New microbiological polysaccharide Gellan gum production technique
The present invention relates to microbial fermentation and foodstuff additive production field, more specifically, the present invention relates to production technique such as the fermentation of microbiological polysaccharide Gellan gum and extraction.
Three during the last ten years, and microbial polysaccharide has obtained very big development, and especially the xanthan gum succeeded in developing is described as the outstanding product " of " of microbial polysaccharide production and application nineteen sixty.Obtained the gelling gum (Gellan Gum) that drugs approved by FDA is used in 1992, be a kind of high-quality gelifying agent and suspension agent, have using value in foodstuff additive, pharmaceutical excipient and fields such as microorganism and plant tissue culture media, be expected to become the outstanding product " of second microbial polysaccharide " after xanthan gum.
So far have the industrial production that the U.S. has realized gelling gum only.China uses as foodstuff additive in approval gelling gum in 1996, but high market value has limited its widespread use at home.The production domesticization and the low cost that realize gelling gum are the keys of dealing with problems.Reaching target comprises in the problem that technical elements need solve:
1, gelling gum is synthetic through carbohydrate metabolism in the suitable culture base by producing the glue microorganism.In the nutrient media components, carbohydrate is that main carbon source, protein is the largest portion that main nitrogenous source constitutes the fermentation raw material cost.Searching can promote product synthetic, and cheap again carbon, nitrogenous source are to realize high yield, the essential consideration of low cost production gelling gum.
2, gellan gum fermentation liquid belongs to high viscosity reaction system (being up to 7000-8000cP).Traditional mechanical agitating fermentation tank designs at the low viscosity fermentation system, have when being applied to high viscosity systems main body mix poor, mass-transfer efficiency is low and shortcomings such as energy expenditure height make the nutriment of reaction system and the limiting factor that oxygen supply becomes the raising fermentation efficiency.Reach the purpose of gellan gum fermentation high-yield and high-efficiency, fermentation equipment is had particular requirement.
3, remove by filter bacterial chip and protein in the fermented liquid, obtain clarifying gelling gum solution and be the difficult point in the leaching process, this step also is the key point that influences product purity, outward appearance and application performance.The reason that causes the removal of impurities difficulty is the existence of fermentation broth viscosity height, protein content height and pigment.
4, comprise the extraction of some compound of polysaccharide of xanthan gum, gelling gum, for making product reach high-quality, edible requirement, generally need to use a large amount of alcoholic solvents (ethanol, Virahol etc.), and the loss of alcoholic solvent and reclaim the energy and often constitute the largest portion of production cost, so the extracting method that finds low solvent usage quantity highly significant.
Therefore, this area presses for the technology of the new production microbiological polysaccharide Gellan gum of exploitation.This technology can reduce the production cost of gelling gum and/or enhance productivity.
First purpose of the present invention provides a kind of production technique of the liquid of gellan gum fermentation cheaply, wherein with the thick amylum hydrolysate of the sugar liquid of cheapness as fermentation raw material.
Second purpose of the present invention provides a kind of extracting method that obtains deacylated tRNA base, transparent gellan gum product cheaply from gellan gum fermentation liquid.This method not only can obtain high-quality gelling gum, and the alcoholic solvent consumption in the leaching process is significantly reduced.
The 3rd purpose of the present invention provides a kind of fermentor tank that is applicable to the inventive method, and this fermentor tank is specially adapted to full-bodied gellan gum fermentation system.
In a first aspect of the present invention, a kind of production method of gelling gum is provided, it comprises fermentation step, described fermentation comprises: gelling gum is produced in the aseptic culture medium that bacterium is inoculated in carbonaceous sources, nitrogenous source, inorganic salt and water, under the condition that is fit to growth, ventilate, stir culture, wherein said carbon source is thick amylum hydrolysate of the sugar liquid.
Preferably, in fermentation, nitrogenous source is a yeast extract paste, and culture condition is pH value 7.0-7.5, temperature 27-29 ℃, fermentation time 50-60 hour.
In another embodiment of the present invention, fermentation is to stir to carry out in aspect ratio is the fermentor tank of 2-4.
