Comprehensive processing of coffee grounds in a single process

Abstract

The subject of the invention is a comprehensive method of processing coffee grounds in a single process comprising the following stages: drying the grounds; extraction of the dried grounds using a non-polar organic solvent to obtain coffee oil; extraction of the grounds from the previous stage using ethanol and / or water to obtain an antioxidant extract; hydrolysis of the grounds from the previous stage in an aqueous solution of sulfuric acid to obtain calcium sulfate and, in the next stage, lignin; optionally enzymatic hydrolysis of the remaining grounds; biofermentation of the sugar hydrolysate, separation of biomass and purification of lactic acid. The method according to the invention allows for obtaining many valuable products in a single process. Due to the lack of formation of harmful products, the lack of use of heavy metals at any stage of production and the use of solvents in closed circuits, the method according to the invention will allow for limiting the exploitation of natural resources.

Description

[0001] Comprehensive processing of coffee grounds in a single process

[0002] The subject matter of the invention is a comprehensive method of coffee grounds processing in one process into a number of products with various applications.

[0003] Coffee, right after water, is one of the most popular drinks in the world. Growing coffee consumption is associated with the increasing environmental pollution caused by the coffee industry as a result of stimulating the greenhouse effect and generating up to 20 million tons of wet coffee grounds (SCG, spent coffee grounds) per year (according to ICO report, 03.2022). Currently, SCG are disposed of together with municipal waste or incinerated, which leads to environmental pollution, soil poisoning, oxygen consumption, greenhouse gas emissions and fermentation odours, as well as the risk of spontaneous combustion. However, high levels of organic compounds in SCG, causing negative consequences during disposal, equate to high content of potentially beneficial industrial compounds.

[0004] Coffee grounds are lignocellulosic biomass that consists mainly of biopolymers such as hemicellulose, cellulose and lignin. Hemicellulose is a heterogeneous polysaccharide. In used coffee grounds, it consists mainly of arabinogalactans and galactomannans. Cellulose is composed of D-glucose molecules linearly linked together by |3-l,4-glycosidic bonds. These sugars are additionally coated with lignin, which is a polymer composed of phenolic alcohol derivatives. The final composition of coffee grounds depends on the methods used to grow, roast and brew the beans.

[0005] It has been suggested that the EU Directive 2018 / 851 has intensified the development of coffee grounds recycling technology (Johnson K. et al., Front. Chem. Eng. 2022). Three directions of SCG applications have been observed: food and cosmetics, energy and materials. Some technologies use SCG as a whole, i.e. compost, feed, fillers or fuels. They can also be used as aggregates in construction materials, but there is still no evidence of successful practical applications in this field. Other recycling technologies separate SCG into different fractions and process each of them separately based on the biorefinery concept. The most common proposal is to use SCG as a raw material for the production of biodiesel and biocomposites.

[0006] In the patent specification inEP0216971 a method for simultaneously hydrolysing spent ground coffee beans and extracting coffee oil therefrom is disclosed. Spent coffee grounds are suspended in water with a water-immiscible solvent and the pH is adjusted by adding acid to the suspension. The water-immiscible solvent combines with the suspension and disperses into fine droplets. The dispersion is then passed through a reactor, preferably a plug flow reactor, to hydrolyse the spent coffee grounds and extract coffee oil into solvent droplets. The solvent containing the coffee oil is then separated from the aqueous hydrolysate and the spent grounds are also separated from the hydrolysate. The coffee oil is recovered from the solvent and the aqueous hydrolysate is neutralized and combined with the soluble coffee extract. Sulphuric acid can be used as the acid and hexane can be used as a water- immiscible solvent.

[0007] Patent description US11066616 describes a method of producing biofuel from used coffee grounds, comprising the steps of: mixing used coffee grounds (without separating the coffee oil from them first) with a 20% sulphuric acid solution and heating to about 70°C for about 3 hours to form a suspension; drying the suspension; mixing the dried suspension with methanol and heating the mixture at about 70°C, for 6-20 hours to produce biofuel. The grounds remaining after the process are used to produce biochar.

[0008] Patent description KR102088764B describes a method of producing lactic acid by simultaneous saccharification and fermentation of coffee grounds. Pre-treatment of the coffee grounds is carried out at 80 to 130°C, for 20 to 80 minutes, by adding a 10% (w / v) to 5% H2SO4 solution. Saccharification and fermentation are simultaneously carried out by treating the ground coffee suspension with a saccharifying enzyme and yeast. Preferably, the saccharifying enzymes are cellulase and p-glucosidase.

[0009] From the publication of the description of the patent application CZ20131002A3 a process for the production of polyhydroxyalkanoates and / or carotenoids or biomass enriched with carotenoids from coffee grounds is known. Accordingly, coffee grounds are extracted with an organic solvent, e.g. hexane, to produce coffee oil and solids, and then the coffee oil is biotechnologically converted to polyhydroxyalkanoates using Cupriavidus necator bacteria. An alternative method is the enzymatic and / or acidic hydrolysis of hemicelluloses and celluloses from coffee grounds to produce coffee hydrolysate, followed by biotechnological conversion of the coffee hydrolysate into polyhydroxyalkanoates and solids using Burkholderia cepacia or Bacillus megaterium. The method also comprises biotechnological conversion of coffee hydrolysate into carotenoids or into carotenoid-rich feed biomass with the participation of carotenogenic yeast Sporobolomyces Roseus, Rhodotorula mucilaginosa, Rhodotorula glutin is and Cystofilobasidium capitatum.

