AIMS: To screen yeasts in relation to the potential to produce single cell oil (SCO) from biodiesel‐derived glycerol and to enhance SCO production in Lipomyces starkeyi and Rhodosporidium toruloides ...yeasts. METHODS AND RESULTS: Yarrowia lipolytica, Cryptococcus curvatus, R. toruloides and L. starkeyi were grown in nitrogen‐limited flask cultures. Yarrowia lipolytica strains produced citric acid and mannitol. Lipomyces starkeyi DSM 70296 and R. toruloides NRRL Y‐27012 showed potential for SCO production, and were cultivated at increasing the initial glycerol concentrations with the initial nitrogen concentration remaining constant. Significant biomass and SCO production were reported even in cultures with high initial glycerol concentrations (i.e. 180 g l⁻¹). Lipid quantities of c. 12 g l⁻¹(lipid in dry cell weight 35–40%) were obtained for both L. starkeyi and R. toruloides, quite high values compared with literature values for oleaginous micro‐organisms growing on glycerol. However, these strains exhibited different kinetic profiles in the synthesis of intracellular polysaccharides. Lipomyces starkeyi produced a significant quantity of polysaccharides (c. 7 g l⁻¹). The yeast lipids contained mainly oleic and palmitic and to a lesser extent linoleic and stearic acids. CONCLUSIONS: Lipomyces starkeyi and R. toruloides are potential SCO producers from crude glycerol. SIGNIFICANCE AND IMPACT OF THE STUDY: Very scarce numbers of reports have indicated the production of SCO by L. starkeyi and R. toruloides growing on glycerol. We report here that these yeasts are able efficiently to convert raw glycerol into SCO, while L. starkeyi also synthesizes intracellular polysaccharides in marked quantities.
•We develop flowsheets for microbial oil production from renewable feedstocks.•We develop flowsheets for biodiesel production from renewable feedstocks.•We perform detailed preliminary economic ...evaluation of alternative technologies.•We perform sensitivity analysis of the cost of manufacturing of oil or biodiesel.
Experimental results from the open literature have been employed for the design and techno-economic evaluation of four process flowsheets for the production of microbial oil or biodiesel. The fermentation of glucose-based media using the yeast strain Rhodosporidium toruloides has been considered. Biodiesel production was based on the exploitation of either direct transesterification (without extraction of lipids from microbial biomass) or indirect transesterifaction of extracted microbial oil. When glucose-based renewable resources are used as carbon source for an annual production capacity of 10,000t microbial oil and zero cost of glucose (assuming development of integrated biorefineries in existing industries utilising waste or by-product streams) the estimated unitary cost of purified microbial oil is $3.4/kg. Biodiesel production via indirect transesterification of extracted microbial oil proved more cost-competitive process compared to the direct conversion of dried yeast cells. For a price of glucose of $400/t oil production cost and biodiesel production cost are estimated to be $5.5/kg oil and $5.9/kg biodiesel, correspondingly. Industrial implementation of microbial oil production from oleaginous yeast is strongly dependent on the feedstock used and on the fermentation stage where significantly higher productivities and final microbial oil concentrations should be achieved.
The transition from a fossil fuel-based economy to a bio-based economy necessitates the exploitation of synergies, scientific innovations and breakthroughs, and step changes in the infrastructure of ...chemical industry. Sustainable production of chemicals and biopolymers should be dependent entirely on renewable carbon. White biotechnology could provide the necessary tools for the evolution of microbial bioconversion into a key unit operation in future biorefineries. Waste and by-product streams from existing industrial sectors (e.g., food industry, pulp and paper industry, biodiesel and bioethanol production) could be used as renewable resources for both biorefinery development and production of nutrient-complete fermentation feedstocks. This review focuses on the potential of utilizing waste and by-product streams from current industrial activities for the production of chemicals and biopolymers via microbial bioconversion. The first part of this review presents the current status and prospects on fermentative production of important platform chemicals (i.e., selected C2-C6 metabolic products and single cell oil) and biopolymers (i.e., polyhydroxyalkanoates and bacterial cellulose). In the second part, the qualitative and quantitative characteristics of waste and by-product streams from existing industrial sectors are presented. In the third part, the techno-economic aspects of bioconversion processes are critically reviewed. Four case studies showing the potential of case-specific waste and by-product streams for the production of succinic acid and polyhydroxyalkanoates are presented. It is evident that fermentative production of chemicals and biopolymers via refining of waste and by-product streams is a highly important research area with significant prospects for industrial applications.
Aims
To study and characterize the lipids produced by Mortierella (Umbelopsis) isabellina, during its growth on mixtures of glucose and xylose.
