The Combined Effect of Lactic Acid Bacteria and Galactomyces geotrichum Fermentation on the Aroma Composition of Sour Whey.

The increase in demand for food flavorings due to the shortening and simplification of food production technology also entails an increase in the demand for new technologies for their production. The biotechnological production of aromas is a solution characterized by a high efficiency, an independence from environmental factors and a relatively low cost. In this study, the influence of the implementation of lactic acid bacteria pre-fermentation into the production of aroma compounds by Galactomyces geotrichum on a sour whey medium on the intensity of the obtained aroma composition was analyzed. The monitoring of the culture in terms of biomass buildup, the concentration of selected compounds, and the pH resulted in the confirmation of interactions between the analyzed microorganisms. The post-fermentation product underwent a comprehensive sensomic analysis for the identification and quantification of the aroma-active compounds. The use of gas chromatography-olfactometry (GC-O) analysis and the calculation of odor activity values (OAVs) allowed 12 key odorants to be identified in the post-fermentation product. The highest OAV was found for phenylacetaldehyde with a honey odor (1815). The following compounds with the highest OAVs were 2,3-butanedione with a buttery aroma (233), phenylacetic acid with a honey aroma (197), 2,3-butanediol with a buttery aroma (103), 2-phenylethanol with a rosy aroma (39), ethyl octanoate with a fruity aroma (15), and ethyl hexanoate with a fruity aroma (14).

Optimization and Modeling of Citrobacter freundii AD119 Growth and 1,3-Propanediol Production Using Two-Step Statistical Experimental Design and Artificial Neural Networks.

1,3-propanediol (1,3-PD) has a wide range of industrial applications. The most studied natural producers capable of fermenting glycerol to 1,3-PD belong to the genera Klebsiella, Citrobacter, and Clostridium. In this study, the optimization of medium composition for the biosynthesis of 1,3-PD by Citrobacter freundii AD119 was performed using the one-factor-at-a-time method (OFAT) and a two-step statistical experimental design. Eleven mineral components were tested for their impact on the process using the Plackett-Burman design. MgSO4 and CoCl2 were found to have the most pronounced effect. Consequently, a central composite design was used to optimize the concentration of these mineral components. Besides minerals, carbon and nitrogen sources were also optimized. Partial glycerol substitution with other carbon sources was found not to improve the bioconversion process. Moreover, although yeast extract was found to be the best nitrogen source, it was possible to replace it in part with (NH4)2SO4 without a negative impact on 1,3-PD production. As a part of the optimization procedure, an artificial neural network model of the growth of C. freundii and 1,3-PD production was developed as a predictive tool supporting the design and control of the bioprocess under study.

A unique, newly discovered four-member protein family involved in extracellular fatty acid binding in Yarrowia lipolytica.

BACKGROUND: Yarrowia lipolytica, a nonconventional oleaginous yeast species, has attracted attention due to its high lipid degradation and accumulation capacities. Y. lipolytica is used as a chassis for the production of usual and unusual lipids and lipid derivatives. While the genes involved in the intracellular transport and activation of fatty acids in different cellular compartments have been characterized, no genes involved in fatty acid transport from the extracellular medium into the cell have been identified thus far. In this study, we identified secreted proteins involved in extracellular fatty acid binding. RESULTS: Recent analysis of the Y. lipolytica secretome led to the identification of a multigene family that encodes four secreted proteins, preliminarily named UP1 to UP4. These proteins were efficiently overexpressed individually in wild-type and multideletant strain (Q4: Δup1Δup2Δup3Δup4) backgrounds. Phenotypic analysis demonstrated the involvement of these proteins in the binding of extracellular fatty acids. Additionally, gene deletion and overexpression prevented and promoted sensitivity to octanoic acid (C8) toxicity, respectively. The results suggested binding is dependent on aliphatic chain length and fatty acid concentration. 3D structure modeling supports the proteins' role in fatty acid assimilation at the molecular level. CONCLUSIONS: We discovered a family of extracellular-fatty-acid-binding proteins in Y. lipolytica and have proposed to name its members eFbp1 to eFbp4. The exact mode of eFbps action remains to be deciphered individually and synergistically; nevertheless, it is expected that the proteins will have applications in lipid biotechnology, such as improving fatty acid production and/or bioconversion.

