Biodiesel-derived Waste Glycerol Research Articles

Biodiesel-Derived Waste Glycerol as a Green Template for Creating Mesopores in the ZSM-5 Catalyst for Aromatics Production Applications.

The present study provides a novel sustainable approach for the synthesis of the ZSM-5 catalyst using biodiesel-derived waste glycerol as a green template as well as a mesopore creator, which is here reported for the first time, to the best of our knowledge. The use of bioglycerol in the preparation of ZSM-5 (Zn-Z-G and Zn-Z-T) materials exhibited a typical MFI zeolite structure, indicating glycerol played a similar role to that of a typical (TPA+) template in the formation of the ZSM-5 zeolite structure. The Zn-Z-G material also exhibited a large mesopore in the ZSM-5 pore structure, suggesting that glycerol played both template and mesopore creator roles. Interestingly, Zn-Z-GT prepared by the dual-template route using bioglycerol along with typical TPA+ showed a MFI zeolite structure with special catalytic features such as hierarchical micromesopores and well-balanced acid sites. These results reveal that the use of bioglycerol along with a typical TPA+ template had a promotional effect on creating such special properties in the Zn-Z-GT material. The Zn-Z-GT catalyst exhibited excellent catalytic performance in the naphtha aromatization reaction, resulting in achieving ∼58 wt % of the aromatic product and useful gas byproduct (14 wt %) with a minimum coke content (∼4 wt %) in a 12 h reaction period ascribed to its combined effect of hierarchical micromesopores and well-balanced acidity with optimum Lewis acid sites. The liquid product possessing high alkyl-aromatics with a high octane value (RON ∼ 109) produced in the present study can be used as an octane booster for liquid gasoline. The high alkyl-aromatics (>50 wt %) content of the liquid product also attracts various petrochemical applications. The effective utilization of waste bioglycerol as a green template and mesopore creator for the preparation of Zn-Z-GT can exhibit sustainability in the resultant material.

Engineering Strategies for Efficient Bioconversion of Glycerol to Value-Added Products by Yarrowia lipolytica

Yarrowia lipolytica has been a valuable biotechnological workhorse for the production of commercially important biochemicals for over 70 years. The knowledge gained so far on the native biosynthetic pathways, as well as the availability of numerous systems and synthetic biology tools, enabled not only the regulation and the redesign of the existing metabolic pathways, but also the introduction of novel synthetic ones; further consolidating the position of the yeast in industrial biotechnology. However, for the development of competitive and sustainable biotechnological production processes, bioengineering should be reinforced by bioprocess optimization strategies. Although there are many published reviews on the bioconversion of various carbon sources to value-added products by Yarrowia lipolytica, fewer works have focused on reviewing up-to-date strain, medium, and process engineering strategies with an aim to emphasize the significance of integrated engineering approaches. The ultimate goal of this work is to summarize the necessary knowledge and inspire novel routes to manipulate at a systems level the yeast biosynthetic machineries by combining strain and bioprocess engineering. Due to the increasing surplus of biodiesel-derived waste glycerol and the favored glycerol-utilization metabolic pathways of Y. lipolytica over other carbon sources, the present review focuses on pure and crude glycerol-based biomanufacturing.

A review over the role of catalysts for selective short-chain polyglycerol production from biodiesel derived waste glycerol

The production of biodiesel production has been surged throughout the decades due to the conventional transesterification process of edible, non-edible, and waste cooking oil to replace fossil-based fuels. Regrettably, this acclaimed process undeniably accompanied by glycerol generation as its primary by-product. The synchronous inclining trend of glycerol production with blooming biodiesel industries urged the wise utilization of market-surplus crude glycerol as well as to boost the market price of glycerol. One of the promising technologies for waste glycerol utilization is catalytic glycerol etherification for valuable polyglycerol (especially di- and triglycerol) production. Thus, the role of the catalysts during the reaction is noteworthy for the excellent glycerol conversion and short-chain polyglycerol yield. In this review, the homogeneous and heterogeneous catalysts reported in previous literature are reviewed and compared. The promising heterogeneous catalysts for glycerol etherification was divided into three main categories, viz. microporous, mesoporous, and macroporous. The recent wide application of cost-effective, highly stable, and environmentally benign natural clays as an alternative heterogeneous catalyst has also been included together with their modification treatments. Overall, this review provides appraisals on various catalysts used and challenges faced upon utilizing low-value surplus glycerol into valuable polyglycerol. Lastly, this review attempts to propose further investigations and explorations on more promising green catalysts as a substitution over commercial catalysts as one of the schemes for the future prospects of glycerol etherification. • Conversion of glycerol into useful products is needed due to its market saturation. • Polyglycerol is useful for pharmaceutical, plasticizer, food emulsifier industries. • Homogeneous catalysts: fast, more selective, and reduce cyclic oligomers formation. • Heterogeneous catalysts: easy recovery, reusable, reactants adsorb on active sites. • Natural clays as alternative catalytic supports are cost-efficient and highly stable.

