Abstract
Biodiesel can replace petroleum diesel as it is produced from animal fats and vegetable oils, and it produces about 10 % (w/w) glycerol, which is a promising new industrial microbial carbon, as a major by-product. One of the most potential applications of glycerol is its biotransformation to high value chemicals such as 1,3-propanediol (1,3-PD), dihydroxyacetone (DHA), succinic acid, etc., through microbial fermentation. Glycerol dehydratase, 1,3-propanediol dehydrogenase (1,3-propanediol-oxydoreductase), and glycerol dehydrogenase, which were encoded, respectively, by dhaB, dhaT, and dhaD and with DHA kinase are encompassed by the dha regulon, are the three key enzymes in glycerol bioconversion into 1,3-PD and DHA, and these are discussed in this review article. The summary of the main research direction of these three key enzyme and methods of glycerol bioconversion into 1,3-PD and DHA indicates their potential application in future enzymatic research and industrial production, especially in biodiesel industry.
Highlights
The demand for biofuels is increasing worldwide; as raw material, it is one of the most promising alternative sources of energy
Biodiesel can replace petroleum diesel as it is derived from vegetable oils and animal fats, and it produces about 10 % (w/w) glycerol as a major byproduct [1,2,3,4,5,6]
The biotechnological synthesis of 1,3-PD appears to be a promising alternative to the chemical synthesis as it offers environmental benefits and allows for the use of renewable feedstock [37, 38]. 1,3PD was originally obtained from glycerol fermentation in 1881 [39]
Summary
The demand for biofuels is increasing worldwide; as raw material, it is one of the most promising alternative sources of energy. The 1,3-PD operon of C. butyricum comprises three genes, a different type of GDHt (dhaB1), its activator protein (dhaB2), and dhaT [33] In this bacterium, GDHt is extremely oxygen sensitive, strongly associated with the cell membrane, and independent of vitamin B12 [33,34,35, 62,63,64]. As all B12-dependent GDHts need a number of coenzymes, vitamin B12 leads to the high cost of biological process for producing 1,3-PD It would be an ideal research direction to modify the B12-dependent GDHt mutate to the B12-independent GDHt (Fig. 2). Even through there are a large number of reports about the cloning and characterization (Fig. 2) of the B12-dependent GDHt, the characterization of coenzyme B12-independent GDHt is poorly understood
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