Polymer-Solvent Interactions in Modified Starches Pastes-Electrokinetic, Dynamic Light Scattering, Rheological and Low Field Nuclear Magnetic Resonance Approach.

Starch paste is a very complex dispersion that cannot be clearly classified as a solution, colloid or suspension and many factors affects its properties. As these ambiguities constitute a barrier to technological development, the aim of this study was to investigate the interaction of starch macromolecules with water by analysing the results of rheological properties, low field nuclear magnetic resonance (LF NMR), dynamic light scattering (DLS) and ζ potential analyses. Starch pastes with a concentration of 1%, prepared with distilled water and buffered to pH values of 2.5, 7.0 and 9.5 were analysed. It was proved that the pH buffering substantially decreased the values of consistency index but the pH value itself was not significant. LF NMR studies indicated that the dissolution of starch in water resulted in a reduction in spin-lattice as well as spin-spin relaxation times. Moreover, changes in relaxation times followed the patterns observed in rheological studies. Electrokinetic and DLS analyses showed that potential values are primarily influenced by the properties of the starches themselves and, to a lesser extent, by the environmental conditions. The conducted research also showed complementarity and, to some extent, substitutability of the applied research methods as well as exclusion chromatography (a method not used in this work).

Analysis of the Ability to Produce Pleasant Aromas on Sour Whey and Buttermilk By-Products by Mold Galactomyces geotrichum: Identification of Key Odorants.

Currently, there is a growing demand for flavorings, especially of natural origin. It is worth paying attention to the biotechnological processes of flavor production, characterized by simplicity, high efficiency and relatively low cost. In this study, we analyzed the ability of the Galac tomyces geotrichum mold to transform by-products of the dairy industry: sour whey and buttermilk to complex flavour mixtures with pleasant, honey-rose aroma. Furthermore, the aroma complexity of the fermentation product has been carefully identified applying a sensomic approach involving the use of gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry (GC-MS) and stable isotope dilution assay (SIDA) to identify and quantify aroma compounds. Based on the calculation of odor activity value (OAV), 13 key aroma compounds were present in both tested variants. The highest OAVs were found for phenylacetaldehyde (honey-like) in the buttermilk variant (912) and 2-phenylethanol (rose-like) in the sour whey variant (524). High values of this indicator were also recorded for phenylacetaldehyde (319) and 3-methyl-1-butanol with a fruity aroma (149) in the sour whey culture. The other compounds identified are 3-methylbutanal (malty), 2,3-butanedione (cheesy), isovaleric acid (cheesy), 3-(methylthio)-propanal (boiled potato), butanoic acid (vinegar), (E)-2-nonenal (fatty), ethyl furaneol (burnt sugar), dimethyl trisulfide (cabbage), and acetic acid (vinegar).

Secretory helpers for enhanced production of heterologous proteins in Yarrowia lipolytica.

Depending on the suboptimal factor, the target protein secretion can be over 1000-fold below the theoretical maximum. The bottlenecks may be alleviated by co-overexpression of "secretory helpers" (SHs). Here we proposed twelve SHs, functionally spanning the whole transcription-translation-translocation-folding-maturation-excretion pipeline. The genes were co-transformed with an easy-to-track reporter, and tested less than two temperatures. Our results indicated a clear distinction in the effects triggered by SHs involved in either synthesis or trafficking of the heterologous polypeptides. For superior operation of synthesis-related SHs, namely RPL3, SSA5 and SSA8, the secretory pathway's capacity must be released by applying decreased temperature (25 °C). The other SHs considered (e.g. SSO1, CWP11) did not give such spectacular results in the amounts of the target heterologous polypeptide, but allowed to maintain secretory capacity under unfavorable thermal conditions. This study provides generalizable guidelines for cloning/culturing strategies aiming at enhancement of heterologous protein secretion in Y. lipolytica.

Impact of overproduced heterologous protein characteristics on physiological response in Yarrowia lipolytica steady-state-maintained continuous cultures.