Methods and Results
Glucose and xylose were utilized as ...carbon sources, solely or in blends, under nitrogen‐limited conditions, in batch‐flask trials (initial sugars at 80 g l−1). Significant lipid production (maximum lipid 17·8 g l−1; lipid in DCW 61·0% w/w; lipid on glucose consumed 0·23 g g−1) occurred on glucose employed solely, while xylose concentration in the growth medium was conversely correlated with lipid accumulation. With increasing xylose concentrations into the blend, lipid storage decreased while xylitol in significant concentrations (up to 24 g l−1) was produced. Irrespective of the sugar blend employed, significant quantities of endopolysaccharides were detected in the first growth steps (in the presence of nitrogen into the medium or barely after its disappearance) while lipids were stored thereafter. Neutral lipids, mainly composed of triacylglycerols, were the main microbial lipid fraction. Phospholipids were quantified both through fractionation and subsequent gravimetric determination and also through determination of phosphorus, and it seemed that the second method was more accurate. Phospholipids were mainly composed of phosphatidylcholine and another nonidentified compound presumably being phosphatidyldimethylethanolamine.
Conclusions
Mortierella isabellina is suitable to convert lignocellulosic sugars into lipids.
Significance and Impact of the Study
Differentiations between metabolism on xylose and glucose were reported. Moreover, this is one of the first reports indicating extensive analysis of microbial lipids produced by M. isabellina.
The biochemical behavior of the yeasts Rhodosporidium toruloides DSM 4444, Yarrowia lipolytica ACA YC 5029, and Y. lipolytica ACA YC 5030 was evaluated on waste glycerol‐based media, added at ...increasing initial concentrations (50–140 g/L), with nitrogen remaining constant. During flask cultivation of Y. lipolytica ACA‐YC 5030, and although medium pH remained >4.8, major metabolites were the polyols mannitol (CMl) and erythritol (CEr) (CMlmax = 32.1 g/L, conversion yield per glycerol consumed =0.23 g/g, and CErmax = 35.5 g/L, yield ≈0.25 g/g). For the strain ACA‐YC 5029, equally in flasks and pH >4.8, the major metabolites were again mannitol and erythritol, with CMlmax = 28.9 g/L (conversion yield ≈0.21 g/g), and CErmax = 33.6 g/L (yield ≈0.24 g/g). In contrast, in batch‐bioreactor experiment, the yeast ACA YC‐5029 produced mainly citric acid (maximum concentration =39 g/L, yield on glycerol =0.42 g/g). R. toruloides DSM 4444 was flask‐cultured at increasing initial glycerol quantities (up to ≈140 g/L) and displayed significant growth producing also satisfactory amounts of lipids. The maximum DCW concentration achieved was 39.1 g/L. Maximum lipids were 13.7 g/L (at that point lipid in DCW was 37.0% w/w). The major cellular fatty acid produced was oleic acid. Phospholipids of R. toruloides were the most unsaturated fraction among lipid fractions quantified.
Practical applications: Industrial glycerol, the main by‐product of biodiesel‐producing facilities, appears in constantly increasing quantities in the market volume due to the worldwide rise of biodiesel production, rendering the valorization of this by‐product as a very important scientific priority. In this report, the yeasts Y. lipolytica ACA YC 5029 and Y. lipolytica ACA YC 5030 were cultivated in submerged batch experiments with industrial glycerol as substrate under nitrogen limitation and appreciable quantities of mannitol and erythritol, compounds presenting significant importance for the food industries, were synthesized. The yeast R. toruloides DSM 4444, equally batch‐cultured on glycerol under nitrogen limitation, produced appreciable quantities of biomass that contained high concentrations of microbial lipids, that could be transformed into “2nd generation” biodiesel. The current study, hence, provides viable possibilities of glycerol valorization through its use as substrate in order metabolic compounds of added‐value to be synthesized.
Crude glycerol, the principal “waste” stream deriving from biodiesel production process, is converted with the aid of microbial fermentations into secondary metabolites useful for the food‐ and biofuels‐producing industries. The metabolic compounds synthesized are microbial lipids (single cell oils) amenable to be converted into 2nd generation biodiesel with fermentations led by a strain of the yeast Rhodosporidium toruloides and mannitol, erythritol and citric acid with fermentations led by strains of the yeast Yarrowia lipolytica.
Crude glycerol, the principal “waste” stream deriving from biodiesel production process, is converted with the aid of microbial fermentations into secondary metabolites useful for the food‐ and biofuels‐producing industries. The metabolic compounds synthesized are microbial lipids (single cell oils) amenable to be converted into 2nd generation biodiesel with fermentations led by a strain of the yeast Rhodosporidium toruloides and mannitol, erythritol and citric acid with fermentations led by strains of the yeast Yarrowia lipolytica.