[0010] The solutions known from the state of the art relate to various processes in which coffee grounds are used as a raw material. However, there is no comprehensive technology in which coffee grounds would become a source of simultaneous acquisition of many valuable products in one process. The aim of the invention is to develop a comprehensive method for fully processing coffee grounds in one process into new value-added products. Closely related to this concept is the idea of a circular economy, which involves maximizing the potential of products, materials and raw materials by reprocessing them into other useful goods, thereby extending the value of these resources and reducing the amount of waste generated.

[0011] The essence of the method according to the invention is the processing of coffee grounds in a multi-stage technological process, where its key stages are carried out in a strictly defined order: first, extraction of dried coffee grounds with hexane (or another organic solvent), then extraction of the remaining grounds with an aqueous solution of ethanol or water, then acid hydrolysis, optionally also enzymatic hydrolysis of the hydrolysateifinally, fermentation of the sugar hydrolysate, separation of the biomass from the solution of the produced lactic acid, its isolation and purification, and finally, possibly additional purification of the lignin formed after acid hydrolysis. Only by carrying out the above steps in a specific order it is possible to obtain all the products from coffee grounds, i.e. coffee oil, antioxidants, lactic acid, lignin and feed additives, in high quality and with good yield.

[0012] The method according to the invention is characterized in that: a) coffee grounds are dried to an average moisture content of no more than 5% w / w, optionally sieved; b) dried coffee grounds are subjected to an extraction process using a non-polar organic solvent from the alkane group, preferably hexane, used in a ratio of 1:2-1:8 w / v (grounds / solvent), at the boiling point of the solvent, and then the entire volume of the suspension is filtered. Filtered and washed grounds are dried and the solvent is distilled off from the filtrate containing the solvent and coffee oil, the solvent is optionally recycled to the process, and the coffee oil is discharged as a product; c) the dried coffee grounds from step b) are subjected to an extraction process with an aqueous ethanol solution with a concentration in the range of 30-60%, preferably 40- 50% v / v, or with water, in a ratio of 1:5-1:20 w / v, preferably 1:8-1:12 w / v (grounds / aqueous ethanol solution or water), at a temperature of 20-80°C, preferably 20-40°C, and then the entire volume of the suspension is filtered. Filtered and washed grounds are dried and the filtrate containing ethanol solution or water and dissolved antioxidants is subjected to the reverse osmosis process, obtaining a concentrated solution containing antioxidants (retentate). The concentrated solution is then subjected to the lyophilization process, or spray drying to obtain solid antioxidants; d) the dried coffee grounds from step c) are hydrolysed in an aqueous solution of sulphuric acid, at a concentration of 1-10%, preferably 2-5% v / v, in a ratio of 1:2-1:15, preferably 1:5-1:10 w / v (grounds / acid solution), at a temperature of 60-100°C, for 3-5 hours, and then the entire volume of the suspension is filtered; filtered and washed grounds are dried, calcium carbonate or other neutralizing agent is added to the filtrate to obtain a solution pH of 5.0-5.5 / 25°C, and the resulting calcium sulphate precipitate is filtered off and dried. The grounds sediment obtained at this stage may, after washing with water and (possibly) neutralization, constitute a lignin material which in this form can be used in other processes; e) dried coffee grounds from step d) are treated with an aqueous solution of sulphuric acid, with a concentration of 5-30%, preferably 15% v / v, and heated at 50-100°C for 2-6 hours, and then the entire volume of the suspension is filtered and the precipitate containing lignin is washed with an aqueous solution of an alkali metal carbonate or an alkali metal hydrogen carbonate or an alkali metal hydroxide or water and dried. Preferably, sodium or potassium bicarbonate, sodium or potassium carbonate and sodium hydroxide are used. The sediment obtained at this stage may, after washing with water and (possibly) neutralization, constitute a lignin material which in this form can be used in other processes; f) optionally, an enzyme solution is added to the filtrate from step d) at a temperature of 40-60°C, which is a mixture of cellulases, hemicellulases and p-galactosidases, where the enzyme added is 4-24%o relative to the amount of coffee grounds used in step d), the solution is kept at a temperature 40-60°C for 12-72 hours, and then the entire volume of the suspension is filtered; g) whey permeate in the amount of 0.5-5.0% w / v and yeast extract in the amount of 0.2- 2.0% w / v are added to the filtrate from step e) or from step f); the whole mixture is sterilized, inoculated with lactic acid bacteria in the amount of 1-10% v / v relative to the volume of the hydrolysate and lactic acid production is carried out at a temperature of 25-37°C for 12-72 hours, maintaining the pH value in the range of 5.5-6.5, and then the post-culture suspension is purified and concentrated by filtration or centrifugation of the biomass, and then in a cascade of membrane processes consisting of microfiltration, ultrafiltration and electrodialysis.

[0013] Preferably, in step a), the grounds are sieved through a sieve with a mesh diameter of 600-800 pm.

[0014] Preferably, in step b), the extraction is carried out for at least 30 minutes.

