Patent Publication Number: US-2022220411-A1

Title: Method of extracting polyhydroxylated fatty alcohols using supercritical co2

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to a method of extracting Polyhydroxylated Fatty Alcohols. More particularly, the present invention relates to a method of extracting Polyhydroxylated Fatty Alcohols using supercritical CO 2 . 
     BACKGROUND OF THE INVENTION 
     Polyhydroxylated Fatty Alcohols have known cosmetic and pharmaceutical benefits, for example, a significant increase in the inhibition of T-cell proliferation which may be highly helpful when treating inflammations and various pathogenic conditions, such as atopic dermatitis, contact dermatitis, rheumatoid arthritis etc. Polyhydroxylated fatty alcohols (PFA) are crystalline lipophilic molecules. PFA molecules have a long aliphatic (mostly C17) chain with one end unsaturated with a double or triple (acetylenic) bond, and the other end having three hydroxyl groups. Some of the PFA molecules are polar and the other are non-polar molecules. The polarity of the different types of PFA molecules depends on the presence of hydroxyl groups, double or triple bonds or other polar groups in the molecule. Therefore, since all known solvents are either polar (e.g., suitable for extracting polar extracts) or non-polar (e.g., suitable for extracting non-polar extracts) it is almost impossible to extract all PFA molecules using the same solvent. 
     Some types of PFA can be extracted form Avocado seeds, using organic solvents, for example, methanol, alkyl acetates (e.g., butyl acetate) and the like. These organic solvents are toxic and environmentally unfriendly. Therefore, any cosmetic and pharmaceutical product that includes PFA extracted using an organic solvent must be cleaned from any residual solvent. 
     There are three solvents that are considered toxin-free (e.g, non-toxic), water, ethanol and supercritical CO 2 . Water and ethanol are polar solvents not suitable for extractions of oils and the non-polar PFA molecules. Supercritical CO 2  is intrinsically non-polar, and it is suitable solvent for extraction of non-polar compounds, such as, oil and some low molecular weight, volatile, polar compounds. However, it is less effective in the extraction of polar phytochemicals embedded in the cell wall, such as polar PFA molecules. 
     Furthermore, even for non-polar extracts such as oils from cursed seeds, the known practice in the field includes the addition of 7-15 wt.% of organic cosolvent, to the supercritical CO 2 . Such an addition is known to be essential for extraction of oils from crushed seeds. Therefore, in all known commercial lines a cosolvent tank is included in the line for adding cosolvent to the supercritical CO 2 . The added cosolvents may enhance the solvation power of supercritical CO 2  and improve the recovery of bioactive compounds (e.g., the diffusion of the bioactive compounds via the cells wall). This process is used for extraction of oils from crushed seeds, such as, lemon, mandarin, orange, watermelon, Cucurbita pepo, tomato and the like. The organic cosolvent, although in smaller amounts than in methods based solely on the organic cosolvent, still needs to be removed and recycled and can make the extracted oil contaminated with residual cosolvent. Any process that uses such cosolvents cannot be regarded as 100% environmentally friendly or non-toxic. 
     Accordingly, there is a great benefit in having a non-toxic process for extracting all molecules of PFA from avocado seeds using a single solvent. 
     SUMMARY OF THE INVENTION 
     Some aspect of the invention may be directed to a method of extracting Polyhydroxylated Fatty Alcohols. Embodiments of the method may include: inserting crushed avocado seeds to one or more extraction chambers; flowing supercritical CO 2  fluid through the crushed avocado seeds in one or more extraction chambers; and separating from the supercritical CO 2  flown through the crushed avocado seeds the Polyhydroxylated Fatty Alcohols extracted and dissolved in the supercritical CO 2 . In some embodiments, the supercritical CO 2  fluid being the only solvent used for dissolving and extracting the Polyhydroxylated Fatty Alcohols. 
     In some embodiments, the method may further include drying the crushed avocado seeds to a humidity level of at most 20 wt.%. In some embodiments, the crushed avocado seeds may have a particle size of at most 2 mm. In some embodiments, the supercritical CO 2  fluid may have a temperature range of 30° C. to 80° C. In some embodiments, the supercritical CO 2  fluid has pressure range of 100 bar to 200 bar. 
     In some embodiments, flowing the supercritical CO 2 fluid may include: obtaining liquidized CO 2 ; increasing the pressure of the liquidized CO 2  to reach a required supercritical pressure; heating the pressurized liquid CO 2  to reach a required supercritical temperature; and inserting the supercritical CO 2  fluid to the one or more extraction chambers. 
     In some embodiments, separating the Polyhydroxylated Fatty Alcohols may include: introducing the supercritical CO 2  flown through the crushed avocado seeds into a separator having two or more separation stages. In some embodiments, for every kilogram (kg) of crushed avocado seeds at least 1 gram (gr) of Polyhydroxylated Fatty Alcohols is extracted and collected. In some embodiments, a time of production of at least lgr of the Polyhydroxylated Fatty Alcohols from 1 kg of crushed avocado seeds is at most 5 hours 
     In some embodiments, the method may further include collecting the CO 2  separated from the Polyhydroxylated Fatty Alcohols; and recycling the collected CO 2 . 
     Some aspects of the invention may be directed to a non-toxic Polyhydroxylated Fatty Alcohols extract comprising less than 0.5 ppm cosolvent. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which: 
         FIG. 1  is an illusration of an extraction system according to some embodiments of the invention; and 
         FIG. 2  is a flowchart of a method of extracting PFA using supercritical CO 2  according to some embodiments of the invention. 
     