Production of gellan gum, an exopolysaccharide, from biodiesel-derived waste glycerol by Sphingomonas spp.

In the present study, biodiesel-derived waste glycerol (WG) was used for the isolation and production of gellan, an exopolysaccharide, on media containing WG as the main carbon source. Two bacterial isolates showed gellan producing potential which were identified as Sphingomonas pseudosanguinis (Accession No. GI:724472387) and Sphingomonas yabuuchiae (GI:724472388) by 16S rRNA gene sequencing. To maximize gellan production by S. pseudosanguinis and S. yabuuchiae, media optimization was performed at different pHs and glycerol concentrations. Morphological observations through microscopic images showed the production of gellan from these isolates. Simple linear regression showed better utilization of WG by S. pseudosanguinis than S. yabuuchiae at pH 6 and pH 7. Though, both the strains showed reverse trend at pH 8. Both the strains were able to produce high amounts of gellan gum (51.6 and 52.6g/l, respectively) using WG (80g/l) as the sole carbon source, in a minimal medium. This is the first report on the efficient degradation of WG and low-cost production of gellan. Owing to these characteristics, S. pseudosanguinis and S. yabuuchiae demonstrate great potential for use in the commercial production of gellan and in the bioremediation of WG.

Repeated batch production of 1,3-propanediol from biodiesel derived waste glycerol by Klebsiella pneumoniae

In this study, 1,3-propanediol production was achieved from waste glycerol using Klebsiella pneumoniae ATCC 8724 under both batch and repeated batch fermentation. The inhibitory effects of the culture conditions were investigated considering the waste glycerol components. Anaerobic conditions showed better performance than aerobic conditions. Significant inhibitory effects in batch fermentation were observed in the following conditions: above pH 8, 60g/L of initial glycerol concentration or 2% (w/v) of salts contents. However, improvement in 1,3-propanediol production and cell growth was represented below 1% (w/v) content of salts (NaCl and KCl). The highest yield of 1,3-propandiol using batch fermentation was achieved at 0.77 and 0.65 (mol/mol) with pure and waste glycerol, respectively. In addition, repeated batch fermentation was demonstrated with immobilized cells using waste glycerol. Compared to the first cycle of cultivation, 83% of 1,3-propanediol was obtained after five cycles of batch cultivation. The highest concentration and yield of 1,3-propanediol were respectively achieved 0.64 (mol/mol) and 20g/L at the second cycle cultivation. The performance of by-products of the repeated batch fermentation with immobilized cells was also investigated for further application.

Novel biocatalysts for glycerol conversion into 2,3-butanediol

Bioconversion of biodiesel-derived waste glycerol into high-value products is proposed as a solution to improve economic viability of biorefineries. Several microorganisms are able to metabolize glycerol into 2,3-butanediol (2,3-BD), a promising bulk chemical with wide applications: solvent, fuel additive, and feedstock for synthetic rubber production, among them. In the present work, a wide screening of microorganisms present both into the waste water treatment system in a biodiesel industry and in culture collections was carried out in order to evaluate their potential as new 2,3-BD producer biocatalysts. Two microorganisms for 2,3-BD production from glycerol as sole carbon source have been selected, namely Raoultella planticola CECT 843 and Raoultella terrigena CECT 4519. Raoultella strains belong to the non‐pathogenic bacteria class (biosafety level 1). This genus has not been previously described as biocatalyst for the studied process. The influence of operational temperature, organic acid addition, and yeast extract concentration on 2,3-BD yield and productivity have been studied through Taguchi design methodology as well as initial glycerol concentration. Based on these results, the feasibility of the process employing pure glycerol and different samples of raw glycerol has been demonstrated.

