292 results about "Lactococcus lactis subsp. lactis" patented technology

The invention relates to a microorganism composite zymocyte agent as well as a preparation method and an application thereof. The invention is characterized in that the active components of the composite zymocyte agent are Cida tropicalis and lactococcus lactis which are mixed according to the mass ratio of (0.5-2): 1. The preparation process comprises the following steps: carrying out oblique plane strain culture on the Cida tropicalis and lactococcus lactis; then carrying out liquid seed amplification culture to obtain a Cida tropicalis liquid and a lactococcus lactis liquid; mixing the Cida tropicalis liquid and lactococcus lactis liquid according to the mass ratio of (0.5-2): 1 and inoculating the mixture into a solid amplification culture medium to obtain the composite zymocyte agent according to the inoculum size of 4-5%(w / v); and adding the composite zymocyte agent to kitchen waste for microbial fermentation. The invention has the advantages of suppressing growth of putrefying bacteria in the kitchen waste and reproduction of pathogenic microorganism, thus featuring good freshness-retaining effect and organoleptic quality while increasing protein content and beneficial flora content of the kitchen waste.

The invention discloses a lactococcus lactis sub-specie lactis strain KLDS4001 having microorganism collection number of CGMCC No. 9964. The strain is strong in lactic acid-producing capability and good in fermentation performance and can be compounded with lactococcus lactis sub-specie cremoris to be applied as a cheddar leavening agent. The invention also discloses an application of the lactococcus lactis sub-specie lactis strain KLDS4001 in preparation of cheddar and a method for preparing cheddar by virtue of the strain. The method comprises the following steps of adding a compound leavening agent, which is prepared by mixing the lactococcus lactis sub-specie lactis strain KLDS4001 and the lactococcus lactis sub-specie cremoris, into raw milk and fermenting. The cheddar prepared by the compound leavening agent has the advantages of good maturity, texture and flavor and has a certain commercial value; and the physical and chemical indicators and microbial indicators of cheddar are in line with national standards.

The invention discloses lactobacillus capable of producing a sour taste. The lactobacillus is Lactobacillus casei YQ336, which is collected in China General Microbiological Culture Collection Center on July 15, 2016, with the collection number of CGMCC No. 12796. A sour-slurry coagulant is prepared by using the screened Lactobacillus casei YQ336 and commercially available lactococcus lactis, and is applied to the production of the sour-slurry tofu. The sour-slurry coagulant is high in fermenting speed and free of pollution caused by infectious bacteria and other pathogenic bacteria, so that the production speed is increased and the eating safety of the tofu is ensured; sour-slurry fermented liquid is used as the tofu coagulant, so that the eating safety of a tofu product can be adequately guaranteed; the sensory quality of the tofu produced in the invention is significantly superior to that of tofu produced by a naturally-fermented sour-slurry tofu coagulant.

The invention provides IgG-containing fermented milk and a preparation method. The IgG-containing fermented milk comprises raw milk, bovine colostrum powder, concentrated milk albumen powder, market cream, white granulated sugar, fructo-oligosaccharide, a compound stabilizer and a compound leavening agent, wherein the percentage of the raw milk, the bovine colostrum powder, the concentrated milk albumen powder, the market cream, the white granulated sugar, the fructo-oligosaccharide and the compound stabilizer is the mass percentage of total mass of raw materials except the compound leavening agent; the compound stabilizer is prepared from pectin and starch according to the mass percentage of the total mass of the raw materials except the compound leavening agent; and the compound leavening agent comprises streptococcus thermophilus, lactobacillus bulgaricus, lactococcus lactis subsp.lactis, lactococcus lactis cremoris and bifidobacterium lactis. The fermented milk prepared by the method has the beneficial effects that the fermented milk has excellent special flavor, excellent texture mouthfeel and good stability in shelf life and is stored in a refrigeration state; the activity of immune globulin can be kept in the warranty period; a whey precipitation phenomenon is less likely to occur in a storage period; and the IgG-containing fermented milk is applied to the technical field of dairy products.