    
    
     It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. 
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components, modules, units and/or circuits have not been described in detail so as not to obscure the invention. Some features or elements described with respect to one embodiment may be combined with features or elements described with respect to other embodiments. For the sake of clarity, discussion of same or similar features or elements may not be repeated. 
     Although embodiments of the invention are not limited in this regard, discussions utilizing terms such as, for example, “processing”, “computing”, “calculating”, “determining”, “establishing”, “analyzing”, “checking”, or the like, may refer to operation(s) and/or process(es) of a computer, a computing platform, a computing system, or other electronic computing device, that manipulates and/or transforms data represented as physical (e.g., electronic) quantities within the computer&#39;s registers and/or memories into other data similarly represented as physical quantities within the computer&#39;s registers and/or memories or other information non-transitory storage medium that may store instructions to perform operations and/or processes. Although embodiments of the invention are not limited in this regard, the terms “plurality” and “a plurality” as used herein may include, for example, “multiple” or “two or more”. The terms “plurality” or “a plurality” may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. The term set when used herein may include one or more items. Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed simultaneously, at the same point in time, or concurrently. 
     Aspects of the invention may be directed to a method of extracting all molecules of PFA, both the polar and non-polar molecules, using supercritical CO 2  without any additional cosolvent. Although, prior art extraction method of oils from seeds using supercritical CO 2  requires the addition of 7-15wt.% of cosolvent, the applicant has surprisingly found that such an addition is not required when extracting PFA using supercritical CO 2  from avocado seeds, while maintaining or even increasing the required production yield. Furthermore, although supercritical CO 2  is known to be non-polar solvent, a method of extraction according to embodiments of the invention resulted in the extraction of both the polar and non-polar PFA molecules. Therefore, unlike the prior art methods, a method and an extract according to some embodiments of the invention may be completely non-toxic, or cosolvent free. A method according to embodiments of the invention may be executed by any known supercritical CO 2  extraction system, for example, the system illustrated in  FIG. 1 . 
     Referring now to  FIG. 1  which is an illusration of an extraction system  100  according to some embodiments of the invention. System  100  may include an extraction unit  110  and a separation unit  120 . Extraction unit  110  may include: a CO 2  reservoir  112  configured to hold CO 2 , a condenser  113  configured to condense and liquidize the CO 2 , a pump  114  (e.g., a dual piston pump) for increasing the extraction pressure of the CO 2  and a heater  115  for heating the pressurized CO 2  to supercritical conditions. Accordingly, the CO 2  leaving heater  115  is a supercritical CO 2  fluid. As used herein, supercritical CO 2  fluid may refer to a CO 2  fluid that may have a density of liquid CO 2 (e.g., 600-1600 kg/m 3 ) and a dissolving power (solubility) of CO 2  gas. In some embodiments, supercritical CO 2  fluid may have a temperature range of 30° C. to 80° C. In some embodiments, supercritical CO 2  fluid may have pressure range of 100 bar to 400 bar, for example, 100 bar to 200 bar. 
     In some embodiments, the supercritical CO 2  fluid is introduced into one or more extraction chambers  116  included in extraction unit  110 . One or more extraction chambers  116  may be preloaded with crushed seeds, for example, crushed avocado seeds. The supercritical CO 2  fluid is flown through the crushed seeds in at least one of one or more extraction chambers  116 . In some embodiments, PFA may be dissolved from the crushed seeds into the supercritical CO 2  fluid to form a supercritical CO 2  solution. In some embodiments, other materials may also be extracted from the crushed avocado seeds in the process, for example, tocopherols, carotenoids, unsaturated fatty acids, etc. It should be appreciated by those skilled in the art that a cosolvent reservoir is not required in systems according to embodiments of the present invention. 
     In some embodiments, the supercritical CO 2  solution that includes the extracted PFA may be introduced into separation unit  120  to be separated. Separation unit  120  may include one or more separators  122  each being in fluid connection to one or more tanks  124 . In some embodiments, separation unit  120  may further include one or more filters and one or more containers (not illustrated) for collecting the separated PFA. In some embodiments, separators  122  may each include a tank at which the supercritical CO 2  solution may be depressurized using aback-pressure regulator and maintained in a desired temperature (e.g., 30-60° C.) until the CO 2  may gradually be converted into gas. In some embodiments, in order to avoid pressure and temperature changes the processes may be carried out is several stages in two or more separators  122 . The evaporated CO 2  may be recycled and condensed back into a liquid CO 2 . 
