7H₂O 0.04％，FeSO₄·7H₂O 0.005％,CuSO₄·5H₂O 0.005％,CoCl₂·6H₂O 0.0005％，CaCO₃0.3％，pH7.2。

Further, the invention provides a method for separating and purifying gentamicin C2, which comprises the following steps: centrifuging the fermentation liquid of the C21591 strain at 3000-₂SO₄Adjusting pH to about 2.0, adding NaOH to neutralize to pH6.8 to obtain neutralized solution, adding 732NH⁴⁺(Na⁺) Performing static adsorption for 5-6 hr under stirring for ion exchange, centrifuging saturated resin to remove foreign substances, and loading saturated resin into column with 7% HCl and NH₄Washing with Cl and deionized water until no Cl is formed^-Desorbing with 0.5N ammonia water, decolorizing with 711-OH type desorbed solution, film concentrating the decolorized solution to obtain concentrated solution, decolorizing with activated carbon, filtering, separating with adsorption macroporous resin, concentrating, gradient resolving with solvent to obtain main peak, and refining to obtain refined product with component content not lower than 95%.

The engineering bacteria of the oriented high-yield gentamicin C2 obtained by screening can be used for oriented high-yield gentamicin C2, the component ratio of gentamicin C2 is improved to more than 85% of the existing component ratio from about 15%, and the fermentation titer of the optimized formula is 1184U/mL to the maximum extent through the Plackett-Burman design, and is improved by 42% compared with the titer of the original formula. But also the whole production period can be shortened; the purity of gentamicin C2 is improved, the production cost is reduced, and the production capacity of gentamicin C2 is greatly improved. Compared with the original strain, the yield of the gentamicin C2 is improved by 3 times, other isomerous isomers or impurities are basically not contained, downstream application can be directly carried out, complex biotransformation and purification are not needed, a large amount of cost is saved, and the industrialization requirement is met.

Drawings

Fig. 1 chromatogram of gentamicin C component before and after mutation, wherein, fig. a is original strain SD2020, and fig. B is mutant strain C21591, wherein, 1: sisomicin; 2: gentamicin C1 a; 3: gentamicin C2; 4: micronomicin; 5: gentamicin C2 a; 6: gentamicin C1.

Examples

Example 1 Normal pressure Room temperature plasma mutagenesis screening

1) Taking a gentamicin producing strain Micromonospora purpurea SD2018 in a strain library of the applicant as a starting strain, sucking 0.1ml of sterilized straw by using 1ml of sterilized straw, inoculating the sucked strain on a sterilized slant culture medium, and carrying out slant spore culture at the culture temperature of 35-37 ℃, standing for 4 days to obtain slant spores of the SD2020 strain;

2) take 1.0cm²Adding the bevel spores prepared in the step 1) into a sterilized triangular flask containing 5ml of normal saline with the mass concentration of 0.9%, and shaking for 20min to obtain spore suspension;

3) taking 500 mu l of the spore suspension prepared in the step 2), adding 250 mu l of lithium chloride aqueous solution with the mass concentration of 20% and 250 mu l of physiological saline with the mass concentration of 0.9%, and shaking and uniformly mixing for 5min to obtain the spore suspension containing the lithium chloride with the mass concentration of 5%; after shaking and uniform mixing, sucking 20 mul of spore suspension containing lithium chloride with mass concentration of 5% by using a pipette, and putting the spore suspension into a sample device of an ARTP (normal pressure room temperature plasma) mutation breeding instrument for mutagenesis, wherein the mutagenesis time is set to be 90 seconds, so as to obtain the spore suspension after mutagenesis; the mutagenesis conditions were: the working power is 120W, the gas source is Ar, and the gas flow is 10L/min. The bacterial suspension after mutagenesis is properly diluted and coated on a separation plate, and is cultured for about 15 days at the constant temperature of 30 ℃ for calculating the lethality rate and screening strains.