The invention discloses an anti-acid-stress component and application thereof, belonging to the field of bioengineering technology. According to the invention, two recombinant Lactococcus lactis strains with substantially improved resistance to acid stress, i.e., L. lactis NZ9000 (pNZ8148 / RecT-A76) and L. lactis NZ9000 (pNZ8148 / RecT-MG1655), are obtained by overexpression of recT genes, originated from Lactococcus lactis L. lactis A76 and Escherichia coli E. coli MG1655, in Lactococcus lactis NZ9000, respectively. After the two recombinant Lactococcus lactis strains suffer from stress in an environment with a pH value of 4.0 for 3h, the survival rates of the two strains are 10.5 times and 1.4 times the survival rates of control strains, respectively; and after the two strains suffer from stress caused by 20% (v / v) ethanol for 6 h, the survival rates of the two strains are 3.7 times and 2.1 times the survival rates of control strains, respectively. The invention also provides a method for improving resistance to acid stress. The method has good industrial application value.

The invention belongs to the field of animal biomedicine engineering, and in particular discloses protein recombinant lactococcus lactis for secretory expression of a core antigen COE of a PEDV (Porcine Epidemic Diarrhea Virus) as well as a preparation method and an application of the protein recombinant lactococcus lactis. The method comprises the following steps: connecting a signal peptide and other sequences onto a gene of the core antigen COE of the PEDV via an overlap extension PCR method by designing multiple primers, connecting the gene to a lactococcus lactis expression vector pNZ8048 and introducing the vector with the gene into a cell of the lactococcus lactis NZ9000 in an electrotransformation manner so as to obtain recombinant bacteria; and inducing the recombinant bacteria with nisin so as to obtain an expression, and directly taking all induced cultures as oral vaccines capable of stimulating mice and inducing strong cellular immune responses. Thus, the protein recombinant lactococcus lactis can serve as a novel oral vaccine product with a good industrial prospect and has a positive effect for reducing harms of the PEDV to pig industry, thereby playing a great practical significance for promoting the healthy development of the pig industry.

The invention discloses an efficient preparation method and applications of food-grade acid ureases, belonging to the technical field of biological engineering. The efficient expression and preparation methods and applications of acid ureases are realized successfully by using food-grade lactococcus lactis expression system, the enzyme activity of the acid ureases reaches 10200 U / L, and the enzyme activity of purified acid ureases is 325.6 U / mg. The specific enzyme activity of purified enzymes to an urethane substrate reaches 243.4 U / mg, and food-grade acid ureases which are prepared by using the method disclosed by the invention and added in a yellow rice or millet wine can efficiently degrade urea (the degradation rate per two days is 100%) and urethane (the degradation rate per three days is 72% %). Recombined acid ureases prepared by using the method disclosed by the invention can be applied to the removal of urea and urethane in fermented food, so that the residue problem of urethane in fermented food can be efficiently solved. The efficient preparation method and applications of food-grade acid ureases disclosed by the invention lay a foundation for the implementation of the industrialized production of food-grade acid ureases.

The invention provides an extraction method of bile salt hydrolase (BSH) and extracellular polysaccharide (EPS) in lactococcus lactis and streptococcus thermophilus, and the BSH and the EPS acting as functional factors and the EPS as a natural stabilizer in a functional dairy product are applicable for developing and producing novel functional food. The method utilizes lactococcus lactis subsp. lactis KS4 (CGMCC No.1807) and streptococcus thermophilus Tx (CGMCC No.1810) of the high-yield BSH and EPS, and obtains lactobacillus bile salt hydrolase and extracellular polysaccharide crude products through optimizing fermentation conditions and the extraction method. The adoption of the optimum ultrasonic cell disruption extraction method can solve the problem of difficult extraction of intracellular bile salt hydrolase; and the extraction rate of EPS is increased by optimizing the extraction conditions of EPS. The fermentation technique and the extraction method for preparing the BSH and EPS are simple, the fermentation period is rather short, and the method has low requirements on equipment and cost, and is applied to the industrialized production.