[0015] Preferably, the permeate from step c) is recycled after determination of the water and ethanol content and used for re-extraction.

[0016] Preferably, ethanol is evaporated from the retentate from step c), which can also be recycled.

[0017] Preferably in step d) an anti-foaming agent is added to prevent foaming during the addition of calcium carbonate. Alternatively, whitewash can be added to neutralise the sulphuric acid.

[0018] Preferably, in the microfiltration step, particles exceeding 10-15 pm in size or, if possible, 2-15 pm in size are separated from the culture fluid.

[0019] Preferably, the ultrafiltration step removes particles larger than the cut-off point of the ultrafiltration membrane (10-20 kDa), the process being carried out in a cross-flow filtration system with a flow rate through the membranes such as to ensure turbulent flow.

[0020] Preferably, all grounds drying processes are carried out under reduced pressure. Preferably, at any stage, the last flow of filtrate or wash is returned to the reactor to rinse out residues.

[0021] Preferably, each filtration is carried out under reduced or increased pressure.

[0022] The first product obtained during the hexane extraction process is coffee oil. It is an oil with a strong and rich aroma of roasted coffee. In terms of properties, it is a sticky substance with an intense colour of cloudy coffee. The resulting product is rich in fatty acids, with significant levels of linoleic, palmitic and oleic acids, making it a beneficial addition to both biodiesel (as an energy supplement) and skin care preparations. It also contains a small amount of caffeine and high levels of vitamin E, phytosterols and antioxidants.

[0023] The second product obtained during the extraction process with an aqueous solution of ethanol or water is a solution containing antioxidants. The pathogenesis of many diseases is based on the phenomenon of oxidative stress. It appears when the balance between free radicals and antioxidants is disturbed. As a result of excessive oxidation, damage may occur to the cell membrane and its receptors, mitochondria, and even nuclear and mitochondrial DNA. This may result in an acceleration of the cellular aging process, as well as the development of diseases such as diabetes, atherosclerosis or neurodegenerative diseases. Additionally, antioxidants regulate inflammation and protect against the harmful effects of UV radiation, and may also prevent heart disease, diabetes, cancer and other diseases. Some studies show that they can prevent neurodegenerative diseases such as Alzheimer's and Parkinson's. In industry, the largest market for substances with antioxidant properties is the food industry, where they are used mainly as preservatives, but also as flavour additives. Some of the most important antioxidants found in coffee grounds are chlorogenic acid and caffeine.

[0024] The third product of the process according to the invention is lignin. Lignin constitutes from 24% to 55% of the mass of coffee grounds accepted for first drying. After depriving the coffee grounds of the oil fraction, antioxidants and sugars, lignin is the next significant component (i.e. above 10% w / w of the original composition) in the composition of the grounds. It can be used as a filler in composites, e.g. with polylactide.

[0025] The fourth product of the process according to the invention is lactic acid, which can then be used to obtain polylactide. Polylactide (PLA) is a fully biodegradable polymer belonging to the group of aliphatic polyesters. It is produced by the polymerization of lactic acid (LA). Depending on the isomeric composition, PLA has different properties. PLLA, created from L-LA, is characterized by high tensile strength, which is why it is used in the packaging market and in medical products. Depending on the PLLA / PDLA ratio, products with different mechanical properties and thermal stability are obtained. Poly-L-lactide (PLLA) exhibits the typical mechanical properties of a rigid thermoplastic and has a long time of complete biodegradation (over 2 years). Poly-D-lactide (PDLA) has mechanical properties similar to rubber and a much shorter biodegradation time (12-16 months). By varying the degree of tacticity of polylactide, it is possible to obtain materials with intermediate properties. In the method according to the invention, the applicants focused on obtaining individual enantiomers of lactic acid. Further polymerization to polylactide can be carried out, for example, according to patents no.: PL222655, PL225851 and PL225850.

[0026] Further products of the method according to the invention are additives to feed or, optionally, to fertilizers: calcium sulphate and lactic acid bacteria biomass. In order to obtain these products, auxiliary materials must be added to the process, bearing in mind that one of the most important tasks of the method according to the invention is not only the full valorization of coffee grounds, but also not generating further waste streams. When designing the entire system, we took into account how we could bring some post-production waste back onto the market. As a result, two products were obtained that can be used as feed additives: calcium sulphate and lactic acid bacteria biomass.

[0027] Calcium sulphate (calcium precipitate) is formed after acid hydrolysis of the suspension of grounds obtained after the hydrolysis process, and neutralisation of the acid hydrolysate with calcium carbonate or another calcium neutralising agent.

[0028] Calcium and sulphur in this form are available to plants.

[0029] Lactic acid bacteria biomass is formed by separating solid elements from the culture liquid from the lactic acid fermentation stage. Biomass is, like calcium sulphate, an additive to animal feed. It is possible to mix both streams together.

[0030] As described above, the processing of coffee grounds begins with drying them. The average moisture content of the grounds was assumed to be 60% m / m, but a lot depends on the delivery time, storage conditions and initial moisture content. Regardless of this, the drying process should reduce the moisture content of the grounds to a level no higher than 5% w / w.