Overproduction of recombinant secretory proteins triggers numerous physiological perturbations. Depending on a given heterologous protein characteristics, the producer cell is faced with different challenges which lead to varying responses in terms of its physiology and the target protein production rate. In the present study, we used steady-state-maintained Yarrowia lipolytica cells to investigate the impact of different heterologous proteins on the physiological behavior of the host cells. Such an approach allowed to uncouple the impact of the overproduction of a particular protein from the phenomena that result from growth phase or are caused by the heterogeneity of the analyzed populations. Altogether, eight variants of recombinant strains, individually overproducing heterologous proteins of varying molecular weight (27-65 kDa) and reporting activity (enzymatic and fluorescent) were subjected to chemostat cultivations. The steady-state-maintained cells were analyzed in terms of the substrate utilization, biomass and metabolites production, as well as the reporter protein synthesis. Simplified distribution of carbon and nitrogen between the respective products, as well as expression analysis of the heterologous genes were conducted. The here-obtained data suggest that using a more transcriptionally active promoter results in channeling more C flux towards the target protein, giving significantly higher specific amounts and production rates of the target polypeptide, at the cost of biomass accumulation, and with no significant impact on the polyols production. The extent of the reporter protein's post-translational modifications, i.e., the number of disulfide bonds and glycosylation pattern, strongly impacts the synthesis process. Specific responses in terms of the protein formation kinetics, the gene expression levels, and transcript-to-protein linearity were observed.Key Points• Eight expression systems, producing different reporter proteins were analyzed.• The cells were maintained in steady-state by continuous chemostat culturing.• Protein- and promoter-specific effects were observed.

The Use of Sour and Sweet Whey in Producing Compositions with Pleasant Aromas Using the Mold Galactomyces geotrichum: Identification of Key Odorants.

Fermented products with a pleasant aroma and with strong honey, rose, and fruit odor notes were developed through the biotransformation of a medium containing sour or sweet whey with the addition of l-phenylalanine by the Galactomyces geotrichum mold. In order to obtain the strong honey-rose aroma, G. geotrichum strains were screened and fermentation conditions were optimized to achieve a preferable ratio (>1) of phenylacetaldehyde to 2-phenylethanol by the Ehrlich pathway. This allowed post-fermentation products with the ratio of concentrations of phenylacetaldehyde to 2-phenylethanol being 1.7:1. Additionally, the use of gas chromatography-olfactometry (GC-O) analysis and the calculation of odor activity values (OAVs) allowed 10 key odorants to be identified in post-fermentation products. The highest OAVs were found for phenylacetaldehyde with a honey odor in both sour and sweet whey cultures (3010 and 1776, respectively). In the variant with sour whey, the following compounds with the highest OAVs were 3-methyl-1-butanol (131), 3-(methylthio)-propanal (119), 3-methylbutanal (90), dimethyl trisulfide (71), 2,3-butanedione (37), and 2-phenylethanol (29). In the post-fermentation product with sweet whey, the following compounds with the highest OAVs were 3-(methylthio)-propanal (112), dimethyl trisulfide (69), and 2,3-butanedione (41).

Molecular Dispersion of Starch as a Crucial Parameter during Size-Exclusion Chromatography.

Starch, α-polyglucan consisting of a large number of anhydroglucose units joined by α-1,4- and α-1,6-glycosidic bonds, seems to be characterized by a simple structure when compared to other natural polymers. Nevertheless, starches of various botanical origins have different physicochemical properties that are related to the differences in molecular and supramolecular structure of this polymer. In terms of the functional value of starch, the behavior of its macromolecules in solution is the most important result of its structural features. Extremely high molecular mass is the fundamental structural property of starch. Water, considered simply as a solvent for solubilization, does not provide molecular dispersion of starch without its degradation. The objectives of this study are to characterize the suitability of a new aqueous media (urea/NaOH) for enhancing the dispersion of native corn and potato starches and its effect on the consequent size-exclusion chromatography (SEC) analysis. The results were referred to other aqueous base solvents used for dispersing starch (NaOH and KOH). The samples were separated using SEC with triple detection and phosphate buffer (pH 8.0) with urea as the eluent. The characteristics of tested normal and waxy starches were compared. The results revealed that urea/NaOH did not degrade starch during the dispersion process. The recovery of starches, however, was not higher than 42%. These results prove that while the urea/NaOH solvent allows to obtain cold-water-soluble starch, the degree of disintegration of the intramolecular interactions of amylopectin chains is still insufficient.

