Streptomyces albus SY6, fermentation seed and application thereof

Abstract

The present application relates to the field of industrial biotechnology, and in particular relates to a Streptomyces albulus SY6, a fermentation seed and application thereof, the Streptomyces albulus SY6 is characterized in that, on November 13, 2024, it is preserved in the China General Microbiological Culture Collection Center, and the preservation number is CGMCC No. 32602, and the classification name is Streptomyces albulus. The Streptomyces albulus SY6 screened in the present application has a better promoting effect in aspects of mediating mold signals and strengthening epsilon-polylysine synthesis.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of industrial biotechnology, in particular to a Streptomyces albulus SY6, a fermentation seed and application thereof. BACKGROUND

[0002] Epsilon-poly-l-lysine is a homocationic polymer synthesized by Streptomyces (such as Streptomyces albulus, Streptomyces diastatochromogenus, and Noriella), which is dehydrated and condensed by the alpha-carboxyl and epsilon-amino of lysine, with a polymerization degree of 25-35 lysine residues, and has the effect of resisting gram-positive / negative bacteria, molds, yeasts, and viruses. It has strong heat resistance, high water solubility, safety, non-toxicity, and environmental degradation, and is currently used as a food preservative. Currently, the fermentation level of epsilon-poly-l-lysine is low, which makes the production cost high, and the high selling price limits its market application and promotion.

[0003] Currently, the strains known to be able to synthesize epsilon-poly-l-lysine include Streptomyces, Noriella, and Bacillus subtilis. However, there are differences in natamycin synthesis ability among different strains, and the yield of epsilon-poly-l-lysine synthesized is relatively low, which is difficult to meet the needs of large-scale industrial production. Therefore, it is of great significance to develop a high-yield and easy-to-cultivate epsilon-poly-l-lysine synthesis strain. SUMMARY

[0004] In order to explore high-yield strains to improve the yield of synthesized epsilon-poly-l-lysine, the present application provides a Streptomyces albulus SY6, a fermentation seed and application thereof. The Streptomyces albulus SY6 provided by the present application can respond to mold signals and improve the synthesis yield of epsilon-poly-l-lysine.

[0005] A Streptomyces albulus SY6, characterized in that it is preserved in the China General Microbiological Culture Collection Center on November 13, 2024, with a preservation number of CGMCC No. 32602, and is classified and named as Streptomyces albulus.

[0006] The Streptomyces albulus SY6 provided by the present application is obtained by using compound physical and chemical mutagenesis to screen Streptomyces albulus CICC 11022. The Streptomyces albulus SY6 screened by the present application can respond to mold signals and strengthen epsilon-poly-l-lysine synthesis, and can be effectively applied to mold signal direct addition fermentation or Streptomyces albulus-mold mixed fermentation, to improve the synthesis yield of epsilon-poly-l-lysine.

[0007] The application provides a fermentation seed of Streptomyces albus SY6, which is obtained by inoculating spores of the Streptomyces albus SY6 into an epsilon-polylysine fermentation seed culture medium and culturing at 25-35 DEG C and 180-220 rpm for 1-3 days.

[0008] The application also provides an application of the Streptomyces albus SY6 in synthesis of epsilon-polylysine.

[0009] Further, the Streptomyces albus SY6 is used to improve the yield of epsilon-polylysine.

[0010] Further, the Streptomyces albus SY6 is used to improve the concentration of epsilon-polylysine.

[0011] The application provides a method for synthesizing epsilon-polylysine by the Streptomyces albus SY6, which comprises the following steps:

[0012] An epsilon-polylysine fermentation culture medium is prepared, sterilized, supplemented with a glucose solution, inoculated with the Streptomyces albus SY6 fermentation seed, fermented at an initial pH of 6.0-7.5 and a temperature of 25-35 DEG C, and the pH is controlled to 3.0-5.0 by using sterilized ammonia water until the fermentation is completed; when the glucose concentration in the fermentation liquor is less than 10 g / L, the glucose concentration in the fermentation liquor is maintained at 10-20 g / L, and when the NH4 + -N concentration in the fermentation liquor is less than 0.5 g / L, the NH4 + -N concentration in the fermentation liquor is controlled in the range of 0.5-1.0 g / L; and the fermentation is completed when the epsilon-polylysine concentration in the fermentation liquor no longer increases.

