the present invention describes a process for increasing the production of β - carotene in a fermentation process with mucor fungi ( blakeslea , choanephora or phymomyces , more specifically blakeslea trispora . the invention consists of culturing the fungus b . trispora in a fermentation medium containing by - products derived from the manipulation of citrics , in particular citric flours , which have been obtained by means of a process of elimination of pectins through treatment with calcium hydroxide and successive treatments of change of ph and washing to concentrate certain components that induce the production of β - carotene . within the citric flours , flours can be used that come , for example , from oranges , grapefruit , mandarin , etc . and within each one of these , the different varieties of each one of them , for example , navel , naveline , clementine , washington , valencia - late etc . on one hand , the invention consists in that the culture medium also contains soy lecithin and on the other hand , on applying a defined strategy for controlling the ph during fermentation . the joint effect of these variables allows an increase in the production of β - carotene and in the relative concentration of this with respect to other minority carotenoids . the organisms used for the fermentation can be isolated strains (+) or (−) or a mixture of strains (+) and (−) of mucor fungi , more specifically b . trispora or else β - carotene super - producing mutants of b . trispora . several mixtures of strains (+) and (−) of the fungus can be used in the fermentation process of the invention . the fermentation process can be performed in any culture medium containing one or more sources of carbon , one or more sources of nitrogen , mineral salts , thiamine and variable proportions of citric flours from a single citric source and a single variety or mixtures of flours from different citric fruits and / or varieties and soy lecithin in variable proportions that range from 0 . 1 % to 10 % and preferably from 0 . 5 % to 5 % and more preferably from 0 . 5 % to 1 . 5 %. the carbon sources that can be used as single or complex nutrients include carbohydrates or fats such as dextrines for example , starches , glucose , sucrose , fructose , animal and vegetable oils . within the nitrogen sources , organic and inorganic sources can be used such as for example soybean hulls , corn flour , soluble distillates , yeast extract , cotton flour , peptones , casein or ammonium sulphate . the mineral salts that can be added to the culture medium include phosphates , sulphates , chlorides of monovalent cations such as sodium , potassium or ammonium or divalent cations such as calcium or magnesium . the proportions of nutrients are determined as a function of the growth needs of the microorganism and the production levels . the fermentation is carried out in aerobic conditions and submerged culture . the fermentation temperature ranges from 20 ° c . to 32 ° c . although the range between 25 ° c . and 28 ° c . is preferred . the ph of the culture evolves freely in the first hours , in which there is an initial growth of the fungus in the fermenter . the ph is then controlled by means of the addition of acid and / or alkali within the range of 6 . 5 - 7 . 2 although preferably 6 . 7 - 6 . 9 . the start of the ph control depends on the evolution of growth , but in general it takes place after between 12 and 50 hours of fermentation , preferably between 24 and 36 hours . the incorporation of lecithin into the medium , due to the amphipatic character of this molecule favours the emulsion of the oils in the culture media in which these are found in high concentration , as is often the case in fermentation media of β - carotene . this action on the one hand favours the use of the oil by the microorganism and on the other it has surprisingly been found that it activates the carotenogenesis pathway favouring the transformation of gamma - carotene into beta - carotene , increasing the production of this latter substance and its relative concentration with respect to other carotenoids , especially the gamma - carotene , and so it leads to an important reduction in the presence of this substance in the final product , increasing the purity of all - trans beta - carotene . in addition , this effect is enhanced when a suitable ph control is performed during the fermentation , so that adjusting the ph after 24 - 36 hours of fermentation favours the reduction of the gamma - carotene in an even more marked fashion , increasing the relative concentration of the beta form . the presence of gamma - carotene in the fermentation broths of mucor fungi in cultures in stationary phase has been described before ( murillo f j , torres - martinez s , aragon c m and carda - olmedo e ( 1981 ) “ substrate transfer in carotene biosynthesis in phycomyces ” eur . j . biochem . 