Optimization of Yarrowia lipolytica-based consolidated biocatalyst through synthetic biology approach: transcription units and signal peptides shuffling.

Nowadays considerable effort is being pursued towards development of consolidated microbial biocatalysts that will be able to utilize complex, non-pretreated substrates and produce valuable compounds. In such engineered microbes, synthesis of extracellular hydrolases may be fine-tuned by different approaches, like strength of promoter, type of secretory tag, and gene copy number. In this study, we investigated if organization of a multi-element expression cassette impacts the resultant Yarrowia lipolytica transformants' phenotype, presuming that different variants of the cassette are composed of the same regulatory elements and encode the same mature proteins. To this end, Y. lipolytica cells were transformed with expression cassettes bearing a pair of genes encoding exactly the same mature amylases, but fused to four different signal peptides (SP), and located interchangeably in either first or second position of a synthetic DNA construction. The resultant strains were tested for growth on raw and pretreated complex substrates of different plant origin for comprehensive examination of the strains' acquired characteristics. Optimized strain was tested in batch bioreactor cultivations for growth and lipids accumulation. Based on the conducted research, we concluded that the positional order of transcription units (TU) and the type of exploited SP affect final characteristics of the resultant consolidated biocatalyst strains, and thus could be considered as additional factors to be evaluated upon consolidated biocatalysts optimization. KEY POINTS: • Y. lipolytica growing on raw starch was constructed and tested on different substrates. • Impact of expression cassette design and SP on biocatalysts' phenotype was evidenced. • Consolidated biocatalyst process for lipids production from starch was conducted.

Protein Phosphatases Type 2C Group A Interact with and Regulate the Stability of ACC Synthase 7 in Arabidopsis.

Ethylene is an important plant hormone that controls growth, development, aging and stress responses. The rate-limiting enzymes in ethylene biosynthesis, the 1-aminocyclopropane-1-carboxylate synthases (ACSs), are strictly regulated at many levels, including posttranslational control of protein half-life. Reversible phosphorylation/dephosphorylation events play a pivotal role as signals for ubiquitin-dependent degradation. We showed previously that ABI1, a group A protein phosphatase type 2C (PP2C) and a key negative regulator of abscisic acid signaling regulates type I ACS stability. Here we provide evidence that ABI1 also contributes to the regulation of ethylene biosynthesis via ACS7, a type III ACS without known regulatory domains. Using various approaches, we show that ACS7 interacts with ABI1, ABI2 and HAB1. We use molecular modeling to predict the amino acid residues involved in ABI1/ACS7 complex formation and confirm these predictions by mcBiFC-FRET-FLIM analysis. Using a cell-free degradation assay, we show that proteasomal degradation of ACS7 is delayed in protein extracts prepared from PP2C type A knockout plants, compared to a wild-type extract. This study therefore shows that ACS7 undergoes complex regulation governed by ABI1, ABI2 and HAB1. Furthermore, this suggests that ACS7, together with PP2Cs, plays an essential role in maintaining appropriate levels of ethylene in Arabidopsis.

Expression profiling of the genes encoding ABA route components and the ACC oxidase isozymes in the senescing leaves of Populus tremula.