[0013] Further, the Streptomyces albus SY6 fermentation seed is inoculated at an inoculation amount of 5-10 g / 100 mL.

[0014] Further, the fermentation liquor further comprises a mold live bacteria solution.

[0015] Further, the mold live bacteria solution is one of a live Aspergillus niger bacteria solution, a live Alternaria alternata bacteria solution and a live Botrytis cinerea bacteria solution.

[0016] Further, the mold live bacteria solution is inoculated at an inoculation amount of 5-20 g / L.

[0017] The culture medium formula adopted by the application is as follows:

[0018] (1) 1L of the Betana culture medium: 10 g of glucose, 1 g of yeast powder, 2 g of proteose peptone, 20 g of agar, and the rest is distilled water, and the pH is 7.5.

[0019] (2) 1L ε-polylysine fermentation seed medium: glucose 20 g, yeast powder 5 g, (NH4)2SO4 10 g, MgSO4·7H2O 0.5 g, K2HPO4·3H2O 0.8 g, KH2PO4 1.36 g, FeSO4·7H2O 0.03 g, ZnSO4·7H2O 0.04 g, the rest is distilled water, pH 6.8.

[0020] (3) 1L ε-polylysine fermentation medium (g / L): glucose 60 g, yeast powder 5 g, (NH4)2SO4 10 g, MgSO4·7H2O 0.5 g, K2HPO4·3H2O 0.8 g, KH2PO4 1.36 g, FeSO4·7H2O 0.03 g, ZnSO4·7H2O 0.04 g, the rest is distilled water, pH 6.8.

[0021] (4) 1L YPD liquid medium: glucose 20 g, yeast extract 10 g, peptone 20 g, the rest is distilled water, pH 6.5.

[0022] All the above involving glucose, the sugar-containing substance is prepared separately from other components, and then combined in the same system medium after high-temperature sterilization at 121°C for 20 min.

[0023] The molds described in the present application include Alternaria alternate CICC 40292, Aspergillus niger CICC 40102, Penicillium chrysogenum CICC 40702, and Rhodotorula mucilaginosa CICC 32140, which are purchased from China Industrial Microbial Culture Collection Center; Botrytis cinerea CGMCC 3.3790 is purchased from China General Microbial Culture Collection Center; Streptomyces albulus CICC 11022 is purchased from China Industrial Microbial Culture Collection Center.

[0024] Streptomyces albulus SY6, referred to as Streptomyces albulus SY6 in the present application, has been preserved in China General Microbiological Culture Collection Center on November 13, 2024, with the preservation number of CGMCC No.32602, and the address of the preservation unit is No.3, Beichen West Road, Chaoyang District, Beijing, China, with the postal code of 100101, and the classification and naming is Streptomyces albulus.

[0025] Compared with the prior art, the present application has the beneficial effects that:

[0026] The Streptomyces albus SY6 provided by the present application is obtained by using compound physical and chemical mutagenesis on Streptomyces albus CICC 11022. The Streptomyces albus SY6 provided by the present application can directly add fermentation to synthesize ε-polylysine, and the yield of fermentation is 2.25 times that of Streptomyces albus CICC 11022. In addition, it can efficiently respond to mold signals and promote the yield of ε-polylysine to increase, wherein the yield of mixed fermentation of Streptomyces albus SY6 and Alternaria alternata is the highest, which is 3.31 times that of Streptomyces albus CICC 11022. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0028] Figure 1 It is ε-polylysine high-yield bacteria screening based on the size of the flat plate inhibition zone. In the figure, red yeast is used as an indicator to screen high-yield bacteria, A is the front of the plate; B is the back of the plate, and the numbers and their circles are high-yield bacteria producing larger inhibition zones.