[0031] The next step is mechanical cleaning of the grounds. Separating impurities from wet grounds would result in very large losses of raw material. It should be assumed that coffee grounds that were originally sorted at the point of production do not enter the installation with contaminants such as metal, paper or plastic fragments, but it cannot be assumed that they will be completely absent, or that other types of contaminants, such as coffee husks from the grinding process, will not get into the coffee grounds. To separate them, the dry grounds must be subjected to a sieving process. During the tests, the sufficient mesh diameter of the sieve was determined to be 600-800 pm. It should be remembered that an additional purpose of this operation is to develop the surface of the raw material by breaking down any lumps that may have formed, for example, at the collection stage. It was assumed that the fraction retained on the sieve, constituting waste, should not exceed 2% of the fraction of sieved grounds that can be subjected to further processing. Coffee oil is obtained in the extraction process using a technically pure solvent, it cannot be a petroleum fraction. The process is carried out with constant stirring at the boiling point of the solvent. After extraction is complete, the suspension is optionally cooled to about 40°C. Then, the entire volume of the suspension is filtered, which contains coffee grounds devoid of coffee oil and the solvent in which the oil is dissolved. The last filtrate (wash) can be returned to the reactor to rinse out any remaining grounds suspension. It is suggested to carry out the filtration process at elevated pressure to minimize solvent losses. The filtered and washed grounds should be subjected to the drying process again. In turn, the solvent-oil fraction is subjected to a solvent distillation process. The process is carried out at the boiling point of the solvent, which, after evaporation, can be used for re-extraction. The remaining coffee oil is the first product of the process.

[0032] The stage of obtaining antioxidants consists in extracting the dry coffee grounds after oil extraction with an aqueous solution of ethanol or DEMI water, filtering and washing the filter cake with an aqueous solution of ethanol or DEMI water. The filtered grounds should be subjected to the drying process again. The filtrate containing the ethanol solution and the antioxidants dissolved in it should be subjected to the reverse osmosis process. The permeate from this process, after determining the water and ethanol content, can be recycled and used for re-extraction. In turn, the retentate stream, which has been significantly concentrated, can be subjected to evaporation of ethanol, which can also be recycled. The remaining stream can be freeze-dried or spray-dried. The product of this stage is a highly concentrated solution containing antioxidants or antioxidants in powder form - the second product of the process.

[0033] After ethanol extraction, the dry grounds are hydrolysed in an aqueous solution of sulphuric acid. The purpose of this step is to initially dissolve and break down the polysaccharide chains in the grounds. The drained grounds constitute the lignin material (the third product of the process), while the filtrate is neutralized with calcium carbonate or another neutralizing agent. At this stage, attention should be paid to the formation of carbon dioxide, which will cause heavy foaming of the process mixture. After reaching the required pH, the resulting suspension should be filtered under reduced pressure. As a result of neutralization, a precipitate is formed, the main component of which is calcium sulphate. The filtered precipitate should be dried. Due to the risk of mould growth, drying should be performed immediately after filtering. The resulting product of the process can be used as a fertilizer or calcium supplement for animal feed. The neutralized filtrate is used as input for enzymatic hydrolysis or directly for biotechnological production of lactic acid.

[0034] Raw lignin only requires neutralization with a base or alkali metal carbonate and washing with water until a neutral pH is obtained in the filtrate.

[0035] Pure lignin is obtained by re-hydrolysis (leaching) with sulphuric acid of a higher concentration of lignin material (raw lignin) of the precipitate filtered after the acid hydrolysis process. After neutralization, washing with water and drying from water, pure lignin is the next product of the process.

[0036] After acid hydrolysis and neutralization, the filtrate is optionally subjected to enzymatic hydrolysis using a commercially available mixture of cellulases, hemicellulases and P-galactosidases, which ultimately degrade the polysaccharide chains into simple sugars, which constitute a source of carbon and energy for lactic acid bacteria. The sediment remaining after enzymatic hydrolysis is carbon impurities originating from the coffee roasting process, which could only precipitate from the solution at this stage - it is a waste fraction (less than 1% of the raw material). The remaining filtrate (neutralized hydrolysate) is the input for the biotechnological production of lactic acid.

[0037] In order to produce lactic acid, it is necessary to use lactic acid bacteria (LAB, lactic acid bacteria). They dominate among the producers of lactic acid used in industry. These bacteria are a phylogenetically heterogeneous group, distinguished by their ability to ferment sugars under microaerophilic or strictly anaerobic conditions with lactic acid as the main product of carbohydrate fermentation. Due to their high nutritional requirements, they are most often found in environments rich in carbohydrates, amino acids and nucleotide derivatives. On the other hand, however, they show considerable adaptability to harsh environmental conditions, thus increasing the spectrum of niches they inhabit. LAB inhabit niches such as plants, milk and dairy products, the digestive tract and the urogenital tract of humans and animals. Depending on the species and culture conditions, LAB can produce lactic acid as the L(+) enantiomer, the D(-) enantiomer, or the racemate. The principles of LAB selection depending on the expected product are well known to those skilled in the art. Strains that demonstrate the ability to biosynthesize lactic acid in the L(+) form are particularly valuable.

[0038] Obtaining lactic acid and lactic acid bacteria biomass requires propagation of the inoculum. This stage includes both banking and storage of bacterial strains and their propagation in a bioreactor cascade. Bacterial stocks must be constantly renewed and checking their purity is an extremely important step, carried out in a dedicated microbiology laboratory. The strains are stored frozen.