Various supports and immobilization techniques have been proposed and tested for application in wine-making, cider-making, brewing, distillates, potable alcohol and novel beverages production. ...Immobilization applications suitable for use by these alcohol-related industries are described together with an evaluation of their potential future impact, which is also highlighted and assessed. Topics in process engineering including immobilized cell bioreactor configurations and the scale-up potential of the various immobilization supports and techniques are also discussed.
•Bioprocess design and costing for 2,3-butanediol production.•Versatile downstream separation of 2,3-butanediol by reactive extraction.•The composition of fermentation media affects the cost of ...2,3-butanediol production.•The prospects of bio-based 2,3-butanediol production is promising.
This study presents the techno-economic evaluation of 2,3-butanediol (BDO) production via fermentation using glycerol, sucrose and sugarcane molasses as carbon sources. Literature-cited experimental data were used to design the fermentation stage, whereas downstream separation of BDO was based on reactive extraction of BDO employing an aldehyde to convert BDO into an acetal that is immiscible with water. The selected downstream process can be used in all fermentations employed. Sensitivity analysis was carried out targeting the estimation of the minimum selling price (MSP) of BDO at different plant capacities and raw material purchase costs. In all cases, the MSP of BDO is higher than 1$/kg that is considered as the target in order to characterize a fermentation product as platform chemical. The complex nutrient supplements, the raw material market price and the fermentation efficiency were identified as the major reasons for the relatively high MSP observed.
Aims
To study the biotechnological production of lipids containing rich amounts of the medically and nutritionally important γ‐linolenic acid (GLA), during cultivation of the Zygomycetes Thamnidium ...elegans, on mixtures of glucose and xylose, abundant sugars of lignocellulosic biomass.
Methods and Results
Glucose and xylose were utilized as carbon sources, solely or in mixtures, under nitrogen‐limited conditions, in batch‐flask or bioreactor cultures. On glucose, T. elegans produced 31·9 g l−1 of biomass containing 15·0 g l−1 lipid with significantly high GLA content (1014 mg l−1). Xylose was proved to be an adequate substrate for growth and lipid production. Additionally, xylitol secretion occurred when xylose was utilized as carbon source, solely or in mixtures with glucose. Batch‐bioreactor trials on glucose yielded satisfactory lipid production, with rapid substrate consumption rates. Analysis of intracellular lipids showed that the highest GLA content was observed in early stationary growth phase, while the phospholipid fraction was the most unsaturated fraction of T. elegans.
Conclusions
Thamnidium elegans represents a promising fungus for the successful valorization of sugar‐based lignocellulosic residues into microbial lipids of high nutritional and pharmaceutical interest.
Significance and Impact of the Study
Xylitol production and cultivation in bioreactor trials is reported for the first time for T. elegans, while cultivation on xylose‐based media resulted in high GLA production by this fungus.
► Valorisation of biodiesel industry by-products for PHA production. ► Replacement of commercial carbon sources and nutrient supplements. ► Replacement of precursors for co-polymer production. ► ...Influence of salt impurities concentration on PHA production. ► Analysis of thermophysical properties of the produced PHAs.
Utilization of by-products from oilseed-based biodiesel production (crude glycerol, rapeseed meal hydrolysates) for microbial polyhydroxyalkanoate (PHA) production could lead to the replacement of expensive carbon sources, nutrient supplements and precursors for co-polymer production. Batch fermentations in shake flasks with varying amounts of free amino nitrogen led to the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)) with a 2.8–8% 3HV content. Fed-batch fermentations in shake flasks led to the production of 10.9g/L P(3HB-co-3HV) and a 55.6% P(3HB-co-3HV) content. NaCl concentrations between 2 and 6g/L gradually became inhibitory to bacterial growth and PHA formation, whereas in the case of K2SO4, the inhibitory effect was observed only at concentrations higher than 20g/L. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and nuclear magnetic resonance (13C NMR) demonstrated that the incorporation of 3HV into the obtained P(3HB-co-3HV) lowered glass transition temperature, crystallinity and melting point as compared to polyhydroxybutyrate. Integrating PHA production in existing oilseed-based biodiesel plants could enhance the viability and sustainability of this first generation biorefinery.
► Significant 1,3-propanediol production by a natural Citrobacter freundii on raw glycerol, the highest one reported by Citrobacter strains so far. ► Growth and 1,3-propanediol production observed at ...very high initial glycerol concentration media. ► Slightly decreased 1,3-propanediol production when glycerol deriving from thermally treated oil was used. ► Enhanced 1,3-propanediol production by C. freundii under completely unsterilized conditions.
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.
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