In another embodiment of the present invention, after fermentation step, also comprise extraction step:
(a) fermented liquid is carried out alkaline purification, to remove the part acyl group in the gelling gum molecule;
(b) fermented liquid through alkaline purification in the step (a) is carried out coarse filtration earlier, carry out micro-filtration again;
(c) fermented liquid of handling after filtration in the step (b) is carried out gelation and handle, form gel;
(d) gel in the step (c) is squeezed dewater;
(e) oven dry.
In a second aspect of the present invention, a kind of extraction gelling gum production method is provided, it comprises step:
(a) fermented liquid that contains gelling gum is carried out alkaline purification, to remove the part acyl group in the gelling gum molecule;
(b) fermented liquid through alkaline purification in the step (a) is carried out coarse filtration earlier, carry out micro-filtration again;
(c) fermented liquid of handling after filtration in the step (b) is carried out gelation and handle, form gel;
(d) gel in the step (c) is squeezed dewater, form film through squeezing;
(e) film in the step (d) is dried.
Preferably, described coarse filtration is to carry out under 80-200 order condition, and micro-filtration is to carry out under 0.2-1.0 micron condition.
In one embodiment of the invention, it is that the adding final concentration is the gelating agent of 0.05-0.2% in hot filtrate that described gelation is handled, and is cooled to room temperature.
In another embodiment of the present invention,, also comprise step: soak the formed film of squeezing with little lower alcohol, to slough residual look in step (d) with (e).
In a third aspect of the present invention, a kind of fermentor tank that is used for the inventive method is provided, the aspect ratio of described fermentor tank is 2-4, stirring progression is the 3-6 level, and bottom stirs and adopts radial flow disk turbine oar, the upper strata is stirred and is adopted the axial flow stirring rake, and the oar diameter is 1/2.5-1/2 with a jar diameter ratio.
In the accompanying drawings, Fig. 1 is the sectional view of fermentor tank of the present invention.
Fig. 2 A and 2B are respectively the front view of disk turbine oar and axial flow stirring rake.
Fig. 3 A and 3B are respectively the vertical view of disk turbine oar and axial flow stirring rake.
Definition
As used herein, term " transparent gellan gum of deacylated tRNA base " refers to the natural gellan gum of fermentation gained is carried out alkali Processing removes acetyl group and glyceroyl, and removes mycoprotein with means such as filtrations, and concentrates and the rear institute of oven dry The aqueous solution that gets is the gellan gum product of transparence. This is the most widely gellan gum commercial form of purposes.
As used herein, term " gelating agent " refers to add and can cause the gellan gum gelation in the gellan gum solution Material. Various reagent for gelation known in the art may be used to the present invention. Suitable gelating agent Example comprise (but being not limited to): calcium chloride, magnesium chloride, lithium chloride etc. The consumption of gelating agent is with solidifying The gelatinizing agent kind is different and different, and those skilled in the art can be by routine test or experience and in addition true Fixed.
At first, the invention provides the production technology of the gellan gum fermentation liquid of a cover optimization, wherein provide especially one Plant cheap thick Starch Hydrolysis liquid glucose as fermentation raw material.
At present, general glucose, sucrose, fructose, the Fructus Hordei Germinatus made from extra care that adopts of carbon source in the gellan gum fermentation culture medium Sugar etc., nitrogenous source generally adopt yeast extract, peptone, corn steep liquor, beancake powder, casein hydrolyzate etc. Yet, The present invention utilizes thick Starch Hydrolysis liquid glucose to make carbon source, and this is based on following consideration:
1. compare cheap many with glucose, sucrose etc.;
2. be rich in the nutrition such as protein in the thick starch.
Can be used for thick starch of the present invention and comprise corn flour, dehydrated potato powder, bean powder and sweet potato powder etc., preferably be Corn flour. Thick starch consumption (take glucose meter) is preferably 3% as the 2-4% of culture medium gross weight. Because with Thick Starch Hydrolysis liquid glucose is made carbon source, the nitrogenous source addition can reduce, take yeast extract as example, usually from 0.5% Consumption drops to 0.2-0.3%. Also comprise inorganic salts commonly used in the culture medium.
Usually, fermentation condition also comprises: fermentation temperature preferably is 27-29 ℃ at 25-35 ℃; The pH model Enclose and be 6.0-8.0, be preferably 7.0-7.5. Adopt the force ventilation stirred fermentor, cultivated 2-4 days, preferably be 50-60 hour.
The production bacterial classification that can be used for producing gellan gum can be waterweed pseudomonad (Pseudomonas for example Elodea) ATCC 53967, also can be waterweed pseudomonad (Pseudomonas elodea) ATCC 31461, or other suitable bacterial classification.
Secondly, the invention provides a kind of mechanical agitation fermentation of the special high viscosity gellan gum fermentation system that is applicable to Tank is characterized in that inside is equipped with the major diameter axial impellers, and tank body adopts the larger ratio of height to diameter design.
At present, traditional mechanical agitating fermentation tank tank body ratio of height to diameter 1.5-1.7, the oar diameter is 1/3 left side with tank diameter ratio Right. In the high viscosity fermentation system, fluid shearing efficient with from paddle apart from increasing and rapidly decay, so The dead band can appear near the tank skin and between every grade of paddle. Increasing oar diameter and tank diameter ratio can overcome this and lack Point, but be the increase of 3 power multiplying powers owing to stir power consumption with diameter of stirring paddle, strengthen then unit of oar diameter absolute value The volume power consumption is too big and inadvisable. So tank diameter should be diminished, adopt the larger ratio of height to diameter tank body, increase the paddle level The design of number. In addition, in high viscosity fermentation, adopt axial impellers, can force the fluid axial flow, have Help eliminate the dead band between the Multi-stage stirring blade.
Therefore, fermentation tank of the present invention has following design feature:
(1) fermentation tank ratio of height to diameter value is 2-4, preferably is 2.5-3.5.
(2) having 3-6 level paddle progression, preferably is 4-5 level paddle progression.
(3) bottom stirs and still adopts radial flow disk turbine oar, disperse to promote bubble, and all employings is stirred on the upper strata Axial impellers; Wherein, axial impellers can adopt big blade face screw.
(4) oar diameter and tank diameter ratio are 1/2.5-1/2.
Now referring to accompanying drawing 1, a kind of fermentation tank of the present invention has 2 axial impellers (1,2) and a footpath To stream disk turbine oar (3), oar diameter and tank diameter ratio 1/2, and ratio of height to diameter is 3.
The structure of disk turbine oar and axial-flow mixing paddle is shown in Fig. 2 A and 2B, and Fig. 3 A and 3B.
Again, the invention provides acquisition deacylated tRNA base, the transparent gellan gum product from gellan gum fermentation liquid that a cover is optimized The extractive technique of product. One of feature of this extractive technique is micro-filtration after the first coarse filtration of employing, and can introduce a small amount of decolouring The method of agent is to obtain the filtrate of high clarity; Two of feature be replace with the gel dewatering process traditional rudimentary The alcohol precipitation method are separated gellan gum, and the alcoholic solvent consumption in the leaching process is reduced to minimum.
At present, extraction process generally comprises successively zymotic fluid alkali treatment, filtration, concentrates and baking step.
The alkali treatment condition and the prior art that are used for the inventive method are as broad as long. At present used various alkali treatments Condition all can be used for the present invention. The purpose of alkali treatment is to remove part acyl group in the gellan gum molecule to strengthen product Gelling performance. Usually, the alkali treatment condition is as follows: temperature is 80-100 ℃, and pH is 9-12, processes 10-After 45 minutes pH is transferred to neutrality. Better condition: temperature is 85-90 ℃, pH10-11, time 15-20 Minute.
Because fermented liquid impurity is many, color is dark, a step is filtered the gelling gum solution that is difficult to obtain clear, and it is too big directly then to load with micro-filtration.Therefore, the present invention has designed special filtration process, it is characterized in that adopting micro-filtration after the first coarse filtration, and introduces the method for a small amount of discoloring agent when coarse filtration, to obtain the filtrate of good clarity.
The effect of coarse filtration is to remove the macrobead bacterial chip and adsorb color to alleviate the pressure of micro-filtration operation.Coarse filtration is usually at the 80-200 order, and preferably the 100-150 order carries out under more preferably about 120 order conditions.Do not have special requirement for flocculating aids and discoloring agent, used various flocculating aidss and the discoloring agent of field of food all can be used for the present invention at present.The example of suitable aid comprises (but being not limited to): diatomite, perlite etc., its consumption is generally 0.5-3%, preferably is 1-2%.Discoloring agent is selected gac for use, and its consumption is generally 0.2-1%, preferably is 0.2-0.5%.