Abscisic acid (ABA) triggers and regulates, while ethylene modulates autumn leaf senescence. The expression profiles of genes encoding ABA route components and the ACC oxidase isozymes were investigated in Populus tremula during the early and moderate stages of autumn leaf senescence. The targets of interest were Ptre-HAB1-like genes (Ptre-HAB1, Ptre-HAB3a and Ptre-HAB3b), the subclass 3 of Ptre-SnRK2s genes (Ptre-SnRK2.6a, Ptre-SnRK2.6b and Ptre-SnRK2.6b) and Ptre-RbohD1, Ptre-RbohF1, and Ptre-RbohF2 genes encoding the poplar components, which are counterparts of the ABA route key regulators or the counterparts of its secondary messengers, such as Homology to ABA-insensitive 1 (HAB1), Sucrose non-fermenting 1-related protein kinases 2 (SnRK2s) or Respiratory burst oxidase D and Respiratory burst oxidase F (RbohD and RbohF, respectively) in Arabidopsis, and Ptre-ACO3, Ptre-ACO5, and Ptre-ACO6 genes encoding ACC oxidase isozymes involved in ethylene biosynthesis. The fold change in their expression levels enabled to distinguish the distinct expression patterns for the following pairs of genes: Ptre-HAB3a and Ptre-SnRK2.6a, Ptre-HAB3b and Ptre-SnRK2.2, and Ptre-HAB1 and Ptre-SnRK2.6b, where each pair involves the genes encoding the negative and positive regulators of ABA route, respectively. Among the investigated genes, the fold change of expression was the highest for Ptre-ACO3, Ptre-ACO6, and Ptre-SnRK2.6b genes during both the studied stages, and additionally for Ptre-HAB1 and Ptre-RbohD1 genes during the moderate stage. In contrast, the Ptre-RbohF1 and Ptre-RbohF2 genes exhibited only the transient upregulation at the early stage of senescence. In an in vitro study, the ability of protein kinases Ptre-SnRK2.6a and Ptre-SnRK2.6b to phosphorylate the N-terminal regions of Ptre-RbohD1 and Ptre-RbohF2 was studied; the activity of Ptre-SnRK2.6b against the studied Ptre-Rbohs was noticeably lower than that exhibited by Ptre-SnRK2.6a. It seems that despite the high similarity of their polypeptides, Ptre-SnRK2.6a and Ptre-SnRK2.6b may play different biological roles; nonetheless, it requires in vivo confirmation. Surprisingly, the highest protein kinase activity against the Ptre-Rbohs was detected in the heterologous reaction with AT-SnRK2.6/OST1 which suggests that the discussed interactions are evolutionary conserved.

The effect of introduction of chicken manure on the biodiversity and performance of an anaerobic digester

Background: Ammonium stress is a prime limiting phenomenon that occurs during methane formation from poultry manure. It is caused by elevated ammonium nitrogen concentrations that result from substrate decomposition. The amounts of methane formed depend on the activity of methanogenic microbes. Results: During the research reported in this paper, the response of a mesophilic consortium inhabiting a biogas reactor to rising load of poultry manure was investigated. The taxonomic composition of bacterial population was mostly typical, however syntrophic bacteria were not detected. This absence resulted in limitation of succession of some methanogenic microorganisms, especially obligate hydrogenotrophs. The methanogenic activity of the consortium was totally dependent on the activity of Methanosaeta. Inhibition of methanoganesis was noticed at ammonium nitrogen concentration of 3.68 g/L, total cessation occurred at 5.45 g/L. Significant amounts of acetic acid in the fermentation pulp accompanied the inhibition. Conclusions: The effectiveness of the consortium was totally dependent on the metabolic activity of the acetoclastic Methanoseata genus and lack of SAOB did not allow hydrogenotrophic methanogens to propagate and lead to cessation of biogas production at an elevated ammonium concentration at which acetoclastic methanogens were inhibited.

Gluten-Free Bread with Cricket Powder-Mechanical Properties and Molecular Water Dynamics in Dough and Ready Product.

Published data indicate that cricket powder (CP) is a good source of not only protein, fat and fiber, but also minerals. Due to the fact that this product naturally does not contain gluten, it is an interesting addition to the enrichment of gluten-free foods. This paper is a report on the results of starch substitution with CP (at 2%, 6% and 10%) on the properties of dough and bread. The rheology of dough and the texture of the final product were studied. While the changes caused in the dough by the introduction of CP were not pronounced, the bread obtained from it was characterized by significantly increased hardness and improved consistency. Analyses of water behavior at the molecular level with the use of 1H Nuclear Magnetic Resonance (NMR) indicated that CP altered both the bound and bulk water fractions. Moreover, examination of water activity revealed a decreased rate of water transport in samples of bread that contained CP. These results indicate improved availability of water to the biopolymers of bread, which likely plays a role in shaping the textural properties of the product.

The Nutritional Value and Biological Activity of Concentrated Protein Fraction of Potato Juice.