Quantitative 'Omics Analyses of Medium Chain Length Polyhydroxyalkanaote Metabolism in Pseudomonas putida LS46 Cultured with Waste Glycerol and Waste Fatty Acids.

Transcriptomes and proteomes of Pseudomonas putida LS46 cultured with biodiesel-derived waste glycerol or waste free fatty acids, as sole carbon sources, were compared under conditions that were either permissive or non-permissive for synthesis of medium chain length polyhydroxyalkanoates (mcl-PHA). The objectives of this study were to elucidate mechanisms that influence activation of biopolymer synthesis, intra-cellular accumulation, and monomer composition, and determine if these were physiologically specific to the carbon sources used for growth of P. putida LS46. Active mcl-PHA synthesis by P. putida LS46 was associated with high expression levels of key mcl-PHA biosynthesis genes and/or gene products including monomer-supplying proteins, PHA synthases, and granule-associated proteins. ‘Omics data suggested that expression of these genes were regulated by different genetic mechanisms in P. putida LS46 cells in different physiological states, when cultured on the two waste carbon sources. Optimal polymer production by P. putida LS46 was primarily limited by less efficient glycerol metabolism during mcl-PHA synthesis on waste glycerol. Mapping the ‘Omics data to the mcl-PHA biosynthetic pathway revealed significant variations in gene expression, primarily involved in: 1) glycerol transportation; 2) enzymatic reactions that recycle reducing equivalents and produce key mcl-PHA biosynthesis pathway intermediates (e.g. NADH/NADPH, acetyl-CoA). Active synthesis of mcl-PHAs was observed during exponential phase in cultures with waste free fatty acids, and was associated with the fatty acid beta-oxidation pathway. A putative Thioesterase in the beta-oxidation pathway that may regulate the level of fatty acid beta-oxidation intermediates, and thus carbon flux to mcl-PHA biosynthesis, was highly up-regulated. Finally, the data suggested that differences in expression of selected fatty acid metabolism and mcl-PHA monomer-supplying enzymes may play a role in determining the monomer composition of mcl-PHA polymers. Understanding the relationships between genome content, gene and gene product expression, and how these factors influence polymer synthesis, will aid in optimization of mcl-PHA production by P. putida LS46 using biodiesel waste streams.

Effects of impurities in biodiesel-derived glycerol on growth and expression of heavy metal ion homeostasis genes and gene products in Pseudomonas putida LS46.

Biodiesel production-derived waste glycerol (WG) was previously investigated as potential carbon source for medium chain length polyhydroxyalkanoate (mcl-PHA) production by Pseudomonas putida LS46. In this study, we evaluated the effect of impurities in the WG on P. putida LS46 physiology during exponential growth and corresponding changes in transcription and protein expression profiles compared with cells grown on pure, reagent grade glycerol. High concentration of metal ions, such as Na(+), and numbers of heavy metals ion, such as copper, ion, zinc, were detected in biodiesel-derived WG. Omics analysis from the corresponding cultures suggested altered expression of genes involved in transport and metabolism of ammonia and heavy metal ions. Expression of three groups of heavy metal homeostasis genes was significantly changed (mostly upregulated) in WG cultures and included the following: copper-responded cluster 1 and 2 genes, primarily containing cusABC; two copies of copAB and heavy metal translocating P-type ATPase; Fur-regulated, TonB-dependent siderophore receptor; and several cobalt/zinc/cadmium transporters. Expression of these genes suggests regulation of intracellular concentrations of heavy metals during growth on biodiesel-derived glycerol. Finally, a number of genes involved in adapting to, or metabolizing free fatty acids and other nonheavy metal contaminants, such as Na(+), were also upregulated in P. putida LS46 grown on biodiesel-derived glycerol.