     It should be understood by one skilled in the art that the invention is not limited to system  100  disclosed herein and illustrated in  FIG. 1 , which is given as an example only. 
     Reference is made to  FIG. 2  which is a flowchart of a method of extracting PFA according to some embodiments of the invention. In step  210 , crushed avocado seeds may be introduced to one or more extraction chambers (e.g., one or more chambers  116 ). In some embodiments, the avocado seeds may be crushed using any known method, for example, grinding, milling, etc. In some embodiments, the crushed avocado seeds may have a particle size (e.g., average diameter) of at most, 2 mm, 1 mm, 500 μm, 150 μm or less. In some embodiments, the smaller the particle size the higher is the specific surface area exposed to the supercritical CO 2  fluid, therefore the higher is the extraction rate of the PFA from each particle. Therefore, the smaller the particle size the higher is the yield of the extraction process. 
     Undried raw avocado seeds may be crushed at room temperature. In some embodiments, the crushed seeds may be dried such that the crushed seeds may have a humidity level of at most 20 wt.%, for example, at most 18 wt.%, at most 15 wt.% at most 12 wt.% or lower. PFA are insoluble in water therefore the presence of water is an impediment to the diffusion of the PFA into the supercritical CO 2  fluid. Furthremore, it is easier to recycle the CO 2  if it does not contain water. 
     In some embodiments, the crushed seeds may be incubated for at least 24 hours, for example, about 48 hours, at a temperature range of 15-45 ° C. 
     In step  220 , supercritical CO 2  fluid may be flown through the crushed avocado seeds in at least one of the one or more extraction chambers (e.g., chambers  116 ). The supercritical CO 2  fluid may be obtained by pressurizing and heating CO 2  into supercritical conditions as disclosed hereinabove with respect to  FIG. 1 . Some embodiments of the invention may include: obtaining liquidized CO 2 , increasing the pressure of the liquidized CO 2  to reach a required supercritical pressure and heating the pressurized liquid CO 2  to reach a required supercritical temperature; and inserting the supercritical CO 2  fluid to at least one extraction chambers. 
     In some embodiments, the supercritical CO 2 fluid may have a density of liquid CO 2 and a dissolving power (solubility) of the PFA in the supercritical CO 2 gas. In some embodiments, the supercritical CO 2 fluid may have a temperature range of 30° C. to 80° C. In some embodiments, the supercritical CO 2 fluid has pressure range of 100 bar to 400 bar, for example, 200 bar. 
     In some embodiments, as the supercritical CO 2 fluid is flowing and wetting the crushed avocado seeds, PFA may be extracted from the surface area of the crushed avocado seed particles. The PFA may be dissolved into the supercritical CO 2 fluid. In some embodiments, the PFA dissolved into the supercritical CO 2 fluid may include both polar and non-polar PFA molecules. 
     In step  230 , PFA extracted and dissolved in the supercritical CO 2 may be separated from the supercritical CO 2 flown through the crushed avocado seeds. In some embodiments, PFA from within the avocado seed cells may diffuse from the cells and dissolve in the supercritical CO 2 . In some embodiments, the supercritical CO 2 fluid may be the only solvent used for dissolving and extracting the PFA. 
     In some embodiments, the extracted PFA may be non-toxic and/or cosolvent free extracted PFA including both polar and non-polar PFA molecules. As used herein, the term non-toxic refers to cosolvent amounts which are lower than the required standard (e.g., lower than 20 ppm) or the lowest detection limit, for example, lower than 0.5 ppm, lower than 0.1 ppm or lower than 0.06 ppm measured, for example, using Headspace Gas Chromatograph (HSGC). In some embodiments, the lowest detection limit may depend form the type of product material (oil, paste, solid, solution, etc.), the type of the toxic cosolvent and the like. 
     In some embodiments, for every kg of crushed avocado seeds at least 1-gram, for example, at least 1.4-gram, 1.5-gram, 2-gram, 3-gram or more. of the PFA may be extracted and collected. In some embodiments, a time of production of at least 1 gram of the PFA from 1 kg of crushed avocado seeds may be at most 5 hours. 
     Experimental results 
     Three batches of 2-4.5 kg of crushed avocado seeds were inserted into extraction chambers, such as chambers  116 . Each batch was exposed to 8 kg of flowing supercritical CO 2  fluid having pressure of: 100, 350 and 450 bar at 45° C. No additional cosolvent was used in the process. The flowing rate of the supercritical CO 2  fluid was 21-25 kg/hour. Table 1 summarized the results of obtained PFA. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Batch No. 
                   
