Fermentable Carbon Sources Research Articles

Acid preservation of Saccharina latissima for application as a carbon source for fermentation to biofuels and chemicals

Cultivated kelps (brown algae) are a sustainable biomass resource and a potential feedstock for conversion to biofuels and chemicals. Due to seasonal variations, and a short period with optimal biomass composition, preservation and storage of the biomass is required for a year-round operation of a seaweed processing plant. For use of the biomass as a carbon source for fermentation to biofuels, only low-cost preservation methods are feasible. Preservation of Saccharina latissima (sugar kelp) by sulphuric and formic acid has been evaluated as a method to maintain the fermentable carbohydrates laminaran and mannitol. In milled biomass, stored anaerobically for up to 6.5 months at different pH values, laminaran and mannitol were efficiently preserved in samples stored at pH below 3.7, obtained by addition of sulphuric acid. When a combination of sulphuric and formic acid was used, no sugar loss could be detected up to pH 4. The content of free glucose increased during the storage period in the well-preserved samples without loss of sugars. The free glucose levels were highest at the highest storage pH, providing strong evidence for the presence of endogenous β-glucanases that hydrolyse laminaran to glucose. Our work was primarily aimed at preservation of the biomass for application as a carbon source for fermentation. However, the method will be equally suited for other applications of the biomass, such as extraction of valuable compounds for use in functional food, feed or other areas.

Extraction of fresh banana waste juice as non-cellulosic and non-food renewable feedstock for direct lipase production

The bulk availability of banana waste in the world has made a move towards the development of alternative novel renewable sugars in present study as the pressed juice from banana frond and pseudostem was found to contain high level of renewable sugars such as glucose, sucrose and fructose. By using a simple sugarcane press, the glucose content in the banana frond juice was 16.6 g/L, which accounts for 55% of the total fermentable sugars. From the results, the lipase production reached ∼200 U/mL in medium comprising banana frond juice and banana pseudostem juice, comparable to basal medium with glucose (206.3 U/mL) as carbon source in basal media. As banana pseudostem possesses high content of starch, microwave heating pretreatment showed 36% enhancement of glucose content (10.4 g/L) in juice as compared to direct pressed juice (7.78 g/L). This result indicates that banana waste juice can be used as an alternative fermentable carbon source for lipase production and has potential as a fermentable carbon source.

Fumaric Acid Production by Rhizopus oryzae ATCC® 20344™ from Lignocellulosic Syrup

Powdered activated carbon-treated lignocellulosic syrup prepared from energy cane bagasse was evaluated as a potential feedstock in the production of fumaric acid by Rhizopus oryzae ATCC® 20344™. Energy cane bagasse was pretreated with dilute ammonia and enzymatically hydrolyzed with commercially available enzymes, Cellic® CTec2 and HTec2. The collected hydrolysate samples were subjected to powdered activated carbon adsorption for the removal of non-sugar compounds (i.e., organic acids, furaldehydes, total phenolic compounds) and concentrated to a final 65°Bx syrup (mostly xylose and glucose sugars). The use of lignocellulosic syrup, the effect of nitrogen source, medium additives, and initial pH in the seed culture medium on fungal morphology were investigated. The carbon to nitrogen (C/N) ratio in the acid production medium was also optimized for maximum yields in fumaric acid production. Optimum seed culture medium conditions (2.0 g/L urea, 3.0 pH) produced the desired compact, smooth, and uniform fungal pellets. Optimum acid production medium conditions (400 C/N ratio, 0.2 g/L urea) resulted in a fumaric acid production of 34.20 g/L, with a yield of 0.43 g/g and a productivity of 0.24 g/L/h. These results were comparable to those observed with the control medium (pure glucose and xylose). The present study demonstrated that lignocellulosic syrup processed from dilute ammonia pretreated energy cane bagasse has potential as a renewable carbon source for fumaric acid fermentation by Rhizopus oryzae ATCC® 20344™.