119 ( 3 ): 511 - 516 ; candau r ., bejarano e r , carda - olmedo e ( 1991 ) “ in vivo channelling of substrates in an enzyme aggregate for beta - carotene biosynthesis ” proc . natl . acad . sci . usa 88 ( 11 ): 4936 - 4940 ; fraser p d , ruiz - hidalgo m j , lopez - matas m a , alvarez m i , eslava a p and bramley pm ( 1996 ) “ carotenoid biosynthesis in wild type and mutant strains of mucor circinelloides ” biochim biophys actal 289 ( 2 ): 203 - 208 ). this presence has also been described in blakeslea trispora ( mehta b j and carda - olmedo e ( 1999 ) “ lycopene cyclization in blakeslea trispora ” mycoscience 40 ( 3 ) 307 - 310 ). in both cases , these inhibitory effects are described for some substances such as nicotine , 2 -( 4 - chlorophenylthio )- triethylamine , alpha - picoline and imidazole on the production of beta - carotene , favouring however the accumulation of lycopene - gamma - carotene due to the blocking of lycopene - cyclase . however , no processes have been described previously aimed at reducing the content of gamma - carotene in the fermentation of b . trispora increasing the production of beta - carotene and therefore the purity of the final product obtained . this effect of reduction of the content of gamma - carotene in the fermentation broths of blakeslea trispora result of the present invention is of importance in the sense that it allows the specifications established both at a pharmacopoeia level and for the food industry of the final product required a purity of beta - carotene of at least 96 % in the final product to be met . given the characteristics of the carotenoid component biosynthesised in the fermentation , on being intracellular , the recovery process from the culture broth , prepared in accordance with the current processes , implies the separation of the biomass of the broth with the aim of eliminating or reducing the losses in the broth without biomass . this separation can be made by the established processes of a ) filtration , using the current filter technologies , either strips , rotary , presses , etc ., in which the barrier constituted by the filtering material separates the biomass and allows the liquid to pass without the biomass , or b ) centrifugation , in which , making use of the different densities between the broth and the biomass ( usually higher ) a machine such as a centrifuge , decanter or similar is used , in which the heavy phase is concentrated and separated from the liquid phase with the lowest possible quantity of biomass . reducing losses and optimising the yield of each respective phase thus achieving the largest quantity of biomass with the highest content of dry residue and eliminating the greatest quantity from the fermentation broth is one of the objectives of this invention . the resulting wet mycelium contains more than 95 % of carotenoids produced in the fermentation , preferably more than 97 % and more preferably more than 99 %. the content in carotenoids of the aqueous phase is , therefore , less than 5 %, preferably less than 3 % and more preferably less than 1 %. this wet solid of mycelium would enable , through subsequent stages , the separation of beta - carotene but the finding that , related to the fermentation , it maintains a relatively high percentage of lipophilic component , between 15 and 20 % ( fatty acids and oils ) and that in subsequent stages purification problems arise , leads to the introduction , due to this point , of a purification stage of the biomass . this purification stage implies a re - suspension of the biomass with a quantity of alcohol , methanol , ethanol , propanol , isopropanol , or any other alcohol in which the solubility of β - carotene is very low , or mixtures thereof , in suitable proportion to achieve the maximum purification of the lipid components , in other words , the wet mycelium is re - suspended with a quantity of alcohol that ranges from 1 ml / g to 10 ml / g of wet mycelium . the temperature of re - suspension ranges between room temperature and the boiling point for alcohol . the contact time ranges between 5 minutes and 24 hours . the alcohol re - suspension thus prepared is filtered or centrifuged , so that the content of solids in the filtrate or supernatant is practically zero . the resulting wet mycelium , that will contain alcohol and water in different proportions , contains more than 93 % of the carotenoids produced in the fermentation , preferably more than 95 % and more preferably more than 97 %. in the resulting mixture of remains of broth with alcohol , the content in carotenoids is