[0039] Lactic acid fermentation takes place in a process bioreactor, in which the input is the hydrolysate obtained in the previous stage after acid hydrolysis, or alternatively enzymatic hydrolysate. Hydrolysate should be supplemented to provide LAB with optimal growth conditions. The culture is inoculated with inoculum obtained at the propagation stage and then grown for a specified period of time. It is extremely important to prevent infections with other microorganisms. The post-culture suspension is purified and concentrated, first by filtering or centrifuging the biomass, then by microfiltration, ultrafiltration and electrodialysis. The purpose of microfiltration is to separate bacterial biomass residues and solid elements, bacterial fragments and high-molecular oligosaccharides, lignin and other objects exceeding 10-15 urn in size or, if possible, even 2-3 pm in size from the post-culture liquid.

[0040] The permeate from microfiltration is sent to ultrafiltration, which is intended to remove the protein from the microfiltration permeate and remove remaining components with sizes below 10-15 pm. The process is carried out in a cross-flow filtration system and must be guided at such a flow rate through the membranes as to ensure turbulent flow. The product obtained is permeate containing lactic acid, other organic acids (in the form of salts), inorganic salts and other low molecular weight compounds. The retentate that remains as waste is 5-10% of the feed volume.

[0041] The lower the cut-off point in microfiltration, the smaller the retentate volume will be. In practice, ultrafiltration is carried out either by using suitably efficient modules or by returning the retentate to the module and running the process several times until the appropriate retentate concentration is achieved. To extend the period between subsequent membrane regenerations, it is recommended to use back flash. Electrodialysis-consists in splitting salts, producing a solution of acid(s) and a stream containing alkali solutions, mainly NaOH. The waste product is the exhausted solution, which theoretically should not contain any ions.

[0042] The method according to the invention makes it possible to obtain many valuable products in one process. The condition for obtaining the above-mentioned products of the required quality and with good yield is to carry out the process according to the invention in a strictly defined sequence of stages, with defined parameters for conducting each stage.

[0043] The method of processing coffee grounds in accordance with the invention has a positive impact on the environment. Net impact on CO2emissions is negative, meaning that carbon dioxide emissions are saved, mainly by recovering SCG in the form of useful products such as polylactide, biodiesel and natural lignin-based biopolymer. The resulting products are an alternative to existing solutions, but their life cycle is much more environmentally friendly.

[0044] Due to the lack of formation of harmful products, the lack of use of heavy metals at any stage of production and the use of solvents in closed circuits, the method according to the invention will allow for the reduction of the exploitation of natural resources.

[0045] It is also worth emphasizing that there is no solid waste harmful to the environment. The gypsum formed at the stage of neutralization of the acid hydrolysate is ready for utilization, while the biomass of lactic acid bacteria is a friendly factor for fertilization, unlike the composting of raw SCG. Waste water streams can be directed to the sewer system. The produced sewage is characterized by negligible content of ammonia, nitrates, phosphorus and detergents. Additionally, low COD (Chemical Oxygen Demand) and BOD5 (Biological Oxygen Demand) values are to be expected, while the pH is within the ranges typical for household waste. A simplified schematic diagram of the method according to the invention is shown in Fig.l.

[0046] The method according to the invention is carried out in an installation as shown in the example embodiment in Fig. 2, which shows a conceptual diagram of the installation. Diagrams of parts of the installation in which the individual steps of the method according to the invention are carried out are shown in Fig. 3 to Fig. 10.

[0047] The method according to the invention is presented in more detail in the Examples.

[0048] Example 1.

[0049] Coffee grounds with a moisture content of 60% are dried at 80°C, under a reduced pressure of 2 bar, for 16 hours. The resulting grounds have a moisture content of 5%. The dried grounds are then sieved through a sieve with a mesh diameter of 600-800 pm. Dry grounds with a bulk density of 350-400 kg / m3are obtained.

[0050] Suggested equipment:

[0051] • Industrial dryer (e.g. chamber, drum, with agitator).

[0052] • Pneumatic separator (sieving) or other suitable means to achieve the goal.

[0053] A diagram of the installation fragment in which stage a) is carried out is shown in Fig.3.

[0054] Example 2.

[0055] The dry and cleaned grounds are extracted with hexane (pure, technical grade). The grounds are poured into the reactor, hexane is added in a ratio of 1:5 w / v (SCG / hexane) and the heating is turned on with constant stirring. Once the boiling point of hexane has been reached (69°C), the process is continued for 30 minutes. After this time, the heating should be turned off and the suspension should be cooled to about 40°C. At this temperature, filtration of the entire reactor volume begins, which contains coffee grounds - devoid of coffee oil - and hexane, in which the oil is dissolved. The last filtrate (wash) is returned to the reactor to rinse out the remaining parts of the grounds suspension. The filtration process is carried out at an increased pressure of 2.0 bar. The filtered grounds should be subjected to the drying process again. In turn, the hexane-oil fraction is subjected to the hexane distillation process. The process is carried out at the boiling point of hexane, which must be distilled into a separate tank and used for re-extraction. The remaining coffee oil is the first product of the process.