The invention relates to a carrier capable of showing and expressing a heterologous gene on the surface of lactococcus lactis, and a preparation method and application of the carrier. The carrier has the nucleotide sequence which is shown as SEQ ID NO.1 in a sequence table, and contains promoter Pnis and lysM genes, a signal peptide secretion sequence ssusp45, a multiple cloning endonuclease site, and replicon repA and repC components. A method for constructing the carrier has the following steps of: amplifying a lactococcus lactis NZ3900 strain autolysin (AcmA) anchoring area gene lysM by applying a polymerase chain reaction (PCR) technology, performing enzyme digestion on the lysM and a carrier pNZ8110 and connecting, wherein a connection product is used for transforming a E.coli MC1061 strain, and extracting recombinant plasmid from positive transformed bacteria which are subjected to enzyme digestion and sequencing identification to obtain the expression carrier. The exogenous gene and the carrier are connected and then transferred into lactococcus lactis NZ3900, and the expression of the exogenous gene and the combination of expression protein and host cell walls can be realized by induction of nisin. The carrier can be used for expressing foreign proteins including vaccine antigens and has a wide application range.

The invention relates to an antibiotic, and a preparation method and an application thereof. The preparation method comprises the following steps: activating Lactococcal lactis ATCC 11454, picking single colony, culturing, centrifuging to remove bacterial strains to obtain a fermentation broth, adjusting the pH value of the fermentation broth to 2, carrying out rotary evaporating concentration, adjusting the pH value of the obtained concentrate to an initial value, centrifuging, taking the obtained supernatant, and filtering to obtain a fermentation concentrate; and mixing the fermentation concentrate with a PBS buffering solution, adding a double water phase system formed by Triton X-114 and MgSO4, centrifuging to realize phase balance of double water phases, taking the obtained upper phase, and diluting the upper phase by using the PBS buffering solution to prepare the antibiotic containing nisin and Triton X-114. The antibiotic has a substantial bacteriostasis effect on Gram-positive bacteria. The antibiotic includes nisin and Triton X-114, and the combination of the nisin and the Triton X-114 makes the antibiotic have high titer. The preparation method has the advantages of simple extraction process and low cost, and is suitable for intermittent and large-scale production and processing of high-tilter and high-yield antibiotics.

The invention discloses a urate oxidase gene recombinant plasmid and a genetic engineering bacterium which produces urate oxidase. The urate oxidase gene recombinant plasmid pRNJ800-U is obtained by inserting a NisA+MCS fragment and a urate oxidase gene in a plasmid vector pRAF800. The recombinant plasmid pRNJ800-U is transformed into Lactococus lactis to obtain the genetic engineering bacterium which produces the urate oxidase. The genetic engineering bacterium can be prepared into a biological preparation for oral administration to ensure that the genetic engineering bacterium is colonized on intestinal mucosa, thereby persistently and effectively decomposing uric acid in an intestinal canal to prevent and treat various diseases related to high uric acid; thus the side effect of drugs can be avoided, and the frequent drug use is also not needed. At the same time, the Lactococus lactis is a probiotic bacterium of the intestinal canal of a human body, is colonized on an inner layer of the intestinal mucosa, has functions of strengthening immunosuppresive pathogen, synthesizing various vitamins, reducing cholesterol and so on, and has a plurality of health care functions.

The invention relates to the technical field of microorganisms, in particular to a bean yogurt suitability strain, a microbial agent and an application thereof. The bean yogurt suitability strain is selected from any one or more of the following strains: 1) Lactobacillus rhamnosus SCB0119 with a preservation number of CGMCC17618; 2) Lactococcus lactis SCB0469 with the preservation accession numberof CGMCC17619; 3) Lactobacillus helveticus SCB0641 with the preservation number of CGMCC17620; all the three strains are preserved in the China Collection of Microorganisms and Cultures, and the preservation time is April 24, 2019. The above-mentioned microbial agent can obtain the microbial agent by reasonable compatibility, and the mixed soymilk is fermented to obtain the bean yoghurt with goodcurdled milk effect and good flavor, soy isoflavone can be subjected to biotransformation, and the content of free soybean isoflavone aglycones can be increased.