Potato protein is recognized as one of the most valuable nonanimal proteins due to the high content of essential amino acids. So far, it has not been used in human nutrition on a large scale due to technological limitations regarding its acquisition. In this study, the protein fraction of potato juice was concentrated with the use of membrane separation. The obtained potato juice protein concentrate (PJPC) was characterized in terms of nutritional value and biological activity, and the amino acid composition, mineral content, and antioxidant properties were determined. Moreover, in vitro cytotoxic activity against cancer cells of the gastrointestinal tract was investigated. The results of the present study indicate that PJPC is an excellent source of lysine and threonine, while leucine is its limiting amino acid, with an amino acid score (AAS) of 65%. Moreover, PJPC contains substantial amounts of Fe, Mn, K, and Cu. As demonstrated experimentally, PJPC is also characterized by higher antioxidant potential than potato itself. Biological activity, however, is not limited to antioxidant activity alone. Cytotoxicity studies using a gastric cancer cell line (Hs 746T), a colon cancer cell line (HT-29), and human colon normal cells (CCD 841 CoN) proved that PJPC is characterized by selective activity against cancer cells. It can thus be concluded that the developed method of producing protein concentrate from potato juice affords a product with moderate nutritional value and interesting biological activity.

Effect of Thermal Processing on Antioxidant Activity and Cytotoxicity of Waste Potato Juice.

Potato juice (PJ), commonly considered a burdensome waste, is rich in various compounds with bioactive properties. It has long been considered a remedy for gastric problems in traditional folk medicine. If valorization of PJ through implementation in the production of functional foods is to be considered, stabilization methods must be developed to allow long-term storage of this seasonal product. It is important that such methods are chosen with regard to their effect on the bioactive value of the obtained product. In this study, the impact of four stabilization methods on the antioxidant and cytotoxic activities of PJ was investigated. Elevated temperatures were used in thermal deproteinization used to obtain DPJW (deproteinated potato juice water) and spray-drying of FPJ (fresh potato juice) that resulted in SDPJ. Freeze drying and cryoconcentration were the low temperature processing methods that yielded PJL (potato juice lyophilisate) and CPJ (cryocorncentrated potato juice), respectively. All processed materials were characterized chemically and compared with raw materials in terms of phenolic compounds content, antioxidant activity as well as cytotoxicity to human tumor cells isolated from the gastric mucosa (Hs476T cell line), colon (Caco-2 and HT-29 cell lines), and normal cells isolated from the small intestine and colon epithelium (IEC-6 and NCM460 cell lines). It was stated that high-temperature processes - thermal deproteinization and spray-drying - yielded products with increased antioxidant potential (TEAC) that also showed increased cytotoxic activity towards intestinal cancer cells. At the same time the cytotoxicity towards normal cells remained on par with that of fresh PJ (IEC-6 cells) or decreased (NCM460 cells). Thermal deproteinization significantly decreased the content of glycoalcaloids in the juice, while spray drying did not have such an effect. The two low-temperature processes investigated - cryoconcentration and freeze drying - did not affect the PJ cytotoxic activity towards any of the cell lines used in the tests, whereas they did affect the antioxidant properties and glycoalcaloids content of PJ.

Production of wheat bread with spray-dried potato juice: Influence on dough and bread characteristics.

Spray-dried potato juice, a raw material with pro-health properties that have already been described in recent literature, was used to substitute a part of wheat flour in bread. Bread was chosen based on its popularity. This paper is a report on the results of this substitution. Three levels of flour replacement were chosen - 2.5, 5.0 and 7.5% (with respect to the mass of flour). The influence of potato juice addition on some of the most important characteristics of wheat bread was determined. Mixes of wheat flour and spray-dried potato juice were analyzed for fermentative and pasting properties. Baked bread samples were analyzed for their texture, color, consumer acceptance and antioxidant activity. The substitution influenced the volume of the loaf as gasses were not retained by the underdeveloped gluten network. Spray-dried potato juice was also found to influence the pasting properties. The viscosity values (peak viscosity, trough and final viscosity) determined with the RVA device were increased in pastes obtained from raw material mixtures with spray-dried potato juice. These crumb also showed increased firmness and chewiness as well as decreased springiness in the performed texture profile analyses. Spray-dried potato juice was also found to impact the color of bread crumb to an extent noticeable to the human eye. The bread that contained spray-dried potato juice was darker than bread produced with sole wheat bread. The color components (CIE L*a*b*) were shifted toward red and yellow. The bread containing spray-dried potato juice was also significantly richer in antioxidant compounds than the control wheat bread. From the perspective of consumer acceptance, the introduction of larger amounts of spray-dried potato juice resulted in deterioration of the sensory quality. Nonetheless, the acceptance of bread with 2.5% of flour substituted with spray-dried potato juice did not differ significantly from the control.