[0056] The obtained coffee oil is characterized by:

[0057] • Water content: max. 0.15%

[0058] • hexane content: <100 ppm

[0059] • dynamic viscosity: 150 - 180 mPa-s

[0060] The obtained oil should be stored in barrels, e.g. with a capacity of 200 litres, in a dark and cooled warehouse. Suggested equipment:

[0061] Two extractors - tanks equipped with a mixer and a heating and cooling system.

[0062] Filtration system with backwash - various driving forces are permitted, i.e. Pressure or vacuum filtration.

[0063] EX industrial dryer (e.g. chamber, drum, with agitator) with condensate recovery Equalizing and storage tanks.

[0064] A diagram of the installation fragment in which stage b) is carried out is shown in Fig.4.

[0065] Example 3.

[0066] Dry coffee oil extraction grounds are poured into the reactor and then treated with an aqueous ethanol solution with a concentration of 42% v / v (pure ethanol, DEMI water). The process is then continued for 2 hours at room temperature, with stirring. After this time, a vacuum filtration process is carried out and the filter cake is washed with DEMI water. The filtered grounds are then subjected to the drying process again. The filtrate containing ethanol solution and antioxidants dissolved in it is subjected to reverse osmosis at room temperature, pressure of 20 bar(g) and permeate flow rate of 90 dm3 / h The permeate from this process, after determining the water and ethanol content, is recycled and used for re-extraction. The retentate stream that has been concentrated is subjected to a freeze-drying process to obtain antioxidants in solid state (powder).

[0067] The products of this stage are antioxidants with the following properties:

[0068] • Antioxidant activity: a) FRAP: 0.218±0.011 mmol FeSO4-7H2O / mL b) DPPH: 0.079±0.001 mmol trolox / mL

[0069] • water content: <1.5% w / w

[0070] • Ethanol content: <0.5% w / w

[0071] The obtained product should be stored in hermetically sealed bags with an input weight of 25 kg in a cold store.

[0072] Suggested equipment:

[0073] Two extractors-tanks equipped with a mixer and a heating and cooling system.

[0074] Filtration system with backwash - a solution enabling efficient and effective phase separation. Various driving forces are permitted, i.e. pressure or vacuum filtration.

[0075] EX industrial dryer (e.g. chamber, drum, with a mixer and filter dryer) with condensate recovery.

[0076] Reverse osmosis installation - either in a two-stage variant or as a cascade with pervaporation.

[0077] Freeze-drying installation or EX spray dryer.

[0078] Equalizing and storage tanks. A diagram of the installation fragment in which stage c) is carried out is shown in Fig.5.

[0079] Example 4.

[0080] The dry grounds after ethanol extraction are hydrolysed in an aqueous solution of sulphuric acid (concentration 2.5% v / v, H2SO4, pure, technical grade, DEMI water). The grounds are poured into the reactor, an acid solution is added in a ratio of 1:6 (w / v) to SCG, then the heating is turned on with continuous stirring. After reaching a temperature of 100°C, the process is continued for 3 hours. After this time, the suspension is cooled to approximately 40°C and then filtered under reduced pressure. The filter cake is washed with DEMI water to rinse out any remaining sugars. The filtered and washed grounds are then dried again under the same conditions as before. The filtrate is transferred to the next tank where the neutralization process takes place. Calcium carbonate (pure, powder) is added until the pH of the solution is in the range of 5.0-5.5 / 25°C. At this stage, attention should be paid to the carbon dioxide that is formed, which causes heavy foaming of the process mixture. After reaching the required pH, the resulting slurry is filtered under reduced pressure. The reaction produces calcium sulphate. The filtered precipitate is dried under reduced pressure. The product obtained in this way is a calcium supplement to animal feed. The neutralized filtrate is the input for fermentation or enzymatic hydrolysis.

[0081] Suggested equipment:

[0082] Two extractors - tanks equipped with a mixer and a heating and cooling system.

[0083] Filtration system with backwash - a solution enabling efficient and effective phase separation. Various driving forces are permitted, i.e. pressure or vacuum filtration.

[0084] Industrial dryer (e.g. chamber, drum, with agitator) with condensate recovery. Equalizing and storage tanks.

[0085] A diagram of the installation fragment in which stage d) is carried out is shown in Fig.6.

[0086] Example 5.

[0087] Dry coffee grounds sediment after acid hydrolysis is poured into the reactor and then treated with an aqueous solution of sulphuric acid (concentration 10% v / v, H2SO4, pure, technical grade, DEMI water). The entire suspension is heated to 100°C with constant stirring. Once this temperature is reached, the process lasts for 3 hours. After this time, the contents of the reactor are cooled to approximately 40°C and then filtered under reduced pressure. The wet precipitate is neutralized by washing the filter cake with an aqueous solution of sodium bicarbonate (pure, powder, DEMI water) and water. The resulting filtrate is waste, while the precipitate is dried under the same conditions as the previous grounds fractions.

[0088] The dried sludge is the final product, which is lignin with the following properties:

[0089] • product content: >98% w / w (as a comparison with the IR spectrum of the standard) • water content: <2% w / w

[0090] • pH: 6.8-7.2 / 25°C

[0091] The received product should be stored in 25 kg bags in the warehouse.

[0092] Suggested equipment:

[0093] Two extractors - tanks equipped with a mixer and a heating and cooling system.