The invention belongs to the technical field of microbial resource utilization, in particular relates to a method for preparing an antibacterial peptide mixed solution generated by lactococcus lactis subsp lactis and lactobacillus sake, and relates to an application of the antibacterial peptide mixed solution in beancurd preservation. The method comprises the following steps of: preserving freshness of beancurd by adopting 10wt% antibacterial peptide mixed solution, and uniformly spraying the antibacterial peptide mixed solution on the surface of a beancurd block in a ratio of adding 2ml of antibacterial peptide mixed solution in every 10g of beancurd. According to the antibacterial peptide mixed solution, the sense score of the beancurd can be effectively prevented from being reduced, the growing speed of spoilage microorganisms can be inhibited, and the growth of total number of bacteria in the beancurd in the storing period can be suspended. Therefore, the antibacterial peptide mixed solution provided by the invention plays an active effect in beancurd preservation, and has better practical value.

The invention discloses a preparation method of a porcine epidemic diarrhea virus genetic engineering subunit oral vaccine. The method comprises the following steps of: 1) synthesizing an M gene; 2) constructing an expression vector; 3) performing protein induction expression; 4) carrying out recombinant strain preservation experiment; and 5) preparing the vaccine. The oral immunization has the advantage of effectively stimulating local immune cells of the intestinal tract to generate secretion type IgA, is especially applicable to the infectious disease of the intestinal mucosa, and avoids stress and vaccine absorption problems resulting from conventional vaccine injection; and as a safe and non-toxic live vector system capable of living on the intestinal mucosa, the lactococcus lactis is the most suitable vector system. The oral vaccine performs antigen presentation through the gastrointestinal mucosa, and produces immune reaction similar to conventional injection through different immune pathways.

The invention discloses acid-stress-resisting recombinant lactobacillus and belongs to the technical field of biological engineering. A GreAB gene obtained from lactococcus lactis (L.lactis NZ9000) isexcessively expressed in the lactococcus lactis (L.lactis NZ9000) to obtain recombinant lactococcus lactis (L.lactis NZ9000) (pNZ8148 / GreAB) with the remarkably improved acid-stress-resisting capability. The survival rate of a recombinant strain is 10.4 times as much as that of a control group after the recombinant strain is stressed for 3h under the condition that the pH (Potential of Hydrogen)is 4.0. The invention further provides a method for improving the acid stress resistance; the method has good industrial application value.

The invention discloses lactococcus lactis KUST48. The preservation number of the lactococcus lactis KUST48 in China General Microbiological Culture Collection Center is CGMCC NO. 20699. The strain isapplied to treatment of zebra fish infected by streptococcus agalactiae, and experimental results show that the strain can significantly inhibit propagation of streptococcus agalactiae in intestinaltracts of zebra fish and reduce the death rate of zebra fish infected by streptococcus agalactiae. The lactococcus lactis aims to replace antibiotics, overcome a series of defects of excessive use ofantibiotics, drug residue, drug resistance, food safety, environmental pollution and the like, improve the immune function of aquatic animals, enhance the disease resistance of the aquatic animals, reduce the use amount of drugs and promote green and ecological development of the aquaculture industry.

The invention aims to provide a specific labeled molecule of lactococcus lactis. The specific labeled molecule is characterized by being a gene for coding the protein Usp45 of lactococcus lactis. The invention also aims to provide a primer pair for detecting lactococcus lactis. The primer pair is characterized in that one primer in the primer pair is the same as the specific labeled molecule of lactococcus lactis in sequence and has a length of 15-40bp, and the other primer in the primer pair is complementary to the specific labeled molecule of lactococcus lactis in sequence and has a length of 15-40bp, and the amplified fragment of the primer pair has a length of 200-1383bp. The specific labeled molecule of lactococcus lactis has the advantages of high detection speed, high specificity, high sensitivity and low cost.