Production of (2R, 3R)-2,3-butanediol using engineered Pichia pastoris: strain construction, characterization and fermentation

Background2,3-butanediol (2,3-BD) is a bulk platform chemical with various potential applications such as aviation fuel. 2,3-BD has three optical isomers: (2R, 3R)-, (2S, 3S)- and meso-2,3-BD. Optically pure 2,3-BD is a crucial precursor for the chiral synthesis and it can also be used as anti-freeze agent due to its low freezing point. 2,3-BD has been produced in both native and non-native hosts. Several pathogenic bacteria were reported to produce 2,3-BD in mixture of its optical isomers including Klebsiella pneumoniae and Klebsiella oxytoca. Engineered hosts based on episomal plasmid expression such as Escherichia coli, Saccharomyces cerevisiae and Bacillus subtilis are not ideal for industrial fermentation due to plasmid instability.ResultsPichia pastoris is generally regarded as safe and a well-established host for high-level heterologous protein production. To produce pure (2R, 3R)-2,3-BD enantiomer, we developed a P. pastoris strain by introducing a synthetic pathway. The alsS and alsD genes from B. subtilis were codon-optimized and synthesized. The BDH1 gene from S. cerevisiae was cloned. These three pathway genes were integrated into the genome of P. pastoris and expressed under the control of GAP promoter. Production of (2R, 3R)-2,3-BD was achieved using glucose as feedstock. The optical purity of (2R, 3R)-2,3-BD was more than 99%. The titer of (2R, 3R)-2,3-BD reached 12 g/L with 40 g/L glucose as carbon source in shake flask fermentation. The fermentation conditions including pH, agitation speeds and aeration rates were optimized in batch cultivations. The highest titer of (2R, 3R)-2,3-BD achieved in fed-batch fermentation using YPD media was 45 g/L. The titer of 2,3-BD was enhanced to 74.5 g/L through statistical medium optimization.ConclusionsThe potential of engineering P. pastoris into a microbial cell factory for biofuel production was evaluated in this work using (2R, 3R)-2,3-BD as an example. Engineered P. pastoris could be a promising workhorse for the production of optically pure (2R, 3R)-2,3-BD.

Influence of rice straw-derived dissolved organic matter on lactic acid fermentation by Rhizopus oryzae

Rice straw can be used as carbon sources for lactic acid fermentation. However, only a small amount of lactic acid is produced even though Rhizopus oryzae can consume glucose in rice straw-derived hydrolysates. This study correlated the inhibitory effect of rice straw with rice straw-derived dissolved organic matter (DOM). Lactic acid fermentations with and without DOM were conducted to investigate the effect of DOM on lactic acid fermentation by R.oryzae. Fermentation using control medium with DOM showed a similar trend to fermentation with rice straw-derived hydrolysates, showing that DOM contained the major inhibitor of rice straw. DOM assay indicated that it mainly consisted of polyphenols and polysaccharides. The addition of polyphenols and polysaccharides derived from rice straw confirmed that lactic acid fermentation was promoted by polysaccharides and significantly inhibited by polyphenols. The removal of polyphenols also improved lactic acid production. However, the loss of polysaccharides during the removal of polyphenols resulted in low glucose consumption. This study is the first to investigate the effects of rice straw-derived DOM on lactic acid fermentation by R.oryzae. The results may provide a theoretical basis for identifying inhibitors and promoters associated with lactic acid fermentation and for establishing suitable pretreatment methods.

Screening of yeasts for the production of 2-phenylethanol (rose aroma) in organic waste-based media.

2-Phenylethanol (2-PE) is an alcohol with a pleasant rosy scent, which is commonly used in the food, fragrance and cosmetic industries as an aroma compound and preservative. Promising sources of 2-PE are yeasts, but still the biotechnological route has not been economically competitive to chemical synthesis. Thus, the first challenging goal to develop biotechnological production of 2-PE is the identification of highly productive yeasts and cheap feedstock. This study demonstrates for the first time the promising production of 2-PE by selected yeasts in organic waste-based media. This could pave the way for development of a cheaper method of 2-PE bioproduction.

Fermentative metabolism impedes p53-dependent apoptosis in a Crabtree-positive but not in Crabtree-negative yeast.

Tumour cells distinguish from normal cells by fermenting glucose to lactate in presence of sufficient oxygen and functional mitochondria (Warburg effect). Crabtree effect was invoked to explain the biochemical basis of Warburg effect by suggesting that excess glucose suppresses mitochondrial respiration. It is known that the Warburg effect and Crabtree effect are displayed by Saccharomyces cerevisiae, during growth on abundant glucose. Beyond this similarity, it was also demonstrated that expression of human pro-apoptotic proteins in S. cerevisiae such as Bax and p53 caused apoptosis. Here, we demonstrate that p53 expression in S. cerevisiae (Crabtree-positive yeast) causes increase in ROS levels and apoptosis when cells are growing on non-fermentable carbon sources but not on fermentable carbon sources, a feature similar to tumour cells. In contrast, in Kluyveromyces lactis (Crabtree-negative yeast) p53 causes increase in ROS levels and apoptosis regardless of the carbon source. Interestingly, the increased ROS levels and apoptosis are correlated to increased oxygen uptake in both S. cerevisiae and K. lactis. Based on these results, we suggest that at least in yeast, fermentation per se does not prevent the escape from apoptosis. Rather, the Crabtree effect plays a crucial role in determining whether the cells should undergo apoptosis or not.

Sustainable carbon sources for microbial organic acid production with filamentous fungi

BackgroundThe organic acid producer Aspergillus oryzae and Rhizopus delemar are able to convert several alternative carbon sources to malic and fumaric acid. Thus, carbohydrate hydrolysates from lignocellulose separation are likely suitable as substrate for organic acid production with these fungi.ResultsBefore lignocellulose hydrolysate fractions were tested as substrates, experiments with several mono- and disaccharides, possibly present in pretreated biomass, were conducted for their suitability for malic acid production with A. oryzae. This includes levoglucosan, glucose, galactose, mannose, arabinose, xylose, ribose, and cellobiose as well as cheap and easy available sugars, e.g., fructose and maltose. A. oryzae is able to convert every sugar investigated to malate, albeit with different yields. Based on the promising results from the pure sugar conversion experiments, fractions of the organosolv process from beechwood (Fagus sylvatica) and Miscanthus giganteus were further analyzed as carbon source for cultivation and fermentation with A. oryzae for malic acid and R. delemar for fumaric acid production. The highest malic acid concentration of 37.9 ± 2.6 g/L could be reached using beechwood cellulose fraction as carbon source in bioreactor fermentation with A. oryzae and 16.2 ± 0.2 g/L fumaric acid with R. delemar.ConclusionsWe showed in this study that the range of convertible sugars for A. oryzae is even higher than known before. We approved the suitability of fiber/cellulose hydrolysate obtained from the organosolv process as carbon source for A. oryzae in shake flasks as well as in a small-scale bioreactor. The more challenging hemicellulose fraction of F. sylvatica was also positively evaluated for malic acid production with A. oryzae.

Bio-butanol separation by adsorption on various materials: Assessment of isotherms and effects of other ABE-fermentation compounds