[0094] Filtration system with backwash - a solution enabling efficient and effective phase separation. Various driving forces are permitted, i.e. pressure or vacuum filtration.

[0095] Industrial dryer (e.g. chamber, drum, with agitator) with condensate recovery. Equalizing and storage tanks.

[0096] A diagram of the installation fragment in which stage e) is carried out is shown in Fig.7.

[0097] Example 6.

[0098] After acid hydrolysis and neutralization, the filtrate is transferred to a reactor equipped with heating and stirring. After bringing the solution to 50°C, the enzyme solution is added. It is a commercially available mixture of cellulases, hemicellulases and p-galactosidases, offered under the trade name Flashzyme Plus 200. The enzyme addition is 6%o relative to the amount of SCG used for acid hydrolysis. The pH in the reaction medium is 5.0-5.5 / 25°C, and the reaction time is 24 h. After this time, the process mixture is cooled to approx. 40°C and then filtered under reduced pressure. The remaining sediment is the waste fraction. The remaining filtrate containing simple sugars is the input for the biotechnological production of lactic acid. Suggested equipment:

[0099] Reactor (pressurized) - a tank equipped with a stirrer and a heating and cooling system.

[0100] Filtration system - a solution enabling efficient and effective phase separation. Various driving forces are permitted, i.e. pressure or vacuum filtration.

[0101] Equalizing and storage tanks.

[0102] A diagram of the installation fragment in which stage f) is carried out is shown in Fig.8.

[0103] Example 7.

[0104] Propagation of inoculum.

[0105] This stage includes both banking and storage of bacterial strains and their propagation in a bioreactor cascade. This stage is carried out in a dedicated microbiology laboratory. The WUT 17 / 2 strain is stored frozen at -80°C in glycerol solution (approx. 15% v / v relative to the volume of the bacterial suspension). The thawed suspensions are added to a bioreactor with a working capacity of 10 dm3, which contains MRS medium at a concentration of 52.2 g / dm3and which has been appropriately prepared (sterilized, connected to the system, etc.). The reproduction stage lasts 24 hours. After this time, the culture suspension is divided into two parts. About 10% of the volume serves as a source of future cultures, so glycerine is added to it, mixed and frozen. The remaining 90% is transferred to a larger bioreactor with a capacity of 100 dm3. There, the bacteria are propagated for a second time, making it possible to service many production lines with one batch. The growth conditions for bacteria are 37°C, gentle agitation, no need for anaerobic conditions, maintaining a constant pH: 6.0 / 37°C and 24 h. It is extremely important to ensure sterility. There is no need to supplement MRS medium.

[0106] The diagram of the installation fragment in which the inoculum preparation is carried out is shown in Fig. 9.

[0107] Suggested equipment:

[0108] Bioreactor (small) - for biomass propagation, equipped with a stirrer, pH and temperature control system. The system must have an appropriate sterilization mechanism.

[0109] Bioreactor (medium size) - for biomass propagation, equipped with a stirrer, pH and temperature control system. The system must have an appropriate sterilization mechanism.

[0110] Example 8.

[0111] The enzymatic hydrolysate obtained according to Example 6 is subjected to lactic acid fermentation. This stage takes place in a process bioreactor. Enzymatic hydrolysate should be supplemented to provide LAB with optimal growth conditions. Whey permeate is added to the hydrolysate in the amount of 3% and yeast extract in the amount of 0.5%. All values given are expressed as w / v relative to the volume of hydrolysate. Everything is mixed and sterilized. After cooling down the bioreactor, the culture is inoculated with the inoculum obtained according to Example 7 at the propagation stage, in an amount of 1% v / v relative to the volume of the hydrolysate. Conditions for the production of lactic acid: 37°C, gentle agitation, no need for anaerobic conditions, maintaining a constant pH: 6.0 / 37°C and 72 h. It is extremely important to ensure sterility. The post-culture suspension is purified and concentrated by filtration or centrifugation of the biomass and then in a three-stage cascade of membrane processes consisting of microfiltration, ultrafiltration and electrodialysis. Once separated, the biomass is, like calcium sulphate, an additive to animal feed. During microfiltration, solid elements, bacterial fragments, high-molecular-weight oligosaccharides, lignins and other objects larger than 10-15 pm are separated from the post-culture liquid. Permeate from microfiltration is fed to ultrafiltration membranes. At this step, particles larger than the membrane cut-off point (20 kDa) are removed. The process is carried out in a cross-flow filtration system, with the flow rate through the membranes such as to ensure turbulent flow. The product obtained is permeate containing lactic acid, other organic acids (in the form of salts), inorganic salts and other low molecular weight compounds. The retentate that remains as waste is 5-10% of the feed volume. The electrodialysis base stream is added at this point as an additional stream. Electrodialysis consists in splitting salts, producing a solution of acid(s) and a stream containing alkali solutions, mainly NaOH. The waste product is the exhausted solution, which theoretically should not contain any ions. This allows the pH to be increased and the streams to be washed.

[0112] The obtained lactic acid is characterized by:

[0113] • lactic acid: >60% w / w

[0114] • other carboxylic acids: <10% w / w

[0115] • pH: <2 / 25°C

[0116] • water content: <30% w / w

[0117] The resulting solution should be stored in barrels with a capacity of, for example, 25 litres in a refrigerated warehouse.