[0029] Figure 2 It is Streptomyces albus SY6 with high yield of ε-polylysine. DETAILED DESCRIPTION

[0030] The specific embodiments of the present application will be described in detail below, but it should be understood that the protection scope of the present application is not limited by the specific embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present application. The experimental methods described in the embodiments of the present application are all conventional methods, and the materials, reagents, etc. used in the following examples are commercially available unless otherwise specified.

[0031] Example 1: Breeding method of Streptomyces albus SY6

[0032] S1. Preparation of single-spore suspension of *Streptomyces cephalosporin* CICC 11022: *Streptomyces cephalosporin* CICC 11022 spores were spread on Betana solid medium and incubated at 30℃ for 8 days. The spores were collected by washing with pre-sterilized 20% glycerol. After adding glass beads, the mixture was placed in a shaking incubator and incubated at 200 rpm for 5 hours. Then, the spores were thoroughly dispersed by ultrasonic cleaning for 20 minutes. Finally, the mixture was filtered five times with pre-sterilized absorbent cotton. The filtered single-spore suspension of *Streptomyces cephalosporin* CICC 11022 was dispensed and stored at -80℃ for later use.

[0033] Preparation of fungal signal extract: scrape 5 rings (approximately 1×10⁻⁶) 3 100 spores of mold (excluding Botrytis cinerea) were inoculated into a 500 mL Erlenmeyer flask containing 80 mL of LYPD medium and cultured at 200 rpm for 4 days in a constant temperature shaking incubator at 30 °C.

[0034] Scrape 5 rings (approximately 1 x 10) 3 One Botrytis cinerea spore was inoculated into a 500 mL Erlenmeyer flask containing 80 mL of LYPD medium and cultured at 23°C and 200 rpm for 4 days in a constant temperature shaking incubator.

[0035] The cultured mold was washed three times with deionized water, and the cells were resuspended in 65% ethanol. The mixture was then ground in a mortar with quartz sand for 10 minutes. After centrifugation, the supernatant was collected, dried in a forced-air drying oven, reconstituted with water, and sterilized at 121°C for 15 minutes to obtain the *Streptomyces leucocephala* signal extract, which was then stored at -20°C. The wet weight ratio of *Streptomyces leucocephala* cells to the volume of water added for reconstitution was 1 g: 3 mL.

[0036] S2,1L strain selection medium: beta medium containing 0.05g LiCl and 120mL of mold signal extract.

[0037] Preparation of the mixture: Add 2.5 μL of 0.5 mg / mL NTG (nitrosoguanidine), 0.5 mL of 5 g / L (pH = 6) citrate buffer, and approximately 0.5 mL of 5.0 × 10⁻⁶ NTG solution. 7 The three components were mixed to obtain a mixture, which was then incubated in a 30°C constant temperature shaking incubator at 100 rpm for 60 min, and diluted to 10. 5 times.

[0038] Spread culture: dilution to 10 -5 Take 1 mL of the mixture and spread it on the culture medium for strain selection prepared in S2, and incubate it in a constant temperature incubator at 30℃ for 8 days until colonies grow successively.

[0039] S3, pre-cultured Rhodotorula: YPD liquid medium was used to culture at 30℃ and 180 rpm for 1 day.

[0040] In the clean bench, the edge of the strain selection medium was lifted and a circle was drawn to separate the strain selection medium from the petri dish. The pre-cultured Rhodotorula was injected into the gap between the strain selection medium and the petri dish, and the system was cultured in a 30℃ incubator for 1 day to obtain the first round of mutagenized strains.

[0041] The size of the Rhodotorula inhibition zone presented by the colonies of the first round of mutagenized strains under the agar block was observed and compared with that of the first round of starting strain S. albulus CICC 11022. Strains with significantly increased inhibition zones were selected for streak purification and expansion culture to obtain spores of the first round of high-yield strains, as shown in Figure 1 .