The invention relates to the technical field of fermented dairy products, and discloses multi-bacteria fermented skim camel milk for resisting diabetes and a production method of the multi-bacteria fermented skim camel milk. The multi-bacteria fermented skim camel milk is prepared from a lactobacillus helveticus leavening agent, a lactobacillus plantarum leavening agent, a lactobacillus paracasei leavening agent, a lactobacillus paracasei hard subspecies leavening agent, a lactobacillus mucosae leavening agent, a Harbin lactobacillus leavening agent, a lactobacillus hilgardii leavening agent, a lactobacillus pentosus leavening agent, a lactobacillus rhamnosus leavening agent, a lactococcus lactis leavening agent, an issatchenkia orientalis leavening agent, a kluyveromyces marxianus leavening agent, a pichia membranefaciens leavening agent and an ethanol candida leavening agent, which are added to the skim camel milk and are fermented. The multi-bacteria fermented skim camel milk is good in taste, the production method is easy to operate and simple in operation method; the obtained multi-bacteria fermented skim camel milk is abundant in nutrient, contains the components such as probiotics, immunomdodulating peptide, anti-oxidative peptide and the like, and has antidiabetic, anti-inflammation and antioxidant effects; and the physique and the overall vitality of people can be enhanced.

The invention discloses a lactococcus lactis lactate subspecies GGMCC No.14024 with high output of hexanoic acid and its application, and belongs to the technical field of food microorganism. The lactococcus lactis lactate subspecies GGMCC No.14024 has the characteristics that (1), a bacterial strain enters a stable period quickly, thus it is good for forming flavor matters; (2), the acid generating property of the bacterial strain is good; (3), the output of hexanoic acid of the bacterial strain is high, and 9.64 mu g / kg can be generated for 18 hours; (4), the fat metabolism ability of the strain is high, and the acid value is 5.33 in the 18th hour.

The invention provides a cold region straw decomposition microbial inoculum as well as a preparation method and application thereof, and belongs to the technical field of agricultural preparations. The cold region straw decomposition microbial inoculum comprises a low-temperature flora and a normal-temperature flora, wherein the low-temperature flora comprises 20%-28% of lactobacillus plantarum, 17%-25% of lactococcus lactis subsp. Lactis, 14%-22% of lactococcus, 11%-22% of arthrobacter globiformis and 9%-18% of rhodococcus, wherein the normal-temperature flora is lignocellulose decompositionflora. The product provided by the invention can start fermentation under a low-temperature condition, promote decomposition of straws under the low-temperature condition, improve the in-situ decomposition efficiency of straws in cultivated land, and solve the problems of seedling death and yield reduction caused by severe decomposition of straws in paddy fields in cold regions in summer in China.

The invention provides a grape pip fermented raw stock cosmetic as well as a preparation method and application thereof. The preparation method of the grape pip fermented raw stock cosmetic comprises the following steps: mixing grape pip dry powder, water and a bacterial solution to obtain an initial system, and carrying out fermental cultivation on the initial system so as to obtain a grape pip fermented raw stock. In the bacterial solution, the culture is lactococcus lactis, specifically can be lactobacillus. The application of the grape pip fermented raw stock in the preparation of the cosmetic with at least one function of the following functions 1) to 4) or the application of the grape pip fermented raw stock directly serving as the cosmetic with at least one function of the following functions 1) to 4) is also in the protective range of the invention: 1) eliminating DPPH free radicals; 2) stimulating collagen generation; 3) resisting oxidation; and 4) resisting aging. The cosmetic is facial mask, essence or toner. According to the method, active substances are extracted from grape pips by using a fermentation engineering technology, the operation is simple, and the prepared grape pip fermented substance, namely the grape pip fermented raw stock, is safe and harmless for the skin due to the fact that no foreign matter is added, so that the cosmetic has higher anti-aging activity.

