Patent GB-689412-A (GB)
Title: Fermentation of wood pulp waste liquor to produce aliphatic carboxylic acids
IPC: C12P7/52
Filed: 1950-12-15
Abstract: Propionic acid is made from wood pulp waste liquor by fermentation with bacteria of the genus Propionibacterium. Smaller quantities of other acids, e.g. acetic and butyric acid may also be formed. Sulphite waste liquor should not contain free or loosely combined sulphur dioxide.  The latter may be removed by steam distillation or reduced pressure treatment or by precipitation as calcium sulphite after pH adjustment to about 8.5-9.5 with lime.  Lignin is also removed with the sulphite if the pH is adjusted to about 10-11. Before fermentation the pH may be adjusted to about 6.5-7.5.  Such adjustment also removes the sulphur dioxide as sulphites but preferably removal of this gas is effected in some other fashion. About 50 per cent of the water of the liquor may be removed before fermentation to give a total solids content of up to a maximum of about 20 per cent. Nutrients, e.g. growth factors such as yeast extract, tryptone and malt and barley sprouts may be added in amounts of about 0.2-1 per cent and nitrogen sources such as urea, ammonium sulphate and dibasic ammonium phosphate may be present in similar quantities. Other sugars, e.g. molasses, may be added to the liquor but the total sugars should not exceed about 10 per cent.  Molasses will also provide growth factors.  Bacteria specified are Propionibacterium shermani, thoenii, pentosaceum and arabinosum and Lactobacillus casei.  The temperature is preferably about 28-34 DEG C. and reaction is preferably effected continuously by passing the liquor through a series of vats containing the bacteria for a total fermentation time of about 3-4 days. Sulpaste waste liquor may also be used.  The propionic and other acids are preferably recovered by solvent extraction as in 689,411 by extracting in one or a plurality of stages with a mixture containing a trialkyl phosphate and a hydrophobic diluent which on distillation forms an azeotrope with water boiling below the boiling-point of the acids, separating the solvent phase, distilling off solvent and water azeotropically therefrom, adding an alkaline buffer to neutralize free sulphuric acid and distilling off the required acids, preferably under vacuum at below about 150 DEG  C.  In examples: (1) a calcium base sulphite waste liquor is steam stripped to remove SO2, concentrated to a solids of 20 per cent, and fermented for 16 days with Propionibacterium shermanii and Lactobacillus casei at pH 6.4-7.5 and at about 30 DEG  C. after the addition of urea and dried yeast extract; (2) a sulphate waste liquor is adjusted to pH 7.0 with CO2 and fermented for 12 days at about 30 DEG  C. and pH 6.5-7.5 with Propionibacterium arabinosum after the addition of dried yeast extract and dibasic ammonium phosphate; (3) the liquor of (1) is adjusted to pH 8.5-9.5 with lime, sulphites removed and fermented with Propionibacterium pentosaceum under conditions similar to (1); (4) the liquor of (1) is adjusted to pH 10-11 with lime, sulphites, sulphates and lignosulphonate removed, molasses added to the waste liquor to give a total sugars of 6 per cent, pH adjusted to 7 with CO2 and fermented for 12 days at about 30 DEG  C. and pH 6.5-7.5 with Propionibacterium arabinosum after the addition of dried yeast extract and dibasic ammonium phosphate; and in (5) the bacterium of (4) is established in three vessels and a steam-stripped calcium base sulphite liquor concentrated to a sugars of 4.0 per cent is adjusted to pH 6.5-7.0 and passed continuously through the vessels at about 30 DEG  C. so as to give a total retention time in the system of 3.2 days, the liquor being fortified with urea and yeast extract.  The acids are recovered in the examples by acidifying the liquor with sulphuric acid and extracting with a solvent for the acids.