The glycerol obtained from transesterification is separated from biodiesel by gravity. The concentration of this type of glycerol is ~50% (wt),which is so-called raw glycerol and contains the contaminants such as alcohol, soap, base catalyst, salts, and untreated organic materials.
Crude glycerol can be obtained through the following purification of raw glycerol:
Crude glycerol purification:
Microbial Conversion of Glycerol to 1,3-Propanediol: Physiological Comparison of a Natural Producer, Clostridium butyricum VPI 3266, and an Engineered Strain, Clostridium acetobutylicum DG1(pSPD5). Abstract: Clostridium acetobutylicum is not able to grow on glycerol as the sole carbon source since it cannot reoxidize the excess of NADH generated by glycerol catabolism. Nevertheless, when the pSPD5 plasmid, carrying the NADH-consuming 1,3-propanediol pathway from C. butyricum VPI 3266, was introduced into C. acetobutylicum DG1, growth on glycerol was achieved, and 1,3-propanediol was produced. In order to compare the physiological behavior of the recombinant C. acetobutylicum DG1(pSPD5) strain with that of the natural 1,3- propanediol producer C. butyricum VPI 3266, both strains were grown in chemostat cultures with glycerol as the sole carbon source. The same “global behavior” was observed for both strains: 1,3-propanediol was the main fermentation product, and the qH2 flux was very low. However, when looking at key intracellular enzyme evels, significant differences were observed. Firstly, the pathway for glycerol oxidation was different: C. butyricum uses a glycerol dehydrogenase and a dihydroxyacetone kinase, while C. acetobutylicum uses a glycerol kinase and a glycerol-3-phosphate dehydrogenase. Secondly, the electron flow is differentially regulated: (i) in C. butyricum VPI 3266, the in vitro hydrogenase activity is 10-fold lower than that in C. acetobutylicum G1(pSPD5), and (ii) while the ferredoxin-NAD reductase activity is high and the NADH-ferredoxin reductase ctivity is low in C. acetobutylicum DG1(pSPD5), the reverse is observed for C. butyricum VPI 3266. Thirdly, actate dehydrogenase activity is only detected in the C. acetobutylicum DG1(pSPD5) culture, explaining why his microorganism produces lactate.
Production of 1,3-Propanediol from Glycerol by Clostridium cetobutylicum and Other Clostridium Species. Abstract: Glyceol was fermented with the production of 1,3-propanediol as the major fermentation product by four strains of Clostridium acetobutylicum, six of C. butylicum, two of C. beijerinckii, one of C. kainantoi, and three of C. butyricum. 1,3-Propanediol was identified by its retention times in gas chromatography and high-pressure liquid chromatography and by its mass spectrum. During growth of C. butylicum B593 in a chemostat culture at pH 6.5, 61% of the glycerol fermented was converted to 1,3-propanediol. When the pH was decreased to 4.9, growth and 1,3-propanediol production were substantially reduced.
Use of Glycerol from biodiesel production: Conversion to added value products. Abstract: A detailed study of main stages of a novel no-conventional process to obtain 1,3-propanediol (PD) from glycerol (Gly) has been made. Initially the volumetric productivity of Gly fermentation with Klebsiella pneumoniae bacterium was optimized for one and two continuous stages, where was necessary to study the multiplicity of stable steady states for the fermentation system selecting the conditions where higher concentrations of PD are found; and under optimal operation conditions the outlet PD concentration and the global yield are 0.4833 mol/l and 0.5481 molPD/molGly, respectively. For PD recovery from fermentation broth a no-conventional separation scheme was proposed, which consists first in a reactive-extraction with iso-butyraldehyde (iBAld) for produce 2-iso-propyl-1,3-dioxane (iPDOx) and water. The iPDOx is removed toward the organic phase by the aldehyde that acts simultaneously as reagent and solvent. The yield of reactive-extraction process is 85%. Finally Static Analysis (SA) for iPDOx hydrolysis system shows that is possible to obtain PD of high purity and recovery the aldehyde at the 88% in a reactive-distillation tower. SA also allowed obtaining the technological configuration of reactive-distillation tower and this technological synthesis was validated starting from simulations to both infinite/infinite and finite/finite (stages/reflux) conditions, using the ASPEN PLUS® software. For finite conditions the simulations showed that a conversion of 69% and 97.5% is reached for reflux ratios of 5.73 and 9.5 respectively.
HIGH PRODUCTION OF 1,3-PKOPANEDIOL FROM GLYCEROL BY Closhdium butyricum VPI 3266 IN A SIMPLY CONTROLLED FEDBATCH SYSTEM. Abstract: A simple fed-batch system which controls substrate feeding by measuring the CO, produced during the fermentation, was developped. This Fed-batch approach allowed high production of 1,3-propanediol from glycerol by Clostridium butyricum by avoiding substrate inhibition phenomena. 65 g/l of 1,3-propanediol was produced with a productivity of 1.21 g/l.h and a yield of 0.56. The concentration of 1,3-propanediol obtained and the productivity were significantly higher than those reached in batch culture.
CATALYTIC CONVERSION OF GLYCEROL AND SUGAR ALCOHOLS TO VALUE-ADDED PRODUCTS. Ph.D.Thesis.
Production of various coproducts via anaerobic fermentation of glycerol by clostridia:
