Recovery of beta glucans from industrial starch effluents through appropriate unit operations

Transcription

1 Recovery of beta glucans from industrial starch effluents through appropriate unit operations A.PATSIOURA, E.GRILLAKIS, V.GEKAS Department of Environmental Engineering, Technical University of Crete, Polytechnioupolis, Chania 73100, Crete, GREECE 1 vassilis.gekas@enveng.tuc.gr Abstract: Beta glucans (b-glucans) are polysaccharides based on the glucose monomer. This polysaccharide can be found in mushrooms, baker s yeast, oat milk (product from oats) and other sources. Medical- and nutritional uses of beta glucans make attractive their recovery from industrial effluents such as non dairy milk effluents. In this paper a process consisting af appropriate unit operations, such as microfiltration, evaporation and drying is proposed for beta glucans recovery from oat milk effluents and the results of a relevant simulation with the help of the Super Pro Designer software are shown. Keywords: b glucans, Super Pro Designer, Maltose Industry, Microfiltration, Recovery 1 Introduction The purpose of this paper is the simulation of b- glucans recovery from effluents from starch industries. B-glucans are polysaccharides made of glucose, with important pharmaceutical and other applications. The simulation of this procedure is provided using the software Super Pro Designer. An example of the above said starch industries are industries that manufacture non-dairy milk from starch hydrolysis towards maltose. Oat milk, for example, is a milk which contains low fat and is beneficial for the organism. Its basic advantage from the common milk, is that it contains maltose, instead of lactose, in which a certain individuals even populations are allergic. The maltose as a sugar, has shown better attributes than lactose. Glucans are polysaccharides that only contain glucose as structural components. Beta 1, 3-D glucans are chains of polysaccharides (complex glucose molecules), with the six-sided glucose rings connected at the 1 and 3 positions. Smaller side chains branch off the 1,3 polysaccharide backbone. The most active form of Beta 1, 3-D glucans are apparently those that contain 1,6 sidechains branching off from the longer beta-1,3 glucan backbone. The formula for this type of compound is beta-1,3/1,6 glucan. Some researchers have suggested that it is the frequency, location, and length of the side-chains rather than the backbone of beta glucans that determine their immune system activity. Another variable is the fact that some of these compounds exist as single strand chains, while the backbones of other beta-1,3 glucans exist as double or triple stranded helix chains. In some cases, proteins linked to the beta-1,3 glucan backbone may also be involved in providing therapeutic activity. Although these compounds have exciting potential for enhancement of the immune system, it must be emphasized that this research is in its infancy, and there are differing opinions on which molecular weight, shape, structure, and source of beta-1, 3 glucans provide the greatest therapeutic benefit. One of the most common sources of Beta 1, 3-D glucan is derived from the cell wall of baker s yeast (Saccharomyces cerevisiae). However, beta- 1,3 glucans are also extracted from the bran of 392 ISSN:

2 some grains such as oats and barley. The Beta 1, 3-D glucans from yeast are often insoluble whereas those extracted from grains tend to be soluble. Other sources include some types of seaweed, and various species of mushrooms such as Reishi, Shiitake, and Maitake. Beta 1, 3-D glucans are being referred to as biological response modifiers because of their ability to activate the immune system. However, it should be noted that the activity of Beta 1, 3-D glucan is different from agents that stimulate the immune system. Agents that stimulate the immune system can push the system to overstimulation, and hence are contraindicated in individuals with autoimmune diseases, allergies, or yeast infections. Beta 1, 3-D glucans seem to make the immune system work better without becoming overactive. They accomplish this by activating phagocytes, which are immune system cells whose function is to trap and destroy foreign substances in our bodies such as bacteria, viruses, fungi, and parasites. In addition to enhancing the activity of phagocytes, beta-1,3 glucans also reportedly lower elevated levels of LDL cholesterol, aid in wound healing, help prevent infections, enhance NK cell function, and help in the prevention and treatment of cancer. Materials come out separated from this unit procedure in 3 currents, depending on their mass density. Realistic removal percentages on that unit procedure is 90% of solids (included b-glucans) 10% of proteins and 10% of starch to the stream of solids. Finally it was supposed a removal of 90% of fat to the third stream designated oils in the figure above. The fats are removed, the final product of the aqueous phase is past in a heat exchanger where its temperature is decreased and becomes ready for bottling, while the solid fraction, containing the bigger portion of the b- glucans is subjected to the next treatment step of. This step is a microfiltration membrane unit operation(mf), followed after a mixing of solids with water. Solids are mixed with water in order to avoid concentration polarization and/or fouling problems on the MF membranes. Microfiltration was selected for two reasons, because a selective splitting of the mixing is desired and because the b-glucans are included to the range that MF can work properly (0,1µm - 3µm). 2. Composition In order to simulate the recommended process, the composition of the main entering stream must be provided to the software. A typical composition of this stream is 88% water, 5.5% maltose 2.2% starch, 1.5% proteins, 1.5% b-glucans, 0.8% fat and 0.5% ash. These ingredients are registered to the software manually or from the component list. A total mass inflow rate of 10000kg/h was selected for the simulation. 3. Unit Procedures Below, it is described the sequence of unit procedures that were used, as well as the reason for which they were selected inter alia. The first stage of treatment was an initial separation of the solids and the fats from the milk in a horizontal centrifuge (decanter): In that procedure, a 90% removal of beta glucans is supposed to the concentrate current. Microfiltration splits the incoming current in two. The filtrate contains maltose and can be added to the main stream of the purified aqueous phase after the decanter (i.e. the maltose stream). The concentrate is enriched in b-glucans and it is further treated in an evaporator. Evaporator is used to increase the concentration of the b- glucans, by removing 90% of the water on an evaporator tower. 393 ISSN:

3 Evaporator splits the input current into two new currents, one with the dense mixture of water and b-glucans and one with the removed water. For further condensation of the mixture, the current which includes b-glucans is directed to a final treatment stage of a spray drier. On that unit procedure there are two input streams and two output stream. The first input stream is the feed and the second is an air stream. Air stream is used for drying. There are two output streams, one for the final product and one for the air outlet. The above stages of treatment lead to a pure final product with high percentage of b- glucans. Below diagram presents the total plant and all input and output streams. Figure 1: Recommended Treatment for b-glucan recovery (The S-107 and S-102 streams should be merged) Recovery factor (RF) of a component is the relation between its quantity in the product and in the initial input stream respectively. RF = (Recovery Flowrate) / (Initial Flowrate). Applying the above relation, the result is 64.28%.. 4. Results of the simulation An overview table (Table 3 below) is provided for the concentration of water, beta glucans and the rest of the ingredients throughout the process with respect to the of b-glucan recovery (red line in Figure 1): 394 ISSN:

4 Ingredients Stream Decant er Mixi ng Microf iltratio n Evapo rator Spray Dryer Water Input (%) 88,00 79,7 7 91,17 78,76 27,00 Output (%) 79,77 91,1 7 78,76 27,00 6,90 11,6 Input (%) 1,50 Beta glucans 0 5,07 17,99 61,79 Output (%) 11,60 5,07 17,99 61,79 78,84 Rest Input (%) 10,50 8,63 3,76 3,25 11,21 ingredients Output (%) 8,63 3,76 3,25 11,21 14,26 heavy phase of the evaporator is at a Table 3: Concentrations of each ingredient for every stage of the b-glucan recovery treatment concentration of 27%. Last in the spray drier, the final concentration of water becomes only 6,9%. Mass balances of the beta glucans : In the entering current, the b-glucans constitute a very small percentage of milk (1.5%). After the treatment in the decanter, the concentration of b- glucans in the solid phase reaches 11,6%. Afterwards, because of mixing with water, the concentration of b-glucans falls to 5,1%. From this stage and on, their concentration increases. In the retentate s exit of microfiltration, the concentration reaches 18%. At the outflow of the two last processes, evaporation and spray drying, the percentage of beta glucans is 61,8% and 78,8% respectively. Maltose: The maltose concentration in the combined streams streams S-107 and S-113 are in Figure 2: Percentages of components throughout the plant. the range of typical values for this kind of products. ( other is the lower MW constituents such as maltose) 5. Conclusions An analysis is provided for the recovery stream through all processes (red stream in fig 1). Followinhg the water balance: The water starts with a initial concentration 88% in the input current. After it enters in decanter, it comes out with concentration 79,8%. Next step is the mixing with clean water, from where the stream comes out with concentration 91,2% in water. Microfiltration is the next process applied. The output stream has a water concentration 78,8%. The next step is evaporation, where the mixture is further concentrated. The water in the exit of the A process is recommended to be applied on crude (i.e. prior the decanter step) oat milk in order to recover the major part of the contained the b- glucans. The sequence of the unit operations are horizontal centrifugation, microfiltration, evaporation and spray drying. The process was simulated by using Super Pro Designer Software. The simulation results show that a final mixture of 6.9% water 78.84% beta glucans and 14.26% rest ingredients (ash, fat, starch and maltose) can be accomplished. The benefit is twofold. Apart from the high value b-glucan by-product the environmental performance of the oat milk 395 ISSN:

5 producing industry is improved in an optimized way. 6. Acknowledgments The authors are thankful to Environmental MSc s Simantiraki Fotini and Tsitsilonis Sotiris for their help in simulation. WE are grateful also to the Intelligen Inc for the academic version of Super Pro Designer software that they have provided us. References [1] Ajithkumar A., Andersson R., Aman P., Content and molecular weight of extractable beta-glucan in American and Swedish oat samples,j Agric Food Chem Feb 23;53(4): [2]Belitz H.D., Grosch W., Schieberle P., Burghagen M.M., Food Chemistry, Third Edition, [3]Estrada A., Yun C.H., Van Kessel A., Li B.,HautaS., Laarveld B., Immunomodulatory activities of oat beta-glucan in vitro and in vivo Microbiol Immunol. 1997;41(12): [4]Bell S., Goldman V.M., Bistrian B.R., Arnold A.H., Ostroff G., Forse R.A., Effect of betaglucan from oats and yeast on serum lipids, Crit Rev Food Sci Nutr March;39(2): Review [5]Lovgren E., Master Thesis, Production of oat milk from whole oat kernels, Lund University, 2000, Sweden. [6]Poppitt S.D., Soluble fibre oat and barley betaglucan enriched products: can we predict cholesterol-lowering effects?, Br J Nutr Jun;97(6): [7]Risveden K., Master Thesis, Screening studies of b-glucan concentrations appearance of exopolysaccharides and probiotics, Lund University, 2002, Sweden. [8]Super pro Designer help manual,version ISSN: