Efficient Utilization of Crude Glycerol as Fermentation Substrate in the Synthesis of Poly(3‐hydroxybutyrate) Biopolymers (original) (raw)
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Brazilian Archives of Biology and Technology, 2011
The aim of this research is to investigate the influence of oleic acid concentration on the cell growth and the physical properties of the polymer formed by cultures of Ralstonia eutropha in mineral medium. Cells were cultivated in Erlenmeyer flasks with 300 mL of mineral medium, containing glucose and fructose as a carbon source (30 g/L) and ammonium sulphate (5.0 g/L) as a nitrogen source. Oleic acid was added as nutritional supplement in different concentrations (0, 0.3, 0.9, 1.5 and 3.0 g/L) and the cells were incubated at 30°C and 150 rpm. The films prepared by casting were evaluated by X-ray diffraction, thermogravimetry and differential scanning calorimetry. These results indicate that the increase of oleic acid concentrations leads to a higher specific growth rate and cell productivity. The characterization of the films revealed that the increase of the concentration of oleic acid from 0 to 1.5 g/L has no influence on thermal behaviour and crystallinity degree. However, the thermal stability, melting temperature, glass transition temperatures and crystallinity degree decreased when 3.0 g/L of oleic acid were used.
Design and analysis of poly-3-hydroxybutyrate production processes from crude glycerol
Process Biochemistry, 2011
The growing biodiesel production has generated a glycerol surplus and consequently a drop of its sale price. The development of biorefineries to convert crude glycerol to higher value products is an urgent need and an opportunity to overcome the negative impact of low glycerol prices in the biodiesel industry. Glycerol fermentation by microorganisms to useful chemicals as poly-3-hydroxybutyrate (PHB) is an interesting alternative. In this article a techno-economical analysis for PHB production from crude glycerol is presented. The glycerol fermentation process was carried out using two qualities of glycerol, either 88 or 98 wt%. Thus, the glycerol purification process was simulated and economically analyzed using Aspen Plus and Aspen Icarus, respectively. The fermentation process is carried out in two stages in which mass cell growth and PHB accumulation occurs, respectively. Also, three downstream processes to isolate and purify the PHB were considered. The process steps, namely mass cell pretreatment, PHB isolation and purification were considered in each scenario and six technological schemes were analyzed. Economical assessment results show that the most appropriate technological scheme requires purifying the crude glycerol until 98 wt%, with a downstream process involving heat pretreatment, enzymatic-alkaline digestion, centrifugation, washing, evaporation, and spray drying.
This study presents Bacillus firmus NII 0830 for producing poly-3-hydroxybutyrate (PHB) using biodiesel industry generated glycerol, a waste by-product, as sole carbon source under submerged fermentation and production process was optimized using statistical experimental design. PHB accumulation was observed up to 1.60 g/l from 4.36 g/l of total bacterial biomass at inoculum size of 3% v/v, incubation temperature 30°C, crude glycerol concentration 5% v/v, 250 RPM, incubation time 60 h and media pH 6.0 during initial statistical design. Further Response Surface design experiments yielded 61% of PHB from B. firmus NII 0830. Glycerol has a low market price and it does not require any further refinement, makes present process more economical. Further, utilization of low-grade waste glycerol solves its disposal problem, hence it is aptly an environmentally friendly 'waste to wealth' bioprocess.