[0042] S4, the first round of high-yield strain spores were scraped off the two circles using a inoculating loop and inoculated into a 250 mL conical flask containing 30 mL of ε-polylysine fermentation seed medium. The high-yield strain spores were inoculated into a 250 mL conical flask containing 30 mL of ε-polylysine fermentation medium at an inoculum of 8 g / 100 mL and cultured in a constant temperature shaking incubator at 30℃ and 200 rpm for 2 days. When the fermentation pH naturally decreased to 4.0, pre-sterilized sodium citrate buffer (pH 4.0) was added to the flask to maintain a final concentration of 10 g / L of citric acid to maintain a constant pH. After fermentation, the ε-polylysine concentration in the fermentation broth was determined to obtain the optimal strain S. albulus SY1 of the first round of mutagenesis.

[0043] S5, S. albulus SY1 was used as the second round of starting strain, and the single spore suspension of S. albulus SY1 was prepared according to the method described in S1.

[0044] S6, the concentration of S. albulus SY1 strain spores was about 1.0 x 10 7 The above plate was irradiated under a 15W ultraviolet lamp at a distance of 30 cm in the clean bench for 1 min, and then cultured in a 30℃ constant temperature incubator for 8 days until the colonies grew successively.

[0045] S7, according to S3, strains with inhibition zones larger than the second round of starting strain S. albulus SY1 were screened, and the highest-yield S. albulus SY2 strain was obtained according to the steps in S4.

[0046] S8, *Streptomyces sy2* was repeatedly subjected to nitrosoguanidine and UV mutagenesis as described above. Using plates with added mold signals as screening conditions and yeast inhibition zones as screening methods, strains exhibiting high responsiveness to *Streptomyces* signals and enhanced ε-polylysine synthesis were selected. After three rounds of repeated mutagenesis, the high-ε-polylysine-producing *Streptomyces sy6* strain was obtained. Figure 2 As shown.

[0047] Streptomyces sy6 was passaged continuously, and its ε-polylysine synthesis capacity was determined as follows: spores (approximately 1 × 10⁻⁶) of three rings of Streptomyces CICC 11022 and SY6 were scraped. 7 (1) Inoculate 60 mL of liquid seed culture medium into a 500 mL Erlenmeyer flask and incubate at 30 °C and 220 rpm for 2 days until a large number of granular mycelial balls are formed. Add mature fermentation seed liquid to 30 mL of ε-polylysine fermentation medium at an inoculation rate of 8 g / 100 mL. Then place the Erlenmeyer flask in an incubator and incubate at 30 °C and 200 rpm for 1 day. In a clean bench, add pre-sterilized sodium citrate buffer (pH = 4.0) with a final concentration of 10 g / L to maintain the pH and return the flask to the incubator to continue incubation for 1 day. After the incubation, measure the polylysine concentration in the fermentation broth.

[0048] Detection of ε-polylysine concentration in fermentation broth: The fermentation broth was appropriately diluted with 0.2 mM sodium phosphate buffer (pH = 7.0), and 2 mL of the diluted solution was mixed with 2 mL of 1 mM methyl orange aqueous solution. The mixture was placed at 30℃ for 30 min, centrifuged at 4000 rpm for 15 min, and the supernatant was diluted 20 times with 0.2 mM sodium phosphate buffer (pH = 7.0). The absorbance was measured at 465 nm using a spectrophotometer, and the actual ε-polylysine concentration in the fermentation broth sample was calculated by substituting the absorbance into the ε-polylysine concentration standard curve.

[0049] The shake-flask fermentation levels of ε-polylysine after 10 consecutive passages of Streptomyces sy6 were as follows:

[0050] Table 1. ε-polylysine fermentation levels (g / L) of Streptomyces sy6 strain after 10 consecutive passages.

[0051]

[0052]

[0053] Note: "Add signal" refers to approximately 1.0 × 10 in S6. 7 Spores of *Streptomyces albopictus* strain per mL were spread onto the strain selection medium; "No signal added" means approximately 1.0 × 10⁶ spores were added to S6. 7Streptomyces albus spores of 1 x 10

[0054] Example 2: ε-poly-L-lysine 5L fermentor synthesis based on Streptomyces albus SY6

[0055] Streptomyces albus SY6 fermentation seed: scrape 3 ring Streptomyces albus SY6 spores (about 1 x 10 7 into a 500 mL flask containing 60 mL liquid seed culture medium, and incubate in a constant temperature shaker incubator at 30°C, 200 rpm for 2 days until a large number of granular mycelial balls are formed, to obtain Streptomyces albus SY6 fermentation seed.