Abstract In the general effort to produce chemicals and fuels from renewable resources there is new interest in the biotechnological route to produce butanol. Acetone-Butanol-Ethanol (ABE) fermentation leads to low product yield because butanol is toxic to microorganisms. Selecting an efficient technology to recover butanol from low concentration butanol (about 2%) solutions is key to a successful implementation of this butanol production process on an industrial scale. Adsorption has been suggested as a potential technology for butanol recovery. This paper reports a systematic investigation of the adsorption of the metabolites that are typically present in the ABE fermentation broth: acetone, butanol, ethanol, acetic acid, butyric acid, yeast extract. The effect of glucose as a carbon source for the ABE fermentation was also investigated. Three adsorbents were characterized: Amberlite XAD-4, Amberlite XAD-7 and Zeolite Y. Batch tests under a wide interval of operating conditions were carried out for the assessment of the adsorption capacities of the three adsorbents. The selectivity of the three adsorbent materials towards the main components of ABE broths was also investigated. These tests were carried out using both dilute model solutions and real fermentation broths. The tests show that Amberlite XAD-7 has the highest affinity for butanol adsorption. The co-presence of all the metabolites in the solution - synthetic broth and real broth - changes the distribution in the adsorbed phase remarkably. The distribution of the concentration of the adsorbed components can be affected by pH. The presence of glucose does not affect butanol adsorption. Amberlite XAD-7 has a great potential as an adsorbent in ABE fermentation coupled with in situ recovery product removal techniques.

Fermentative Bacteria Influence the Competition between Denitrifiers and DNRA Bacteria.

Denitrification and dissimilatory reduction to ammonium (DNRA) are competing nitrate-reduction processes that entail important biogeochemical consequences for nitrogen retention/removal in natural and man-made ecosystems. The nature of the available carbon source and electron donor have been suggested to play an important role on the outcome of this microbial competition. In this study, the influence of lactate as fermentable carbon source on the competition for nitrate was investigated for varying ratios of lactate and nitrate in the influent (Lac/N ratio). The study was conducted in an open chemostat culture, enriched from activated sludge, under strict anoxia. The mechanistic explanation of the conversions observed was based on integration of results from specific batch tests with biomass from the chemostat, molecular analysis of the biomass enriched, and a computational model. At high Lac/N ratio (2.97 mol/mol) both fermentative and respiratory nitrate reduction to ammonium occurred, coupled to partial oxidation of lactate to acetate, and to acetate oxidation respectively. Remaining lactate was fermented to propionate and acetate. At a decreased Lac/N ratio (1.15 mol/mol), the molar percentage of nitrate reduced to ammonium decreased to 58%, even though lactate was supplied in adequate amounts for full ammonification and nitrate remained the growth limiting compound. Data evaluation at this Lac/N ratio suggested conversions were comparable to the higher Lac/N ratio, except for lactate oxidation to acetate that was coupled to denitrification instead of ammonification. Respiratory DNRA on acetate was likely catalyzed by two Geobacter species related to G. luticola and G. lovleyi. Two Clostridiales members were likely responsible for lactate fermentation and partial lactate fermentation to acetate coupled to fermentative DNRA. An organism related to Propionivibrio militaris was identified as the organism likely responsible for denitrification. The results of this study clearly show that not only the ratio of available substrates, but also the nature of the electron donor influences the outcome of competition between DNRA and denitrification. Apparently, fermentative bacteria are competitive for the electron donor and thereby alter the ratio of available substrates for nitrate reduction.

Cost-Effective Production of Surfactin from Xylose-Rich Corncob Hydrolysate Using Bacillus subtilis BS-37

Corncob hydrolysate, feather hydrolysate waste (FHW) and glutamate mill waste (GMW) are inexpensive raw materials derived from agricultural waste biomass. The aim of the study was to optimize the production of surfactin from the xylose-rich corncob hydrolysate and low-cost residues rich in organic nitrogen using Bacillus subtilis BS-37. Hydrolysis of corncob was carried out with 1.5% H2SO4, FHW or GMW was used as nitrogen source to produce surfactin. Sugar compositions of corncob hydrolysate and surfactin titer were determined by HPLC. The dry weight method was used to measure biomass in fermentation broth. We discovered that the efficient surfactin producer B. subtilis BS-37 can use xylose as sole carbon source, but the addition of organic nitrogen sources was essential for surfactin production. Consequently, the xylose-rich corncob hydrolysate and low-cost residues rich in organic nitrogen were used to produce surfactin. Strain BS-37 was able to tolerate significant concentrations of several inhibitory compounds found in corncob hydrolysate, whereby acetic acid even enhanced surfactin production. Furthermore, NaOH-neutralized corncob hydrolysate was more suitable for surfactin production than the traditional Ca(OH)2-neutralized feedstock. We achieved a maximal surfactin yield of 523 mg/L from NaOH-neutralized corncob hydrolysate and feather hydrolysate waste. Furthermore, the product contained 55.3% of the most desirable surfactin isoform C15. To our best knowledge, this is the first report of surfactin production with xylose as the main fermentable carbon source.