4) Centrifuging the separated single colony fermented broth by conventional fermentation to obtain supernatant, adding a sulfuric acid solution with the mass concentration of 20% to acidify to the pH value of 1.5-2.0, uniformly mixing and standing for 20min, filtering by qualitative filter paper (medium speed), taking 10 mu l of filtrate, and detecting fermentation units and components by a high performance liquid chromatograph, wherein the chromatographic conditions are as follows: a chromatographic column: GRACE Apollo C18(4.6 mm. times.250 mm,5 μm); mobile phase: 0.2mol/L trifluoroacetic acid solution-methanol (96:4, V/V), the flow rate is 0.6mL/min, the column temperature is 35 ℃, and the sample injection amount is 25 mu L; the ELSD drift tube temperature is 110 ℃, the carrier gas (nitrogen) flow is 2.5L/min, and the gain is 1. The product of one mutant strain was found to have a very specific gain at the peak C2, and a significant inhibition at the other peak C component (fig. 1), which was designated C21591 and was subjected to laboratory and biological preservation.

Example 2 high efficiency fermentation of gentamicin C2

The Plackett-Burman design was developed in the middle and late 20 th century as a near-saturating, two-level test design. The method is based on the principle of incomplete balancing block, can estimate the main effect of the factors with the least number of tests, and quickly and effectively screens out the most important factors from a plurality of factors for further research. The method has simple data processing, and compared with the current commonly used partial factor test and random equilibrium test, the method has the most efficient and accurate screening of important factors, thereby being widely applied to the optimization of the culture conditions of microorganisms and obtaining better results. In the examples, many factors in the fermentation medium formula of gentamicin C2 are considered and evaluated through the Plackett-Burman experimental design of DesignExpert7.0, a plurality of important influence factors are screened out from the fermentation medium formula, and the fermentation medium is further optimized through an orthogonal experiment.

Reagents, raw materials and the like used in the examples are all conventional choices in the field, are mature and commercially available products, and the information of the sources, the specific purities and the like is not described again.

Recovering the screened strain C21591, coating on a slant plate, culturing at 37 deg.C for 12d, inoculating fresh spore to seed culture medium, culturing at 37 deg.C and 230r/min for about 48 h; inoculating to fermentation medium at 5.0%, placing at 37 deg.C, and culturing at 230r/min for 120 h.

Wherein, slant culture medium: 2.0 percent of soluble starch, 0.05 percent of L-asparagine and K₂HPO₄ 0.05％，MgSO₄0.05％，NaCl 0.05％，KNO₃ 0.1％，CaCO₃ 0.1％，FeSO₄0.001%, agar 2.0%, pH7.2-7.4.

Seed culture medium: soluble starch 1.5%, glucose 0.5%, peptone 0.5%, yeast powder 0.5%, (NH)₄)₂SO₄ 0.05％， K₂HPO₄·3H₂O 0.05％，NaCl 0.05％，MgSO₄·7H₂O 0.05％，CaCO₃ 0.1％，pH7.2。

The fermentation medium comprises: soluble starch, sucrose, casein, corn steep liquor, MgSO₄·7H₂O， FeSO₄·7H₂O,CuSO₄·5H₂O,CoCl₂·6H₂O，CaCO₃。

Screening out significant influence factors according to 9 components in a fermentation medium, reserving 1 empty item F (dummy) as an error item in a table, determining a high level and a low level (the low level is the original medium formula) of each variable respectively, and setting a response value as the titer of gentamicin C2; after the significant influencing factors are screened out, the factors are further optimized by an orthogonal experiment (see table 1).

TABLE 1 Plackett-Burman experiment design factor level table

Numbering	Factors of the fact	High level	Low level
				A	Soluble starch	6	2
B	Sucrose	2	0.5
				C	Casein as a food additive	4	1
D	Corn steep liquor	1	0.5
				E	MgSO4·7H2O	0.1	0.04
F	FeSO4·7H2O	0.01	0.005
				G	CuSO4·5H2O	0.01	0.005
H	CoCl2·6H2O	0.001	0.0005
				I	CaCO3	1	0.3
J	Empty item	1	-1

According to the factor level setting of the table 1, a PB design table of Plackett-Burman is selected as a table 2, 11 groups of experiments are adopted to perform effect evaluation on 9 influence factors of an initial fermentation medium, and regression analysis is performed on gentamicin C titer data to obtain partial regression coefficients and significance of the influence factors. And then, according to the results of the Plackett-Burman screening experiment, arranging an orthogonal experiment by using a four-factor three-level orthogonal table.