Pasta Fortified with Potato Juice: Structure, Quality, and Consumer Acceptance.

The potential of potato juice in relieving gastrointestinal disorders has already been proven. Work continues on implementation of this active component into products that are widely consumed. In this article, results of an attempt to fortify pasta with potato juice are presented and discussed. Fortification is performed using fresh and dried juice. The influence of the addition on culinary properties of the final product, such as cooking weight and cooking loss, as well as microstructure, color, texture, and consumer acceptance were evaluated. It was found that potato juice can be used for fortification of pasta both in its fresh and dried forms, however the effects on different responses depend on the potato juice form used. The addition of potato juice influenced the color of the product reducing its lightness and shifting color balances from green to red, yellow color saturation was decreased as well. Changes in color were more significant in the case of fresh juice addition. The firmness and microstructure of pasta was also influenced. The surface microstructure of pasta containing fresh potato juice was different from that of the other 2 products being a likely explanation of the lower cooking loss observed in its case. In contrast, the consistency of dough was strengthened by addition of dried potato juice. Principal components analysis indicated that the color change had the most pronounced effect on consumer acceptance. Other physicochemical changes were slightly less significant. Nevertheless, sensory evaluation proved that functional pasta produced with fresh potato juice finds consumer acceptance comparable with that of classic pasta.

Effect of 1,3-propanediol, organic acids, and ethanol on growth and metabolism of Clostridium butyricum DSP1.

Knowledge of tolerance of bacteria to toxic stress is important, especially for processes targeted at high final titers of product. Information on environmental limits and stress responses may help during selection of strains or design and control of processes. The influence of the main product and its co-products on the process of 1,3-propanediol (PD) synthesis was determined. Adaptation to toxic compounds was noticed as Clostridium butyricum DSP1 was less sensitive to the addition of these factors during its exponential growth on glycerol than when the factor was present in the medium before inoculation. It was also shown that the response of the tested strain to the toxicity of 1,3-propanediol (1,3-PD) has different proteomic profiles depending on the stage of culture when this substance is introduced. Relatively satisfactory activity of the analyzed strain was sustained up to a concentration of 1,3-PD of 40 g/L while 80 g/L of this metabolite was lethal to the bacterium. As for the by-products, acetic acid was determined to be the most toxic among the acids excreted during the process.

Conversion of glycerol to 1,3-propanediol by Citrobacter freundii and Hafnia alvei - newly isolated strains from the Enterobacteriaceae.

In this study, nearly 4000 bacterial strains from the family of Enterobacteriaceae isolated from different environments were screened for ability to convert glycerol to 1,3-propanediol (1,3-PD). The aim of the research was to isolate 1,3-PD producers from the natural environment, identify and characterize the best isolates. Three selective media were tested to usefulness in the isolation of bacteria from the family Enterobacteriaceae. Only, 28% of examined isolates could synthesize 1,3-PD from glycerol. 1,3-PD producing bacteria were identified by API 20E tests and 16S rRNA sequences to be Klebsiella pneumoniae, Klebsiella oxytoca, Citrobacter freundii and Hafnia alvei. It is the first time, when the fermentation glycerol to 1,3-PD by H. alvei was investigated. The selected strains (C. freundii AD119 and H. alvei AD27) were analyzed on a bioreactor scale under constant pH value 7.0 at temperature of 30°C and 37°C. After 40h in batch fermentation, H. alvei AD27 produced 11.3g/L of 1,3-PD at 37°C. For C. freundii AD119, the best results were obtained at temperature of 30°C. After 24h of fermentation, the 1,3-PD concentration reached above 23 g/L of 1,3-PD.