Optimization of the biotechnological production of a novel class of anti-MRSA antibiotics from Chitinophaga sancti

BackgroundRecently, the discovery of the elansolids, a group of macrolides, was reported. The molecules show activity against methicillin-resistant Staphylococcus aureus as well as other gram-positive organisms. This fact renders those substances a promising starting point for future chemical development. The active atropisomers A1/A2 are formed by macrolactonization of the biosynthesis product A3 but are prone to ring opening and subsequent formation of several unwanted side products. Recently it could be shown that addition of different nucleophiles to culture extracts of Chitinophaga sancti enable the formation of new stable elansolid derivatives. Furthermore, addition of such a nucleophile directly into the culture led exclusively to formation of a single active elansolid derivative. Due to low product yields, methods for production of gram amounts of these molecules have to be established to enable further development of this promising compound class.ResultsProduction of elansolid A2 by C. sancti was enabled using a synthetic medium with sucrose as carbon source to a final concentration of 18.9 mg L−1. A fed-batch fermentation was ensued that resulted in an elansolid A2 concentration of 55.3 mg L−1. When using glucose as carbon source in a fed-batch fermentation only 34.4 mg L−1 elansolid A2 but 223.1 mg L−1 elansolid C1 were produced. This finding was not unexpected since elansolids A1/A2 and A3 have been reported to easily react with nucleophiles like anthranilic acid, a precursor of tryptophan biosynthesis. Due to the fact that nucleophiles can be incorporated in vivo, a fed-batch cultivation under identical conditions, with addition of anthranilic acid was carried out and lead to almost exclusive formation of elansolid C1 (257.5 mg L−1).ConclusionReproducible elansolid A2 and C1 production is feasible in different synthetic media at relatively high concentrations that will allow further investigation and semi-synthetic optimization. The feeding of anthranilic acid enables the exclusive production of the stable elansolid derivative C1, which reduces product loss by unspecific reactions and eases downstream processing. This derivative shows activity in the same range as the elansolids A1/A2. Hence, the method can possibly serve as a model-process for incorporation of other nucleophiles and biotechnological production of specifically designed molecules.

Saccharomyces cerevisiae displays an increased growth rate and an extended replicative lifespan when grown under respiratory conditions in the presence of bacteria.

Individual cells of the budding yeast Saccharomyces cerevisiae have a limited replicative potential, referred to as the replicative lifespan. We have found that both the growth rate and average replicative lifespan of S. cerevisiae cells are greatly increased in the presence of a variety of bacteria. The growth and lifespan effects are not observable when yeast are allowed to ferment glucose but are only notable on solid media when yeast are forced to respire due to the lack of a fermentable carbon source. Growth near strains of Escherichia coli containing deletions of genes needed for the production of compounds used for quorum sensing or for the production of the siderophore enterobactin also still induced the lifespan extension in yeast. Furthermore, the bacterially induced increases in growth rate and lifespan occur even across gaps in the growth medium, indicating that the bacteria are influencing the yeast through the action of a volatile compound.