[0056] Prepare 3L ε-poly-L-lysine fermentation medium, add to a 5L liquid fermentor, sterilize at 121°C for 20 min, and add all of a separately sterilized (121°C for 20 min) 500 mL solution containing 240 g glucose using a peristaltic pump, set the initial parameters as temperature 30°C, 200 rpm stirring paddle speed and 1 vvm aeration. With an inoculum of 8 g / 100 mL, inoculate the obtained Streptomyces albus SY6 fermentation seed, and start fermentation using 12.5% ammonia water to adjust pH = 6.8. When the pH naturally drops to 4.0, dynamically feed 12.5% ammonia water to maintain pH = 4.0, and use speed and dissolved oxygen coupling settings to control the dissolved oxygen at 33%, until the fermentation is completed at 192 h. When the glucose concentration in the fermentation broth is less than 10 g / L, exogenously feed 600 g / L pre-sterilized glucose solution through a peristaltic pump to maintain the glucose concentration in the fermentation broth in the range of 15 g / L. When the NH4 + -N concentration is less than 0.5 g / L, supplement 200 g / L (NH4)2SO4 solution to the fermentation broth through a peristaltic pump to control the NH4 + -N concentration in the range of 0.75 g / L. During the fermentation process, sample the fermentation broth every 12 h, and determine the ε-poly-L-lysine concentration, cell dry weight, residual glucose, and NH4 + -N concentration according to the procedures described in the determination method.

[0057] Determination of ε-poly-L-lysine concentration in the fermentation broth: appropriately dilute the fermentation broth with 0.2 mM sodium phosphate buffer (pH = 7.0), take 2 mL and mix with 2 mL 1 mM methyl orange aqueous solution, place in a 30°C water bath for 30 min, centrifuge at 4000 rpm for 15 min, dilute the supernatant 20 times with 0.2 mM sodium phosphate buffer (pH = 7.0), and determine the absorbance at 465 nm on a spectrophotometer, and calculate the actual ε-poly-L-lysine concentration in the fermentation broth sample by substituting into the ε-poly-L-lysine concentration standard curve.

[0058] Detection of glucose concentration in fermentation broth: 300 μΐ of fermentation broth and 700 μΐ of absolute ethanol were mixed, and after standing for 1 h, the supernatant was obtained by centrifugation and then filtered through a 0.45 μιη filter membrane before HPLC detection. An organic acid test column (Aminex HPX-87H, 300 x 7.8 mm; Hercules, USA) was used, with a mobile phase of 5 mM sulfuric acid, a column temperature of 60 °C, and an injection volume of 10 μΐ.

[0059] Dried cell weight (DCW) was detected by filter paper differential weight method. 10 mL of fermentation broth was taken from a 5 L fermenter, centrifuged at 4,000 x g for 10 min, and the precipitate was washed twice with distilled water, filtered with a filter paper (Φ7 cm, medium speed, SCRC) that had been pre-dried at 105 °C and weighed, and then dried at 105 °C until constant weight. The difference between the weights before and after drying was calculated, and the dried cell weight in the fermentation broth was calculated based on the volume of the original 10 mL of fermentation broth.

[0060] The ε-polylysine concentration produced by S. albulus SY6 after final fermentation was 20.9 g / L, and the dried cell weight was 28.2 g / L. The starting strain S. albulus CICC 11022 was cultured using the same fermentation process, and the final ε-polylysine concentration was 9.3 g / L, and the dried cell weight was 24.6 g / L. The high-yield strain S. albulus SY6 synthesized ε-polylysine with a yield that was 2.25 times that of the starting strain S. albulus CICC 11022.