The invention discloses Lactococcus lactis fermented at low temperature and a method for preparing yoghurt by using the Lactococcus lactis. The Lactococcus lactis is obtained by separating fermented yak milk of Gannan Tibetan Autonomous Prefecture, Gansu Province by an improved M17 culture medium. Milk can be condensed by fermenting the strain for 12h at the temperature of 25 DEG C. The yoghurt prepared from the strain has the characteristic of high viscosity, and is weakly post-acidified when stored.

The invention discloses a method for producing nisin and lactic acid through simultaneous saccharification and fermentation and an application of nisin and lactic acid in a feed. The method comprises the steps of with lignocelluloses as raw materials, hydrolyzing lignocelluloses by using cellulose to form monosaccharide, synchronously converting monosaccharide by using Lactococcus lactis subsp.lactis capable of producing nisin and lactic acid to produce lactic acid and nisin. Lignocelluloses such as crop stalks, rice straw or wood chips and the like are synchronously converted into nisin and lactic acid which both have high additional values; in addition, the produced lactic acid and nisin are used in feed additives for cattle and sheep, so that bacteria in greenfeed can be inhibited from breeding, and the greenfeed cannot be corrupted within 20d; after nisin and lactic acid are used in the feed to breed cattle and sheep, the daily grain is 10% more than that of a control group, the feed is saved by 10%, the breeding profit is increased, meanwhile, the excrement quantities of cattle and sheep are reduced and can be reduced by 5% at most, and the pungent odor is weakened, so that the conditions that the utilization ratio of the feed is increased and the favorable environment-friendly effect is achieved are proved from the side view.

The invention relates to a helicobacter pylori NapA protein expressed recombinant vector, a recombinant strain and preparation methods and application thereof and belongs to the technical field of biology. According to the helicobacter pylori NapA protein expressed recombinant vector disclosed by the invention, when recombinant plasmid pNZ8110 delta sp-napA is constructed, a secretion signal sequence in the pNZ8110 is removed; thus, NapA molecules expressed by the recombinant vector disclosed by the invention does not carry secretion signal peptide, molecular weight is 15KD, adverse effects toNapA biological activity are avoided, and the adverse effects are caused by the fact that signal peptide cannot be excised in thalli when the recombinant strain fails in secretion expression protein.The helicobacter pylori NapA expressed lactococcus lactis recombinant strain disclosed by the invention not only can be applied to preparing immune adjusting drugs, but also can be applied to producing health care food with an immune adjusting effect; the helicobacter pylori NapA expressed lactococcus lactis recombinant strain also has important significance in preventing and treating diseases offood allergy, immunosuppression, tumor and the like and can generate considerable social and economic benefits.

The invention relates to the field of poultry infectious disease prevention, and in particular to a protective antigen of avibacterium paragallinarum and expression and application of the protective antigen. The amino acid sequence of the protective antigen of avibacterium paragallinarum is of SEQ ID NO.1 as shown in the specification. The invention further discloses an expression vector for expressing the protective antigen of avibacterium paragallinarum, and an establishment method of the expression vector. The expression vector can be expressed in food-grade lactococcus lactis. The invention further provides application of the protective antigen of avibacterium paragallinarum, that is, application in preparing a chicken infectious rhinitis vaccine. By adopting the vaccine, the resistance of chickens to three serum type avibacterium paragallinarum bacteria A, B and C is remarkably improved, the protection effect of the vaccine is prior to those of whole-bacterial inactivated vaccines, and the vaccine can be adopted to prevent chicken infectious rhinitis caused by different serum type avibacterium paragallinarum bacteria.

The invention relates to Lactococus lactis HKS2 having lactic acid activity and a separating and screening method and application thereof. A classification name of the strain is Lactococus lactis HKS2which is already collected at the China Center for Type Culture Collection on 31st May, 2017 under a collection number of CCTCC NO:M2017296. The strain is obtained by separating a mixture of Hainan tropical aquaculture seawater and penaeus vannamei gastrointestinal tract. The Lactococus lactis HKS2 has no hemolytic activity, has high hydrophobic activity, self-coagulation rate, high resistance toartificial gastrointestinal fluid and cholate and high bacteriostatic ability. Aquaculture experiments verify that the Lactococus lactis HKS2 when serving as a feed additive to be fed to penaeus vannamei can improve organism immunity and promote growth, is stable in effect and has good application prospect.