TABLE 2 Plackett-Burman Experimental arrangement and results

The fermentation medium is optimized by combining a Plackett-Burman significant influence factor screening experiment and an orthogonal experiment, and finally the most suitable fermentation medium is determined as follows: 3% of soluble starch, 0.7% of cane sugar, 1.5% of casein, 1% of corn steep liquor and MgSO₄·7H₂O 0.04％，FeSO₄·7H₂O 0.007％,CuSO₄·5H₂O 0.007％,CoCl₂·6H₂O 0.0005％，CaCO₃0.5%, pH7.2. Compared with the original fermentation formula, the fermentation titer of the optimized formula is 1184U/mL at most, and is improved by 42% compared with the titer of the original formula, which shows that the fermentation titer of the optimized culture medium formula can be obviously improved.

EXAMPLE 3 purification of gentamicin C2

Performing amplification culture by the fermentation method, diluting the fermentation broth after amplification fermentation with 10% tap water, adding hydrochloric acid or sulfuric acid, acidifying to pH1.0-3.0, and stirring for 1-4 hr; then adjusting pH to 5.0-7.0 with sodium hydroxide solution, adding 732NH⁴⁺The resin is statically absorbed for 6 to 8 hours. The resin dosage is calculated according to about 5 wu/mL. Collecting adsorption saturated resin, and using tap waterRinse clean (no floating mycelium). Loading saturated resin into a column, pickling the saturated resin with 0.5M HCl solution twice the volume of the saturated resin, washing the saturated resin with deionized water to be neutral, then carrying out alkali washing with 0.01% ammonia water, connecting the effluent to an 711 resin column with the same volume when the pH of the effluent is higher than 9.0, eluting with 4% ammonia water, wherein the using amount of the ammonia water is 8-10 times the volume of the saturated resin, controlling the elution time to be 8-10 hours, and collecting the eluate.

Concentrating the eluate to 25-30 ten thousand u/mL by film, adjusting pH to 5.5-6.0 with concentrated sulfuric acid, decolorizing with active carbon until the transmittance reaches above 92%, slowly adding 95% ethanol dropwise into the concentrated solution under stirring, crystallizing, standing overnight, collecting the filtered product, and eluting with 85% ethanol solution to obtain wet product. And (3) drying the wet finished product in vacuum (the vacuum degree is more than 500mmHg, the temperature is 600 ℃, and the drying time is 6 hours) to obtain a gentamicin sulfate C2 finished product, wherein the yield is more than 85%.

Performing thin-layer chromatography (TLC) (according to pharmacopoeia of the people's republic of China (2010 version), preparing a developing solvent system comprising chloroform, methanol, ammonia water (25%): 1:1:1, preparing 15ml of mixed solution, standing for 2h, using the lower layer solution as developing solvent), performing High Performance Liquid Chromatography (HPLC) (referring to pharmacopoeia of the people's republic of China (2005 version), using octadecyl carbon silica gel as filler, using sodium heptanesulfonate solution (0.02mol/L) prepared from water-glacial acetic acid-methanol (25:5:70) as mobile phase, detecting wavelength of 330nm, sampling, adding appropriate amount of o-phthalaldehyde and isopropanol, mixing, heating in water bath at 60 deg.C for 15min, cooling, filtering, measuring 10 μ L, injecting into high performance liquid chromatograph), and performing Mass Spectrometry (MS) (Agilent 6520 four-level rod flight time tandem mass spectrometer), setting parameters: ESI (+), 100-800 m/z; the flow rate is 8.0 L.min < -1 >; the temperature is 350 ℃; nebulizer pressure, 2.07 × 105 Pa; vcap 3500V; collision voltage, 135V), and comprehensive TLC, HPLC and MS analysis results show that the engineering bacteria C21591 intensively accumulate gentamicin C2, trace C1a, C1 and micronomicin, but no other metabolites can be detected. Compared with the original strain, the yield of the gentamicin C2 in the original strain is 298 mug/mL, the yield of the gentamicin C2 in the C21591 strain reaches 894 mug/mL, the yield is improved by 3 times compared with the yield of the gentamicin C2 in the original strain, other isomerous isomers or impurities are basically not contained, downstream application can be directly carried out, complex biotransformation and purification are not needed, a large amount of cost is saved, and the industrialization requirement is met.