Lipid production in the under-characterized oleaginous yeasts, Rhodosporidium babjevae and Rhodosporidium diobovatum, from biodiesel-derived waste glycerol

The growth, lipid production, and carbon use efficiency of two oleaginous yeasts, Rhodosporidium babjevae and Rhodosporidium diobovatum, were compared under nitrogen-limiting conditions with glycerol as the carbon source. Final biomass concentrations of R. babjevae and R. diobovatum were 9.4±0.80g/L and 12.0±0.82g/L, respectively, after 120h of growth. Final lipid accumulation in for R. babjevae and R. diobovatum were 34.9±3.0% cell dry weight (cdw) and 63.7±4.5% cdw, respectively. Biomass production increased to 9.9±0.2g/L for R. babjevae and 14.1±0.2g/L for R. diobovatum in medium containing biodiesel-derived waste glycerol, but lipid accumulation decreased in both species. In a 7L bioreactor with biodiesel-derived glycerol as carbon source, R. diobovatum produced 13.6±0.4g/L biomass and accumulated lipids to 50.7±2.2% cdw, matching flask experiments.

Biodiesel derived waste glycerol as an economic substrate for biosurfactant production using indigenous Pseudomonas aeruginosa

Biodiesel plant waste glycerol as low-cost substrate for biosurfactant production.

Enhanced 1,3-propanediol production by a newly isolated Citrobacter freundii strain cultivated on biodiesel-derived waste glycerol through sterile and non-sterile bioprocesses

The production of 1,3-propanediol (PD) by a newly isolated Citrobacter freundii strain [FMCC-B 294 (VK-19)] was investigated. Different grades of biodiesel-derived glycerol were employed. Slightly lower PD biosynthesis was observed in batch experiments only when crude glycerol from waste-cooking oil trans-esterification was utilized and only at elevated initial substrate concentrations employed. Batch bioreactor cultures revealed the capability of the strain to tolerate elevated amounts of substrate (glycerol up to 170g/L) and produce quantities of PD in such high substrate concentrations. Nevertheless, maximum PD quantities (45.9g/L) were achieved at lower initial glycerol concentrations (∼100g/L) employed, suggesting some inhibition exerted due to the increased initial substrate concentrations. In order to improve PD production, a fed-batch fermentation was carried out and 68.1g/L of PD were produced (the highest PD quantity achieved by C. freundii strains so far) with yield per glycerol consumed ∼0.40g/g and volumetric productivity 0.79g/L/h. Aiming to perform a more economical and eco-friendlier procedure, batch and fed-batch fermentations under completely non-sterile conditions were carried out. During non-sterilized fed-batch process, 176g/L of raw glycerol were converted to 66.3g/L of PD, suggesting the potentiality of the non-sterile fermentation by C. freundii FMCC-B 294.

Effect of impurities in biodiesel-derived waste glycerol on the performance and feasibility of biotechnological processes

The rapid development of biodiesel production technology has led to the generation of tremendous quantities of glycerol wastes, as the main by-product of the process. Stoichiometrically, it has been calculated that for every 100 kg of biodiesel, 10 kg of glycerol are produced. Based on the technology imposed by various biodiesel plants, glycerol wastes may contain numerous kinds of impurities such as methanol, salts, soaps, heavy metals, and residual fatty acids. This fact often renders biodiesel-derived glycerol unprofitable for further purification. Therefore, the utilization of crude glycerol though biotechnological means represents a promising alternative for the effective management of this industrial waste. This review summarizes the effect of various impurities-contaminants that are found in biodiesel-derived crude glycerol upon its conversion by microbial strains in biotechnological processes. Insights are given concerning the technologies that are currently applied in biodiesel production, with emphasis to the impurities that are added in the composition of crude glycerol, through each step of the production process. Moreover, extensive discussion is made in relation with the impact of the nature of impurities upon the performances of prokaryotic and eukaryotic microorganisms, during crude glycerol bioconversions into a variety of high added-value metabolic products. Finally, aspects concerning ways of crude glycerol treatment for the removal of inhibitory contaminants as reported in the literature are given and comprehensively discussed.

