Biodiesel Residual Glycerol Metabolism by Klebsiella pneumoniae: Pool of Metabolites Under Anaerobiosis and Oxygen Limitation as a Function of Feeding Rates

Abstract

The metabolism of residual glycerol from biodiesel synthesis by Klebsiella pneumoniae BLh-1 was investigated in this study. Batch and fed-batch cultivations were performed in bioreactors under anaerobic and oxygen limitation conditions. Results of batch cultivations showed that the main product was 1,3-propanediol (1,3-PD) in both conditions, although the higher yields and productivities (0.46 mol mol(-1) glycerol and 1.22 g L(-1) h(-1), respectively) were obtained under anaerobic condition. Large amounts of ethanol were also produced under batch anaerobic condition, peaking at 12.30 g L(-1). Batch cultivations under oxygen limitation were characterized by faster growth kinetics, with higher biomass production but lower conversions of glycerol into 1,3-PD, with yields and productivities of 0.33 mol mol(-1) glycerol and 0.99 g L(-1) h(-1), respectively. The fed-batch cultivations were carried out in order to investigate the effects of feeding of raw glycerol on cells. Fed-batch under anaerobiosis showed that 1,3-PD and ethanol concentrations increased with the feeding rate, with maximal productions of 26.12 and 19.2 g L(-1), respectively. The oxygen limitation conditions diverted the bacterium metabolism to an elevated lactic acid formation, reaching 59 g L(-1) in higher feeding rates of glycerol, but lowering the production of ethanol.

Exponential Fed-Batch Cultures of Klebsiella pneumoniae under Anaerobiosis Using Raw Glycerol as a Substrate to Obtain Value-Added Bioproducts

“…Microorganism maintenance and inoculum preparation K. pneumoniae BLh-1 was isolated and characterized in the work of Rossi et al 7 Certified stocks of this bacterium are kept at the Microbiology Culture Collection of BiotecLab (Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Rio Grande do Sul, Brazil). Cultures were maintained on a Luria-Bertani agar slant at 4 o C, and new subcultures were started every 4 weeks.…”

“…This bacterium is a facultative anaerobic, metabolically versatile microorganism, which has been investigated in the production of 1,3-propanediol (1,3-PDO), 2,3-butanediol (2,3-BDO), ethanol, and several organic acids. 7 Among such metabolites, 1,3-PDO, 2,3-BDO, and ethanol are of special interest. On the other hand, the formation of acetic acid and lactic acid in the fermentation process is undesirable, since they are known inhibitory metabolites and will lead to lower yields of the main fermentation products.…”

“…13 It may keep inhibitory products at lower concentrations as well as direct metabolic flux towards the production of desired products. Efforts towards the fed-batch production of 1,3-PDO from glycerol have been concentrated in continuous or batch-pulsed feeding, as well as linked to pH control, 7,[14][15][16][17][18][19][20][21] and have generally resulted in higher titers, yields and productivities, compared to batch fermentation. However, exponential fedbatch cultures (EFBC) have not been reported.…”

Biosynthesis of poly(3-hydroxypropionate) from glycerol using engineeredKlebsiella pneumoniaestrain without vitamin B12

“…Glycerol is both a cell metabolite and a carbon substrate for growth. 2 It can be converted into many valuable products, such as 1,3-propanediol, 3 lactate, 4 succinate, 5 3HP, 6 and polyhydroxyalkanoates (PHAs). 1 Poly(3-hydroxypropionate) (P3HP) is one kind of PHA exhibiting high rigidity, ductility, and exceptional tensile strength in drawn films, and was regarded as one of the alternatives to petrochemical-derived plastic.…”

Microbial production of lactic acid

“…Wild-type Klebsiella pneumoniae generates a surprisingly high concentration of D-lactic acid when subject to microaerobic conditions and high glycerol feed rates (Rossi et al 2013). If one thus accepts the generation of by-products, the organism is suitable for the co-production of 1,3-propanediol and D-lactic acid, which may readily be separated from each other (Song et al 2013).…”