less than 2 %, preferably less than 1 %. through this treatment with alcohol , it is possible to eliminate a series of lipophilic substances soluble in alcohol that vary as a function of the characteristics of the broth used , performing a prior extremely important purification and one which will allow us to obtain a final crystalline product of high purity . in addition , the elimination of a variable proportion of water from the initial wet mycelium considerably facilitates the drying process . as an alternative to the set of these two stages of separation of the biomass and purification by re - suspension , the possibility is considered of directly mixing the harvested broth with alcohol in proportions of volume between 1 : 0 . 5 and 1 : 5 ( broth / alcohol ) and at temperatures between room temperature and that of the boiling point of the mixture , preferably between room temperature and 50 ° c ., keeping the minimum contact time a purification effect equivalent to that described is achieved , whereby the process is simplified through the elimination of the operation of solid / liquid separation . the fact that the carotenoid product is intracellular implies that the purified biomass requires conditioning by drying and grinding , drying and disintegration or only disintegration of the biomass , which favours mixing with solvents and facilitates extraction . the dehydrated purified mycelium is dried . the drying can be performed using normal processes in solid batches or continuously . the drying temperature ranges from room temperature to 150 ° c ., preferably should not exceed 60 ° c . and more preferably should be below 50 ° c . the drying time depends on the temperature used , ranging from 1 hour to 72 hours . due to the possible decomposition of these carotenoids through oxidation by atmospheric oxygen , it is convenient to perform this drying process in the absence of oxygen , either under nitrogen atmosphere or at least under vacuum . in order to allow the solvent good access to the carotenoid to be extracted , it is necessary to carry out a prior rupture operation on the mycelium , so that the surface area of contact is maximised . the optimum particle size of the dry and broken mycelium should be less than 3 mm , preferably less than 1 mm and more preferably less than 0 . 5 mm . the biomass disintegration can be carried out on the dry product by conventional means , for example by using mechanical grinding means with rotating or fixed parts : pestles , sieves , etc ., by passing through rotating cylinders pressing against one another or by a flash - type drying in the jet - mill equipment where the wet product is fed to a current of circulating gas at a high temperature , such that the residence time is minimised in order to achieve vaporisation of the content of the liquid components , and it is transported , due to differences in the densities of the product , to a cyclone where it is recovered . during the drying time and its travel there is a homogenisation effect as the particles collide with the walls . for the extraction of β - carotene from mycelium conditioned as described here , different organic solvents can be used . this invention relates to the use of food - grade solvents considered as natural , such as acyl esters , preferably ethyl , propyl , isopropyl , butyl , isobutyl esters , or mixtures thereof which combine reasonably high solubility for the carotenoid components with their compatibility as solvents included in the group of class iii of the ich . these solvents are admissible both in spain and within the european community , for both pharmaceutical and food applications ( rdl 12 / 04 / 96 and rdl 16 / 10 / 96 ). the extraction temperature varies between room temperature and that of the boiling point of the solvent , preferably between 50 ° c . and 80 ° c . the extraction time will be the minimum necessary to achieve solubilisation , between 1 second and 1 hour , preferably between 1 minute and 15 minutes . the quantity of solvent used depends on the temperature and the richness of the mycelium in carotenoids , ranging between 5 ml / g and 20 ml / g . the number of extractions varies from 1 to 3 . the quantity of carotenoids extracted is greater than 85 %, preferably greater than 90 % and more preferably greater than 95 %. once the extract rich in carotenoids has been obtained it is necessary to concentrate it to a certain volume . the final concentration of carotenoids in the solvent after concentration varies preferably between 10 and 40 g / l . the concentration temperature should be less than 80 ° c ., preferably less than 70 ° c . and more preferably less than 50 ° c . the concentration time should be less than 1 hour , preferably less