1,3-Propanediol production from crude glycerol by Clostridium butyricum DSP1 in repeated batch

AbstractBackgroundThe production of biofuels from renewable energy sources is one of the most important issues in industrial biotechnology today. The process is known to generate various by-products, for example crude glycerol, which is obtained in the making of biodiesel from rapeseed oil. Crude glycerol may be utilized in many ways, including microbial conversion to 1,3-propanediol (1,3-PD), a raw material for the synthesis of polyesters and polyurethanes.ResultsThe paper presents results of a study on the synthesis of 1,3-propanediol from crude glycerol by a repeated batch method with the use of Clostridium butyricum DSP1. Three cycles of fermentation medium replacement were carried out. The final concentration of 1,3-PD was 62g/L and the maximum productivity, obtained during the second cycle, reached 1.68g/L/h. Additionally, experiments conducted in parallel to the above involved using the entire quantity of the culture broth removed from the bioreactor to inoculate successive portions of fermentation media containing crude glycerol at concentrations of 80g/L and 100g/L. Under those conditions, the maximum 1,3-PD concentrations were 43.2g/L and 54.2g/L.ConclusionsThe experiments proved that by using a portion of metabolically active biomass as inoculum for another fermentation formula it is possible to eliminate the stage of inoculum growth and thereby reduce the length of the whole operation. Additionally, that strategy avoids the phase of microbial adaptation to a different source of carbon such as crude glycerol, which is more difficult to utilize, thus improving the kinetic parameters of 1,3-PD production

The effect of high concentrations of glycerol on the growth, metabolism and adaptation capacity of Clostridium butyricum DSP1

Background: The production of biofuels from renewable energy sources is one of the most important issues in biotechnology today. The process is known to generate various by-products, for example glycerol that is obtained in the making of biodiesel from rapeseed oil. Crude glycerol may be utilized in many ways, including microbial conversion to 1,3-propanediol. The main drawback of that technology is the use of high concentrations of glycerol, which inhibits the growth of bacterial cells. Results: This study investigated the impact of crude glycerol on Clostridium butyricum DSP1 and its ability to adapt to an environment of high osmotic pressure. It was found that a crude glycerol concentration of up to 70 g/L did not have an inhibitory effect on C. butyricum DSP1. Adaptation procedures involving the passage of metabolically active biomass from a fermentation medium with a lower concentration of crude glycerol to one with a greater substrate concentration allowed breaking the barrier of high osmotic pressure (150 g/L crude glycerol) and receiving a 1,3-PD concentration of 74 g/L in a batch culture operation. The work looked into intracellular modifications shown by proteomic profiling in order to explain the mechanisms underlying the response and adaptation of bacterial cells exposed to unfavorable environmental conditions. Conclusions: This study of the effect of glycerol on the growth and metabolism of C. butyricum DSP1 demonstrated that the maximum substrate concentrations that do not inhibit the metabolic activity of bacterial cells are 90 g/L and 70 g/L for pure and crude glycerol, respectively

An increasing of the efficiency of microbiological synthesis of 1,3-propanediol from crude glycerol by the concentration of biomass

Background: 1,3-Propanodiol (1,3-PD), is used in the production of polytrimethylene terephthalate (PTT), an aromatic polyester that exhibits high elastic recoveries. It is also employed as a supplement with low solidification properties, a solvent and a lubricant in the formof propylene glycol. 1,3-PD is effectively synthesized by a microbiological way from crude glycerol. The main problem of this technology is using a high concentration of glycerol, which is a limiting factor for bacteria cells growth (especially in batch fermentation). Results: In this work, the influence of different glycerol concentration in batch fermentation on Clostridium butyricum DSP1 metabolism was investigated. The biomass was concentrated for two times with the use of membrane module (in case of increasing kinetic parameters). Increased optical density of bacteria cells six times increased the productivity of 1,3-PD in cultivation with 20 g/L of glycerol at the beginning of the process, and more than two times in cultivation with 60–80 g/L. Also the possibility of complete attenuation of 140 g/L of crude glycerol in the batch fermentation was investigated. During the cultivation, changes of protein profiles were analyzed. The most significant changes were observed in the cultivation in the medium supplemented with 80 g/L of glycerol. They related mainly to the DNA protein reconstructive systems, protective proteins (HSP), and also the enzymatic catalysts connected with glycerol metabolic pathway. Conclusions: The application of filtration module in batch fermentation of crude glycerol by C. butyricum DSP1 significantly increased the productivity of the process

