Abstract
BackgroundThe surplus of glycerol has increased remarkably as a main byproduct during the biofuel’s production. Exploiting an alternative route for glycerol utilization is significantly important for sustainability of biofuels.ResultsA novel biocatalyst that could be prepared from glycerol for producing 2-oxo-carboxylates was developed. First, Pseudomonas putida KT2440 was reconstructed by deleting lldR to develop a mutant expressing the NAD-independent lactate dehydrogenases (iLDHs) constitutively. Then, the Vitreoscilla hemoglobin (VHb) was heterologously expressed to further improve the biotransformation activity. The reconstructed strain, P. putida KT2440 (ΔlldR)/pBSPPcGm-vgb, exhibited high activities of iLDHs when cultured with glycerol as the carbon source. This cost-effective biocatalyst could efficiently produce pyruvate and 2-oxobutyrate from dl-lactate and dl-2-hydroxybutyrate with high molar conversion rates of 91.9 and 99.8 %, respectively.ConclusionsThe process would not only be a promising alternative for the production of 2-oxo-carboxylates, but also be an example for preparation of efficient biocatalysts for the value-added utilization of glycerol.
Highlights
The surplus of glycerol has increased remarkably as a main byproduct during the biofuel’s production
Regulatory networks of glycerol and lactate metabolism in P. putida KT2440 Owing to its versatile metabolic activities, P. putida KT2440 can use various organics as carbon and energy sources, which make this strain an ideal industrial microorganism used for biotransformation and biodegradation [21]
Take glycerol and lactate as examples, both of these two compounds can be used as carbon and energy sources for P. putida KT2440 [9, 22]
Summary
The surplus of glycerol has increased remarkably as a main byproduct during the biofuel’s production. Glycerol is generated in both bioethanol and biodiesel production processes [1]. About 10 kg of crude glycerol will be generated from every 100 kg of biodiesel production by the transesterification of fats and oils with alcohol [2]. Significant amounts of glycerol surplus, created by the increasing bioethanol and biodiesels production, have given rise to a sharp drop in glycerol price [1,2,3]. Glycerol can be converted into various high-value products via either chemical transformations or biological conversions [4, 5]. Due to its advantages of higher specificity, milder reaction conditions, and lower levels of chemical contaminants, biological conversion is more desirable for environment-friendly production of those valuable chemicals from glycerol [3, 4, 7]
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