than 30 minutes , and more preferably less than 15 minutes . once the extract has been concentrated to the required volume , it is necessary to add a carotenoid insolubiliser , specifically an alcohol and more specifically anhydrous methanol , ethanol , isopropanol , or any other alcohol in which the solubility of β - carotene is low , in proportions between 1 / 1 and 6 / 1 with respect to the volume of solvent after concentration , by which the yield of crystalline β - carotene increases considerably . the addition of the alcohol also has a purifying effect , recovering a purer product than when it is not added . the crystallisation time varies between 15 minutes and 24 hours , preferably between 1 hour and 12 hours and more preferably between 3 and 8 hours . the crystallisation temperature should be less than 25 ° c ., preferably less than 5 ° c . the separation of the crystals from the waters of crystallisation can be performed by filtration or centrifugation , displacing the waters of crystallisation that bathe the crystals washing them with the same alcohol used to insolubilise them . the crystals obtained are dried under vacuum at room temperature for at least 1 hour until a residual content of solvent in accordance with the specifications of maximum concentration established by legislation is attained and in the case of β - carotene , a loss on drying of & lt ; 0 . 2 % is established . the beta - carotene purity of the crystals obtained corresponds to a titre determined by spectrophotometry by reading the absorption at 455 nm dissolved in cyclohexane ( e1 % 1 cm = 2500 ) according to the spectrophotometric method of the usp , ep , bp , greater than 90 %, preferably greater than 95 % and more preferably greater than 98 % with a content in other carotenoids less than 4 %, preferably less than 2 %. similarly the crystalline product obtained can be handled and marketed as such or forming part of formulations in which the proportion of β - carotene varies between 1 and 85 %, mixing with different excipients or compounds , such as soybean oil , corn oil , olive oil , etc ., with different degrees of purity and accompanied by an anti - oxidant of the tocopherol type . an object of the present invention is to provide a formulation of carotenoids dispersible in water , which contains approximately 1 to 25 parts by weight of dry powder of carotenoids encapsulated in a starch matrix of food quality that provides β - carotene included in the powder encapsulated in a stable condition . different types of starch may be used . the product of the present invention are solid formulations of β - carotene , dispersible in water . the preferred starches used are modified cornstarches of food quality with a high molecular weight , which allows a simple emulsification of the organic phase in water . after separating the solvent , the dispersion satisfies the range of colours of β - carotene . this modified food starch does not produce sufficient re - dispersibility of the dry powder . thus , another starch is also added . the second variety is a mixture of starches of food quality of different molecular weights in a range of 1 , 000 - 700 , 000 ; this second type of starch provides a good dispersibility of the final product . as β - carotene is sensitive to oxidation , antioxidants can be dissolved in the solvent containing the β - carotene to intensify the stability against deterioration . in the present invention , any antioxidant authorised in foods can be used , including among others , β - tocopherol of natural or synthetic origin . the antioxidant level will be sufficient to protect the β - carotene . this must be 0 . 1 to 0 . 3 the amount of β - carotene . ascorbyl palmitate can also be added to the formulation due to the synergic antioxidant effect of the association of the two antioxidants . the method of this invention is especially applicable for the recovery of crystalline β - carotene from a microbial source , preferably algae , fungi or yeasts , more preferably from fungi of the mucor order , and more preferably from b . trispora . the extreme purity attained in the crystals obtained by the present methodology and the use of solvents considered as natural means that these crystals are applicable in the food industry , pharmaceutical industry or cosmetics industry . the addition of soy lecithin to the culture medium reduces the content of gamma - carotene when it is fermented in a flask . an inoculum medium is prepared that contains per litre : soybean hulls , 23 g ; corn flour , 47 g ; monopotassium phosphate , 0 . 5 g ; thiamine hydrochloride , 0 . 002 g . its initial ph is 6 . 