A kind of preferable coarse filtration condition is: 120 order industrial filter cloths, add 1-2% flocculating aids (diatomite) in the fermented liquid, and 0.2-0.5% discoloring agent (gac) is while hot through filter press;
The effect of micro-filtration is to hold back impurity such as high molecular weight protein to obtain clear liquid.Usually, micro-filtration carries out under 0.2-1.0 micron condition.A kind of preferable micro-filtration condition is: temperature 70-80 ℃, the filter membrane aperture is the 0.2-1.0 micron.
For avoiding consuming a large amount of alcoholic solvents, the present invention substitutes alcohol precipitation dewatering process with the gel dewatering process and separate gelling gum from solution.Adopt the basis of gel dewatering process to be:
When 1. positively charged ion being arranged especially divalent-metal ion existing, the easy gel of deacylated gellan sol solution;
2. gel has good bleed under the higher cation concn, especially when pressurized;
3. remaining soluble proteins in the filtrate as can be with the gelling gum coprecipitation with the pure precipitator method, and be easily removed with separating out water with gel dehydration rule, thereby is improved the gelling gum product purity.
Gel dewatering process of the present invention comprises gelation processing and two processes of gel squeezing.
Described gelation treating processes is: add the solution that contains gelating agent (as calcium chloride) in hot filtrate, make ultimate density reach 0.05-0.1% (is example with calcium chloride), force to be cooled to room temperature;
Described gel expressing process is: with the gel piece pack, the hydropress squeezing dewaters.
The squeezing gained the moisture 60-75% of half-dried film, after 50-70 ℃ of oven dry, pulverize finished product.Use little lower alcohol (as alcohol, Virahol) to soak squeezing gained film in case of necessity, to slough residual look and to shorten drying time.
The invention has the advantages that:
(1) uses thick amylum hydrolysate of the sugar liquid (place of glucose or sucrose) as the carbon source of gellan gum fermentation substratum, make fermentation raw material cost decline 20-40%.
(2) adopt larger ratio of height to diameter, big diameter of propeller blade to make gelling gum content raising about 20% in the fermented liquid with the fermentor tank of tank diameter ratio.
(3) take micro-filtration after the first coarse filtration, and introduced the filtration process of a small amount of discoloring agent.This technology has overcome the problem that is difficult to obtain good clarity filtrate in the gelling gum extraction, has guaranteed the purity of finished product.
(4) substitute traditional alcohol precipitation evaporation with the gel evaporation and from solution, separate gelling gum, make the alcoholic solvent waste of unit product descend about 80%, alcohol reclaims energy-output ratio and descends about 90%, the cost of supplementary product that is used in extraction descends more than 50%, makes the product protein content reduce about 20%.
Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiment only to be used to the present invention is described and be not used in and limit the scope of the invention.In addition, unless stated otherwise, otherwise all per-cent all is weight percent.
Embodiment 1
Fermentative production gelling gum polysaccharide
A. seed preparation
To plant daughter bacteria (Pseudomonas elodea ATCC 53967) from the nutrient agar medium inclined-plane and insert broth culture, 30 ℃ of shake-flask culture 24 hours are to be first order seed; Above-mentioned seed liquor is inserted secondary seed medium (the same fermention medium of nutritive ingredient), cultivated 16 hours for 30 ℃, insert fermention medium with 5% amount then
B. zymotechnique
Fermentation culture based component and consumption see Table 1.
Substratum is prepared with tap water, and regulates pH to 7.5 with 2N NaOH.Fermenting process is controlled pH7-7.5 with 10%NaOH, 27 ℃-29 ℃ of temperature maintenance, and fermentation time is 58 hours.
Table 1 gellan gum fermentation substratum is formed
Composition consumption (%)
Corn hydrolysis sugar 3.0 (with glucose meter)
Yeast extract paste 0.2
MgSO
4.7H
2O 0.01
Na
2HPO
4 0.05
KH
2PO
4 0.05
C. fermentation equipment
Adopt the special mechanical agitating fermentation tank shown in the accompanying drawing 1 with larger ratio of height to diameter fermentation tank body and major diameter, axial flow stirring rake.