Bioethanol Production from Waste Potatoes as a Sustainable Waste-to-energy Resource via Enzymatic Hydrolysis

Ever increasing demand of energy and corresponding looming depletion of fossil fuels have transpired into a burning need of time to vie for alternative energy resources before the traditional energy sources are completely exhausted. Scientists are continuously working on sustainable energy production as an alternate source of energy to meet the present and future requirements. This research deals with conversion of the starch to fermentable carbon source (sugars) by fermentation through liquefaction by using yeast and alpha- amylase. The results show that the significant bioethanol production was achieved while using the parameters like temperature (30 °C) pH (6) and incubation time of 84 hrs. About 90 ml of bioethanol was produced from potato intake of 800 g. Pakistan being an agricultural country is rich in potato crop and this research bodes well to open new vistas to arrest the energy shortage in this part of the world

Recycling Of Peneapple Waste Using Lactobacillus Delbroeckii to Lactic Acid

The liquid pineapple waste contain mainly sucrose, glucose, fructose, and other nutrients. It therefore can potentiall be used as carbon source for organic acid fermentation. Recently, lactic acid has been considered to be an important raw material for production of biodegradadable lactace polymer. The experiments weree carried out in shake flash fermentation using lactobacillus delbroeckii. Effect of some parameters such as temperature, initial Ph, initial substrate concentration, yeast extract concentration and fermentation time to the yield have been studied. The highest yield was 85.65% achieved at 40 0C, PH 6.00, 52.2 g/l sugar concentration with 5 g/l yeast extract. There was no significant increasing in lactic acid production was observed if supplementation of yeast extract above 10%.Keyword : lactic acid fermentation, liquid pineapple waste, lactobacillus delbrueckii

Solid And Liquid Pineapple Waste Utilization For Lactic Acid Fermentation

The liquid and solid pineapple waste contain mainly sucrose, glucose,fructose, and other nutrients. It therefore can potentially be used as carbon source for fermentation to produce organic acid. Recently, lactic acid has been considered to be an important raw material for production of biodegradable lactate polymer, the experiments were carried out in batch fermentation using the liquid and solid pineapple waste to produce lactic acid. The anaerobic fermentation of lactic acis were performed at 40 0C, ph 6, 5% inocolum, and 50 rpm. Initially results show that the liquid pineapple waste by using Lactobacillus delbrueckii can be used as carbon source for lactic acid fermentation. The production of lactic acid are found to be 79% yield, while only 56% yield was produced y using solid waste.Keywords : Lactic acid fermentation, Pineapple waste, Lactobacillus delbrueckii

An overview on the biotechnological production of propionic acid: From up to downstream processes

The increasing demand for propionic acid production and wide applications in several industries especially in food (as preservative and satiety-inducer) has led looking for biosynthesis of this acid with a low total cost. This paper gives an overview on biotechnological aspects of propionic acid production and moves on to the introducing of Propionibacterium as the most popular one. Also all process variables influencing on production yield, different simple and complex carbon sources, metabolic pathway of production, engineered mutants with increased productivity, and modified tolerance against high concentrations of acid have been described. Then possible methods of extraction and analysis of this organic acid as well as several applied bioreactors, the different culture systems and substrates have been introduced. It can be concluded maximum biomass and propionic acid production may be achieved by using metabolic engineering microorganisms, and study on the most significant factors influencing on yield. To date, the maximum reported yield for propionic acid (PA) production is 0.973 g.g -1 obtained from cultivation of Propionibacterium acidipropionici in a three-electrode amperometric culture system with medium containing 0.4 mM cobalt sepulchrate. Also, the best promising substrate for PA bioproduction may be achieved by glycerol as a carbon source in an extractive continuous fermentation. Simultaneous production of propionic acid and vitamin B 12 is suggested, and finally limitations and strategies for competitive microbial production with respect to chemical process from economical view of point are proposed and presented. Finally some future trends for bioproduction of propionic acid is suggested. Normal 0 false false false EN-US X-NONE AR-SA /* Style Definitions */ table.MsoNormalTable {mso-style-name:Tabla normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Arial; mso-bidi-theme-font:minor-bidi;}