3 . the medium is distributed in 500 ml erlenmeyer flasks at either 67 or 100 ml . after sterilisation , they are seeded with suspensions of spores of b . trispora strain (+) and b . trispora strain (−) in separated flasks and incubated at 25 ° c . for 48 hours . the base fermentation medium is prepared that contains per litre : soybean hulls , 44 g ; corn flour , 19 g ; orange flour , 10 g ; thiamine hydrochloride , 0 . 002 g ; vegetable oil 100 g . the culture medium that contains soy lecithin is prepared according to the previous description and supplemented with 1 % lecithin . the ph is adjusted to 6 . 3 . the medium is distributed in 250 ml erlenmeyer flasks in portions of 20 ml . for the fermentation of β - carotene , the flasks that contain the fermentation medium are inoculated with 10 % of mixed culture of strains of b . trispora (+) and b . trispora (−). all flasks are incubated at 25 ° c . in an orbital shaker at 250 rpm . after 48 hours of fermentation , β - ionone is added to the flasks at a ratio of 1 ml per litre of culture medium and the mycelium is collected on the 6 th day of fermentation . the extraction of β - carotene is carried out using any described method of cell rupture that allows the intracellular content to be released . it is solubilised in any solvent in which it is soluble such as acetone for example . its concentration can be assessed by means of spectrophotometry but the use of liquid chromatography is preferred ( hplc ), using any of the methods described in the literature . the addition of soy lecithin increases the production of β - carotene by 5 % and reduces the production of γ - carotene by 60 % ( see fig1 ). this experiment shows that lecithin allows the production of β - carotene to be increased and also helps the production of a purer product . the incorporation of lecithin into the culture medium increases the production of beta - carotene and reduces the relative level of gamma - carotene in a pilot fermenter . when it is combined with the control of ph , the effect on the production of gamma - carotene is even greater . an inoculum medium is prepared that contains per litre : soybean hulls , 23 g ; corn flour , 47 g ; monopotassium phosphate , 0 . 5 g ; thiamine hydrochloride , 0 . 002 g . its initial ph is 6 . 3 . the medium is distributed in 2000 ml erlenmeyer flasks , with 500 ml in each flask . after sterilisation , they are seeded with suspensions of spores of b . trispora strain (+) and b . trispora strain (−) in separated flasks and incubated at 25 ° c . for 48 hours with orbital shaking at 250 rpm and 5 cm eccentricity . each one of the strains is transferred under sterile conditions to an intermediate growth tank with a culture medium with the following composition per litre : pharmamedia , 29 g ; corn flour , 47 g ; monopotassium phosphate 0 . 5 g ; thiamine hydrochloride , 0 . 002 g ; anti - foaming agent , 1 g . its initial ph is 6 . 0 . after incubating for 36 - 48 hours , a mixture of the (+) and (−) strains is made and 10 % of the mixture is used to seed the base fermentation medium , whose composition per litre is as follows : soybean hulls , 50 g ; corn flour , 25 g ; orange flour , 15 g ; monopotassium dibasic phosphate 0 . 5 g ; isoniazid , 0 . 28 g ; thiamine hydrochloride , 0 . 002 g ; vegetal oil 80 g , anti - foaming agent , 0 . 175 g . this culture medium is supplemented with 1 % soy lecithin . the fermentation is verified at a temperature of 25 - 280 c with variable stirring between 150 and 250 rpm and an aeration of 1 - 1 . 5 v / v / m . the ph control is performed with ammonia or sulphuric acid , keeping two different conditions depending on the test : without control of ph with a range between 6 . 5 and 7 . 5 or with control at 6 . 8 ± 0 . 1 after 36 hours of fermentation . between 40 and 50 hours of fermentation , 10 g / l of a 10 % solution of β - ionone in vegetal oil are added . between 50 and 60 hours , 10 g / l of a 2 . 5 % solution of ethoxyquin in vegetal oil are added . the fermentation is extended for 100 - 140 hours , after which time the production of β - carotene is assayed : the extraction of β - carotene is performed by any method described with cell rupture that allows the intracellular content to be released . it is solubilised in any solvent in which it is soluble , for example , acetone . its concentration can be determined by spectrophotometric means , but the use of liquid chromatography ( hplc ) is preferred , using any of the methods described in the literature . the results of the tests performed with the culture medium with and without lecithin and the two ph control conditions mentioned above are presented in the following table : gamma - carotene beta - (% with culture carotene respect to meduim ph (%) beta - carotene ) without range 100 5 . 6 lecithin 6 . 5 - 7 . 