[0118] Suggested equipment:

[0119] Filtration system - a solution enabling efficient and effective phase separation. Various driving forces are permitted, i.e. pressure or vacuum filtration.

[0120] Process bioreactor (large) - equipped with a stirrer, pH and temperature control system. The system must have an appropriate sterilization mechanism.

[0121] Membrane process cascade - used for the final purification of the post-culture fluid. The first step is microfiltration, then ultrafiltration, and finally electrodialysis.

[0122] Lactic acid purification installation - used to purify the final product, lactic acid, after the electrodialysis process.

[0123] The diagram of the part of the installation where the lactic acid fermentation stage is carried out is shown in Fig. 10.

[0124] A diagram of a part of the installation in which the microfiltration, ultrafiltration and electrodialysis processes are carried out is shown in Fig. 11.

Claims

Claims1. A comprehensive method for processing coffee grounds in a single process comprising the step of obtaining coffee oil by extraction with an organic solvent, characterized in that: a) coffee grounds are dried to an average moisture content of no more than 5% w / w, optionally sieved; b) dried coffee grounds are subjected to an extraction process using an organic solvent from the alkane group, preferably hexane, used in a ratio of 1:2-1:8 w / v (coffee grounds / solvent), at the boiling point of the solvent, then the entire volume of the suspension is filtered, the filtered grounds are dried, and the solvent is distilled off from the filtrate containing the solvent and coffee oil, and the coffee oil is removed as a product; c) the dried coffee grounds from step b) are subjected to an extraction process with an aqueous ethanol solution with a concentration in the range of 30-60%, preferably 40- 50% v / v, or with water, in a ratio of 1:5-1:20 w / v, preferably 1:8-1:12 w / v (grounds / aqueous ethanol solution or water), at a temperature of 20-80°C, preferably 20-40°C, the entire volume of the suspension is then filtered, filtered grounds are dried and the filtrate containing ethanol solution or water and dissolved antioxidants is subjected to a reverse osmosis process to obtain a concentrated solution containing antioxidants (retentate), and then the concentrated solution is subjected to a freeze- drying or spray-drying process to obtain solid antioxidants; d) the dried coffee grounds from step c) are hydrolysed in an aqueous solution of sulphuric acid, at a concentration of 1-10%, preferably 2-5% v / v, in a ratio of 1:2-1:15, preferably 1:5-1:10 w / v (grounds / acid solution), at a temperature of 60-100°C, for 3-5 hours, and then the entire volume of the suspension is filtered, the filtered grounds are dried, and calcium carbonate is added to the filtrate or other neutralizing agent to obtain a solution pH in the range of 5.0-5.5 / 25°C, and the resulting calcium sulphate precipitate is filtered off and dried; e) the dried coffee grounds from step (d) are treated with an aqueous solution of sulphuric acid, at a concentration of 5-30%, preferably 15% v / v, and heated at 50-100°C for 2-6 h, and then the entire volume of the suspension is filtered, and the precipitate containing the lignin is washed with an aqueous solution of alkali metal carbonate or alkali metal bicarbonate or alkali metal hydroxide or water and dried; f) optionally, to the filtrate from step d) at a temperature of 40-60°C an enzyme solution is added, which is a mixture of cellulases, hemicellulases and p-galactosidases, the enzyme addition being 4-24%o relative to the amount of coffee grounds used in step d),the solution is maintained at a temperature of 40-60°C for 12-72 h, and then the entire volume of suspension is filtered; g) whey permeate in the amount of 0.5-5.0% w / v and yeast extract in the amount of 0.2- 2.0% w / v are added to the filtrate from step e) or from step f); the whole mixture is sterilized, inoculated with lactic acid bacteria in the amount of 1-10% v / v relative to the volume of the hydrolysate and lactic acid production is carried out at a temperature of 25-37°C for 12-72 hours, maintaining the pH value in the range of 5.5-6.5, and then the post-culture suspension is purified and concentrated by filtration or centrifugation of the biomass, and then in a cascade of membrane processes consisting of microfiltration, ultrafiltration and electrodialysis.

2. Method according to claim 1, characterized in that in step a) the grounds are sieved through a sieve with a mesh diameter of 600-800 pm.

3. Method according to claim 1, characterized in that in step b) the extraction is carried out for at least 30 minutes.

4. Method according to claim 1, characterized in that the permeate from step (c), after determining the water and ethanol content, is returned and used for re-extraction.

5. Method according to claim 1, characterized in that ethanol is evaporated from the retentate of step (c), which can also be recycled.

6. Method according to claim 1, characterized in that in step d) an anti-foaming agent or whitewash is added.

7. Method according to claim 1, characterized in that during the microfiltration step, particles exceeding 10-15 pm in size or 2-15 pm in size are separated from the culture fluid.

8. Method according to claim 1, characterized in that in the ultrafiltration stage particles larger than the cut-off point of the ultrafiltration membrane are removed, the process being carried out in a cross-flow filtration system with a flow rate through the membranes such as to ensure turbulent flow.

9. Method according to claim 1, characterized in that all grounds drying processes are carried out under reduced pressure.

10. Method according to claim 1, characterized in that at any stage the last filtrate or washings are returned to the reactor to wash the residue.

11. Method according to claim 1, characterized in that each filtration is carried out under reduced or increased pressure.

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