Various amino acids have utility as food additives and in medical applications.
ID: 1034120 • Letter: V
Question
Various amino acids have utility as food additives and in medical applications. They are often synthesized by fermentation using a specific microorganism to convert a substrate (ie a sugar) into the desired product. Small quantities of other species also may be formed and msut be removed to meet product specifications. For example, isoluencine (Ile), which has a molecular weight of 131.2, is an essential amino acid produced by fermentation, and other amino acids such as leucine and valine also are found in the fermentation broth. The broth is subjected to several processing steps to remove these and other impurities, but final processing by crystallization is required to meet stringent specifications on purity. The strategy is to crysstallize the hyddrated acid form of Ile (Ile.HCl.H2O), whose crystals exclude other amino acids, and then to redissolve, neutralize, and crystallize the final Ile product.
In a batch process designed to manufacture 2500kg of Ile per batch, an aqueous feed solution containing 35g Ile/dL and much lower concentrations of leucine and valine is fed to the final purification stages. The pH of the solution is 1.1 and its specific gravity is 1.02. The solution is heated to 60 degrees Celsius and 35-wt% HCl solution is added in a ratio of 0.4kg per kg of feed. The addition of HCl causes the formation of crystals of Ile.HCl.H2O, and the production of these crystals is further increased by slowly lowering the temperature ot 20 degrees Celsius. At the final crystallizer conditions the Ile solutbility is 5g Ile/100 g solution. The resulting slurry is sent to a centrifuge where the crystals are seperated from the liquid solution and the crystal cake is washed with water. The solids leaving the centrifuge contain 12% free water (ie not part of the crystal structure) and 88% pure crystals of Ile.HCl.H2O.
The washed crystals are redissolved in water to from a solution that is 4.0g Ile/dL with a specific gravity of 1.1. The solution is sent to an ion exhcnage unit where HCl is removed. Upon leaving the lion exhcange unit the solution has a pH of about 5.5. it is sent ot a second crystallizer where the temperature is gradually reduced to 10 degrees Celsisu and the Ile solubility is 3.4 g Ile/ 100 g H2O. The crystals are separated from the slurry by centrifugation, washed with pure water, and sent to a dryer for final processing.
(A) Construct a labeled flowchart for the process
(B) Choosing a basis of 1kg of feed solution, estimate (i) the mass of HCl solution added ot the system, (ii) the water added to redissolve the Ile.HCl.H2O crystals, (iii) the mass of HCl removed in the ion exchange unit, and (iv) the mass of final Ile product.
(C) Scale the quantities calcuated in Part (B) to production rate of 2500 kg Ile/batch.
(D) Estimate the active volume (in liters) of each of the crystallizers.
Explanation / Answer
Various amino acids are synthesized by fermentation using microorganism to convert subtrate into required product. Additional species may also be produced like isoluencine, others like leucine valine are also formed in the fermentation broth. Processing to remove impurities and final processing by crystallization to meet purity requirements. Crystallization, redissolution, neutralization and crystallization again of hydrated acid. To prepare 2500kg ,a feed solution of 35g lle/dL is fed to purification step. Solution is heated to 60 degree while maintainy pH and specific gravity. Addition of 35-wt% of HCL. Resulting slurry is sent to centrifuge where separation of crystals occur. crystals are washed with water. Washed crystals are redissolved in water, the solution is sent to ion exchange unit to remove HCL. The crytals are sent to second crystallizers where desired conditions are maintained ,centrifugation again and finally crytals are washed with pure water and sent to dryer.
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