O POTENCIAL DO STREPTOMYCES ISOLADOS NA REGIÃO DE MAUÉS NA PRODUÇÃO DE ENZIMAS HIDROLÍTICAS

The enzymes of microbial production area has grown in the last decades due to use in various industrial fields, and with that the research needs to innovations of existing products. The hydrolytic enzymes are biological catalysts of great commercial importance for low cost and high availability. This enzyme class has received special attention about his versatility in several areas of industrial biotechnology. The Brazil-nuts is a possible source of nutrients for the growth of micro-organisms in search of effective enzyme production and low cost. Were used two strains of Streptomyces sp. or production of protease, lipase, amylase and alkaline phosphatase using the residue Brazil-nut as carbon source in fermentation, semi-solid and liquid for the medium ISP-2 at pH 7.2 at a temperature 37°C for 15 days. The results showed that the best enzymatic activity was to protease secreted by Streptomyces sp. (1N) in semi solid fermentation. Concomitantly, was carried out an enzyme production kinetics with peak activity of 0.196 U / ml activity for 144 hours. The specific activity was observed a value of 2.17 U / mg protein for 240 hours. The production of enzymes excreted by Streptomyces sp. using the residue of Brazil-nuts is a resource for obtaining enzymes with high potential for solid state fermentation.

Knowledge integration strategies for untargeted metabolomics based on MCR-ALS analysis of CE-MS and LC-MS data

In this work, two knowledge integration strategies based on multivariate curve resolution alternating least squares (MCR-ALS) were used for the simultaneous analysis of data from two metabolomic platforms. The benefits and the suitability of these integration strategies were demonstrated in a comparative study of the metabolite profiles from yeast (Saccharomyces cerevisiae) samples grown in non-fermentable (acetate) and fermentable (glucose) carbon source. Untargeted metabolomics data acquired by capillary electrophoresis-mass spectrometry (CE-MS) and liquid chromatography-mass spectrometry (LC-MS) were jointly analysed. On the one hand, features obtained by independent MCR-ALS analysis of each dataset were joined to obtain a biological interpretation based on the combined metabolic network visualization. On the other hand, taking advantage of the common spectral mode, a low-level data fusion strategy was proposed merging CE-MS and LC-MS data before the MCR-ALS analysis to extract the most relevant features for further biological interpretation. Then, results obtained by the two presented methods were compared. Overall, the study highlights the ability of MCR-ALS to be used in any of both knowledge integration strategies for untargeted metabolomics. Furthermore, enhanced metabolite identification and differential carbon source response detection were achieved when considering a combination of LC-MS and CE-MS based platforms.

An overview of biotechnological production of propionic acid: From upstream to downstream processes

Abstract The increasing demand for propionic acid (PA) production and its wide applications in several industries, especially the food industry (as a preservative and satiety inducer), have led to studies on the low-cost biosynthesis of this acid. This paper gives an overview of the biotechnological aspects of PA production and introduces Propionibacterium as the most popular organism for PA production. Moreover, all process variables influencing the production yield, different simple and complex carbon sources, the metabolic pathway of production, engineered mutants with increased productivity, and modified tolerance against high concentrations of acid have been described. Furthermore, possible methods of extraction and analysis of this organic acid, several applied bioreactors, and different culture systems and substrates are introduced. It can be concluded that maximum biomass and PA production may be achieved using metabolically engineered microorganisms and analyzing the most significant factors influencing yield. To date, the maximum reported yield for PA production is 0.973 g·g-1, obtained from Propionibacterium acidipropionici in a three-electrode amperometric culture system in medium containing 0.4 mM cobalt sepulchrate. In addition, the best promising substrate for PA bioproduction may be achieved using glycerol as a carbon source in an extractive continuous fermentation. Simultaneous production of PA and vitamin B12 is suggested, and finally, the limitations of and strategies for competitive microbial production with respect to chemical process from an economical point of view are proposed and presented. Finally, some future trends for bioproduction of PA are suggested.