[0061] Example 3: ε-polylysine 5 L fermenter synthesis based on S. albulus SY6 and various mold signals

[0062] A 3 L ε-polylysine fermentation medium was prepared, added to a 5 L liquid fermenter, sterilized at 121 °C for 20 min, and 500 mL of a solution containing 240 g of glucose, which had been sterilized separately (121 °C for 20 min), was added in its entirety using a peristaltic pump. The initial parameters were set as a temperature of 30 °C, a stirring paddle speed of 200 rpm, and a ventilation rate of 1 vvm. The fermentation was started by inoculating 8 g / 100 mL of the fermentation seed liquid of S. albulus SY6 obtained in Example 2 into the fermenter, and adjusting the pH to 6.8 using 12.5% ammonia water. At 24 h of fermentation, 500 mL of the mold signal extract described in S1 in Example 1 was added to the fermenter in one batch. When the pH naturally decreased to 4.0, 12.5% ammonia water was dynamically added to maintain the pH at 4.0, and the stirring speed and dissolved oxygen were coupled to control the dissolved oxygen at 30-35%, until the fermentation was completed at 192 h. When the glucose concentration in the fermentation broth was less than 10 g / L, 600 g / L of pre-sterilized glucose solution was added to the fermentation broth to maintain the glucose concentration at 15 g / L. When the NH4 +- When the concentration of N is lower than 0.5 g / L, the (NH4)2SO4 solution with the concentration of 200 g / L is added into the fermentation broth by peristaltic pump to control the concentration of NH4 + - The concentration of N is controlled in the range of 0.75 g / L. The fermentation broth is sampled every 12 h during the fermentation process, and the concentration of ε-polylysine, dry cell weight, residual glucose, NH4 + - The concentration of N.

[0063] The detection is carried out according to the detection method in Example 2. Finally, using Streptomyces albulus SY6: (1) adding Aspergillus niger signal in ε-polylysine fed-batch fermentation, the ε-polylysine concentration is 48.7 g / L after 192 h fermentation, and the dry cell weight is 43.6 g / L. The starting strain Streptomyces albulus CICC 11022 is cultured in the same fermentation process, and the final ε-polylysine concentration is 16.2 g / L, and the dry cell weight is 36.2 g / L. Under the condition of exogenous addition of Aspergillus niger signal, the yield of ε-polylysine fed-batch fermentation of Streptomyces albulus SY6 is 2.85 times that of the starting strain Streptomyces albulus CICC 11022.

[0064] (2) Adding Alternaria alternata signal in ε-polylysine fed-batch fermentation, the ε-polylysine concentration is 51.2 g / L after 192 h fermentation, and the dry cell weight is 46.8 g / L. The starting strain Streptomyces albulus CICC 11022 is cultured in the same fermentation process, and the final ε-polylysine concentration is 17.9 g / L, and the dry cell weight is 37.4 g / L. Under the condition of exogenous addition of Alternaria alternata signal, the yield of ε-polylysine fed-batch fermentation of Streptomyces albulus SY6 is 2.86 times that of the starting strain Streptomyces albulus CICC 11022.

[0065] (3) Adding Botrytis cinerea signal in ε-polylysine fed-batch fermentation, the ε-polylysine concentration is 43.2 g / L after 192 h fermentation, and the dry cell weight is 40.1 g / L. The starting strain Streptomyces albulus CICC 11022 is cultured in the same fermentation process, and the final ε-polylysine concentration is 13.8 g / L, and the dry cell weight is 32.2 g / L. Under the condition of exogenous addition of Botrytis cinerea signal, the yield of ε-polylysine fed-batch fermentation of Streptomyces albulus SY6 is 3.13 times that of the starting strain Streptomyces albulus CICC 11022.

[0066] (4) In the ε-polylysine fed-batch fermentation of ε-polylysine, the signal of P. chrysogenum was added, and after 192 h of fermentation, the ε-polylysine concentration was 49.2 g / L, and the dry weight of the bacteria was 44.3 g / L. The same fermentation process was used to culture the starting strain Streptomyces albulus CICC11022, and the final ε-polylysine concentration was 18.8 g / L, and the dry weight of the bacteria was 39.1 g / L. Under the condition of exogenous addition of P. chrysogenum signal, the yield of ε-polylysine in the fed-batch fermentation of Streptomyces albulus SY6 was 2.62 times that of the starting strain. The above data shows that Streptomyces albulus SY6 can respond to the four different mold signals together and efficiently, and greatly strengthens the biosynthesis of ε-polylysine activated by the signal.