Journal of Applied Polymer Science, 2012
This study focused on the characterization of polyhydroxybutyrate (PHB) produced from crude glycerol (CG) using mixed microbial consortia (MMC). PHB recovered from two biomass drying treatments (65 C oven drying and lyophilization) was characterized comparatively along with a commercially sourced PHB (PHB-C). Characterization results showed that ovendrying method caused PHB partial hydrolysis, as indicated by its lower molecular weight (M w) (PHB-O, 144,000 g mol À1), which further affected its physical and chemical properties. Lyophilization helped alleviate PHB hydrolysis during drying process, leading to PHB (PHB-L) of higher M w (309,000 g mol À1) and material properties comparable with commercial PHB. Furthermore, crystallization and morphological studies showed that PHB-L featured faster crystallization rates and smaller spherulites as compared with PHB-C, probably due to its lower M w. In general, the results from this study suggested that CG-MMC-derived PHB-L possessed material properties comparable with those of pure substrate/culture produced PHB. V
Principles of Glycerol-Based Polyhydroxyalkanoate Production
2015
The article addresses the contemporary quest for inexpensive carbon feedstocks to be used for cost efficient biomediated polymer production; such polymers can potentially be applied in the food technology sector, mainly for packaging purposes. In particular, the work shines a light on crude glycerol, a surplus stream of the globally tremendously emerging biodiesel industry. Crude glycerol can be upgraded to a convenient substrate for microbial polyhydroxyalkanoate production without interfering with food- or feed production. The article covers the challenges of using crude glycerol as a feedstock in biotechnology, and gives an insight into the metabolic background of glycerol-based polyhydroxyalkanoate production. Particularities of glycerol-based polyhydroxyalkanoate biosynthesis, such as the characteristic formation of low-molecular mass polyesters, and the resulting impact on polymer processing, are also discussed in this review.
Potential applications of crude glycerol in polymer technology–Current state and perspectives
Renewable & Sustainable Energy Reviews, 2016
The increasing use of bio-based fuels and fuel additives, among them biodiesel, causes significant surplus of crude glycerol on the market which creates new challenges in terms of its sustainable utilization. A lot of ways for the incorporation of this by-product into different branches of industry requires purification by expensive and complicated processes. Therefore, researchers are seeking for applications of untreated crude glycerol. Among the possibilities, much attention is drawn to the polymer chemistry and technology. This branch of industry is one of the biggest consumers of glycerol after food, pharmaceutical and personal care applications sectors, and probably the biggest one that does not require complicated purification of glycerol resulting from biodiesel technology. Crude glycerol can be applied in the number of processes such as fermentation, oxidation, esterification and transesterification, biomass liquefaction, oligomerization and polymerization, carboxylation, glycerolysis, hydrogenolysis, dehydration or dihydroxylation. This paper summarizes the use of glycerol in polymer technology and the attempts of crude glycerol incorporation into this field reported in literature.
Applied and Environmental Microbiology, 2009
Industrial production of biodegradable polyesters such as polyhydroxyalkanoates is hampered by high production costs, among which the costs for substrates and for downstream processing represent the main obstacles. Inexpensive fermentable raw materials such as crude glycerol, an abundant by-product of the biodiesel industry, have emerged to be promising carbon sources for industrial fermentations. In this study, Zobellella denitrificans MW1, a recently isolated bacterium, was used for the production of poly(3-hydroxybutyrate) (PHB) from glycerol as the sole carbon source. Pilot-scale fermentations (42-liter scale) were conducted to scale up the high PHB accumulation capability of this strain. By fed-batch cultivation, at first a relatively high cell density (29.9 ± 1.3 g/liter) was obtained during only a short fermentation period (24 h). However, the PHB content was relatively low (31.0% ± 4.2% [wt/wt]). Afterwards, much higher concentrations of PHB (up to 54.3 ± 7.9 g/liter) and hi...
Impact of oxygen limitation on glycerol-based biopolymer production by bacterial enrichments
Water Research, 2013
The increasing production of bioethanol and biodiesel has resulted in the generation of a massive amount of crude glycerol, inducing the need for effective valorization of these waste streams. One of the valorization options could be through conversion of crude glycerol into a biopolymer using microbial community engineering in a feastefamine process. A complicating factor in the production of biopolymers from glycerol encountered in previous works is that two different types of polymers can be formed; polyhydroxyalkanoate (PHA) and polyglucose. Here we describe the effect of limiting the oxygen supply rate on the polymer distribution with the aim of defining the conditions that favour the conversion of glycerol in one single polymer. The decrease of oxygen supply rate during the biopolymer maximization step did not influence glycerol partitioning among PHA and polyglucose, but oxygen limitation during the community enrichment step favoured polyglucose storage over PHA.