D. result
Followingly carry out Crude polysaccharides assay in the fermented liquid: with fermented liquid with double 95% alcohol mixing of its volume, get precipitation, 60 ℃ of dryings 2 hours.The result shows, gelling gum Crude polysaccharides concentration is 1.3g/100ml in the fermented liquid that obtains by present embodiment.It is about 30% that cost descends, and the polysaccharide concentration comparison is according to (conventional fermentor tank) high about 20%.
Embodiment 2
The preparation of deacylated tRNA base, clarification gelling gum
Alkali pretreatment
A. the 500L fermented liquid is heated to 90 ℃;
B. transfer pH to 10 with NaOH, be incubated 85 ℃-90 ℃, 15 minutes;
C. transfer pH to 6-8 with dilute hydrochloric acid or dilute sulphuric acid;
Filtration process
D. the diatomite that adds fermentating liquid volume 1%, 0.2% gac, by filtering through the diatomaceous plate-and-frame filter press of precoating, pressure is 0.2-0.3Mpa, the temperature for the treatment of filtrate is 80-90 ℃;
E. filter filtrate micro-filtration (temperature is greater than 70 ℃) while hot, use PallSep
TMThe industry micro-strainer carries out;
Gel process
F. constantly stir the calcium chloride solution that in hot filtrate, slowly adds 10L 5% down, be cooled to room temperature and form gel;
The gel squeezing process
G. gel piece is smashed in the bag that the filter cloth of packing into makes, tying places the 10Mpa hydropress under and squeezed 2 hours;
H. will contain the gelling gum amount and be 30% half-dried film and put into the alcohol of 2 times of weight and soak half an hour, slough residual look;
Oven dry and pulverizing
I.60 ℃ oven dry is 3 hours, pulverizes and is finished product.
The result
After measured, the gellan gum finished product that obtains by present embodiment is 55% to the extraction yield of gelling gum Crude polysaccharides.The alcohol waste of unit product is than using traditional pure precipitator method to descend about 80%, and the energy consumption that alcohol reclaims descends more than 90%.The product specific performance that obtains sees Table 2:
The product performance of table 2 deacylated tRNA base, transparent gellan gum
Product appearance loss on drying (%) ash (%) protein content (%) 0.5% concentration solution appearance 0.5% concentration solution viscosity (cP) 0.5% concentration gel strength (g/cm2)
| Off-white powder (60 order) 7.1 8.0 1.5 colourless, clears 30 1000 |
Embodiment 3
The preparation of deacylated tRNA base, clarification gelling gum
Alkali pretreatment
A.500L fermented liquid is heated to 90 ℃;
B. transfer pH to 10 with KOH, be incubated 85 ℃-90 ℃, 15 minutes;
C. transfer pH to 6-8 with dilute hydrochloric acid or dilute sulphuric acid;
Filtration process
D. the diatomite that adds fermentating liquid volume 1%, 0.2% activated carbon, by filtering through the diatomaceous plate-and-frame filter press of precoating, pressure is 0.2-0.3Mpa, treats 80-90 ℃ of filtrate temperature;
E. filter filtrate micro-filtration (temperature is greater than 70 ℃) while hot, use PallSep
TMThe industry micro-strainer carries out;
Gel process
F. constantly stir the magnesium chloride solution that in hot filtrate, slowly adds 5L 5% down, be cooled to room temperature and form gel;
The gel squeezing process
G. gel piece is smashed in the bag that the filter cloth of packing into makes, tying places the 10Mpa hydropress under and squeezed 2 hours;
H. will contain the gelling gum amount and be 30% half-dried film and place the alcohol of 2 times of weight to soak half an hour, slough residual look;
Oven dry and pulverizing
I.60 ℃ oven dry is 3 hours, pulverizes and is finished product.
The gellan gum finished product that obtains by present embodiment is 54% to the extraction yield of gelling gum Crude polysaccharides; The alcohol waste of unit product is than using traditional pure precipitator method to descend about 80%, and the energy consumption that alcohol reclaims descends more than 90%.
Should be understood that read of the present invention above-mentioned tell about content after, those skilled in the art can make various changes or modifications the present invention, these equivalent form of values fall within the application's appended claims institute restricted portion equally.