[0067] Example 4: ε-polylysine 5L fermenter synthesis based on mold-Streptomyces albulus SY6 mixed culture system

[0068] Preparation of mold live bacteria liquid: 5 rings (about 1 x 10 3 spores of each mold (except Botrytis cinerea) were inoculated in a 500 mL triangular flask containing 80 mL of YPD medium, and cultured in a constant temperature shaking incubator at 30°C at 200 rpm for 4 days.

[0069] 5 rings (about 1 x 10 3 spores of Botrytis cinerea were inoculated in a 500 mL triangular flask containing 80 mL of YPD medium, and cultured in a constant temperature shaking incubator at 23°C at 200 rpm for 4 days.

[0070] Prepare 3L ε-polylysine fermentation medium, add to a 5L liquid fermenter, sterilize at 121°C for 20 min, and add 500mL solution of 240g glucose dissolved separately (sterilized at 121°C for 20 min) with a peristaltic pump, set the initial parameters as temperature 30°C, 200rmp stirring paddle speed and 1vvm aeration. Inoculate Streptomyces albulus SY6 fermentation seed obtained in Example 2 at a dose of 8g / 100mL, and start fermentation with 12.5% ammonia water to adjust pH to 6.8. At 24h of fermentation, add 500mL of live culture liquid of one of the four molds obtained to the fermenter from the inoculation port under the protection of a fire ring. When the pH naturally drops to 4.0, dynamically add 12.5% ammonia water to maintain pH 4.0, and use speed and dissolved oxygen coupling settings to control the dissolved oxygen at 33%, until the end of 192h fermentation. When the glucose concentration in the fermentation broth is less than 10g / L, exogenously add 600g / L of pre-sterilized glucose solution through a peristaltic pump to maintain its concentration in the fermentation broth to 15g / L. When the NH4 + -N concentration is less than 0.5g / L, supplement 200g / L of (NH4)2SO4 solution to the fermentation broth through a peristaltic pump to maintain the NH4 +- N concentration was controlled at 0.75 g / L. The fermentation broth was sampled every 12 h during the fermentation process, and the ε-polylysine in the fermentation broth, dry cell weight, residual glucose, NH4 + - N concentration.

[0071] The detection was performed according to the detection method in Example 2. Finally, using Streptomyces albulus SY6: (1) adding the culture solution with living Aspergillus niger in the ε-polylysine fed-batch fermentation, the ε-polylysine concentration was 60.2 g / L after 192 h fermentation, and the dry cell weight was 45.1 g / L. The original strain Streptomyces albulus CICC 11022 was cultured in the same fermentation process, and the final ε-polylysine concentration was 20.5 g / L, and the dry cell weight was 38.5 g / L. Under the condition of exogenous addition of living Aspergillus niger culture solution, the yield of ε-polylysine fed-batch fermentation of Streptomyces albulus SY6 was 2.93 times that of the original strain Streptomyces albulus CICC 11022.

[0072] (2) Adding the culture solution with living Alternaria alternata in the ε-polylysine fed-batch fermentation, the ε-polylysine concentration was 65.9 g / L after 192 h fermentation, and the dry cell weight was 44.3 g / L. The original strain Streptomyces albulus CICC 11022 was cultured in the same fermentation process, and the final ε-polylysine concentration was 19.9 g / L, and the dry cell weight was 39.4 g / L. Under the condition of exogenous addition of Alternaria alternata signal, the yield of ε-polylysine fed-batch fermentation of Streptomyces albulus SY6 was 3.31 times that of the original strain Streptomyces albulus CICC 11022.