The invention discloses recombinant lactococcus lactis yielding nisin highly and a construction method. The construction method comprises the following step: importing a lipoprotein signal peptidase gene lspA into lactococus lactis subsp.lactis YF11, the preservation number of which is CGMCC No.12429, to obtain recombinant lactococcus lactis YF11-lspA, wherein the nucleotide sequence of the lipoprotein signal peptidase gene lspA is as shown in SEQ ID NO.1. The recombinant lactococcus lactis improves the nisin endurance capacity of nisin producing strains so as to reduce inhibition of nisin togrowth of the strains in the fermenting process, so that the output of nisin is improved and the output of nisin of the lactococus lactis subsp.lactis YF11 is improved obviously.

The invention provides construction and usage of lactobacillus single-plasmid Nisin inducible expression vector, which belongs to the field of biotechnology. The construction comprises: a, acquisition and identification, the preparation of chromosome DNA producing Nisin lactococcus lactis, the design and synthesis of primer, the PCR amplification, recovery, pGEM-T connection and transformation ofa nisRK gene, and the identification of the nisRK gene; and b, the construction of pW425N, the recovery, connection and identification of the nisRK gene and a basic vector pW425et, the acquisition and identification of inducible promoter nisA gene, and the construction of pW425N. The usage comprises: a, the acquisition and identification of a green fluorescent protein gfp gene; b, the construction and identification of a recombinant expression vector; c, the determination of the inducible expression function of a Nisin inducible expression vector for green fluorescent protein; and d, the detection of lactobacillus stability. The invention has the advantages of avoiding the troublesome operation of integrating chromosomes of host bacteria in the prior system and simplifying the construction of recombinant genetic-engineering lactic acid bacteria.

The invention provides a vegetable leavening agent and a preparation method thereof. The preparation method comprises the following steps: firstly preparing four strains, i.e., Leuconostoc mesenteroides, lactobacillus plantarum, lactococcus lactis and Rhodosporidium diobovatum, to produce leavening agents, wherein the viable count of the leavening agent produced from each of the strains is no less than 10<9> / ml; subjecting the leavening agents produced from the four strains to freeze-drying; and then weighing, on the basis of the weight of freeze-dried strain powder, 3 to 5 parts of the component A Leuconostoc mesenteroides powder, 2 to 3 parts of the component B lactobacillus plantarum powder, 2 to 3 parts of the component C lactococcus lactis powder and 1 to 2 parts of the component D Rhodosporidium diobovatum powder and carrying out complete mixing and vacuum packaging so as to obtain the vegetable leavening agent which can be used for production of fermented vegetable, wherein the addition amount of the freeze-dried powder of the vegetable leavening agent accounts for 0.02% of the weight of fresh vegetable.

The invention discloses Lactococcus lactis subsp. lactis and application thereof in preparation of soybean milk, and belongs to the technical field of microbiology. The Lactococcus lactis subsp. lactis CCFM 1092 has the following properties that (1) strains grow fast, and enter a stable period in 8 h in MRS, and the increment of the viable count can reach 2 orders of magnitude in 6 h in the soybean milk, and the strains are suitable for industrial fermentation; (2) the strains have a high speed of acid production, and the soybean milk curds and reaches the end of fermentation when the strainsare applied to fermentation of the soybean milk, so that production of curd and flavor substances is facilitated; and (3) the strains have a high yield of 3-methyl butanol, and 476.05 [mu]g / kg of 3-methyl butanol can be produced in 6 h. When the Lactococcus lactis subsp. lactis CCFM 1092 is used as a fermentation agent for food fermentation, the fruit flavor of the fermented soybean milk can be improved, and a very broad application prospect is achieved.