Use of ceramic-based cell immobilization to produce 1,3-propanediol from biodiesel-derived waste glycerol with Klebsiella pneumoniae

The feasibility of the continuous production of a valuable bioplastic raw material, namely 1,3-propanediol (1,3-PDO) from biodiesel by-product glycerol, using immobilized cells was investigated. In addition, the effect of hydraulic retention time (HRT) was also analysed. Ceramic balls and ceramic rings were used for the immobilization of a locally isolated strain; Klebsiella pneumoniae (GenBank no. 27F HM063413). HRT of 1 h is the best one in terms of volumetric production rate (g 1,3-PDO l(-1) h(-1)). The results indicated that ceramic-based cell immobilization achieved a 2-fold higher production rate (10 g 1,3-PDO l(-1) h(-1)) in comparison with suspended cell system (4·9 g 1,3-PDO l(-1) h(-1)). Continuous cultures with immobilized cells revealed that 1,3-PDO production was more effective and more stable than suspended culture systems. Furthermore, cell immobilization had also obvious benefits especially for resistance of the production for extreme conditions (high organic loading rates, cell washouts). The results were important for understanding the significance of continuous immobilization process among other well-known 1,3-PDO fermentation processes. This work is a promising process for further studies, as the immobilized micro-organism was able to reach high volumetric production rates at short HRT, it has an important role in tolerating and converting glycerol during fermentation. Therefore, HRT is a very significant operational parameter (P value <0·05) directly affecting the bioreactor performance and production rate.

Biotechnological conversions of biodiesel derived waste glycerol by yeast and fungal species

Fifteen eukaryotic microorganisms were tested for their ability to assimilate biodiesel derived waste glycerol and convert it into value-added metabolic products. For this purpose yeast and Zygomycetes strains were cultivated in nitrogen-limited raw glycerol-based media (initial glycerol concentration 30 g/L). Yeasts tested accumulated restricted lipid quantities (up to ∼22%, wt/wt, in the case of Rhodotorula sp), while differentiations in their fatty acid composition were recorded in relation to the yeast strains employed and the fermentation time. On the contrary, fungi accumulated higher quantities of lipid inside their mycelia (ranging between 18.1 and 42.6%, wt/wt, of dry biomass) that contained in variable amounts the medically important GLA (γ-linolenic acid). Moreover, Yarrowia lipolytica, Pichia membranifaciens and Thamnidium elegans were further studied in media having increased initial glycerol concentrations. In these conditions Y. lipolytica secreted significant amounts of acetic acid (29.2 g/L), as well as mannitol (19.4 g/L) while P. membranifaciens reached 28.4 g/L of biomass at glycerol concentration 90 g/L. T. elegans produced 11.6 g/L of oil, with 71.1%, wt/wt, of fat in biomass, while the maximum concentration of GLA was 371 mg/L. Detailed analysis of T. elegans lipids indicated that the phospholipids fraction was particularly rich in polyunsaturated fatty acids.

Biotechnological conversions of bio-diesel derived waste glycerol into added-value compounds by higher fungi: production of biomass, single cell oil and oxalic acid

Waste bio-diesel derived glycerol was used as the sole carbon source by higher fungi; two Lentinula edodes strains were flask cultured in carbon-limited conditions and displayed satisfactory growth in media presenting weak agitation, pH 4.0 and temperature 25 °C. Maximum biomass of 5.2 g/l was produced. Mycelia were synthesized, containing around 0.1 g of fat per g of biomass, with linoleic acid ( Δ9,12C18:2) being the principal cellular fatty acid produced. Two Aspergillus niger strains were grown in nitrogen-limited flask cultures with constant nitrogen and two different initial glycerol concentrations into the medium. In 250-ml flask cultures, large-sized pellets were developed, in contrast with the trials performed in 2-l flasks. Nitrogen limitation led to oxalic acid secretion and intra-cellular lipid accumulation; in any case, sequential production of lipid and oxalic acid was observed. Initially, nitrogen limitation led to lipid accumulation. Thereafter, accumulated lipid was re-consumed and oxalic acid, in significant quantities, was secreted into the medium. In large-sized pellets, higher quantities of intra-cellular total lipid and lower quantities of oxalic acid were produced and vice versa. Maximum quantities of oxalic acid up to 20.5–21.5 g/l and lipid up to 3.1–3.5 g/l (corresponding to 0.41–0.57 g of fat per g of biomass) were produced. Lipid was mainly composed of oleic ( Δ9C18:1) and linoleic ( Δ9,12C18:2) acids.

Screening of PHA-Producing Bacteria Using Biodiesel-Derived Waste Glycerol as a Sole Carbon Source

Screening of PHA-Producing Bacteria Using Biodiesel-Derived Waste Glycerol as a Sole Carbon Source