[0073] (3) Adding the signal of Botrytis cinerea in the ε-polylysine fed-batch fermentation, the ε-polylysine concentration was 49.2 g / L after 192 h fermentation, and the dry cell weight was 44.6 g / L. The original strain Streptomyces albulus CICC 11022 was cultured in the same fermentation process, and the final ε-polylysine concentration was 16.3 g / L, and the dry cell weight was 37.2 g / L. Under the condition of exogenous addition of Botrytis cinerea signal, the yield of ε-polylysine fed-batch fermentation of Streptomyces albulus SY6 was 3.02 times that of the original strain Streptomyces albulus CICC 11022.

[0074] (4) In the fed-batch fermentation of ε-polylysine with the addition of signal of P. chrysogenum, the concentration of ε-polylysine was 62.9 g / L and the dry weight of Streptomyces ambyochromogenes SY6 was 47.2 g / L after 192 h fermentation. The same fermentation process was used to culture the original strain Streptomyces ambyochromogenes CICC11022, and the final concentration of ε-polylysine was 21.2 g / L and the dry weight of Streptomyces ambyochromogenes CICC11022 was 43.4 g / L. Under the condition of exogenous addition of signal of P. chrysogenum, the yield of ε-polylysine in the fed-batch fermentation of Streptomyces ambyochromogenes SY6 was 2.97 times that of the original strain Streptomyces ambyochromogenes CICC11022. The above data show that Streptomyces ambyochromogenes SY6 can respond to the four different mold signals together and efficiently, and the biosynthesis level of ε-polylysine can be greatly enhanced under the effect of coexistence with molds.

[0075] Although preferred embodiments of the application have been described, those skilled in the art will be able to make additional modifications and variations without departing from the spirit and scope of the application.

[0076] Obviously, various modifications and changes can be made to the present application by those skilled in the art without departing from the spirit and scope of the present application. Accordingly, it is intended that the present application embrace all such modifications and changes as fall within the scope of the appended claims and their equivalents.

Claims

1. A type of white Streptomyces ( Streptomyces albulus SY6, characterized in that, It was deposited on November 13, 2024, at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 32602, and classified as *Streptomyces spp.* Streptomyces albulus .

2. A fermentation seed of *Streptomyces syringae* SY6 as described in claim 1, characterized in that, The fermentation seed of Streptomyces sy6 was obtained by inoculating Streptomyces sy6 spores into ε-polylysine fermentation seed medium and culturing for 1-3 days at 25℃~35℃ and 180rpm~220rpm.

3. The application of the Streptomyces SY6 strain described in claim 1 in the synthesis of ε-polylysine, characterized in that, The Streptomyces SY6 strain is used to increase the production of ε-polylysine. The Streptomyces SY6 strain is used to increase the concentration of ε-polylysine.

4. A method for synthesizing ε-polylysine using *Streptomyces syringae* SY6 as described in claim 1, characterized in that, Includes the following steps: Prepare and sterilize an ε-polylysine fermentation medium, add glucose solution, and inoculate with the *Streptomyces syringae* SY6 fermentation seed. Fermentation is carried out at an initial pH of 6.0–7.5 and a temperature of 25–35°C, with the pH controlled at 3.0–5.0 using sterilized ammonia water until fermentation is complete. When the glucose concentration in the fermentation broth is less than 10 g / L, maintain the glucose concentration at 10–20 g / L. When the NH4+ concentration in the fermentation broth is less than 10 g / L, maintain the glucose concentration at 10–20 g / L. + When the -N concentration is below 0.5 g / L, the NH4+ in the fermentation broth will be reduced. + The ε-N concentration was controlled within the range of 0.5 g / L to 1.0 g / L; fermentation ended when the concentration of ε-polylysine in the fermentation broth no longer increased. The fermentation seed of *Streptomyces syringae* SY6 was inoculated at an inoculation rate of 5 g / 100 mL to 10 g / 100 mL; The fermentation broth also includes live mold cells in a bacterial solution; The live mold culture solution is one of the following: Aspergillus niger live culture solution, Alternaria alternata live culture solution, Penicillium chrysogenum live culture solution, and Botrytis cinerea live culture solution; The live mold culture solution was inoculated at an inoculation rate of 5 g / L to 20 g / L.

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