5 without control 6 . 8 95 3 . 2 lecithin from 38 h onwards with lecithin range 105 4 . 4 6 . 5 - 7 . 5 with lecithin control 6 . 8 105 2 . 1 from 38 h onwards these data clearly indicate that the incorporation of lecithin to the culture medium increases the production of beta - carotene ( 5 % increase ) and reduces the relative level of gamma - carotene ( by 43 %). when combined with a control of ph , the effect on the production of gamma - carotene is even greater ( 63 %). three litres of fermentation broth are harvested . the titre of the broth is 6 g of β - carotene per litre . the biomass of these broth is recovered by means of a buchner filtration , obtaining 1000 g of wet biomass . the wet biomass is re - suspended in 3 l of azeotropic isopropanol 85 / 15 and shaken for 30 minutes . the purified biomass is once again recovered by a buchner filtration . this biomass is dried in an oven under vacuum at a temperature less than 45 ° c . and for 18 hours , until the content of residual solvents is in the range of 1 - 2 %. a total of 270 g of dry biomass are obtained and purified with a β - carotene content equivalent to a purity of 6 . 5 %. the dry biomass is ground in a hammer mill and 1 mm sieve to give a solid with the same specific purity and conditioned to allow extraction with the solvent . the extraction is carried out by mixing 270 g of ground biomass with 4500 ml of isobutyl acetate at 70 ° c ., keeping stirring for 5 minutes . the depleted biomass is separated from the rich solvent by filtering through a filter plate . the depleted biomass is washed with 500 ml of warm isobutyl acetate over the filter itself , mixing the two solvents . the total of rich isobutyl acetate is concentrated under vacuum with the temperature kept between 45 ° c . until the volume is reduced to 700 ml , at which point part of the β - carotene has crystallised . to complete the crystallisation and obtain purer β - carotene , 2100 ml of isopropanol are added . the mixture is kept shaking at between 0 and 5 ° c . under nitrogen for 3 hours . it is filtered through a buchner funnel , washing the crystals with 25 ml of isopropanol over the buchner funnel . the crystals are collected and dried , obtaining 14 g of crystals of β - carotene with a purity of 96 % as measured by spectrophotometry . approximately 500 l of fermentation broth are harvested , with a β - carotene titre of approximately 5 . 5 g / l . this is mixed directly with 1500 l of azeotropic isopropanol with water 85 - 15 and the mixture is heated to 40 ° c . after keeping stirring for 30 minutes , the biomass is separated from the liquid by centrifugation with a decanter . around 180 kg of purified wet biomass is collected . this biomass is dried in a rotary drier under vacuum until attaining a residual solvent content in the range of 1 - 2 %. the temperature has to be less than 45 ° c . and the time in the range of 12 - 24 h . 45 kg of dry biomass is obtained with a β - carotene content equivalent to a specific richness of 5 . 9 %, a slightly lower purity . the dry biomass is ground in a hammer mill and 1 mm sieve to give a solid with the same specific purity and conditioned to allow extraction with the solvent . as an alternative , the wet biomass is dried in a flash turbo drier ( jet - mill type ) in which case the grinding step is not necessary . the extraction is performed mixing the 45 kg of ground solid with 800 l of isobutyl acetate at 70 ° c ., maintaining shaking for 15 minutes . the depleted biomass is separated from the rich solvent by centrifugation with decanter . the total of isobutyl acetate is concentrated under vacuum with the temperature kept below 45 ° c . until the volume has been reduced to 110 l , at which point part of the β - carotene has crystallised . to complete the crystallisation of β - carotene , 330 l of isopropanol are added . the mixture is kept shaking while it cools , for 3 h at 0 - 5 ° c . it is filtered through a buchner funnel collecting the crystals of beta - carotene that are dried . 2 . 1 kg of product are obtained with a purity of 96 % as measured by spectrophotometry . a : percentage production of β - carotene with lecithin ( right column ) or without lecithin ( left column ). b : percentage production of γ - carotene with lecithin ( right column ) or without lecithin ( left column ).
the invention relates to a novel method for the production of β - carotene from submerged cultures of mucoral fungi such as blakeslea , choanephora or phycomyces by adding lectin to the culture medium and performing ph control once fermentation has started . the method involves β - carotene recovery stage that makes it possible to simplify the process , optimize yields and increase purification of the product .