Microbial Purification of Postfermentation Medium after 1,3-PD Production from Raw Glycerol

1,3-Propanediol (1,3-PD) is an important chemical product which can be used to produce polyesters, polyether, and polyurethanes. In the process of conversion of glycerol to 1,3-PD by Clostridium large number of byproducts (butyric, acetic and lactic acid) are generated in the fermentation medium. The aim of this work was to isolate bacteria strains capable of the utilization of these byproducts. Screening of 30 bacterial strains was performed using organic acids as carbon source. Selected isolates were taxonomically characterized and identified as Alcaligenes faecalis and Bacillus licheniformis. The most active strains, Alcaligenes faecalis JP1 and Bacillus licheniformis JP19, were able to utilize organic acids almost totally. Finally, it was find out that by the use of coculture (C. butyricum DSP1 and A. faecalis JP1) increased volumetric productivity of 1,3-PD production (1.07 g/L/h) and the yield equal to 0.53 g/g were obtained in bioreactor fermentation. Moreover, the only by-product present was butyric acid in a concentration below 1 g/L

Kinetic modeling of simultaneous saccharification and fermentation of corn starch for ethanol production

Fuel ethanol production, using a simultaneous saccharification and fermentation process (SSF) of native starch from corn flour, has been performed using Saccharomyces cerevisiae and a granular starch hydrolyzing enzyme. The quantitative effects of mash concentration, enzyme dose and pH were investigated with the use of a Box-Wilson central composite design protocol. Proceeding from results obtained in optimal fermentation conditions, a kinetics model relating the utilization rates of starch and glucose as well as the production rates of ethanol and biomass was tested. Moreover, scanning electron microscopy (SEM) was applied to investigate corn starch granule surface after the SFF process. A maximum ethanol concentration of 110.36 g/l was obtained for native corn starch using a mash concentration of 25%, which resulted in ethanol yield of 85.71%. The optimal conditions for the above yield were found with an enzyme dose of 2.05 ml/kg and pH of 5.0. These results indicate that by using a central composite design, it is possible to determine optimal values of the fermentation parameters for maximum ethanol production. The investigated kinetics model can be used to describe SSF process conducted with granular starch hydrolyzing enzymes. The SEM micrographs reveal randomly distributed holes on the surface of granules

Evaluation of the ability to metabolize 1,2-propanediol by heterofermentative bacteria of the genus Lactobacillus

Background: New directions of research on lactic acid bacteria include investigation of metabolic pathways for the synthesis and/or metabolism of 1,2-propanediol, commonly used in the food and chemical industry, medicine, pharmacy and cosmetology as well as agriculture. The objective of this study was to compare the capacity of strains representing three diverse heterofermentative species belonging to the genus Lactobacillus to synthesize and/or transform 1,2-PD as well as to suggest new directions of research aimed at commercial use of this metabolite. Results: The novel strain of Lactobacillus buchneri A KKP 2047p, characterized as exhibiting an unusual trait for that species in the form of capacity to metabolize 1,2-PD, grew poorly in a medium containing 1,2-PD as a sole carbon source. The supplementation with glucose facilitated rapid growth of bacteria and use of 1,2-PD for the synthesis of propionic acid. A similar observation was noted for Lactobacillus reuteri. On the other hand, Lactobacillus diolivorans effectively metabolized 1,2-PD which was the sole carbon source in the medium, and the addition of glucose inhibited the synthesis of propionic acid. The experiments also investigated the effect of cobalamin as a diol dehydratase coenzyme involved in the propionic acid synthesis from 1,2-PD whose addition promoted the yield of the reaction in the case of all tested strains. Conclusions: All tested isolates showed the ability to effectively metabolize 1,2-PD (in the presence of cobalamin) and its conversion to propionic acid, which reveals that investigated bacteria meet the essential requirements of microorganisms with a potential application