                 1 
                   
                 2 
                 3 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 Avocado species 
                 Reed 
                 Hass 
                 Pinkerton 
               
               
                   
                 Weight of crushed 
                 2.02 
                 4.5 
                 3.2 
               
               
                   
                 seeds [Kg] 
               
               
                   
                 Moisture content 
                 8-12% 
                 8-12% 
                 8-12% 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Total production time 
                 4 
                 h 
                 4 
                 h 
                 4 h 35 min 
               
               
                   
                 Total quantity of PFA 
                 26.0 
                 gr 
                 65.1 
                 gr 
                 53.0 gr 
               
               
                   
                 extraction ** 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Total Production Yield 
                 1.3% 
                 1.4% 
                 1.7% 
               
               
                   
                 (%, dry weight) 
               
               
                   
                   
               
               
                   
                 ** PFA extraction may include PFA (e.g., 10-40 wt. %) and other additives, such as, tocopherols, carotenoids and unsaturated fatty acids. The PFA included both polar and non-polar PFA molecules. 
               
            
           
         
       
     
     As known in the art the typical production yield of solvents (e.g., ethyl acetate, hexane, etc.) based extraction process is 0.6-0.8%. As clearly shown in Table 1 above, a process according to embodiments of the invention may result in a higher production yield without the use of any cosolvent. 
     Using the same raw material as in the previous experiments, additional five batches of 10-15 kg and 2 batches of 87-92 kg of crushed avocado seeds were inserted into extraction chambers, such as chambers 116. Small scale batches were exposed to 115-430 kg of flowing supercritical CO 2 fluid and Large-scale batches were exposed to 1,350 kg of flowing supercritical CO 2 fluid, having pressure of: 100, 120, 160 and optionally also 280 bar at 45° C. No additional cosolvent was used in the process. The flowing rate of the supercritical CO 2  fluid was 30-67 kg/hour for small scale batches and 430 kg/hour for large-scale batches. Table 2 summarized the results of obtained PFA. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Batch No. 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
               
               
                   
               
             
            
               
                 Avocado species 
                 Reed 
                 Reed 
                 Reed 
                 Reed 
                 Reed 
                 Reed 
                 Hass 
               
               
                 Weight of crushed 
                 15.0       
                 13.5       
                 13.5       
                 13.5       
                 10.0       
                 87.7       
                 91.5  
               
               
                 seeds [Kg] 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Extraction Pressure 
                 100 bar 
                 280 bar* 
                 100 bar 
                 120 bar 
                 160 bar 
                 120 
                 bar 
                 160 
                 bar 
                 120 
                 bar 
                 160 
                 bar 
                 160 bar 
               
               
                 (bar) 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Total quantity of 
                 320 g 
                 295 g*** 
                 227 
                 g 
                 310 
                 g 
                 142 
                 g 
                 2.09 
                 kg 
                 2.12 
               
               
                 PFA extraction ** 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Total Production 
                 2.1% 
                 2.2% 
                 1.7% 
                 2.3% 
                 1.4% 
                 2.4% 
                  2.3% 
               
               
                 Yield (%, dry weight) 
               
               
                   
               
               
                 *A larger number of undesirable compounds were extracted at this stage using pressure of 280 bar 
               
               
                 ** PFA extraction may include PFA (e.g., 10-40 wt. %) and other additives, such as, sterols, tocopherols, carotenoids and unsaturated fatty acids. The PFA included both polar and non-polar PFA molecules. 
               
               
                 ***The highest percent of PFA in the extract obtained at the higher pressure. 
               
            
           
         
       
     
     As shows in table 2, as pressure increases the yield increases and the selectivity decreases, accordingly, more compounds are extracted which lead to a change in the appearance and odor of the whole extract. Batches that were extracted above 200 bar appear as dark green extract with an unpleasant odor and larger number of undesirable compounds (such as pigments). Higher pressure during extraction enable producing in higher yields. 
     Therefore, process according to embodiments of the invention is toxin-free (e.g., non-toxic) and may provide a high quality PFA, free of any possible residual toxic solvents. 
     While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. 
     Various embodiments have been presented. Each of these embodiments may of course include features from other embodiments presented, and embodiments not specifically described may include various features described herein.