GB694795A - Improvements in or relating to a process of treating steep liquor and the product resulting therefrom - Google Patents

Abstract

A process of treating corn steep liquor or sorghum grain steep liquor comprises incubating the steep liquor to form lactic acid therein, adding sulphuric acid to decrease the pH to a value not exceeding 2.0, removing the lactic acid, adding an alkaline earth metal hydroxide to adjust the pH to about 5.5 to 7.5, autoclaving the entire mixture at about 10 to 20 pounds per square inch steam pressure, separating the liquid and solid phases and drying the liquid phase. Either light steep liquor, i.e. that drawn directly from the steeps, or heavy steep liquor, i.e. that concentrated to about 30 DEG B<\>e, is satisfactory. The lactic acid may be removed by extraction with butanol or any alcohol selected from butyl, amyl or hexyl alcohols, thus butanol may be added to the acidified steep liquor and the mixture agitated to extract the lactic acid or the extraction may be effected in continuous countercurrent manner. The extracting alcohol may be anhydrous or water-laden. The extract containing the lactic acid is then separated and treated to convert the lactic acid therein to the ester, e.g. by concentrating under vacuum and then refluxing, or by evaporating at atmospheric pressure until essentially all of the water is removed and then either evaporating or refluxing at atmospheric pressure to complete the esterification. The esterified liquor is then cooled and the pH adjusted to 4.5 to 6.0 to prevent hydrolysis and steam is then passed through rapidly until the distillate layer no longer separates into two phases; the lactic acid ester is recovered from the upper layer of the distillate by fractional distillation. The acidified steep liquor is then treated for the recovery of a nutrient for micro-organisms by first removing residual extract by means of steam and then adding an alkaline earth metal hydroxide, especially calcium hydroxide, to adjust the pH to 5.5 to 7.5 and the material is then autoclaved as with steam as described above. The autoclaved material is then filtered, e.g. by centrifugation, preferably at 80-90 DEG C., and the cake obtained consisting mainly of calcium phytate and calcium sulphate is washed with water and the centrifugates combined and spray dried to yield a nutrient soluble in water and containing nitrogeneous materials, together with inorganic material and small amounts of carbohydrates and salts of lactic acid. The filter cake containing calcium phytate and calcium sulphate is then treated for recovery of purified calcium phytate by dissolving the latter in hydrochloric acid at a pH of about 1.0 to 2.0 and filtering or centrifuging the suspension to leave the undissolved calcium sulphate as filter cake. The filtrate is then treated with calcium hydroxide suspension to adjust the pH to 5.0 to 5.5 so as to precipitate the calcium phytate which is then separated and dried. An example is given in which corn steep liquor is employed as starting material, and butanol is used as the lactic acid extractant, butyl lactate, calcium phytate and nutrient material being recovered as above.ALSO:Nitrogenous materials useful as nutrients for certain micro organisms are recovered from corn steep liquor or sorghum grain steep liquor by incubating the steep liquor to form lactic acid therein, adding sulphuric acid to decrease the pH to a value not exceeding 2.0, removing the lactic acid, adding an alkaline earth metal hydroxide to adjust the pH to about 5.5 to 7.5, autoclaving the entire mixture at about 10 to 20 pounds per square inch steam pressure, separating the liquid and solid phases and drying the liquid phase. Either light steep liquor, i.e. that drawn directly from the steeps, or heavy steep liquor, i.e. that concentrated to about 30 DEG B<\>ae. is satisfactory. The lactic acid may be removed by extraction with an alcohol selected from butyl, amyl, or hexyl alcohols; thus butanol may be added to the acidified steep liquor and the mixture agitated to extract the lactic acid. The extraction may also be effected in continuous countercurrent manner. The extracting alcohol may be anhydrous or water-laden. The acidified steep liquor is then treated for the recovery of the nutrient material by first removing any residual extractant by passing steam through the liquor, adding an alkaline earth metal hydroxide especially calcium hydroxide to adjust the pH to 5.5 to 7.5 and then autoclaving the entire mixture with steam as described above. The autoclaved material is then filtered, e.g. by centrifugation, preferably at 80-90 DEG C., and the cake obtained is washed with water and the centrifugates washed and spray dried to yield the nutrient material which is soluble in water and contains nitrogenous materials together with inorganic material and small amounts of carbohydrates and salts of lactic acid. An example is given in which nutrient material is recovered from corn steep liquor, butanol being employed as the lactic acid extractant and calcium hydroxide as the alkaline earth metal hydroxide.